The Florida Institute of Phosphate Research was created in 1978 by the Florida Legislature (Chapter378.101, Florida Statutes) and empowered to conduct research supportive to the responsibledevelopment of the state’s phosphate resources. The Institute has targeted areas of researchresponsibility. These are: reclamation alternatives in mining and processing, including wetlandsreclamation, phosphogypsum storage areas and phosphatic clay containment areas; methods for moreefficient, economical and environmentally balanced phosphate recovery and processing; disposal andutilization of phosphatic clay; and environmental effects involving the health and welfare of the people,including those effects related to radiation and water consumption

FIPR is located in Polk County, in the heart of the central Florida phosphate district. The Instituteseeks to serve as an information center on phosphate-related topics and welcomes information requestsmade in person, or by mail, email, or telephone.

Research Staff

Executive DirectorPaul R. Clifford

Research Directors

G. Michael Lloyd, Jr.J. Patrick ZhangSteven G. RichardsonGordon D. Nifong

-Chemical Processing -Mining & Beneficiation-Reclamation-Environmental Services

Florida Institute of Phosphate Research1855 West Main StreetBartow, Florida 33830

(863) 534-7160Fax: (863) 534-7165

http://www.fipr.state.fl.us

DEVELOPMENT OF PROCESS TO MANUFACTURE GLASS PRODUCTS FROM PHOSPHOGYPSUM

FINAL REPORT

Chris Chapman, Richard Peters and Bogdan Wojak Principal Investigators

VITRIFICATION INTERNATIONAL TECHNOLOGIES INC. 2119 Davison Avenue

Richland, Washington 99352

Prepared for

FLORIDA INSTITUTE OF PHOSPHATE RESEARCH 1855 West Main Street

Bartow, Florida 33830 USA

Contract Manager: G. Michael Lloyd, Jr. FIPR Project Number: 98-01-153

August 1999

DISCLAIMER

The contents of this report are reproduced herein as received from the contractor.

The opinions, findings and conclusions expressed herein are not necessarily those of the Florida Institute of Phosphate Research, nor does mention of company names or products constitute endorsement by the Florida Institute of Phosphate Research.

iii

PERSPECTIVE

It is always exciting to be able to take a low-value by-product or waste and con-vert it into a high-value material that has the potential for numerous applications. This is exactly what has happened under this proposal, where phosphogypsum would be con-verted to a glass. And when a market survey indicates a substantial interest in the struc-tural products that would be generated, it would appear that this approach has significant merit.

The method used to make the glass is similar to the techniques used to vitrify

high-level radioactive wastes so that they can be safely stored and handled. Phosphogyp-sum-based glass is non-leaching, does not emit radon, and as a result does not pose an unacceptable risk when used for structural products such as roofing tiles. And when, as in this case, the economics are decidedly favorable, it would seem that this should be the way to go.

The question of how much phosphogypsum would be used for this purpose is al-ways before us. It should be obvious that this approach will not consume all the phosphogypsum produced immediately and that the most likely way to use all the phosphogypsum produced is to develop a number of stand-alone uses that have the potential to grow with time.

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ABSTRACT

Over 30 million tons of phosphogypsum are being placed on piles, or gyp stacks, each year. Some productive use for this potential resource is desired. It has been pro-posed that this phosphogypsum and tailings sand, also associated with the phosphate mining operations, be used to produce high value glass or glass-ceramics products while returning the sulfuric acid back to the mining operations. Phase one successfully demon-strated feasibility of making glass from these materials. The current phase was to re-search the marketing of a product made from these materials and to complete an initial risk assessment. Glass-ceramics made with high concentrations of calcia or gypsum appear attractive for making a variety of products and yield strong, abrasion and corro-sion resistant products. Wall, floor and roof tile were selected as the products. The method for identifying and selecting the product is reported. A preliminary risk assess-ment indicates that radon exposure attributable to these tile are much lower than for other construction materials. Annual gamma dose from maximal use of tile, all floors and roof, and conservatively exposure times was less than 50 mrem/y. With a more realistic tile use, limited to the kitchen, bathroom and entry way, the estimated exposures were less than 10 mrem/y.

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ACKNOWLEDGMENTS

The authors would like to thank Dr. Lowe and Mr. Stolys of SENES Consultants Limited for their determinations of radon and gamma dose from products manufactured from gypsum. The authors would also like to thank Corporate representatives from IMC Agrico, specifically Dr. Astley, Messrs. Keating, Gliksman, Whitt, Sabatino and Jardine and Mr. Morris of Cargill for taking the time to provide an industrial perspective of a pro-posed gypsum to glass products plant. Finally, we would like to thank Mr. G. Michael Lloyd of the Florida Institute of Phosphate Research for his knowledgeable and experi-enced responses to our inquiries.

vii

TABLE OF CONTENTS

PERSPECTIVE................................................................................................................... ii ABSTRACT.........................................................................................................................v ACKNOWLEDGMENTS ................................................................................................. vi EXECUTIVE SUMMARY .................................................................................................1

Marketing ........................................................................................................................1 Risk Assessment..............................................................................................................3 Radon...............................................................................................................................3 Gamma Radiation............................................................................................................4

INTRODUCTION AND BACKGROUND ........................................................................7 METHODOLOGY AND APPROACH ..............................................................................9

Compositional Constraints for Potential Products ..........................................................9

Glasses High in Calcia and Silica....................................................................................9 Flat and Container Glasses..................................................................................9 Fiberglass. .........................................................................................................11

Glass-ceramics...............................................................................................................11 Summaries of Selected High Calcia Patents Yielding Glass-Ceramics ........................14

Method for Manufacturing Low Temperature Fired Ceramics.........................14 High-strength Glass-ceramic Containing Apatite Crystals and a Large

Quantity of Wollastonite Crystals and Process for Producing Same. ..........15 Objects of Marble-like Glass-ceramic. .............................................................16 High Strength Glass-Ceramic Containing Apatite and Alkaline Earth

Metal Silicate Crystals and Process for Producing the Same.......................18 Marble-like Glass-ceramic ................................................................................20 Canasite-apatite Glass-ceramics .......................................................................22 No Alkali Containing Biocompatible Glass-ceramic with Apatite,

Wollastonite and Diopside Crystals Mixed..................................................22 Artificial Stone and Method for Making...........................................................24 Vitroceramic Materials and Process of Making the Same................................25

Abrasive Products..........................................................................................................27 Cements .........................................................................................................................27

Hydraulic Cement from Glass Powder .............................................................28

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TABLE OF CONTENTS (CONTINUED)

Mineral Product.................................................................................................30 Glass Composition Suitable for Production of Fibrous Wollastonite,

Method for Producing Said Wollastonite, and Wollastonite Obtained Thereby.........................................................................................30

Identification of All Potential Products.........................................................................31 SIC 32: Stone, Clay, Glass, and Concrete Products......................................................32 Can Vitrification Consume 15% of the Annual Gypsum Generated from Phos-

phate Mining? ...........................................................................................................46 Value of Shipments .......................................................................................................46 Assessment of 15% Gypsum Utilization.......................................................................52 Selection of Products for First Vitrification Plants .......................................................53 Ceramic Tile, Floor, Wall and Roof..............................................................................56

The Tile Council of America (TCA).................................................................58 National Tile Roof Manufacturing Association................................................59

Wollastonite...................................................................................................................60 Consumption .....................................................................................................60 Prices .................................................................................................................61 Foreign Trade ....................................................................................................61 World Review ...................................................................................................61 Outlook..............................................................................................................61

Marketing Analysis .......................................................................................................62 Tiles ...................................................................................................................62 Acicular Wollastonite........................................................................................63

Risk Assessment............................................................................................................63 Assumptions ......................................................................................................64 Radon.................................................................................................................64 Gamma Radiation..............................................................................................65 Risk Conclusions...............................................................................................69

CONCLUSIONS AND RECOMMENDATIONS ............................................................71

Recommendations .........................................................................................................72 REFERENCES ..................................................................................................................73

ix

LIST OF TABLES

Table Page 1. Typical Commercial Glasses and Their Approximate Chemical Compositions. .... 10 2. Analyses of Various Container Glasses (Weight Percent). ..................................... 10 3. Compositions of Fiber Glass, Rock Wool and Wollastonite. .................................. 11 4. Selected Glass-ceramic Compositions with High Calcia......................................... 13 5. Glass and Final Fired Product Composition, Wt%.................................................. 15 6. High-Strength Glass-ceramic with Apatite and a Large Quantity of Wollastonite

Crystals. Base Composition and Properties. ............................................................ 16 7. Marble-Like Glass-ceramic, Compositions and Properties ..................................... 17 8. High Strength Glass-Ceramic Containing Apatite and Alkaline Earth Metal Silicate

Crystals (Examples 1-6)........................................................................................... 18 8. High Strength Glass-Ceramic Containing Apatite and Alkaline Earth Metal Silicate

Crystals, Continued (Examples 7-12) ...................................................................... 19 8. High Strength Glass-Ceramic Containing Apatite and Alkaline Earth Metal Silicate

Crystals (Examples 13-20)....................................................................................... 19 9. High Strength Glass-Ceramic Containing Apatite and Alkaline Earth Metal Silicate

Crystals. ................................................................................................................... 20 10. Marble-Like Glass-ceramic. .................................................................................... 21 11. Canasite-Apatite Glass-Ceramics. ........................................................................... 22 12. No Alkali Containing Glass-ceramic with Apatite, Wollastonite and Diopside

Crystals Mixed. ........................................................................................................ 23 13. Artificial Stone and Properties................................................................................. 25 14. Vitroceramic Materials and Properties. ................................................................... 26 15. Composition of Cupola Slag.................................................................................... 27 16. Hydraulic Cement From Glass Powder In Weight %.............................................. 29 17. Hydraulic Cement From Glass Powder Treatment And Resulting Compressive

Strength. ................................................................................................................... 29 18. Hydraulic Cement From Glass Powder Treatment Enhanced Strength with

KH2PO4. .................................................................................................................. 30 19. Glass Compositions Suitable for Production of Fibrous Wollastonite. ................... 31 20. Qualitative Evaluation Codes for Listed Products................................................... 32 21. Value of Manufactured Product Shipments, in Millions, Proportionately

Extrapolated from 1996 to 1998, at the Industry Level. .......................................... 47 22. Value of Manufactured Product Shipments, in Millions, Proportionately

Extrapolated from 1996 to 1998, at the Product Level....................................... 48-50 23. Tons of Calcia (Gypsum) Used with a Market Share of 4% ................................... 52 24. Percent of Value Shipped by General Category, Including Profits. ........................ 54 25. Percent of Cost of Production by General Category................................................ 54 26. Scoring and Ranking of Potential Vitrification Plant Products by

Several Criteria ....................................................................................................... 56

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LIST OF TABLES (CONTINUED)

Table Page

27. Tile Characteristics .................................................................................................. 64 28. Estimated Exposures from Ceramic Tiles Fabricated Using Phosphogypsum........ 66 29. Estimated Annual Doses Due to Ceramic Tiles Fabricated Using

Phosphogypsum ....................................................................................................... 68

1

EXECUTIVE SUMMARY

In a previous project it was demonstrated on the laboratory scale that glass could be made from gypsum and tailings sand. In this follow-on work the scope was to identify one or more products, complete marketing of a selected product and complete a risk assessment on the selected product. MARKETING

To improve the potential for successful deployment of a glass plant using other-wise waste materials, the plant should exploit its competitive advantages. The apparent market advantages for a new vitrification manufacturing facility in central Florida would include:

• Nearby low-cost raw materials, thus reducing the materials cost and their transportation costs

• Close proximity to a relatively large market, thereby reducing the delivery costs for wholesalers and retailers.

The abundant local materials are gypsum and a relatively pure silica source, tail-

ings sand. Glass and glass-ceramics compositions that could be used for the manufacture of a wide variety of products should thus maximize the content of these materials, specifically gypsum or calcium oxide. An extensive review of publications and the U.S. patents were completed to discover glass and glass-ceramics that had high calcia content and the potential to make a diversity of products. This research led to glass-ceramics with calcia contents in the range of 25 to 40 wt % calcia. With appropriate heat treatment of the parent glass, glass-ceramics exhibit high strength, toughness and excellent chemi-cal resistance. Nearly all form wollastonite (CaSiO3) as the dominant crystal.

Slagsitall, a glass-ceramic that uses blast furnace slags with the addition of sand and clay, has been used in Eastern Europe for over thirty years. The primary crystalline phases are wollastonite (CaSiO3) and diopside (CaMgSi2O6) in a matrix of aluminosili-cate glass. These products have moderately high mechanical strengths of ~ 100 MPa (~15 ksi), high hardness, good to excellent wear and corrosion resistance. Slagsitall materials have found wide use in the construction, chemical, and petrochemical industries. Appli-cations include abrasion and chemical-resistant floor and wall tiles, industrial machinery parts, chimneys, plungers, parts for chemical pumps and reactors, grinding media, and coatings for electrolysis baths. These materials presently constitute the largest volume applications for crystallized glass.

Many similar compositions high in calcia with a variety of different manufactur-ing techniques were discovered during comprehensive searches of U.S. patents. The different manufacturing techniques ranged from conventional glass-making, to forming with subsequent heat treatments. In principle these are the same as conventional glass-making except the duration of heating is extended for glass-ceramics. At the other end of

2

the spectrum, a glass high in calcia is melted, quenched, ground to the appropriate size and then used as a raw material in more traditional ceramics processes. This approach would allow the broadest range of different products to be manufactured and uncouple

the melting from the forming operations. It could allow significant changes in the products manufactured from the same facility by simply changing the molds and firing schedules for the different products. This research indicated that both high-calcia or gypsum-containing products were quite feasible and that a very broad range of products could be manufactured.

To discover what market advantage a plant of this type, low-cost source materials and low shipping, might possess, the U.S. Department of Commerce, Bureau of the Census data files were analyzed for comparable industries. The analyses suggested that the market advantages of assumed free raw materials (gypsum and tailings sand) and lowered transportation of input materials could be cost-competitive by about 12 to 24 % on a cost of production basis for reasonably similar industries. These results indicated that there is a basis for optimism for a plant that produces the appropriate marketable product.

The selection of a specific product was completed by review of all potential prod-ucts under the standard industrial codes of Stone, Clay, Glass, And Concrete Products. From the reduced list of products, several criteria were used to rank these products. The highest ranked products were as follows. From this process and the favorable anticipated characteristics, ceramic tile was selected as the product.

Evaluation Criteria Manufacturing Industry Calcia

use Process Competitive Risk Value Total

Score 3253 Ceramic Wall And Floor Tile 8 12 17 10.5 15 62.5 3281 Cut Stone And Stone Products 8 12 15 10.5 16 61.5 3296 Mineral Wool [Rock Wool] 13 17 17 3 9 59.0 3295 Minerals And Earths, [Acicular Wollastonite]

16 17 14 2 10 59.0

3291 Abrasive Products 16 17 17 7 1 58.0 3211 Flat Glass 3 12 10.5 17 12 54.5

Discussions with local retailers, the director of the Tile Council of America, and selected international participants at the Coverings ’99 conference in Orlando were generally encouraging. However, to gain agreements for retailing or wholesaling, representative tile samples were required. The initial proposal consisted of four interac-tive tasks; 1) Pilot Melter Testing, 2) Risk Assessment for Proposed Products, 3) Evalu-ate Market for Glass Products, 4) Conceptual Design and Cost Estimate. The board chose to fund only tasks 2 and 3. Since the scope of the authorized tasks did not include the Pilot Melter Testing that would produce samples, tiles could not be made and sent to retailers or wholesalers for evaluation and feedback. Sample tiles of different designs could not be tested for strength as required for roof tiles. Tile sales are strongly depend-ent upon subjective aesthetics that the producer warrants will be consistent. Discussion

3

with companies at the 1999 Coverings Conference held in Orlando confirmed this requirement. Thus the extent of the marketing could go no further than is reported here.

RISK ASSESSMENT

After ceramic tiles were selected as the reference product, SENES Consultants Limited was tasked with determining the risk for gypsum tile use in households. The tiles were assumed to be manufactured with a CaO/SiO2 weight ratio of 25/75. Given that the Ra-226 content of the gypsum is 26 pCi/g, the concentration of Ra-226 in the CaO was estimated to be 79.9 pCi/g. The Ra-226 content of the silica is 5.1 pCi/g. Accordingly, the characteristics of the tiles used in this analysis were determined as indicated in the following table.

Tile Characteristics

Ra 226 = 23.9 pCi/g density = 2.6 g/cm3 thickness = 0.76 cm (0.3 inches) (floor and wall tiles)

= 1.0 cm (0.39 inches) (roof tile) radon emanation = 0.05 pCi cm-2 day-1 = 0.0058 pCi m-2 s-1

RADON

The contribution to the radon in the air of the dwelling due to the tiles was esti-mated using a simple one-room model: For purposes of this calculation, the dwelling was conservatively assumed to be 10 m x 10 m x 2m (V=200 m3 ) and the floor and walls were assumed to be completely covered with tiles (A=180 m2). (It was assumed that any roof tiles would not contribute to the indoor radon in the occupied areas of the house.). A nominal air exchange rate of 1 air change per hour (f = 1/3600 s-1) was also assumed. Under these assumptions, the indoor radon concentration due to the tiles would be

C = 18.7 pCi/m3 (0.0187 pCi/L).

This increment is a very small fraction of both the mean radon level of 1.25 pCi/L in U.S. homes and the U.S. EPA action limit for mitigation of 4 pCi/L for total indoor radon. This increment is small relative to the impact of basic building products on indoor radon. For example, (Quindos and others 1988) estimated that the contribution from concrete to indoor radon ranged from 15 to 105 Bq /m3 (0.4 to 2.8 pCi/L), including 40 Bq/m 3 (1.1 pCi/L) for U.S. concrete containing 1 pCi/g of Ra-226.

For perspective on the estimated incremental radon concentration due to tile use, continual exposure (18 h/d) to an indoor radon concentration of 0.0187 pCi/L would result in an annual dose of: 1.4 mrem/y.

4

GAMMA RADIATION Potential gamma radiation doses were estimated for two types of exposure

conditions: 1) maximal conditions which assumed large areas of tile use, and extended exposure durations; and 2) more typical conditions which assumed more "typical" tile coverage and exposure durations. The estimates of potential gamma radiation exposure rates for various source geometries were made using the MicroShield computer code.

The floor and roof were each assumed to be 10 m x 10 m and to be completely covered with tiles in order to represent maximal exposure conditions. The exposure rates were calculated at the center of the room and at a more likely average off-center location (2 m from one edge) for the floor and roof to show the effect of receptor location within the room. The more typical conditions assumed tile use in the kitchen, bathroom and house entrance way. The dimensions of these rooms were arbitrarily chosen, but are felt to be conservative and unlikely to underestimate tile usage in typical residences.

The exposure rates were combined with assumed exposure durations to estimate annual doses. The exposure durations in the kitchen, bathroom and entrance hall for the more typical areas of tile use were considered realistic, slightly conservative estimates. In all cases, the resultant doses are directly proportional to the assumed exposure dura-tion.

Estimated Annual Doses Due to Phosphogypsum Ceramic Tiles.

Exposure rate Duration Annual dose Exposure sources (micro R/h) (h/d) (mrem/y)

Maximal conditions 10 m x 10 m floor: adult 4.6 18 18.1

(off-center) child 8.1 18 37.3 plus roof: adult 7.4 18 29.2

child 10.0 18 46.0 More typical conditions

kitchen: adult 2.9 8 5.1 child 6.7 4 6.8

bathroom: adult 4.6 1 1.0 child 8.3 1 2.1

entrance hall: adult 1.8 0.25 0.1 child 5.5 0.25 0.4

total: adult 6.2 child 9.3

Considering the maximal exposure conditions, the calculations indicate maximal

annual doses of less than 50 mrem/y if both the floor and roof are entirely covered with tiles. Because of the conservative nature of the calculations (i.e., area of tile coverage), these may be considered as bounding, upper limits. For example, O'Brien (1997) esti-mated that continual exposure in a 5 m x 5 m x 3 m room in which the walls and ceiling

5

are lined with 1 cm thick PG plaster-board containing 0.4 Bq/g (10.8 pCi/g) of Ra-226 would lead to a dose of 13 mrem/y. If this estimate is pro-rated to the parameters used in this analysis (18 h/d and 23.9 pCi/g Ra-226), the annual dose would be 22 mrem/y. This

supports the notion that the dose estimates in the table for maximal conditions are con-servative. It should be noted that gamma radiation doses from "background" building materials are comparable to the maximal dose estimates shown in the table. Indoor levels due to building materials have been observed experimentally to be of the order of 40 mrem/y (UNSCEAR 1988).

O'Brien et al. (1998) estimated the annual dose for continual exposure to tiles glazed with zircon-containing material (with up to 80 pCi/g or more of Ra-226 in the glaze) to be about 37 mrem/y in the center of a 3 in x 3 in x 3 in room. O'Brien et al. (1998) also suggested that most members of the public would be exposed to such tiles only 2 to 3% of a full year, and actual exposures would be correspondingly lower. In the present study, exposures under more typical conditions indicate doses of less than 10 mrem/y.

7

INTRODUCTION AND BACKGROUND

The feasibility of making glass products from current waste streams within the phosphate mining process was demonstrated in laboratory-scale testing in Phase One (Peters and Chapman 1998). The objective of this project was to:

1) determine the potential for marketing glass or glass-ceramic products made of these materials,

2) make an assessment of the potential of supporting the Florida Institute of Phosphate Research’s (FIPR’s) goal of finding a productive use for 15% of these otherwise waste materials,

3) complete a risk assessment for a marketed product.

One practical approach for implementing the largest productive use of these mate-rials would be to define a profitable product for the initial production plant and then expand the volume of glass and glass-ceramic products from this self-supporting base to the largest practical capacity. After the first production plant’s experience with process-ing, operations and sales experience, future production would be expanded to the maxi-mum capacity practical. At some capacity the market for glass and glass-ceramic prod-ucts will become saturated and further expansion will not be profitable. The capacity for market saturation cannot be accurately estimated at this time because it will involve the positive influence of future new inventions and adaptive applications for the glass and the negative impacts of competing products and their innovations.

The approach used in this project was to first identify all potential markets for glass products and then narrow the list to the most promising. From the broader, more encompassing list, one can subjectively assess if glass products from phosphate mining by-products can support the goal of the Institute. The winnowed list can be used to focus the design and implementation of the first glass production plant. After the first produc-tion plant’s processing, operations and sales experience, future production would be expanded to the maximum capacity practical.

To identify the size and nature of the potential products, the Bureau of Economic Analysis and Census data were reviewed. The primary industries in which these glass products might be applicable are within the stone, clay, and glass products group and associated industries as defined by the U.S. Department of Commerce.

9

METHODOLOGY AND APPROACH

A summary of the approach used to narrow the potential products while avoiding potentially important opportunities was:

1. Identify all compositionally consistent materials, their properties and potential products that maximize use of gypsum, tailings sand and any other local mate-rials.

2. Identify all potential products that could be manufactured either as a substitute or functional alternate using the standard industrial code (SIC) listings as a general source.

3. Eliminate products that are outside the compositional constraints of relatively high gypsum (calcium oxide) and silica.

4. From this reduced list, apply subjective judgements to prioritize the listing to focus on the first production facility. Although a product may be quite prom-ising, the first product(s) would be less favored if it had to compete with

• A high industrial maturity, with only a few dominant large corpora-

tions leading in its production, • A product for which the materials cost fraction of the shipped product

is relatively small, • Limited or no real market outlet in the state of Florida or the Southeast

United States.

5. Contact distributors to gain an understanding of the potential for sales of the product.

COMPOSITIONAL CONSTRAINTS FOR POTENTIAL PRODUCTS

To assure that all feasible glass or glass-ceramic products were identified, the range of compositions that had high concentrations of calcia (gypsum) and sand were investigated. The following sections examine the typical compositions found in the different product manufacturing categories. Glasses High in Calcia and Silica

Flat and container glasses. By far the largest quantity of glass produced is com-positionally around the soda-lime-silica composition. These general compositions are typical for the large volume products of flat glass and container glass. Although many important variations in minor constituents exist, the concentration of calcia and silica are similar.

10

Table 1 summarizes the general compositional range for different glass products

currently being produced. This table is only partially representative of all compositions that are, or have been, used to produce commercial products. Within the various prod-

ucts there can be significant variations. Differences can be due to the availability of lower-cost materials, proprietary compositions patented by one or the other competing companies and the technical method used to make the product. For example, European glass frequently has higher calcia content compared to the U.S. glass because calcite and dolomite are respectively lower-cost on the respective continents. Technical evolutions are also an important factor. The use of more calcia and silica is preferred due to lower costs but the melting and forming technology is not as productive overall compared to compositions with high and more costly sodium oxide. High calcia and silica increases the potential of devitrification of the glass during machine-forming of the product. The compositional shift to lower-calcia container glass is suggested in Table 2 (Scholes and Greene 1975). As container manufacturing shifted from hand feeding of gobs to total machine operations, the concentration of calcia lowered from ~ 14% to about 10% where it remains today.

Devitrification “spoils” the appearance of glass and is most pronounced in the temperature range of the forehearth conditioning zone and forming. The longer the time at temperature, the higher the likelihood of devitrification defects. This is also true for the large-capacity float glass systems. However, rolled or imprinted flat glass transitions from molten glass to chilled formed glass quickly. This allows the calcia concentration of rolled glass to increase to ~15 wt% or higher.

Table 1. Typical Commercial Glasses and Their Approximate Chemical Compositions.

Type of glass \Oxide SiO2 Na2O CaO MgO Al2O3 K2O B2O3 Flat glass 71 16 9 3 1 Container glass 74 14 11 1 Domestic Glassware 74 16 5 3 3 1 1 Ovenware 80 4.5 5 12 Fluorescent lighting 72.5 14.6 5.7 2.9 2.6 1.2 0.3 Light bulbs 72.5 15.9 6.5 3 1.3 0.3

Table 2. Analyses of Various Container Glasses (Weight Percent).

Sample \ Oxide SiO2 A12O3 Fe2O3 CaO MgO Na2O SO3 K2O MnO Hand-fed to O'Neill machine

70.9 1.4 2.2 14.0 0.5 10.7

Av. of 32 German glasses, 1930

73.9 6.4 2.4 13.9 1.2 9.4 - 2.0 0.8

U.S. 1948 72.6 1.9 10.0 14.8 0.8 - U.S. 1949 72.0 2.1 10.2 14.9 0.8 -

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Fiberglass. A process that transitions glass very quickly through the devitrifica-

tion range is fiberglass. Within the many types of fiberglass and rock wools for differ-ent purposes, the concentration of calcia is typically much higher than for flat and

container glasses. The dominant fiberglass is E glass. It is used to make textiles, insula-tion, and as the strengthening component in plastic composites and associated products. Very high concentrations of calcia are reported for certain rock wool compositions that frequently use steel slags with high dolomite concentrations. Another fibrous glass that is heat-treated to form a crystalline wollastonite uses high concentrations of calcia. These wollastonite fibers are used to reinforce concrete due to their ability to endure the highly alkaline conditions. To exploit the maximum use of calcia derived from gypsum, fiber-glass, rock wool and synthetic production of wollastonite fibers appear to be an attractive product class. Typical compositions for these fiber products appear in Table 3.

Table 3. Compositions of Fiber Glass, Rock Wool and Wollastonite.

E Glass Rock Wool Wollastonite fibers (Tooley 1991) (Goode and others 1973) (Kume and Mizuno 1984) Range, wt % wt % wt % Oxide Low High SiO2 52 56 41 50 MgO 0 6 14.1 CaO 16 25 35.3 40 Al2O3 12 16 4.5 3.5 Na2O 0 3 0.17 2 K2O 0.82 4 ZnO MnO Fe2O3 0.05 0.4 1.6 B2O3 8 13 3.5

Glass-ceramics

Glasses with high calcia content are vulnerable to devitrification, particularly when cooled too slowly through the peak devitrification range. This characteristic may be exploited when making glass-ceramic materials. A glass-ceramic is a material having at least one crystalline phase thermally developed in a uniform pattern throughout at least a portion of a glass precursor. “Glass-ceramics have been known for over 30 years since being described in U.S. Pat. No. 2,920,971. They find application in diverse areas. One area of particular interest is the fabrication of articles used in the preparation and serving of food. Such articles include cookware, bakeware, tableware and flat cooktops.” (Wol-cott 1994)

12

In general, production of a glass-ceramic material involves three major steps:

• melting a mixture of raw materials, usually containing a nucleating agent such as fluorides, sulfides, chromia and others, to produce a glass; • forming an article from the glass and cooling the glass below its transforma-tion range; • crystallizing ("ceramming") the glass article by an appropriate thermal treat-ment. The thermal treatment usually involves a nucleating step at a temperature slightly above the transformation range, followed by heating to a somewhat higher temperature to cause more rapid crystal growth on the nuclei.

Glass-ceramics possess many attractive characteristics. Generally, they are

stronger, harder, less vulnerable to cracking and can have even better chemical durability than the parent glass. The typical challenge is to achieve homogeneous, dispersed nucleation so the final product is uniform and the crystal phase is not too large, leading to potentially lower-than-optimum strength.

Review of U.S. patents since 1976 are replete with a broad range of glass–ceramic formulations that use high-calcia compositions. Nearly all form wollastonite (CaSiO3) as the dominant crystal for high calcia compositions. Slagsitall, a glass-ceramic that uses blast furnace slags with the addition of sand and clay, has been used in Eastern Europe for over thirty years. The primary crystalline phases are wollastonite (CaSiO3) and diopside (CaMgSi2O6) in a matrix of aluminosilicate glass. These products have moder-ately high mechanical strengths of ~100 MPa (~15 ksi), high hardness, good-to-excellent wear and corrosion resistance. Slagsitall materials have found wide use in the construc-tion, chemical, and petrochemical industries. Applications include abrasion and chemi-cal-resistant floor and wall tiles, industrial machinery parts, chimneys, plungers, parts for chemical pumps and reactors, grinding media, and coatings for electrolysis baths. These materials presently constitute the largest volume applications for crystallized glass (Pinckney 1991). As indicated, the application of these materials is to a very broad range of products. A listing of selected patents that use high concentrations of calcia and sand are summarized in Table 4 with a medley of expanded summaries of these and other U.S. patents following this table.

13

Table 4. Selected Glass-ceramic Compositions with High Calcia.

Reference footnote >

A B C D E F G H J K

SiO2 59 53.2 32 44 41.5 53 50.6 37 55.5 59 CaO 19.1 31 28 49.3 36 40.9 27.8 28 24.8 23 MgO 9.3 19.9 13 2.9 -- 2.2 1.5 BaO 4.2 Al2O3 6.8 0.5 1.9 -- 4.25 8.3 8 Na2O 1.7 6.1 1.3 7.5 5.4 4.5 K2O 1.6 0.1 5.7 0.6 Fe2O3 0.2 26 0.3 0.2 B2O3 0.6 1 -- 4 P2O5 15.6 6.5 8.5 3 ZnO 6.8 Cr2O3 0.75 ZrO2 4 F2 0.5 0.2 5.3

A: (Nakamura 1976) "Objects of marble-like glass-ceramic" B: (Kubovits and others 1979) “Artificial stone and method for making” C: (Yoshida and Nakagawa 1985) “High-strength glass-ceramic containing apatite and

alkaline earth metal silicate crystals and process for producing the same” D: (Kasuga and others 1987) “High-strength glass-ceramic containing apatite crystals and

a large quantity of wollastonite crystals and process for producing same” E: (Shibuya and others 1988) “No alkali containing biocompatible glass-ceramic with

apatite, wollastonite and diopside crystals mixed” F: (Goto and others 1990) “Sintered ceramic body with excellent refractories (heat

resistance) and machinability and method of manufacture of the same” G: (Wolcott 1994) “Canasite-apatite glass-ceramics” H: (Le Bras 1977) “Vitroceramic materials and process of making the same” J: (Pinckney 1991) Slagsitall K: (Rothenberg 1976) “Method of making crystalline glass products of strip or tube”

Some of the approaches used to nucleate the crystals is to water quench the mol-ten glass to make small, millimeter-sized pieces that are subsequently ground to desired sizes. This is followed by conventional ceramics manufacturing techniques of pressing into shape, often with some binder and then firing the object. Some of these materials have very high strength (modulus of rupture /bending strength of ~25,000 psi and higher) or some other desired property. These techniques allow the material to be formed into the broadest range of products. Intricate shapes and forms can be manufactured so there are few products that cannot be made at least as an alternate to many commercial prod-

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ucts. In the next section, selected patents that provide a more detailed understanding of the potential products are summarized.

Summaries of Selected High Calcia Patents Yielding Glass-Ceramics

Method for Manufacturing Low Temperature Fired Ceramics (Nishigaki and others 1988). Low-temperature fired ceramics are produced for various applications, such as electronic components, heat-resistant articles, tablewares, kitchen utensils or decorative articles. The products are quite useful due to a combination of superior properties; particularly high heat resistance, high mechanical strength, low thermal expansion and low dielectric constant. A ceramic material is shaped into a green sheet and then converted to a dense-fired ceramic product by rapid firing in air.

Summary of the invention. The objective of this invention is to provide a method and an apparatus for manufacturing low-temperature fired ceramics with a single- or multi-layered configuration in a considerably reduced firing time. The ceramics have a large size (20 cm x 20 cm or larger) compared to the low-temperature fired ceramics reported previously that exhibited an excellent heat resistance, high mechanical strength, small thermal expansion coefficient and low dielectric constant, which are adequate for the intended applications.

The method comprising the steps of:

• forming a glass of the desired composition • grinding the glass to a powder suitable for forming a green ceramic • forming a green sheet from a ceramic raw material fired at a temperature of

800 to 1000oC and • continuously firing the green sheet in an air furnace, where the firing is carried

out by rapidly heating at a heating rate of 10 to 200oC/min, preferably 20 to 200oC /min., in order to reduce the firing time.

The ceramic raw material is fired at a temperature of 800 to 1000oC, preferably

has a composition consisting of, by weight percentage: (a) 50 to 65% of powder glass consisting of 10 to 55% of CaO, 45 to 70% of

SiO2, 0 to 30% of Al2O3 and up to 10% impurities; and (b) 50 to 35% of powder Al2O3 containing up to 10% of impurities. Further, preferably the ceramic composition contains B2O3 in an amount of up to

20% based on the total weight of the foregoing composition.

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Table 5. Glass and Final Fired Product Composition, Wt%.

Glass Additive Finish Fired Product

Sample No. CaO SiO2 Al2O3 B2O3 CaO SiO2 Al2O3 B2O3 1 27.3 59.1 4.5 9.1 16.4 35.5 42.7 5.5 2 18.2 54.5 18.2 9.1 10.9 32.7 50.9 5.5 17 27.3 50.0 13.6 9.1 16.4 30.0 48.2 5.5 20 31.8 40.9 18.2 9.1 19.1 24.5 50.9 5.5 22 23.0 62.0 15.0 0.0 15.0 40.3 44.8 0.0 23 8.3 58.3 16.7 16.7 5.0 35.0 50.0 10.0 24 8.3 50.0 25.0 16.7 5.0 30.0 55.0 10.0 26 31.8 40.9 18.2 9.1 19.1 24.5 50.9 5.5 35 45.5 45.5 0.0 9.1 25.0 25.0 45.0 5.0

High-strength Glass-ceramic Containing Apatite Crystals and a Large Quan-tity of Wollastonite Crystals and Process for Producing Same (Kasuga 1987). This invention provides a glass-ceramic having improved strength over the conventional products and to provide a process for producing such high-strength glass-ceramic. This invention relates to a glass-ceramic comprising apatite crystals and a large quantity (at least 50% by weight) of wollastonite crystals, which contains 45 < CaO < 56, 30 < SiO2 < 50, 0 < MgO+Y2O3 < 5, 1 < P2O5 <10, 0 < F2 < 5, 0 < Na2O < 5, 0 < K2O < 5, 0 < Li2O < 5, 0 < Al2O3 < 5, 0 < TiO2 < 5, 0 < ZrO2 < 5, 0 < SrO < 5, 0 < Nb2O5 < 5, 0 < Ta2O5 < 5

wherein the total content of CaO, P2O5 and SiO2 is at least 90% by weight.

The invention also includes a process for producing the above-described glass-ceramic that includes:

• molding a glass powder having the above-described composition and a parti-cle size of not greater than 75 micron

• heat-treating the glass powder at a sintering temperature and • heat-treating at a temperature for forming an apatite crystal and a wollastonite

crystal.

The glass powder of 75 micron or smaller is molded in a desired shape. The molded article is heat-treated at a sintering temperature (generally from 700 to 900oC) for the glass powder. The sintered glass is then subjected to heat treatment at a crystallization temperature (preferably from 850 to 1,200oC) in which an apatite crystal and a wollas-tonite crystal are precipitated. The former heat treatment is important for obtaining glass-ceramic with a small pore content and high mechanical strength, while the latter heat treatment is important for precipitation (formation) of an apatite crystal and a large

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quantity of a wollastonite crystal. A table showing the compositions and resulting properties follows.

Table 6. High-Strength Glass-ceramic with Apatite and a Large Quantity of Wollastonite Crystals. Base Composition and Properties.

Composition (wt %) Sample No. 1 2 3 4 5 6 7 8 9 10 11 12 15 CaO 49.5 49.3 49.3 49.3 49.3 48.2 55.5 49.3 47.9 48.3 48.3 47.4 48.3 P2O5 6.5 8.5 6.5 5 3 2.1 6.3 1 6.3 6.3 6.3 6.3 6.3 SiO2 44 42 44 45.5 47.5 49.5 38 49.5 42.6 43.2 43.2 42.1 43.2 F2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 K2O 3 Al2O3 2 TiO2 2 ZrO2 4 Ta2O5 2 Heating Temp. (C)

1,100 1,150 1,150 1,150 1,000 1,000 900 1,100 900 1,150 1,150 1,150 1,150

Bending Strength (ksi)

28 24 30 28 27 27 26 24 27 28 28 26

Objects of Marble-like Glass-ceramic (Nakamura 1976). This invention yields a material that combines the appearance of natural marble with the chemical resistance and other desirable properties of glass. Objects of the marble-like material may be prepared by heating a batch of raw material having the required overall composition to a temperature between 1400oC and 1500oC until fused, shaping the melt into a desired configuration, and permitting the shaped mass to cool. It assumes the marble-like appearance when reheated to a temperature between 1000oC and 1200oC, and held at that temperature for about two to three hours. For example, the mixed materials were fused at 1440oC in an electric furnace for five hours. The fused glass was poured into a die, pressed into the shape of a plate, and then slowly cooled to ambient temperature. The plate was then heated in a furnace to 1150oC at a rate of 120oC per hour and held at that temperature for two hours. At about 1000oC, the formation of needle-like crystals started from the surface of the plate, and the crystals grew inward from the surface until the plate, upon completion of the heat treatment, appeared to consist of an aggregate of needle-like crystals similar in appearance and texture to natural marble, but actually embedded in an amorphous matrix. The crystalline phase was identified as beta-wollastonite by X-ray diffraction.

Neither marble nor the glass of Batch No. 1 cracks when specimens 50 mm square and 10 mm thick are heated to 400oC and then immersed in cold water. The glass composition, of course, is not affected by immersion in an aqueous acid which com-

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pletely dissolves marble. The compositions and associated properties are presented in Table 7.

Table 7. Marble-like Glass-ceramic, Compositions and Properties.

No. 1 2 3 4 5 6 7 SiO2 59.1 58.4 61.6 61.7 59.7 63.9 60.6 Al2O3 6.8 8.9 7.1 7.1 6.9 5.3 7 CaO 19.1 21.8 20 20 19.3 19.5 19.6 K2O 1.6 1.8 1.7 1.7 1.6 1.8 Na2O 1.7 1.8 1.8 1.8 1.7 1.8 B2O3 0.6 2.2 0.6 0.9 0.6 0.6 ZnO 6.8 5.1 7.8 7.1 9.9 7.1 7 BaO 4.3 Fusion temp oC 1440 1395 1430 1435 1440 1495 1425 Molding temp oC 1290 1270 1290 1295 1275 1330 1270 Liquidus temp.oC 1230 1225 1240 1220 1195 1245 1230

Table 7. Marble-like Glass-ceramic, Compositions and Properties, Continued.

Color Green Brown Blue Green Black No. 8 9 10 11 12 13 14 SiO2 56.6 59 59 59 59 60.7 59 Al2O3 6.5 6.8 6.8 6.8 6.8 6.8 6.8 CaO 18.3 19.1 19.1 19.1 19.1 20.8 19.1 K2O 1.7 1.6 1.6 1.6 1.6 1.6 Na2O 3.5 1.7 1.7 1.7 1.7 1.7 B2O3 0.6 0.6 0.6 0.6 0.6 0.6 0.6 ZnO 6.5 6.8 6.8 6.8 6.8 6.8 6.8 BaO 8.2 4.2 4.3 4.3 4.2 4.3 4.2 CuO 0.2 NiO 0.1 CoO 0.1 Fe2O3 0.2 Fe2O3 3.5 Fusion temp oC 1425 1440 1440 1440 1440 1450 1430 Molding temp oC 1265 1290 1290 1290 1290 1295 1270 Liquidus temp.oC 1220 1230 1230 1230 1230 1190 1185

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High Strength Glass-Ceramic Containing Apatite and Alkaline Earth Metal

Silicate Crystals and Process for Producing the Same (Yoshida 1985). This inven-tion yields a high strength glass-ceramic containing apatite and alkaline earth metal

silicate (diopside/forsterite/akermanite) crystals.

Glass compositions as shown in Tables 8 and 9 below were prepared using ox-ides, carbonates, phosphates, fluorides and the like. Each glass composition was placed in a platinum crucible and melted at 1,400oC to 1,500oC for 1 hour. The glass was quenched by pouring it into water in the molten state and dried. It was then placed in a pot mill and pulverized to a size of 350 mesh or less. A mixture of the glass powders and 5 wt% of paraffin as a binder was placed in a metallic mold and press-molded into a desired form under a pressure of 600 kg/cm2. The molding was placed in an electric furnace, and heated from room temperature to a prescribed temperature, between 950 and 1,050oC, at a constant temperature-rising rate of 3oC /min and maintained at that temperature for 2 hours to achieve sintering and crystallization. Then, the molding was gradually cooled to room temperature in the furnace.

The glass-ceramic was ruptured, and the rupture cross-section was examined by scanning electron microscopy. It was found that the glass-ceramic had a dense structure in which almost no air bubble could be found. The glass sample was pulverized, and precipitated crystals were identified by X-ray diffraction analysis. In all cases, it was observed that, together with a large amount of apatite crystals, large amounts of alkaline earth metal silicate crystals such as diopside, forsterite and akermanite precipitated. The type of crystals precipitated is also shown in the table below.

Some samples were measured for a bending strength by using a 5 x 5 x 25 mm prism, the surface of which was polished with No. 1000 aluminum abrasive particles. The results are also shown in Tables 8 and 9 below. As can be seen from Table 8, the glass-ceramic of the present invention has a bending strength as high as from 1,500 to 1,800 kg/cm2.

Table 8. High Strength Glass-Ceramic Containing Apatite and Alkaline Earth Metal Silicate Crystals (Examples 1-6).

Example No. 1 2 3 4 5 6 MgO 8 12.1 20.1 20.8 19.9 20.1 CaO 42.9 36.2 28.1 29.2 28 28.1 SiO2 32.9 32.1 32.2 33.3 32 32.2 P2O5 15.7 15.6 15.6 16.2 15.6 15.6 F2 0.5 0.5 SrO 4 B2O3 4 F2 0.5 Al2O3 4 TiO2 4 Bending Strength (ksi) 25.56 25.56 22.7 21.3

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Table 8. High Strength Glass-Ceramic Containing Apatite and Alkaline Earth

Metal Silicate Crystals, Continued (Examples 7-12).

Example No. 7 8 9 10 11 12 MgO 29.2 12.1 12.1 21.9 18.6 28.7 CaO 16.6 40.2 40.2 30.6 26.1 24.6 SiO2 37.5 28.1 28.1 35 29.8 28.7 P2O5 16.2 15.6 15.6 12 23 16 F2 0.5 Nb2O5 4 Ta2O5 4 F2 0.5 F2 0.5 K2O 2 Li2O 2 Bending Strength (ksi) 21.3 21.3 24.1

Table 8. High Strength Glass-Ceramic Containing Apatite and Alkaline Earth Metal Silicate Crystals (Examples 13-20).

Example No. 13 14 15 16 17 18 19 20 MgO 20.1 19.9 12 28 12 27.8 12.4 12 CaO 28.1 28 36 15.9 40 23.9 36.9 35.8 SiO2 32.2 32 32 36 28 27.8 32.8 31.8 P2O5 15.6 15.6 15.5 15.6 15.5 15.5 15.9 15.4 ZrO2 4 4 4 4 4 4 2 5 F2 0.5 F2 0.5 F2 0.5 F2 0.5 Na2O 1 Bending Strength (ksi) 25.5 29.8 21.3 22.7 25.5

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Table 9. High Strength Glass-Ceramic Containing Apatite and Alkaline Earth

Metal Silicate Crystals.

Example No. 21 22 23 24 25 26 27 MgO 11.7 28.1 28.1 28.1 28.1 28.1 28.1 CaO 35.1 24.1 24.1 24.1 24.1 24.1 24.1 SiO2 31.1 28.1 28.1 28.1 28.1 28.1 28.1 P2O5 15.1 15.7 15.7 15.7 15.7 15.7 15.7 ZrO2 7 2 2 2 2 2 2 TiO2 2 SrO 2 Ta2O5 2 Nb2O5 2 K2O 2 B2O3 2 Bending Strength (ksi) 21.3 21.3

Marble-like Glass-ceramic (Kurahashi and others 1995). This invention

yields a marble-like glass-ceramic which consists essentially of, by weight percent, 50-75% SiO2, 1-15% Al2O3, 6-16.5% CaO, 0.1-5% Li2O, 0-1.5% B2O3, 10-17.5% CaO+ Li2O + B2O3, 2.5-12% ZnO, 0-12% BaO, 0.1-15% Na2O + K2O, and 0-10% coloring agents, said ceramic comprising beta-wollastonite precipitated as a major crystal. The coloring agents comprises at least one selected from a group of Fe2O3, NiO, CoO, MnO2, Cr2O3, and CuO. The marble-like glass-ceramic may further comprises at least one of As2O3 and B2O3 of up to 1% as refining agents, at least one of up to 1.5% MgO and up to 1.5% SrO so as to improve meltability of the glass, and at least one of up to 1% TiO2, up to 1% ZrO2, and up to 1% P2O5 so as to make the glass stable and less devitrifiable.

Raw materials are blended and mixed into the above-mentioned composition and are melted into the molten glass. Then, the molten glass is poured into water and quenched, thereby forming small glass masses. The small glass masses are placed and accumulated in a refractory mold of a desired shape, and are subjected to a heat treat-ment. By the heat treatment, the small glass masses softened and deformed and integrally fusion-bonded to one another, and at the same time, needle-like beta-wollastonite crystals precipitated inwardly from the surface of each of the small glass masses. Thus, a glass-ceramic article of a desired shape is produced. When the surface of the glass-ceramic article is polished, it has a marble-like appearance due to the shape of each of small masses.

The glass-ceramic articles having various colored patterns can be produced by

mixing small glass masses with inorganic pigments and accumulating the mixture in the mold, or by accumulating small glass masses having different colors.

The invention is explained in detail with reference to the following examples which are given for illustration of the invention. Tables 10 show examples (Samples

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Nos. 1 to 15) of the present invention and comparing examples (Samples No. 16-19).

Table 10. Marble-Like Glass-ceramic.

Example No. 1 2 3 4 5 6 7 8 9 10 Oxides (wt %) SiO2 61 60 69 64 61 60 69 63 63 64 Al2O3 6 7 3 5 6 7 3 5 6 5 CaO 16 14 9 14 16 14 9 14 15 14 Li2O 1 0.5 2.5 1 0.5 0.2 1.5 1 1 1 B2O3 -- -- -- -- -- 0.3 -- 1 -- -- ZnO 6 9 3 6 6 9 3 6 5 6 BaO 5 2 4.5 5 5 2 4.5 5 4 4 Na2O 3 4 7 3 3.5 4 8 3 5 3 K2O 2 3.5 2 2 2 3.5 2 2 1 2 MgO -- -- -- -- -- -- -- -- -- 1 COLOR white white white white white white white white white white Acid Resistance (mg / cm2)

0.10 0.06 0.13 0.04 0.08 0.05 0.1 0.04 0.06 0.04

Alkali resistance (mg/ cm2)

0.45 0.43 0.4 0.46 0.45 0.43 0.4 0.45 0.46 0.46

Bending strength (ksi)

7,100 6,390 5,822 6,390 7,100 6,390 5,822 6,390 6,532 6,532

Table 10. Marble-Like Glass-ceramic, Continued.

Example No. 11 12 13 14 15 16 17 18 19 Oxide wt % SiO2 63.9 63.6 63.8 63.5 65.6 64.8 61.8 64.8 57.8 Al2O3 5 5 5 5 2.9 7 5 7 7 CaO 14 14 14 14 8.5 12 13 8 16 Li2O 1 1 1 1 2.4 -- 1 1 1 B2O3 -- 0.3 -- 0.3 -- -- 3 0.5 1 ZnO 6 6 6 6 2.9 7 6 7 6 BaO 5 5 5 5 4.3 4 5 4 4.5 Na2O 3 3 3 3 6.6 3 3 4.5 3.5 K2O 2 2 2 2 1.9 2 2 3 2 NiO 0.1 0.1 0.1 0.1 -- 0.1 0.1 0.1 0.1 CoO -- -- 0.05 0.05 0.3 0.05 0.05 0.05 0.05 Fe2O3 -- -- -- -- 3.8 -- -- -- -- MnO -- -- -- -- 0.8 -- -- -- COLOR beige beige gray gray black gray gray gray -- Acid Resistance (mg / cm2) 0.05 0.05 0.06 0.06 0.13 0.11 0.03 0.08 -- Alkali resistance (mg/ cm2) 0.47 0.47 0.48 0.48 0.43 0.48 0.4 -- Bending strength (psi) 6,248 6,248 6,248 6,248 5,680 6,106 6,532 5,680

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Canasite-apatite Glass-ceramics (Wolcott 1994). This invention describes

glass-ceramics having high strength and toughness, a family of glasses from which the glass-ceramic can be produced, and a method of production. The material has a primary

crystal phase of F-canasite and a secondary crystal phase of F-apatite. The glass family is SiO2 --CaO-- Na2O -- K2O -- P2O5 --F. The method may be a single-stage heat treatment, or a two-stage involving an initial nucleation and a subsequent crystallization.

The invention resides in part in a glass-ceramic having a bending strength greater than 25,000 psi (172 MPa), a fracture toughness greater than 2.5 MPa m1/2 (2.3 Kpsi x in1/2), a primary crystal phase of F-canasite, a secondary crystal phase of F-apatite, a crystal phase structure including interlocking blades of F-canasite with at least a portion of the F-apatite crystals within the interlocking F-canasite blades, and a residual glassy phase. The invention further resides in a glass capable of being cerammed to a glass-ceramic containing F-canasite and F-apatite crystals consisting essentially of, as calcu-lated in weight percent, on an oxide basis:

Table 11. Canasite-Apatite Glass-Ceramics.

Glass SiO2 CaO Na2O K2O P2O5 F Al2O3 B2O3 MgO 1 60.6 20.6 7.8 6.1 1.6 5.6 -- -- -- 2 50.1 25.6 8 6.1 2.4 7 -- -- 0.7 3 59.9 20.5 7.8 6.1 2.5 5.6 -- -- -- 4 50.6 27.8 7.5 5.7 3 5.3 -- -- -- 5 49 26.8 7.5 5.7 3 8 -- -- -- 6 56.7 23.1 7.8 6.1 3.1 5.5 -- -- -- 7 49.9 27.6 7.1 5.4 3.9 5 -- -- 1.1 8 46.3 28 7.1 5.4 4 8 -- -- 1.1 9 54.8 22 7.6 5.9 6.8 5 -- -- -- 10 48.3 27.4 7.6 5.9 7.6 5.5 -- -- -- 11 44.1 28.6 7.5 5.7 8.2 5.9 -- -- -- 12 42.4 25.2 7.5 5.7 8.2 11 -- -- -- 13 47 28.5 7.5 5.7 8.2 3 -- -- -- 14 47.1 26.1 7.5 5.7 8.2 5.3 -- -- -- 15 44.7 23.9 9.7 7.4 8.3 6 -- -- -- 16 44.7 21.9 9.7 7.4 8.3 6 2 -- -- 17 44.7 21.9 9.7 7.4 8.3 6 -- 0.2 -- 18 53.5 21.8 7.8 5.9 8.4 4.9 -- -- -- 19 43.8 24.2 7.5 5.8 13.4 5.3 -- -- -- 20 39 21.8 7.5 5.7 18 8 -- -- -- 21 31.7 25.1 6.1 4.7 19.7 4.9 -- 7.7 --

No Alkali Containing Biocompatible Glass-ceramic with Apatite, Wollaston-ite and Diopside Crystals Mixed (Shibuya and others 1988). A glass-ceramic com-prises, by weight, 7-16% MgO, 20-45% CaO, 41-50% SiO2, 8-30% P2O5, 0-5% B2O3, 0-5% F2, and 0-10% Al2O3, and has a crystal structure where a number of fine crystals of

23

apatite, wollastonite, and diopside are densely dispersed and interlace with one another in a glass phase. The glass-ceramic is non-porous and has an increased mechanical strength of 2,000 Kg f/cm2. The glass-ceramic contains no alkali.

In the glass-ceramic according to this invention, the fine and dense crystals com-

prise apatite crystals, wollastonite crystals, and diopside crystals which extend in respec-tive particles of the powder inwardly from their outer surfaces and interlace in a compli-cated structure. The fine and dense crystals enhance the mechanical strength and the mechanical machinability of the glass-ceramic, so that the glass-ceramic can be easily machined into a desired shape without any crack and chipping of the ceramic.

A glass batch comprising ingredients for each sample was prepared using oxides, carbonates, phosphates, fluorides and the like. The glass batch was inserted in a platinum crucible and was melted in an electric furnace at 1400oC -1500oC for 4 hours. Then, the molten glass was flowed between rolls cooled by water to form a glass ribbon. The ribbon was crushed down or milled to form a glass powder having a particle size of 200 mesh or less. The powder was pressed to a compact body having a desired shape by use of a hydraulic press. The compact body was heated in an electric furnace from the room temperature to an elevated temperature of 1050oC at a rate of 30-60oC/hour and was kept at 1050oC for 2-10 hours for sintering and crystallizing the body. Then the body was cooled to the room temperature at a rate of 30-120oC/hour, and a glass-ceramic was obtained.

Table 12. No Alkali Containing Glass-ceramic with Apatite, Wollastonite and Diopside Crystals Mixed.

MgO CaO SiO2 P2O5 B2O3 F2 Al2O3 Bending strength,

(psi) 1 13.0 36.0 41.5 8.5 1 32,645 2 7.5 37.5 41.5 9.5 4 31,226 3 8.0 32.5 44.5 14 1 31,226 4 11.0 25.0 41.5 21.5 1 31,935 5 14.0 30.0 43.0 12.4 0.6 31,226 6 11.2 35.0 43.5 8.2 0.1 2.0 32,645 7 13.0 33.4 44.0 9.2 0.4 32,645 8 12.9 25.5 47.0 12.6 2 29,806 9 9.7 28.5 47.3 13 1 0.5 28,387 10 11.5 30.0 47.5 10 1 31,226 11 12.5 33.5 44.0 9.2 0.8 31,935 12 13.0 31.4 43.2 12.2 0.2 31,935 13 11.5 27.0 44.0 9 2.5 6 29,806 14 12.3 25.1 46.5 13.1 2 1 31,226 15 9.5 25.0 41.5 20 1.5 2.5 31,226 16 12.5 34.3 44.0 9.2 32,645 17 11.0 35.0 43.0 9.9 1.1 32,645

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Artificial Stone and Method for Making (Kubovits and others 1979). A mix-

ture is prepared from quartz sand, dolomite and/or limestone, sodium carbonate and/or cryolite and having a composition of

• from about 30 to about 60% SiO2, • from 0 to about 5% Al2O3, • from 0 to about 2% FeO+Fe2O3, • from about 5 to about 30% MgO, • from about 20 to about 40% CaO, and • from about 2 to about 10% Na2O and/or K2O.

Within the above limits the ratio of the components can vary within the following ranges:

• SiO2 /CaO = 1.6-2.25, • SiO2 /MgO = 2.8-5.7, • CaO/MgO = 1.5-3.4, • SiO2 +MgO = 2.8-5.7, • SiO2 /CaO+MgO = 1-1.42.

The foregoing mixture is melted between 1,250°C and 1,400oC, then it is allowed

to stand, depending on the mass and the casting form used, for a period of 1-4 hours. The melt is cooled in the casting forms between 1,250°C and 1,050oC for a period of 0.5 to 1.5 hours, with or without maintenance of a substantially constant temperature within that temperature range for 15-90 minutes while spontaneous crystallization takes place without reheating and without the presence of a nucleating agent. After crystallization the shaped mass is cooled at a rate of between 10°C and 200oC/hour. The resulting product can be white, or if a coloring metal and/or metal compound is added, then colored throughout the body of the material, having a single crystalline phase with the individual crystalline aggregates being in the order of magnitude of about a millimeter to about a centimeter. The resulting product is resistant against acids and bases and has an easily polishable natural crystalline surface.

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Table 13. Artificial Stone and Properties.

Example: 1 2 3 4 5 6 7 8 9 10

SiO2 50.3 52.8 52.8 52.8 52.8 53.8 52.8 52.8 52.8 52.8 Al2O3 1.6 0.3 0.3 0.3 0.3 0.9 0.3 0.3 0.3 0.3 Fe2O3 0.2 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.3 0.3 MgO 16.5 15.9 15.9 15.9 15.9 16.8 15.9 15.9 15.8 15.8 CaO 24.2 25.5 25.5 25.5 25.5 26.4 25.5 25.5 25.4 25.4 Na2O 5.6 5.1 5.1 5.1 5.1 1.8 5.1 5.1 5.1 5.1 K2O 1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.2 0.2 Coloring agent 0.3 0.3 0.3 0.2 0.3 0.1 0.1 0.1 0.3 0.3 Compress Strength. ksi

29.1 28.4 34.1 29.8 26.3 31.2 31.2 31.2 33.3 25.5

Flex. strgth. ksi 2.6 2.6 3.1 2.6 2.1 3.0 3.0 3.1 3.1 2.0

Table 13. Artificial Stone and Properties, Continued.

Example: 11 12 13 14 15 16 17 18 19 20.0 SiO2 53.1 55.6 46.5 53.2 49.5 52.8 52.8 51.2 51 52.2 Al2O3 0.26 1.9 1.8 0.5 1.8 0.3 0.3 1.2 1 1.2 Fe2O3 0.06 1.2 1.1 0.2 1.1 0.06 0.06 0.50 1 0.5 MgO 17.1 12.5 16.2 9.3 16.2 15.9 15.9 16.7 17 16.60 CaO 26.9 23.3 28.6 31 25.6 25.5 25.5 24.1 24.1 23.20 Na2O 2.4 5 5 6.1 5 5.1 5.1 5 5 5 K2O 0.1 0.5 0.9 0.1 0.9 0.1 0.1 0.8 1 1 Coloring agent 0.03 0.05 Compress Strength. ksi

21.3 27.0 28.4 35.5 32.6 32.6 33.3 31.2 35.5 35.5

Flex. strgth. ksi 1.8 2.3 2.6 3.1 3.0 3.0 3.1 2.8 3.1 3.1

Vitroceramic Materials and Process of Making the Same (Le Bras 1977). A vitroceramic product which is economical to produce and has excellent resistance to bending and abrasion, comprising at least 90% by weight of said product of the following ingredients expressed in percent by weight thereof;

• SiO2 + Al2O3 + B2O3 from 40 to 50%, • iron oxide from 16 to 30%, • CaO + MgO from 24 to 40%; • the sum of the Al2O3 + B2O3 being from 2 to 15 percent and • the product including at least 0.5% by weight of nucleus forming agent.

The present invention relates to the manufacture of vitroceramic (glass-ceramic)

materials which possess good physical and chemical properties and are inexpensive to

26

produce. Materials of this type are in great demand for many applications, particularly for wall and floor coverings and laboratory benches, etc. The vitroceramic materials according to the invention are specifically characterized by their good mechanical

resistance to bending and their wear resistance. The vitroceramic products, according to this invention, were developed in the course of research carried out on low-cost vitrifiable mixtures, more particularly those which avoid the use of alkaline oxides, as the high cost of the raw materials for the latter would considerably increase the cost of the vitrifiable mixture for numerous vitroceramics.

The present invention relates to vitroceramic products in which mainly silicon, iron and calcium oxides are used. These raw materials are readily available as they can be obtained, for example, from quarry products or industrial waste products and are thus inexpensive. In using compositions of this type the applicant was also seeking to obtain certain features of the ternary diagrams.

Table 14. Vitroceramic Materials and Properties. No SiO2 Fe2O3 CaO MgO B2O3 Al2O3 Na2O Cr2O3 Bending strength, (ksi) 2 30 22 39 4 4.25 0.75 8 3 32 22 37 4 4.25 0.75 12 4 34 22 35 4 4.25 0.75 17 5 40 22 29 4 4.25 0.75 18 6 42 22 27 4 4.25 0.75 14 9 37 18 36 4 4.25 0.75 18 9' 37 18 36 4 4.25 0.75 20 10 37 20 34 4 4.25 0.75 19 11 37 24 30 4 4.25 0.75 17 12 37 26 28 4 4.25 0.75 19 13 37 28 26 4 4.25 0.75 13 15 44.00 15 32 4 4.25 0.75 11 16 41.00 18 32 4 4.25 0.75 15 17 39 20 32 4 4.25 0.75 20 18 35.00 24 32 4 4.25 0.75 19 19 33.00 26 32 4 4.25 0.75 17 20 30.00 29 32 4 4.25 0.75 10 21 40.00 28 23 4 4.25 0.75 . 22 34.00 31 26 4 4.25 0.75 12 23 34.00 15 42 4 4.25 0.75 . 24 40 13 38 4 4.25 0.75 . . 25 37 22 30 2 4 4.25 0.75 18 26 37 22 26 6 4 4.25 0.75 17 27 37 22 22 10 4 4.25 0.75 10 28 37 21 31 4 4.25 2 0.75 11 30 36.75 22 32 4 4.25 0.5 17 31 36.25 25 31.5 4 4.25 2 12

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Abrasive Products

The manufacture of abrasive products is another application for a high-calcia, de-vitrified glass. Development of an abrasive product by devitrifying a calcia-rich cupola slag is described by Agarwal (Agarwal and Speyer 1992). After melting the glass, it is fritted by quenching in water, with subsequent heat treatment at 1,000oC for one hour. The calcia rich material showed good potential for use as an abrasive. Its composition is presented in Table 15 below. From this paper it is apparent that gypsum and tailings sand could be used for an abrasive product.

Table 15. Composition of Cupola Slag.

Oxide Component CaO-Rich Composition (wt.%) SiO2 37.6 CaO 40.9 MgO 9.9 Al2O3 7.2 MnO2 2.7 Residual 1.7

Cements

It is unconventional that melting is used for making cements. However, some patents would suggest that even this approach is feasible and possibly advantageous. The most relevant is the patent by Miller (1987). This invention relates to a novel process for melting calcium oxide, silica and alumina to form calcium silicates and aluminates and dispersing the resulting liquefied compounds with simultaneous quenching to retain specific characteristics which enables these compounds (upon hydration) to form high-strength cements. The method is that of producing a cement component which does not require activation with lime. It comprises

(a) quenching a liquid-phase reaction product of calcium oxide, silica and alu-mina from a temperature in excess of 1,500oC (more specifically 1,600oC or preferably 1,660oC) to a temperature of less than 400oC and

(b) simultaneously forming the reaction product into fibers having diameters which do not exceed 15 microns.

By following this process, the obtained dicalcium silicate is in a stabilized beta

phase. One purpose of this invention is to provide a system to fuse required minerals together without fine grinding, obtaining a liquid product, dispersing such product into fibers which do not exceed 15 microns in diameter, disintegrating the fibers into fine powder, to which gypsum may be added to produce high-strength cement. Previous cement-making processes require fine milling of the raw materials, sintering the mixture, fine grinding of formed clinker and activation with lime.

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The advantages of this invention are to eliminate fine grinding, which entails a

large portion of the capital and operating costs of cement production; to provide a better heat-transfer system to effect fuel economy; to prevent dust pollution; and the elimina-

tion and need for activation with lime. Thus melting a glass using high concentrations of calcia (gypsum), approaching ~60 %, could be pursued.

Hydraulic Cement from Glass Powder (Farrauto and Haynes 1973). Glass powders passing through a 140 mesh screen, i.e., having diameters less than 105 microns, and having the general composition of R2O-RO-SiO2, where R2O consists of Na2O and/or K2O and RO consists of at least one alkaline earth oxide, will react with water and set up to a strong, useful cement. The hydraulic cement is prepared by:

(1) melting a batch for a glass consisting in weight percent on the oxide basis, of 5 to 40% R2O, where R2O consists of Na2O and/or K2O, 5 to 70% RO, where RO consists of 0 to 50% CaO, 0 to 30% MgO, 0 to 70% SrO, and 0 to 35% BaO, and 20 to 80% SiO2;

(2) cooling the melt to a glass body; (3) reducing the glass body to a powder passing through a 140 mesh screen; (4) mixing water to the glass powder at temperatures between the freezing and

boiling points of the water in water-to-powder ratios of 0.25 to 0.50; and (5) maintaining the mixture within the temperature range for a period of time

sufficient to cure it to a solid body. The addition of H2PO4 anion to the glass powder prior to the preparation of a wa-

ter slurry promotes a significant increase in strength. Hence, additions of 5 to 15% by weight of NaH2PO4 and/or KH2PO4 have been observed to increase the reactivity of the glass powder by a factor of as high as five and the ultimate strength by a factor of four.

The process is of particular significance with glasses in the Na2O -CaO- SiO2 composition system since ordinary glass bottles and window panes are a source of these constituents. This factor has prominent ecological overtones since such articles, particu-larly the nonreturnable bottle, can provide a source of raw batch material. Hence, a second use for such "waste" material is plainly established. In a typical illustration of this practice, a group of nonreturnable bottles was crushed and ball milled and additional CaCO3 was added to bring the composition to 10% Na2O, 40% CaO, and 50% SiO2.

Table 16 reports glass compositions, expressed in weight percent on an oxide ba-sis, which exhibit good reactivity with water at temperatures between the freezing point and boiling point thereof and which will produce a body demonstrating substantial compressive strength after a set time of seven days.

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Table 16. Hydraulic Cement from Glass Powder in Weight %.

Sample #> 1 2 3 4 5 6 7 17 22 SiO2 42 53 67 63 53 42 40 70 45 MgO 20 CaO 33 42 13 12 42 33 50 Al2O3 Na2O 25 5 20 K2O 25 5 25 10 35 BaO 10 20

Table 17 recites the curing times and temperatures utilized with the glass powders of Table 16 as well as compressive strength measurements conducted on samples thereof. As in the case with portland cement, various filters such as sand, gravel, dirt, fly, ash, etc., can be blended with the glass powders prior to the reaction with water. In certain instances these additions will increase the compressive strength. Generally, additions of up to 30% can have this effect but beyond that the reactivity is deleteriously impaired and the strength decreases. Several examples of such combinations are also recorded in Table 2. The compressive strength of portland cement after a 30-day cure at room temperature is stated to average about 12,000 psi.

Table 17. Hydraulic Cement from Glass Powder Treatment and Resulting Compressive Strength.

Sample no. Curing treatment Compressive strength, psi 1 20oC, 7 days 1,000 2 21oC, 7 days 1,600 2 70oC, 7 days 4,000 3 70oC, 7 days 2,500 4 70oC, 7 days 2,500 5 70oC, 7 days 2,500 6 70oC, 7 days 1,000 7 70oC, 7 days 3,000 17 25oC 3 days; +50oC for 4 days 18,000 22 70oC, 7 days 1,000

Table 18 recites several examples of glass compositions set out in Table 16 which were combined with KH2PO4. In each instance, four grams of KH2PO4 were blended with 50 grams of the glass powder and this mixture then combined with water in wa-ter-to-powder ratios of 0.25 to 0.50. The curing time and temperature utilized for each product are recorded along with a measurement of the compressive strength obtained.

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Table 18. Hydraulic Cement from Glass Powder Treatment Enhanced Strength

with KH2PO4.

Sample No. Curing Treatment Compressive Strength, psi 1 25oC, 7 days 6,000 6 70oC, 7 days 2,500 17 25oC for 4 days+ 50oC for 6 days 22,500 22 70oC for 7 days 5,500

Mineral Product

Wollastonite is the common crystalline phase for many of the high calcia glass-ceramics. Mined wollastonite with some treatment has been expanding. For the many positive characteristics and uses, wollastonite’s synthetic manufacture has been disclosed in several U.S. patents. Some of these patents are summarized below.

Glass Composition Suitable for Production of Fibrous Wollastonite, Method for Producing Said Wollastonite, and Wollastonite Obtained Thereby (Kume and Mizuno 1984). Wollastonite has a molecular formula of CaSiO3, and is a crystal com-posed of equimolar amounts of SiO2 and CaO. Theoretically, therefore, when the weight ratio of SiO2 to CaO is equal to a ratio of molecular weights of SiO2 and CaO (60:56), the maximum yield can be obtained. Actually, however, in an SiO2 -CaO two-component system, vitrification can be achieved only when the molar percent of SiO2 is within the range of 64.5 to 84.5 (when expressed in % by weight, 66 to 85). Furthermore, in order to stabilize the glass and lower the melting temperature, other components should be added as well as the two components of SiO2 and CaO. Moreover, when the base glass is heated, crystallization of needlelike wollastonite (hereafter simply "needle wollastonite") does not always necessarily occur. Normally, wollastonite has three crystal forms. "Wollastonite crystal" as used herein refers to a low-temperature type wollastonite which shows fibrous growth.

According to the particular base glass composition, the yield of wollastonite from the base glass can be increased to at least 80%, and a heat treatment for crystallization to crystallize needle wollastonite from the base glass can be carried out without the use of such precise control as was required in the prior art. That is, needle wollastonite is crystallized in the base glass in the form of bundles by merely maintaining the base glass at a temperature of from 750oC to 1,150oC for several hours, resulting in the formation of a crystallized glass in which needle wollastonite and the residual glassy matrix phase coexist. Therefore, when the crystallized glass is physically and/or chemically treated to cause cleavage, the fibrous wollastonite can be easily obtained. Further, with the glass composition of the invention, the needle wollastonite can be produced directly by pre-cisely controlling the rate of cooling in the course of solidification of the molten base glass without the application of a secondary step of heat treatment for crystallization. The compositions evaluated are listed in Table 19. Sample 1 is from prior art, samples 2

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and 3 are outside the range of this patent. Samples 4 to 7 are glass compositions particu-larly suitable for the production of fibrous wollastonite with high aspect ratio and currently demand higher price.

Table 19. Glass Compositions Suitable for Production of Fibrous Wollastonite.

Sample No.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

SiO2 53 55 51 50.5 50 50 49.5 36 40 58 50 49.2 48 51.5 49.5 50 50 49.5 49.8 CaO 30 35 38 40.3 40 40 39.5 35 54 30 40 39.2 40 40 39.5 40 40 39.7 39.8 B2O3 1 4 2 5 27 5 5 5 5 4 3 4.5 3 2 6 6 40 39.7 39.8 Li2O 1 0.2 1 1 2 1 1 1 3 1 1 0.5 1 0 0.5 0.5 Al2O3 15 5 10 5.5 4 6 4 1 4 4 3.3 8 1 1.5 1 0.3 0.4 Na2O 5 2 2 1 1 1 1 1 K2O 0.5 2 2 1 1 MgO 2 4 2 BaO 4 MnO 3 ZnO 6 Fe2O3 4 TiO2 4

The above section reviewed some of the potential products that can be produced with differing concentrations of calcia and silica. Generally, the spectrum of products that could be made did not appear to be too limiting unless a minimum concentration of calcia is demanded. The next section approaches the selection from a different perspec-tive by reviewing the exhaustive list of potential products. This was completed to increase the potential for discovery of products. IDENTIFICATION OF ALL POTENTIAL PRODUCTS

As a means of identifying all potentially marketable products that gypsum glass or glass-ceramics could be used to manufacture, the standard industrial codes (SIC) and products found within each subclass were reviewed. Most of these products are classified under 32 Stone, Clay, Glass, and Concrete Products. A listing of these potential products are presented in Table 20. Superimposed on the product listings, a subjective judgement is indicated on the apparent applicability or priority for gypsum glass and glass-ceramics for the different products. The basis for down grading the potential product is sometimes identified within brackets. This superimposed judgement code is defined as follows:

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Table 20. Qualitative Evaluation Codes for Listed Products.

Estimated Applicability or Priority Font Format of Product Description Potentially Promising Product identification or description Bold Just Average or Unclear Product identification or description; normal Questionable or Low Product identification or description; font italicized Not Applicable Product identification or description; strike through

SIC 32: STONE, CLAY, GLASS, AND CONCRETE PRODUCTS

This major group includes establishments engaged in manufacturing flat glass and other glass products, cement, structural clay products, pottery, concrete and gypsum products, cut stone, abrasive and asbestos products, and other products from materials taken principally from the earth in the form of stone, clay, and sand. When separate reports are available for mines and quarries operated by manufacturing establishments classified in this major group, the mining and quarrying activities are classified in Divi-sion B, Mining. When separate reports are not available, the mining and quarrying activities, other than those of Industry 3295, are classified herein with the manufacturing operations.

If separate reports are not available for crushing, grinding, and other preparation

activities of Industry 3295, these establishments are classified in Division B, Mining. Industry Group 321 Flat Glass 3211 Flat Glass This industry also produces laminated glass, but establishments primarily engaged in manufacturing laminated glass from purchased flat glass are classified in Industry 3231. Building glass, flat [purity & consistency of gypsum - sand unknown] Cathedral glass Float glass [purity & consistency of gypsum - sand unknown] Glass, colored: cathedral and antique Glass, flat Insulating glass, sealed units-mitse [purity & consistency of gypsum - sand unknown] Multiple-glazed insulating units-mitse [purity & consistency of gypsum - sand unknown] Opalescent flat glass Ophthalmic glass, flat [purity and consistency doubtful, low volume of product] Optical glass, flat [purity and consistency doubtful, low volume of product] Picture glass Plate glass, polished and rough Sheet glass Skylight glass

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Structural glass, flat Tempered glass-mitse Window glass, clear and colored

Industry Group 322 Glass and Glassware, Pressed or Blown

This group manufactures glass and glassware, pressed, blown, or shaped from glass produced in the same establishment. Establishments primarily engaged in manufac-turing glass products made from purchased glass are classified in Industry 3231. 3221 Glass Containers

Manufactures glass containers for commercial packing and bottling, and for home canning. Ampoules, glass [volume too low] Bottles, containers, jars and jugs for packing, bottling, and canning: glass Carboys, glass Cosmetic jars, glass Fruit jars, glass Medicine bottles, glass Milk bottles, glass Packers' ware (containers), glass Vials, glass: made in glassmaking establishments [volume too low] Water bottles, glass 3222 Pressed and Blown Glass and Glassware, Not Elsewhere Classified

Manufacturing of glass and glassware, not elsewhere classified, pressed, blown, or shaped from glass produced in the same establishment. Establishments primarily engaged in manufacturing textile glass fibers are also included in this industry, but establishments primarily engaged in manufacturing glass wool insulation products are classified in Industry 3296. Establishments primarily engaged in manufacturing fiber optic cables are classified in Industry 3357, and those manufacturing fiber optic medical devices are classified in Industry Group 384. Establishments primarily engaged in the production of pressed lenses for vehicular lighting, beacons, and lanterns are also in-cluded in this industry, but establishments primarily engaged in the production of optical lenses are classified in Industry 3827. Establishments primarily engaged in manufactur-ing glass containers are classified in Industry 3221, and those manufacturing complete electric light bulbs are classified in Industry 3641. Art glassware, made in glassmaking plants Ashtrays, glass Barware, glass Battery jars, glass [volume too low] Blocks, glass Bowls, glass Bulbs for electric lights, without filaments or sockets-mitse Candlesticks, glass

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Centerpieces, glass Chimneys, lamp: glass-pressed or blown Christmas tree ornaments, from glass-mitse [volume too low]

Clip cups, glass Cooking utensils, glass and glass-ceramic Drinking straws, glass [volume too low] Fiber optics strands [ purity not adequate, low volume] Fibers, glass, textile Flameware, glass and glass-ceramic Frying pans, glass and glass-ceramic Glass blanks for electric light bulbs Glass brick Glassware: art, decorative, and novelty Goblets, glass Industrial glassware and glass products, pressed or blown Insulators, electrical: glass Lamp shades and parts, glass Lantern globes, glass: pressed or blown Lens blanks, optical and ophthalmic [purity too high, low product volume] Lenses, glass: for lanterns, flashlights, headlights, and searchlights Level vials for instruments, glass [volume too low] Lighting glassware, pressed or blown Novelty glassware: made in glassmaking plants Ophthalmic glass, except flat [volume too low] Photomask blanks, glass Reflectors for lighting equipment, glass: pressed or blown Refrigerator dishes and jars, glass Scientific glassware, pressed or blown: made in glassmaking plants Stemware, glass Tableware, glass and glass-ceramic Tea kettles, glass and glass-ceramic Technical glassware and glass products, pressed or blown Television tube blanks, glass [quality requirements too high, value added after melting too high] Textile glass fibers Tobacco jars, glass Trays, glass Tubing, glass Tumblers, glass Vases, glass Industry Group 323 Glass Products, Made of Purchased Glass 3231 Glass Products, Made of Purchased Glass

Manufactures glass products from purchased glass.

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Aquariums and reflectors Art glass, Christmas tree ornaments, cut and engraved glassware [volume too low]

Decorated glassware: e.g., chipped, engraved, etched, sandblasted Doors Enameled glass Encrusting gold, silver, or other metals on glass products [volume too low] Flowers, foliage, fruits and vines: artificial glass [volume too low] Fruit, artificial: [volume too low] Furniture tops, glass: cut, beveled, and polished Glass, scientific apparatus: for druggists', hospitals, laboratories Glass, sheet: bent- [potentially too much iron in gypsum and sand] Grasses, artificial Ground glass Industrial glassware Laboratory glassware Laminated glass Leaded glass Medicine droppers [volume too low] Mirrors, framed or unframed Mirrors, transportation equipment: Multiple-glazed insulating units Novelties, glass: e.g., fruit, foliage, flowers, animals Ornamented glass Plants and foliage, artificial Reflector glass beads, for highway signs and other reflectors: Safety glass Silvered glass Stained glass Table tops Technical glassware Tempered glass Test tubes Vials Watch crystals Windows, stained glass Windshields Industry Group 324 Cement, Hydraulic 3241 Cement, Hydraulic

Manufactures hydraulic cement, including portland, natural, masonry, and poz-zolana cements.

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Industry Group 325 Structural Clay Products

3251 Brick and Structural Clay Tile Manufactures brick and structural clay tile. Establishments primarily engaged in

manufacturing clay firebrick are classified in Industry 3255; those manufacturing nonclay firebrick are classified in Industry 3297; those manufacturing sand lime brick are classi-fied in Industry 3299; and those manufacturing glass brick are classified in Industry 3229. Book tile, clay Brick: common, face, glazed, vitrified, and hollow-clay Building tile, clay Ceramic glazed brick, clay Chimney blocks, radial-clay Corncrib tile Facing tile, clay Fireproofing tile, clay Floor arch tile, clay Flooring brick, clay Furring tile, clay Partition tile clay Paving brick clay Silo tile Slumped brick Structural tile, clay 3253 Ceramic Wall and Floor Tile

Manufactures ceramic wall and floor tile. Establishments primarily engaged in manufacturing structural clay tile are classified in Industry 3251, and those manufactur-ing drain tile are classified in Industry 3259. Ceramic tile, floor and wall Enamel tile, floor and wall: clay Faience tile Mosaic tile, ceramic Promenade tile, clay Quarry tile, clay 3255 Clay Refractories

Manufactures clay firebrick and other heat resisting clay products. Establishments primarily engaged in manufacturing nonclay refractories and all graphite refractories, whether of carbon bond or ceramic bond, are classified in Industry 3297. [not sufficiently refractory] 3259 Structural Clay Products, Not Elsewhere Classified

Establishments primarily engaged in manufacturing clay sewer pipe and structural clay products, not elsewhere classified. Adobe brick

37

Architectural terra cotta Blocks, segment: clay Chimney pipe and tops, clay

Conduit, vitrified clay Coping, wall: clay Drain tile, clay Liner brick and plates, for lining sewers, tanks, etc.: vitrified clay Lining, stove and flue: clay Roofing tile, clay Sewer pipe and fittings, clay Thimbles, chimney: clay Tile, filter underdrain: clay Tile, sewer: clay Industry Group 326 Pottery and Related Products 3261 Vitreous China Plumbing Fixtures & China and Earthenware Fittings & Bathroom Accessories

Manufactures vitreous china plumbing fixtures and china and earthenware fittings and bathroom accessories. Bathroom accessories, vitreous china and earthenware Bidets, vitreous china [insufficient volume] Bolt caps, vitreous china and earthenware [insufficient volume] Closet bowls, vitreous china Drinking fountains, vitreous china [insufficient volume] Faucet handles, vitreous china and earthenware [insufficient volume] Flush tanks, vitreous china Laundry trays, vitreous china Lavatories, vitreous china Plumbing fixtures, vitreous china Sinks, vitreous china Soap dishes, vitreous china and earthenware Toilet fixtures, vitreous china Towel bar holders, vitreous china and earthenware Urinals, vitreous china 3262 Vitreous China Table and Kitchen Articles

Manufactures vitreous china table and kitchen articles for use in households and in hotels, restaurants, and other commercial institutions for preparing, serving, or storing food or drink. Establishments primarily engaged in manufacturing fine (semivitreous) earthenware (whiteware) table and kitchen articles are classified in Industry 3263. Bone china Commercial and household tableware and kitchenware: vitreous china Cooking ware, china Dishes: commercial and household-vitreous china

38

Table articles, vitreous china 3263 Fine Earthenware (Whiteware) Table and Kitchen Articles

Manufactures fine (semivitreous) earthenware table and kitchen articles for pre-paring, serving, or storing food or drink. Establishments primarily engaged in manufac-turing vitreous china table and kitchen articles are classified in Industry 3262. Cooking ware, fine earthenware Earthenware: commercial and household-semivitreous Kitchenware, semivitreous earthenware Tableware: commercial and household-semivitreous Whiteware, fine type semivitreous tableware and kitchenware 3264 Porcelain Electrical Supplies

Manufacturing porcelain electronic and other electrical insulators, molded porce-lain parts for electrical devices, spark plug and steatitic porcelain, and electronic and electrical supplies from clay and other ceramic materials. Alumina porcelain insulators [not an alumina material] Beryllia porcelain insulators [not a beryllia material] Cleats, porcelain Ferrite Insulators, porcelain Knobs, porcelain Magnets, permanent: ceramic or ferrite [not magnetic] Porcelain parts, molded: for electrical and electronic devices Spark plugs, porcelain Titania porcelain insulators Tubes, porcelain 3269 Pottery Products, Not Elsewhere Classified

Establishments primarily engaged in firing and decorating white china and earth-enware for the trade and manufacturing art and ornamental pottery, industrial and labora-tory pottery, stoneware and coarse earthenware table and kitchen articles, unglazed red earthenware florists' articles, and other pottery products, not elsewhere classified. Art and ornamental ware, pottery Ashtrays, pottery Ceramic articles for craft shops Chemical porcelain Chemical stoneware (pottery products) China firing and decorating, for the trade Cones, pyrometric: earthenware [limited volume, different physical characteristics] Cooking ware: stoneware, coarse earthenware, and pottery Crockery Decalcomania work on china and glass, for the trade Earthenware table and kitchen articles, coarse Encrusting gold, silver, or other metal on china, for the trade Figures, pottery: china, earthenware, and stoneware

39

Filtering media, pottery Florists' articles, red earthenware Flower pots, red earthenware

Forms for dipped rubber products, pottery Grinding media, pottery Heater parts, pottery Kitchen articles, coarse earthenware Lamp bases, pottery Pottery: art, garden, decorative, industrial, and laboratory Pyrometer tubes [likely not refractory enough] Rockingham earthenware Smokers' articles, pottery [Insufficient volume] Stationery articles, pottery Textile guides, porcelain Vases, pottery (china, earthenware, and stoneware) Industry Group 327 Concrete, Gypsum, and Plaster Products 3271 Concrete Block and Brick

Manufactures concrete building block and brick from a combination of cement and aggregate. Contractors engaged in concrete construction work are classified in Division C, Construction, and establishments primarily engaged in mixing and delivering ready-mixed concrete are classified in Industry 3273. Architecture block concrete: e.g. fluted, screen, split, slump, groundface Blocks, concrete and cinder Brick, concrete Paving block, concrete Plinth blocks, precast terrazzo 3272 Concrete Products, except Block and Brick

Establishments primarily engaged in manufacturing concrete products, except block and brick, from a combination of cement and aggregate. Contractors engaged in concrete construction work are classified in Division C, Construction, and establishments primarily engaged in mixing and delivering ready-mixed concrete are classified in Industry 3273.

If the patent described by Miller (1987) is economic for the gypsum application, all of these products could be produced from the resulting cement. The following priori-ties attempt to consider the potential use of glass-ceramics as competitive alternatives. Art marble, concrete Ashlar, cast stone Bathtubs, concrete Battery wells and boxes, concrete [insufficient production volume] Building stone, artificial: concrete Burial vaults, concrete and precast terrazzo

40

Cast stone, concrete Catch basin covers, concrete Ceiling squares, concrete

Chimney caps, concrete Church furniture, concrete [insufficient production volume] Columns, concrete Concrete products, precast: except block and brick Concrete, dry mixture Conduits, concrete Copings, concrete Cribbing, concrete Crossing slabs, concrete Culvert pipe, concrete Cylinder pipe, prestressed concrete Cylinder pipe, pretensioned concrete Door frames, concrete Drain tile, concrete Fireplaces, concrete Floor filler tiles, concrete Floor slabs, precast concrete Floor tile, precast terrazzo Fountains, concrete Fountains, wash: precast terrazzo Garbage boxes, concrete Grave markers, concrete Grave vaults, concrete Grease traps, concrete Housing components, prefabricated: concrete Incinerators, concrete Irrigation pipe, concrete Joists, concrete Laundry trays, concrete Lintels, concrete Manhole covers and frames, concrete Mantels, concrete Mattresses for river revetment, concrete articulated Meter boxes, concrete Monuments, concrete Panels and sections, prefabricated: concrete Paving materials, prefabricated concrete, except blocks Pier footings, prefabricated concrete Piling, prefabricated concrete Pipe, concrete Pipe, lined with concrete Poles, concrete Posts, concrete

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Pressure pipe, reinforced concrete Prestressed concrete products Roofing tile and slabs, concrete

Septic tanks, concrete Sewer pipe, concrete Shower receptors, concrete Siding, precast stone Sills, concrete Silo staves, cast stone Silos, prefabricated concrete Slabs, crossing: concrete Spanish floor tile, concrete Squares for walls and ceilings, concrete Steps, prefabricated concrete Stools, precast terrazzo Storage tanks, concrete Tanks, concrete Terrazzo products, precast Thresholds, precast terrazzo Ties, railroad: concrete Tile, precast terrazzo or concrete Tombstones, precast terrazzo or concrete Wall base, precast terrazzo Wall squares, concrete Wash foundations, precast terrazzo Well curbing, concrete Window sills, cast stone 3273 Ready-Mixed Concrete

Manufactures portland cement concrete manufactured and delivered to a pur-chaser in a plastic and unhardened state. This industry includes production and sale of central-mixed concrete, shrink-mixed concrete, and truck-mixed concrete. Central-mixed concrete Ready-mixed concrete, production and distribution Shrink-mixed concrete Truck-mixed concrete 3274 Lime

Establishments primarily engaged in manufacturing quicklime, hydrated lime, and "dead-burned" dolomite from limestone, dolomite shells, or other substances. 3275 Gypsum Products

Establishments primarily engaged in manufacturing plaster, plasterboard, and other products composed wholly or chiefly of gypsum, except articles of plaster of paris and papier-mache.

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Industry Group 328 Cut Stone and Stone Products

3281 Cut Stone and Stone Products Establishments primarily engaged in cutting, shaping, and finishing granite, mar-

ble, limestone, slate, and other stone for building and miscellaneous uses. Establishments primarily engaged in buying or selling partly finished monuments and tombstones, but performing no work on the stones other than lettering, finishing, or shaping to custom order, are classified in Division F, Wholesale Trade or Division G, Retail Trade. The cutting of grindstones, pulpstones, and whetstones at the quarry is classified in Division B, Mining. Altars, cut stone Baptismal fonts, cut stone Benches, cut stone Blackboards, slate Burial vaults, stone Church furniture, cut stone Curbing, granite and stone Cut stone products Desk set bases, onyx Dimension stone for buildings Flagstones Furniture, cut stone Granite, cut and shaped Lamp bases onyx Limestone, cut and shaped Marble, building cut and shaped Monuments, cut stone: not including only finishing or lettering to order Paving blocks, cut stone Pedestals, marble Pulpits, cut stone Roofing, slate Slate and slate products Statuary, marble Stone, cut and shaped Stone, quarrying and processing of own Stone products Table tops, marble Tombstones, cut stone: not including only finishing or lettering to order Urns, cut stone Vases, cut stone

43

Industry Group 329 Abrasive, Asbestos, and Miscellaneous Nonmetallic Mineral Products

3291 Abrasive Products Manufactures abrasive grinding wheels of natural or synthetic materials, abrasive-

coated products, and other abrasive products. The cutting of grindstones, pulpstones, and whetstones at the quarry is classified in Division B, Mining. Abrasive buffs, bricks, cloth, paper, sticks, stones, wheels, etc. Abrasive grains, natural and artificial Abrasive-coated products Abrasives, aluminous Aluminum oxide (fused) abrasives Boron carbide abrasives Bort, crushing Buffing and polishing wheels, abrasive and nonabrasive Cloth: garnet, emery, aluminum oxide, and silicon carbide coated Corundum abrasives Diamond dressing wheels Diamond powder Emery abrasives Garnet abrasives Grinding balls, ceramic Grindstones, artificial Grit, steel Hones Metallic abrasives Oilstones, artificial Pads, scouring: soap impregnated Paper: garnet, emery, aluminum oxide, and silicon carbide coated Polishing rouge (abrasive) Polishing wheels Pumice and pumicite abrasives Rouge, polishing Rubbing stones, artificial Sandpaper Scythe-stones, artificial Silicon carbide abrasives Sponges, scouring: metallic Steel shot abrasives Steel wool Tripoli Tungsten carbide abrasives Wheels, abrasive: except dental Wheels, diamond abrasive Wheels, grinding: artificial Whetstones, artificial

44

3292 Asbestos Products [Wollastonite substitution]

Establishments primarily engaged in manufacturing asbestos [wollastonite] tex-tiles, asbestos building materials, except asbestos paper, insulating materials for cover-

ing boilers and pipes, and other products composed wholly or chiefly of asbestos. Estab-lishments primarily engaged in manufacturing asbestos paper are classified in Industry 2621, and those manufacturing gaskets and packing are classified in Industry 3053. Asbestos cement products: e.g., siding, pressure pipe, conduits, ducts Asbestos products: except packing and gaskets Blankets, insulating for aircraft: asbestos Boiler covering (heat insulating material), except felt Brake lining, asbestos Brake pads, asbestos Building materials, asbestos: except asbestos paper Carded fiber, asbestos Cloth, asbestos Clutch facings, asbestos Cord, asbestos Felt, woven amosite: asbestos Floor tile, asphalt Friction materials, asbestos: woven Insulation, molded asbestos Mattresses, asbestos Millboard, asbestos Pipe and boiler covering, except felt Pipe covering (insulation), laminated asbestos paper Pipe, pressure: asbestos cement Roofing, asbestos felt roll Rope, asbestos Sheet, asbestos cement: flat or corrugated Shingles, asbestos cement Siding, asbestos cement Table pads and padding, asbestos Tape, asbestos Textiles, asbestos: except packing Thread, asbestos Tile, vinyl asbestos Tubing, asbestos Wick, asbestos Yarn, asbestos 3295 Minerals and Earths, Ground or Otherwise Treated

Establishments operating without a mine or quarry and primarily engaged in crushing, grinding, pulverizing, or otherwise preparing clay, ceramic, and refractory minerals; barite; and miscellaneous nonmetallic minerals, except fuels. These minerals are the crude products mined by establishments of Industry Groups 145 and 149, and by those of Industry 1479 mining barite. Also included are establishments primarily crushing

45

slag and preparing roofing granules. The beneficiation or preparation of other minerals and metallic ores, and the cleaning and grading of coal, are classified in Division B, Mining, whether or not the operation is associated with a mine.

Roofing granules 3296 Mineral Wool

Manufactures mineral wool and mineral wool insulation products made of such siliceous materials as rock, slag, and glass, or combinations thereof. Establishments primarily engaged in manufacturing asbestos insulation products are classified in Industry 3292, and those manufacturing textile glass fibers are classified in Industry 3229. Acoustical board and tile, mineral wool Fiberglass insulation Glass wool Insulation: rock wool, fiberglass, slag, and silica minerals Mineral wool roofing mats 3297 Nonclay Refractories

Establishments primarily engaged in manufacturing refractories and crucibles made of materials other than clay. This industry includes establishments primarily engaged in manufacturing all graphite refractories, whether of carbon bond or ceramic bond. Establishments primarily engaged in manufacturing clay refractories are classified in Industry 3255. 3299 Nonmetallic Mineral Products, Not Elsewhere Classified

Establishments primarily engaged in the factory production of goods made of plaster of paris and papier-mache, and in manufacturing sand lime products and other nonmetallic mineral products, not elsewhere classified. Ceramic fiber (wollastonite)

The range of potential products that contain calcia and silica in sufficient concen-tration that qualitatively could be considered for use in a production operation has been reviewed. The next section will attempt to assess if there is sufficient volume in the production of these different products to meaningfully achieve the Institute’s goal.

46

CAN VITRIFICATION CONSUME 15% OF THE ANNUAL GYPSUM GEN-ERATED FROM PHOSPHATE MINING?

One goal of the Institute is to reduce the accumulation of phosphogypsum by

15%. The simplified approach used to assess this question was:

• discover the total value of shipments of manufactured products to which gyp-sum vitrification may be applicable,

• for this value of shipments, determine the market share required to achieve the Institute’s goal of 15% of annual gypsum utilization depending upon the cal-cia concentration in the product (10 to 60 wt %), and a range of shipment val-ues ($100 to $500 per ton of product.

• Based upon the required market share, make a judgement about the feasibility of vitrification’s ability to consume 15% of the generated gypsum.

This approach allows one to qualitatively address the achievement of the Insti-

tute’s goal. In the paragraphs that follow, these data are developed and a graphical summary made based upon the data discovered and the variables of calcia concentration and sales price in dollars per short ton. First the identification of the entire potential market is explained. Value of Shipments

The value of product shipments data represents net selling values, free on board at the production plant, after discounts and allowances and excluding freight charges and excise taxes. The most recent detailed data discovered is reported in the U.S. Department of Commerce publication (USDOC 1998). It reports the details down to the five digit product codes for the year 1996. More recent data is available but only at the higher level, major industry code, SIC 32: Stone, Clay, Glass, And Concrete Products (USDOC 1999). The clearly non-applicable industries to which vitrification cannot make a compa-rable or competitive product were deleted from the value shipped in industry code 32. The gross value of the potentially applicable list was then proportionately extrapolated from the 1996 details to 1998. These data and the extrapolation at the industry code level is presented in Table 21. From this simple perspective, the total gross market into which vitrification of gypsum appears applicable either as a direct competitor or as a functional competitor totaled in 1998 to about $85 billion. The extrapolated list for 1998 at the product class is presented in the next table, Table 22.

47

Table 21. Value of Manufactured Product Shipments, in Millions, Proportionately Extrapolated from 1996 to 1998, at the Industry Level.

Industry and product class code Description 1996 edited 1996 1997 1998 32- Stone, Clay, Glass, And Con-

crete Products, total 82,399.9 90,215.0 96,168.0

Gross potential market applica-

ble to gypsum vitrification manufactured products

72,826.3 87,675.6

3211– Flat glass 3,665.8 3,665.8 4,278.3 3221– Glass containers 4,270.7 4,270.7 4,984.3 3229– Pressed and blown glass, n.e.c. 8,801.9 8,801.9 10,272.6 3231– Products of purchased glass 10,009.1 10,009.1 11,681.5 3241– Cement, hydraulic 5,650.1 5,650.1 6,594.2 3251– Brick and structural clay tile 1,293.4 1,293.4 1,509.5 3253– Ceramic wall and floor tile 839.2 839.2 979.4 3255– Clay refractories 950.6 3259– Structural clay products, n.e.c. 171.0 171.0 199.6 3261– Vitreous plumbing fixtures 977.0 977.0 1,140.2 3262– Vitreous china table and kitch-

enware 330.6 330.6 385.8

3263– Semivitreous table and kitch-enware

70.0 70.0 81.7

3264– Porcelain electrical supplies 1,630.3 1,630.3 1,902.7 3269– Pottery products, n.e.c. 730.2 730.2 852.2 3271– Concrete block and brick 2,595.7 2,595.7 3,029.4 3272– Concrete products, n.e.c. 7,937.9 7,937.9 9,264.2 3273– Ready ~ mixed concrete 14,801.3 14,801.3 17,274.4 3274– Lime 750.6 3275– Gypsum products 3,712.2 3281– Cut stone and stone products 1,307.2 1,307.2 1,525.6 3291– Abrasive products 3,988.9 3,988.9 4,655.4 3292– Asbestos products – – 3295– Minerals, ground or treated 1,863.2 3296– Mineral wool 3,756.0 3,756.0 4,383.6 3297– Nonclay refractories 1,376.8 1,606.8 3299– Nonmetallic mineral products,

n.e.c. 920.2 1,074.0

48

Table 22. Value of Manufactured Product Shipments, in Millions, Proportionately

Extrapolated from 1996 to 1998, at the Product Level.

Description Year Industry and product class code 1998 32- Stone, Clay, Glass, And Concrete Products, total 96,168 Gross potential market applicable to gypsum vitrification manufactured

products 87,676

3211– Flat glass 4,278 32113 Laminated glass (D) 32114 Other glass products (D) 32115 Flat glass 3 2,066 32110 Flat glass, n.s.k. 1 3221– Glass containers 4,984 32210 Glass containers 4,986 3229– Pressed and blown glass, n.e.c. 10,273 32293 Glass fiber, textile ~ type 2,177 32295 Machine ~ made table, kitchen, art, and novelty glassware 2 3 1,117 32296 Machine ~ made lighting, automotive, and electronic glassware 2 3 1,859 32297 All other machine ~ made glassware 2 3 837 32298 Handmade pressed and blown glassware 2 3 (S) 32290 Pressed and blown glass, n.e.c., n.s.k. 207 3231– Products of purchased glass 11,682 32311 Machine ~ made pressed and blown glassware 2 3 1,553 32312 Handmade pressed and blown glassware 2 3 (S) 32313 Laminated glass 2 (D) 32315 Mirrors (decorated or undecorated) 1,343 32318 Other glass products (D) 32310 Products of purchased glass, n.s.k. 699 3241– Cement, hydraulic 6,594 32410 Cement, hydraulic (including cost of shipping containers) 6,597 3251– Brick and structural clay tile 1,510 32510 Brick and clay tile 3 1,510 3253– Ceramic wall and floor tile 979 32530 Clay floor and wall tile 3 980 3255– Clay refractories 32550 Clay refractories 3 3259– Structural clay products, n.e.c. 200 32591 Vitrified clay sewer pipe and fittings 3 60 32592 Other structural clay products, n.e.c. (except clay refractories) 78

49

Table 22. Value of Manufactured Product Shipments, in Millions, Proportionately

Extrapolated from 1996 to 1998, at the Product Level (Continued).

32590 Structural clay products, n.e.c., n.s.k. 62 3261– Vitreous plumbing fixtures 1,140 32610 Vitreous plumbing fixtures, accessories, and fittings 1,141 3262– Vitreous china table and kitchenware 386 32620 Vitreous china and porcelain table and kitchenware

(including bone and feldspar) for household, hotel, or commercial use 386

3263– Semivitreous table and kitchenware 82 32630 Earthenware table and kitchenware (semivitreous) 82 3264– Porcelain electrical supplies 1,903 32640 Porcelain, steatite, and other ceramic electrical products 1,903 3269– Pottery products, n.e.c. 852 32690 Pottery products, n.e.c. (including china decorating for the trade) 853 3271– Concrete block and brick 3,029 32710 Concrete brick and block 3,031 3272– Concrete products, n.e.c. 9,264 32721 Concrete pipe 2,033 32722 Precast concrete products 4,417 32723 Prestressed concrete products 1,961 32720 Concrete products, n.e.c., n.s.k. 858 3273– Ready ~ mixed concrete 17,274 32730 Ready ~ mixed concrete 1 5,606 3274– Lime 32740 Lime (including cost of containers) 3275– Gypsum products 32751 Gypsum building materials 32752 Other gypsum products 32750 Gypsum products, n.s.k. 3281– Cut stone and stone products 1,526 32811 Dressed dimension granite (including gneiss, syenite, diorite, and cut

granite) 812

32812 Dressed dimension limestone (including dolomite, travertine, calcare-ous, tufa, and cut limestone)

198

32813 Dressed dimension marble and other stone 320 32810 Cut stone and stone products, n.s.k. 196

50

Table 22. Value of Manufactured Product Shipments, in Millions, Proportionately Extrapolated from 1996 to 1998, at the Product Level (Continued).

3291– Abrasive products 4,655 32915 Nonmetallic sized grains, powders, and flour abrasives (including

graded products only) 585

32916 Nonmetallic abrasive products (including diamond abrasives) 989 32917 Nonmetallic coated abrasive products and buffing wheels, polishing

wheels, andlaps 2,107

32918 Metal abrasives (including scouring pads) 853 32910 Abrasive products, n.s.k. 124 3292– Asbestos products 32922 Asbestos friction materials 32927 Other asbestos products 32920 Asbestos products, n.s.k. 3295– Minerals, ground or treated 32950 Minerals and earths, ground or otherwise treated 3296– Mineral wool 4,384 32961 Mineral wool for thermal and acoustical envelope insulation

(for insulating homes, commercial and industrial buildings) 3,281

32962 Mineral wool for industrial, equipment, and appliance insulation 1,014 32960 Mineral wool, n.s.k. 90 3297– Nonclay refractories 1,607 32970 Nonclay refractories (except dead ~ burned magnesia)3 1,607 3299– Nonmetallic mineral products, n.e.c. 1,074 32990 Other nonmetallic mineral products, n.e.c. 1,074

Note that the bold rows in the above table are industry subtotals. These subtotals sum to the applicable product total presented in the earlier table.

With the total potential market of $87 billion, the market share required to achieve the Institute’s goal of 15% of gypsum generated was then calculated for all potential gypsum vitrification products as a function of calcia concentration and value of ship-ments in dollars per short ton.

The assumed annual gypsum generation rate was 35 million short tons/year. With 15% to be utilized then 5.25 million short tons of gypsum or 1.73 million tons of calcia need to be consumed in products to achieve the Institute’s goal. The dependence of the market share by calcia concentration in the product and its cost per short ton is presented graphically in the following figure.

51

0%

2%

4%

6%

8%

10%

12%

0% 10% 20% 30% 40% 50% 60%

Concentration of Calcia in Glass or Glass - Ceramic, %

Perc

ent o

f Ent

ire M

arke

t Nee

ded,

%$100/ton$200/ton$300/ton$4000/ton$500/ton

Range for Flat and container glass and

automation

Range for Glass - Ceramics and E fiber

glass

Wollastonite

Cement

The figure includes typical ranges for calcia in traditional glasses, glass-ceramics,

wollastonite and portland cement. The lowest range is between 10 and 16 wt%. This is the range typical of containers and flat or float glasses and is the most common glass formulations used today. The range 20 to 40 wt % includes calcia concentrations typical of some glass-ceramics and the broadly used E fiber glass or rock wool. At 48 wt % calcia, the concentration is that of the natural mineral wollastonite, sometimes syntheti-cally produced. Finally, the concentration for portland cement is also included based upon the potential feasibility of using the general patent of Miller (Miller 1987).

This graphical presentation essentially requires the assumption that one general product class, such as glass- ceramics, must be used to make a qualitative assessment of credibility for 15% use of gypsum. A more detailed approach would be to assume a market share for all classes of manufactured products and then determine what fraction of gypsum would be used. This was done for the extrapolated 1998 gross manufactured sales and is presented in Table 23.

Figure 1. Required Gypsum Glass Products Market Share For 15% Gypsum Utilization.

52

Table 23. Tons of Calcia (Gypsum) Used with a Market Share of 4%.

Mill

ion,

$

4 %

Mar

ket

shar

e, M

illio

n, $

Ship

ping

val

ue

Wt%

CaO

in

Prod

uct

Thou

sand

s of

tons

of C

aO

Thou

sand

s of

tons

of C

aO,

No

Cem

ent

32 Stone, Clay, Glass, And Concrete Products, total

96,168 $/ton wt% CaO

CaO used Ktons/yr

CaO used Ktons/yr

3211 Flat glass 4,278 171 500 10% 34 34 3221 Glass containers 4,984 199 350 10% 57 57 3229 Pressed and blown glass, n.e.c. 10,273 411 500 10% 82 82 3231 Products of purchased glass 11,682 467 500 10% 93 93 3241 Cement, hydraulic 6,594 264 100 60% 1,583 3251 Brick and structural clay tile 1,510 60 150 40% 161 161 3253 Ceramic wall and floor tile 979 39 500 25% 20 20 3259 Structural clay products, n.e.c. 200 8 200 40% 16 16 3261 Vitreous plumbing fixtures 1,140 46 500 25% 23 23 3262 Vitreous china table and kitchenware 386 15 500 25% 8 8 3263 Semivitreous table and kitchenware 82 3 500 25% 2 2 3264 Porcelain electrical supplies 1,903 76 500 40% 61 61 3269 Pottery products, n.e.c. 852 34 200 25% 43 43 3271 Concrete block and brick 3,029 121 150 30% 242 242 3272 Concrete products, n.e.c. 9,264 371 200 25% 463 463 3273 Ready ~ mixed concrete 17,274 691 100 10% 691 3281 Cut stone and stone products 1,526 61 500 25% 31 31 3291 Abrasive products 4,655 186 200 35% 326 326 3296 Mineral wool 4,384 175 200 30% 263 263 3297 Nonclay refractories 1,607 64 200 40% 129 129 3299 Nonmetallic mineral products, n.e.c. 1,074 43 200 40% 86 86 Total Calcia used (CaO), thousands of

tons/year 4,412 2,139

Total Gypsum (CaSO4*2H2O), thou-sands of tons/year

13,545 6,565

Gross potential market applicable to gypsum vitrification manufactured products, $ millions

87,676 3,507

Assessment of 15% Gypsum Utilization

Table 23 indicates that with a 4% market share in all relevant product classes, the indicated concentration of calcia in each product and the gross value of the shipped product, the total quantity of gypsum used would be about 13.5 million tons per year. This compares favorably to the goal of 15% which is 5.25 million tons per year. Even if one assumes that cement production is not credible and it is eliminated from the potential markets, the use still exceeds the Institute’s goal.

53

From this general analysis it is arguably apparent that the potential for achieving

15% of gypsum utilization is credible. However, this will require plant capital invest-ments in excess of $2 to $5 billion. Clearly this will require an extended span of time to

realize and is not unique to this new industry. The market penetration is most credible when the calcia concentration is highest and delivered value is lowest. Since these characteristics are congruent with the presumed competitive advantages for the proposed vitrification plant, the feasibility for achieving the Institute’s goal would seem credible.

The presumption is that this new central Florida industry would evolve as others

have. It would first enter the market place with a small plant that is most profitable. With the profits from the first plant it would expand out into related plants most likely with different products similar to other major materials industries. As the industry evolves it will discover new niches for its products and be taught by its competitors where to focus. With this assumption, the focus of this marketing study is to identify the product for this first plant. SELECTION OF PRODUCTS FOR FIRST VITRIFICATION PLANTS

The apparent market advantages for a new vitrification manufacturing facility in central Florida would include:

• Raw materials on site, thus reducing the materials and their transportation costs to near nothing

• Close proximity to a relatively large market, thereby reducing the delivery costs for wholesalers and retailers

The major apparent competitive advantage is that of low-cost materials and their

transportation to the manufacturing facility. To assess the importance of these factors the U.S. Bureau of Economic Analysis report (Lawson 1997) and associated database were used to extract these fractional costs of the value shipped. These are presented in Table 24 for the industries in which gypsum vitrification may be a competitor. The first table shows these factors as a fraction of value shipped while the next table, Table 24, shows these values as a fraction of costs. The “Other value added” column is here assumed to be the industries’ profit. The rows do not sum to 100% because other cost categories, not relevant to the question of materials and shipping, were excluded. Only major or relevant categories are presented. The manufacturing industry is limited to those shown because these were the only ones discovered.

54

Table 24. Percent of Value Shipped by General Category, Including Profits.

Manufacturing Industry

Labor Other Value Added

Energy Materials Transpor- tation

Sum of Materials and 50% Trans-

portation Glass Products 31.1% 21.4% 4.3% 17.9% 2.9% 19.3% Glass Container 31.8% 19.7% 7.3% 7.3% 3.9% 9.2% Ceramic Tile 39.8% 11.4% 7.5% 7.2% 12.8% 13.6% Concrete Block 33.0% 16.4% 3.9% 22.2% 8.6% 30.8% Concrete Products, Not Block

41.8% 13.1% 3.0% 23.1% 6.2% 26.2%

Cut Stone and Stone Products

38.8% 11.8% 3.3% 15.8% 2.3% 16.9%

Mineral Wool 27.8% 24.1% 8.2% 9.8% 4.9% 12.3%

The previous table was recalculated by subtracting the “other value added” from the total and dividing the respective columns by the remainder. This would then repre-sent a qualitative industry average of the respective column’s fraction of manufacturing costs.

Table 25. Percent of Cost of Production by General Category.

Manufacturing Industry

Labor Energy Materials Transportation Sum of Materials and 50% Transportation

Glass Products 39.6% 5.5% 22.7% 3.7% 24.6% Glass Container 39.6% 9.1% 9.1% 4.8% 11.5% Ceramic Tile 44.9% 8.5% 8.1% 14.4% 15.3% Concrete Block 39.4% 4.7% 26.5% 10.3% 36.8% Concrete Products, Not Block

48.0% 3.4% 26.6% 7.2% 30.1%

Cut Stone and Stone Products

43.9% 3.7% 17.9% 2.6% 19.2%

Mineral Wool 36.6% 10.8% 13.0% 6.5% 16.2%

Only the categories that included inorganic materials were summed in the materi-als column. Other materials such as wood (pallets), paper (packaging) , organics (paint) were excluded.

The two tables above would suggest that the stated market advantages of assumed free raw materials (gypsum and tailings sand) and lowered transportation of input materi-als could be cost-competitive by 9 to 19% on a value shipped basis or about 12 to 24 %

55

on a cost of production basis for reasonably similar industries (excludes concrete and concrete products).

To exploit the low cost of raw materials, the product should maximize the content of calcia and tailings sand. Since the majority of conventional glass products, container and flat glass, has an upper limit of 10 to 12 wt % calcia in the final product, these materials would not be able to fully exploit the market advantages at this time.

To concentrate the product focus from the many to the few, the various product categories were scored against five different qualitative criteria. They included:

Calcia and silica use. Highest use of the indigenous materials of calcia (gypsum) and silica should receive the highest score.

Process. [simplicity] Attempts to grade the industry from an overall process sim-plicity perspective. Those industries that have several process steps after the vitrification step are not scored as highly. This criteria also implicitly captures the characteristic that many subsequent processing operations add more technology risk and more capital investment so that the materials costs become less and less important in the value of the end product. Under this condition, the gypsum vitrification plant would become less and less competitive. For example, textile fiber glass involves very sophisticated processing subsequent to melting. The textile product may sell for ~$1,500/ton, of which ~$100/ton is for its melting.

Competitive. This category is a subjective method of consolidating several is-sues. The industry maturity and dominance by a few large companies would not allow a high score. When competitive pressures from other materials have, and continue to, force low profit margins such as container glass, a low score would be assigned.

Risk. This is a ranking of the different products based upon the subjective criteria of perceived risk from radon emanation and gamma radiation. If the product has high relative surface area and/or has high concentration of calcia (radium), its score would be lower.

A listing of potentially relevant manufacturing industries were selected from the SIC. Each industry was then ranked within each category, with the highest score going to the industry with the greatest promise for gypsum glass products. Each category was assumed to have the same loading on the product’s overall score. A high score for a product class is more favorable. This technique was used and is reported in Table 26.

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Table 26. Scoring and Ranking of Potential Vitrification Plant Products by Several Criteria.

Manufacturing Industry Calcia

Use Process Com-

petitive Risk Value Total

Score 3253 Ceramic Wall and Floor Tile 8 12 17 10.5 15 62.5 3281 Cut Stone and Stone Products 8 12 15 10.5 16 61.5 3296 Mineral Wool [Rock Wool] 13 17 17 3 9 59 3295 Minerals and Earths, [Acicular Wollastonite]

16 17 14 2 10 59

3291 Abrasive Products 16 17 17 7 1 58 3211 Flat Glass 3 12 10.5 17 12 54.5 3264 Porcelain Electrical Supplies 16 3 7 13.5 14 53.5 3263 Fine Earthenware (Whiteware) Table and Kitchen Articles

8 2 10.5 13.5 17.5 51.5

3262 Vitreous China Table and Kitchen Articles

8 1 10.5 13.5 17.5 50.5

3251 Brick and Structural Clay Tile 13 8.5 10.5 8.5 7 47.5 3259 Structural Clay Products, Nec* 13 8.5 10.5 8.5 7 47.5 3269 Pottery Products, Nec* 8 8.5 10.5 13.5 7 47.5 3231 Glass Products, 3 5 6 17 12 43 3221 Glass Containers 3 8.5 2 17 12 42.5 3241 Cement, Hydraulic [Miller 1987]

18 15 5 1 2.5 41.5

3272 Concrete Products, Except Block and Brick

8 5 4 5.5 4.5 27

3271 Concrete Block And Brick 8 5 3 5.5 4.5 26 3273 Ready-Mixed Concrete 1 14 1 4 2.5 22.5

*Nec : not elsewhere classified

Based upon this qualitative scoring, ceramic tile and wollastonite were investi-gated further. Following are the results of the investigations and telephone interviews. The next section is an extract of a study by the U.S. Bureau of the Census (Pitcher 1993). Ceramic Tile, Floor, Wall and Roof

Following declines during the 1990-91 recession, the ceramic wall and floor tile industry (SIC 3253) experienced an upsurge in shipments in 1992 and 1993 to 472 and 495 million square feet, respectively (Pitcher 1993). This compares with the shipments’ peak of 543 million square feet in 1989. New single-family housing construction and greater levels of improvements to existing structures spurred the gain. This level of shipments by domestic producers still represents less than half the U.S. market. The

57

annual U.S. import-to-consumption ratio for tile has ranged between 50 and 60 percent for many years.

The industry consists of about 90 firms operating 110 plants. Many of these firms produce only accessories and special tiles. The ceramic tile market has a broader geo-graphical base than most construction materials. Sales go well beyond local markets near plants, to regional, national, and sometimes international customers.

Ceramic tile prices rose modestly in both 1992 and 1993 (about 1 percent), ac-cording to the Producer Price Index. This followed a drop of about 1 percent in 1991.

International Competitiveness: The imports-to-consumption ratio for ceramic tile is among the highest for all construction materials. It was 53 percent in 1992 and may reach 57 percent in 1993. Among the specific types of tile, the ratio is usually higher for glazed and unglazed wall and floor tile than for mosaic and unglazed (quarry) tile.

Ceramic tile imports should reach about 655 million square feet in 1993. This is about 21 percent more than in 1992, and more than one-third more than the recession level of 1991. U.S. imports peaked in 1989 at 712 million square feet. Tile imports usually respond to U.S. demand, especially from new residential and nonresidential building construction, and the growing renovation market. Italy is the largest supplier, accounting for about 40 percent of total U.S. imports in both 1991 and 1992. The volume of imports from Mexico is rising rapidly. Other major suppliers are Spain, Japan, Brazil, Thailand, Venezuela, and Germany.

U.S. exports of ceramic tile are modest. The $12 million exported in 1988 grew to $21 million in 1991. Exports declined to about $19 million in 1992 but were about $20 million in 1993.

Outlook For 1994: Ceramic tile consumption should rise 3 to 4 percent in 1994, to 1.2 billion square feet. Of the total, domestic shipments should make up about 510 million square feet and imports about 680 million square feet. This would be the second highest level for both domestic shipments and imports. The projection is based on the popularity of ceramic tile and the level of new residential construction and renovation work. Continued weakness in the private nonresidential construction sector will be a negative factor.

Long-Term Prospects: U.S. ceramic tile consumption should grow 4 to 5 percent annually over the next five years. The import-to-consumption ratio will likely continue in the 50-to-60 percent range. Use of ceramic tile for bathroom walls and floors, kitchens, and foyers will continue to grow. Nonresidential applications include rest rooms, exercise areas, lobbies, and hallways. The alterations, repairs, and additions market will be a growing factor for ceramic tile demand. Because of ceramic tile’s beauty, durability, and ease of maintenance, its popularity should continue to grow despite the higher cost of fashionable decorative tiles and the cost of installation.

58

The potential for significantly higher levels of ceramic tile imports from Mexico

is strong under NAFTA. Only as U.S. tariffs on Mexican tile decrease and Mexican sales to the United States rise will it become clear how much such sales will affect the

U.S. industry and how much imports from other countries will be affected.

The Tile Council Of America (TCA). In a personal telephone conversation with the director of the Tile Council of America (Daniels 1999), Mr. Daniels made the com-ments summarized below.

• Growth in 1998 is expected to have been 12%. • Florida and California make up about 42% of the U.S. tile sales; add Texas,

it’s 52%. The balance is within large cities such as New York, Chicago. Be-ing located near southern Florida is a benefit.

• Total U.S. tile market is 1.7 billion square feet/yr; world market is 50 billion square feet/yr, so U.S. market is not that significant in total sales. TCA has as a goal to continue to expand the tile market in the U.S. and hopefully expand exports.

• Asian producers are currently keeping in production and selling at cost; Tai-wan is at 50%, China 30% capacity and driving down the price.

• Mass production of “gray” tile, one with no consistency nor frill, sells for (wholesale) ~ $0.40/ft2. [ @ 3#/ft2 ! ~$225 to $250/ton]

• Consistent, quality tile either “porcelain” like or rustic wholesales at $1 to $3/ft2) [$550 to $1,500/ton ]

• 65% of market is residential; of this, 50% or (32%) is for remodeling. The balance, 35%, is commercial.

• Recommends that the new manufacturer start and work with local outlet and then expand into the closest areas around them. Typically the problem is not being able to make enough to satisfy demand.

• Believed by showing their tiles to one or two local independent distributors, they could get a sense of marketability through customer and retailer feed-back.

• Ceramic Tile Distributors Association (CTDA) should be able to provide a link to various outlets. This is the association of independent distributors.

• LD Brinkman and Shaw Carpet are expanding into tile for their product lines. They may be interested in purchasing for their retail outlets. Other “chain” markets are Home Depot and Lowe’s.

• The major international sales of tiles in the U.S. is from Italy, then Spain and Mexico. Many of the Mexican tiles are U.S-owned. Italy sells primarily in the high end markets and has a technology edge in manufacturing that they re-tain.

• Large tiles such as 18” x 18” or 16” x 16” are apparently becoming popular with the same prices/ ft2.

• White, gray and beige tiles are the default tile color when market declines or loss of other orders occurs. Thus they are the lowest-cost, but the most read-ily sold if the price is low enough.

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Market advantages are associated with the following tile characteristics:

• Adequate breaking strength • Coefficient of friction and consistency over time • Wear-resistance with consistent color throughout. • Make the same color now and in the future so distributors can sell repair or

replacement tiles that “match” and can be marketed with confidence. • Replacement size and flatness is crucial • Acceptable water absorption (low). • Commercial users of tiles are very interested in coefficient of friction (COF);

high COF and a tile’s sustaining a high COF over its useful life because there is ~$150 million in losses to employee and customer falls on slippery tiles.

• Product Specifications: Although there are no legal requirements, architects typically specify ANSI-A137; the ISO standard for which the TCA is also the secretariat will be output in a couple of months (ISO 13006).

• Large tile manufacturers typically have their own lab for testing and maintain-ing consistency, since the manufacturer warrants all their products. The capi-tal cost of the lab is ~$80,000, so many of the small producers contract out this work.

• Mass production is about 45,000 ft2 / day (80 to 100 short tpd).

National Tile Roof Manufacturing Association. The following general infor-mation was obtained from a representative of the National Tile Roof Manufacturing Association (Lundin 1999) during a telephone conversation summarized below.

• Tile roofing is dominated by the lower-cost concrete material. • Southern California and Southwest Florida have nearly 80% tile roofing. • General range of producer prices received for tile roofing.

Roof Tile Material Range of Producer Price, Price/Square Foot

Concrete 0.40 to 0.45 Natural Slate 4.00 to 5.00 Glazed Tile 3.00 to 5.00

• Approximately 65% of the market is in the replacement business so weight load on roof is a discriminator.

• Concrete is currently about 10 pounds per square foot and is sometimes too heavy.

• Durable, non asphalt product with weight of 5 to 6 pounds per square foot could be of great interest to market.

• Larger pieces (fewer tiles per square foot) with high coverage but that can be handled by roofers are also of interest.

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Wollastonite

Wollastonite (Virta 1997) is a calcium metasilicate (CaSiO3). It has a theoretical composition of 48.3% calcium oxide and 51.7% silicon dioxide. The mined mineral may contain trace to minor amounts of aluminum, iron, magnesium, manganese, potassium, and sodium. Wollastonite occurs as massive or short prismatic crystals that cleave into massive to acicular fragments. Wollastonite is the only pure white extender that is acicular in shape with aspect ratios ranging from 3:1 to 20:1. Because of its unique cleavage properties, wollastonite breaks down during crushing and grinding into lath-like or needle-shaped particles of varying acicularity. This particle morphology imparts high strength and is, therefore, of considerable importance in many markets, including re-placement for short fiber milled fiberglass and short-fiber asbestos as well as a reinforc-ing filler. Wollastonite is used in applications ranging from ceramic tile to vehicle brake pads, from bowling balls to car bumpers and from thermal insulation board to paints and protective industrial coating. This, in turn, has led to coatings with better mechanical strength and improved durability and weathering for improved resistance to cracking and checking. In addition, wollastonite is a replacement for less desirable fibrous reinforce-ments, such as asbestos.

Wollastonite's pH of 9.9, along with its property of maintaining an alkaline pH in long-term storage, make it a logical choice for use in latex paints to ensure better stability and maintenance of viscosity. The pigment is a valuable asset in oil-based paints too. Wollastonite, because of its added alkalinity, has been found to improve resistance to mildew growth. It has also been noted that wollastonite-based coatings have better initial brightness and color than paints made with other extenders, as well as reduced sheen with better burnish resistance.

In ceramics, wollastonite is also a valuable material. Since CaO does not react significantly below 1100 oC, wollastonite can perform a dual role in fired ceramics. Below this temperature it is valuable in clay bodies to reduce fired shrinkage and thus greatly improve a body’s resistance to thermal expansion. At higher temperatures, it is valuable as a source of CaO in glazes which might have excessive suspended micro-bubbles because of the decomposition of whiting (calcium carbonate). Also, wollastonite has the ability to seed crystals, and can be valuable to create special effects which depend on devitrification (crystallization during cooling). In clay bodies, wollastonite reduces drying and fired shrinkage and adds fired strength.

Deposits of wollastonite have been found in Arizona, California, Idaho, Nevada, New Mexico, New York, and Utah. These deposits are typical skams containing wollas-tonite as the major component and calcite, diopside, garnet, idocrase, and/or quartz as minor components.

Consumption. The major uses of wollastonite are in ceramics, paint, and plas-tics, and as a substitute for asbestos. It also is used in adhesives, friction products (brakes and clutches), joint compounds, refractories, wallboard, and metallurgical applications. In

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ceramics, wollastonite decreases shrinkage and gas evolution during firing, increases green and fired strength, permits fast firing, and reduces crazing, cracking, and glaze defects. As a filler in paint, wollastonite reinforces the paint film, acts as a pH buffer,

improves its resistance to weathering, reduces pigment consumption, and acts as a flatting and suspending agent. In plastics, it improves tensile and flexural strength, reduces resin consumption, and improves thermal and dimensional stability at elevated temperatures.

Surface treatments are used to improve the adhesion between the wollastonite and the polymers into which they are added. As a substitute for asbestos in floor tiles, friction products, insulating board and panels, paint, plastics, and roofing products, wollastonite is resistant to chemical attack, inert, stable at high temperatures, and a good reinforcer. In Europe, another major use is as a flux for welding and controlling casting-speed during continuous casting of steel.

Prices. Prices per metric ton, for wollastonite, ex-works, acicular, were $180 for -200 mesh material, $224 for -325 mesh material, and $248 for -400 mesh material.

The prices per ton, ex-works, were $308 for acicular, high-aspect-ratio material and $620 for ground (10 micron) material. Prices per ton for wollastonite, f.o.b. plant, bulk, were $170 for 200 mesh material and $214 for 325 mesh material (Industrial Minerals 1997c).

Foreign Trade. The Journal of Commerce (JOC) Port Import/Export Reporting Service indicates that 1,719 tons of wollastonite were imported in 1997, excluding shipments by truck or rail through Canada and Mexico. Wollastonite was imported from China (26.6% of the tonnage), Finland (2.5%), India (70.1%), and Sweden (0.8%). Total imports, including shipments from or through Canada and Mexico, were estimated to be less than 3,000 tons. The JOC Port Import/Export Reporting Service indicates that 3,431 tons were exported in 1997, excluding shipments by truck or rail through Canada and Mexico. Major importers were Brazil (27% of the tonnage), China (17%), Japan (16%), and Australia (10%). Other importers of U.S. wollastonite were Argentina, Brazil, Chile, Colombia, the Dominican Republic, Ecuador, Guatemala, Japan, Malaysia, the Nether-lands, the Republic of Korea, and Venezuela. With shipments through Canada and Mexico included, exports are estimated to be between 25,000 and 35,000 tons annually.

World Review. Worldwide production of wollastonite is estimated to be between 450,000 and 500,000 tons in 1997. Wollastonite production was estimated to be 23,000 tons in Finland; 80,000 tons in India; and 29,000 tons in Mexico. Production in China is estimated to be between 200,000 and 250,000 tons. Chile, the Czech Republic, Namibia, North Korea, Pakistan, South Africa, and Turkey also produce small amounts of wollas-tonite. Industry experts place U.S. production at 150,000 tons.

Outlook. World wollastonite production has grown from an estimated 150,000 tons in 1982 to 450,000 tons in 1997, an annual average growth of 13%. Production in the United States increased at an annual average rate of approximately 10% during this same time period. This rapid growth reflects the major inroads that wollastonite made

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into the asbestos substitute, ceramics, paint, and plastics markets. The asbestos substi-tute, ceramics (that account for over 40% of demand), and paint markets are approach-ing mature market status for wollastonite. Therefore, sales for these markets will proba-

bly increase at a rate of 3% to 6% per year, following the growth patterns for these particular industries.

Plastics, however, will continue to be the major growth market for wollastonite. It would not be unexpected for sales of wollastonite for the plastics market to increase at a rate of 10% per year for the next few years. MARKETING ANALYSIS

For the first gypsum vitrification plant, the range of products was narrowed to two different general products, tiles (wall, floor and roof) and acicular wollastonite fibers. The process for both products is similar at the melting end. Tailings sand and gypsum plus a minimum of additives are melted. The oxides of sulfur are exhausted either to a sulfuric acid plant or are scrubbed using ammonia to make a fertilizer product. The molten glass is then formed and heat-treated. In the case of tiles, the gobs of glass are pressed into the desired size and then crystallized into a strong glass-ceramic product. For wollastonite fibers the glass composition is higher in calcia and is water-quenched to form a millimeter-sized frit that is heat-treated to grow in the acicular fibers. Tiles

Glass-ceramic tiles made with high calcium oxide content would form a large fraction of strong wollastonite crystals. The fundamental color would be white, the most popular color. The glass-ceramic tiles made in this manner would have the following highly positive characteristics:

• Be stronger than the conventional ceramic tile by approximately 2 to 4 times. This could allow a thinner tile, with lower weight or larger size. Lighter and larger would allow more rapid installation and be attractive to the installation companies without loss of function. Since the installation costs could be low-ered, it would also be more attractive to the consumers because the installed price could be lower.

• For roof tiles the high strength of the material may allow lighter tile to fulfill the function and be applicable to many more roofs without replacement of the roof support structure.

• The tile would have essentially no water absorption and be nearly a uniform color throughout. Thus, they could last a very long time and presumably de-mand a premium price or be functionally competitive at the same price. Since the color is dominated by the very white wollastonite crystals in the entire body, its replication could be maintained over extended times since it is com-positionally consistent, not as a glaze “paint” over a clay body that may

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change over time. Tile color could also be modified by the addition of rela-tively small amounts of colorants (Kubovits and others 1979, Nakamura 1976) so it could expand into a range of different colored tiles after initial

startup with the market’s feedback. Different colors could be made rather quickly by mixing the colorant(s) in the melter’s forehearth.

The initial proposal for this project included additional tasks that made sample

products but were not funded. Since the scope of this project was limited to market evaluation and did not have tile samples, the marketing study was limited. Tile sales are strongly dependent upon subjective aesthetics that require actual samples and a commit-ment to a consistent product. Discussion with companies at the 1999 Coverings Confer-ence held in Orlando confirmed this requirement. One company with whom we spoke had both the production facilities and retail outlets. They stated that they require tile samples, even the most modest changes, before they proceed with production. Thus, development of agreements or commitments for selling product tiles was not possible.

Roof tiles are less sensitive to aesthetic acceptance, although still important.

However, sample tiles are required for strength testing and acceptance against the differ-ent building codes. Sample tiles of different designs could not be tested for strength, as required for roof tiles. Thus, the extent of advancement in marketing of glass-ceramic roof tiles was also limited. Acicular Wollastonite

Acicular wollastonite is more like a commodity. The more desirable high-aspect-ratio fibers are more highly valued because of the contribution to strength. Synthetic production as described by Kume and Mizuno (1984) can yield a more consistent and reliable product for sales. Due to its relative simplicity in product and more commodity-like sales characteristics, this could have been the preferred product for the first gypsum production plant. However, the diversity of applications (ceramics, paint, plastics, a substitute for asbestos, adhesives, friction products-brakes and clutches, joint compounds, refractories, wallboard, and metallurgical applications) complicates the risk assessment. Due to the limited funding available for risk assessment, the risk for the different path-ways and end products would overwhelm the budget. Due to this factor and the relatively high surface area of acicular wollastonite and associated higher radon emanation, this product was not pursued at this time. RISK ASSESSMENT

After ceramic tiles were selected as the reference product, SENES Consultants Limited was tasked with determining the risk for gypsum tile use in households. Their letter report is reformatted and follows.

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Assumptions

The tiles may be manufactured with varying mixtures of CaO (converted from gypsum) and SiO2 (silica) but a CaO/ SiO2 weight ratio of 25/75 is assumed. Given that the 226Ra content of the gypsum is 26 pCi/g, the concentration of 226Ra in the CaO was estimated to be 79.9 pCi/g. The 226Ra content of the silica is 5.1 pCi/g. Accordingly, the salient characteristics of the tiles used in this analysis were determined as indicated in Table 27.

Table 27. Tile Characteristics.

226Ra = 23.9 pCi/g Density = 2.6 g/cm3 Thickness = 0.76 cm (0.3 inches) (floor and wall tiles)

= 1.0 cm (0.39 inches) (roof tile) Radon Emanation = 0.05 pCi cm-2 day-1 = 0.0058 pCi m-2 s-1

The radon emanation rate assumed in these calculations is believed to strongly

overstate the actual rate from ceramic tiles. This belief is based on measurements and calculations of radon emanation from vitrified wastes with 226Ra concentrations 10,000 times greater than the reference concentrations assumed here for the ceramic tiles (Merrill and Janke 1993). If the ceramic tiles behave identically to the vitrified wastes, the emanation rate per pCi/g of 226Ra would be about 3,000 times smaller than assumed here. Radon

The contribution to the radon in the air of the dwelling due to the tiles was esti-mated using a simple one-room model, e.g. O'Brien and others (1998):

C = J x A / (V x (λ + f))

where:

C = radon concentration (pCi/m3) J = radon emanation rate (pCi /m-2 s-1) A = emanating surface area of the tiles (m2) V = volume of the building (m3) λ = radon decay constant (2. 1 x 10-6 s-1) f= ventilation rate of the building (s-1)

For purposes of this calculation, the dwelling was conservatively assumed to be 10 m x 10 m x 2m (V=200 m3 ) and the floor and walls were assumed to be completely covered with tiles (A=180 m2). (It was assumed that any roof tiles would not contribute to the indoor radon in the occupied areas of the house.). Assuming a larger room (e.g.,

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3 m high) would reduce the estimated concentrations proportionately. A nominal air exchange rate of 1 air change per hour (f = 1/3600 s-1) was also assumed. Under these assumptions, the indoor radon concentration due to the tiles would be

C = 18.7 pCi/m3 (0.0187 pCi/L)

This increment is a very small fraction of both the mean radon level of 1.25 pCi/L in U.S. homes (Marcinoski and others 1994) and the U.S. EPA action limit for mitigation of 4 pCi/L for total indoor radon (U.S. EPA 1992). Because the area of tile coverage in potentially occupied areas would typically be less than assumed here, actual increments in indoor radon due to the tiles, if the emanation rate used is appropriate, would likely be smaller.

This increment is small relative to the impact of basic building products on indoor radon. For example, Quindos and others (1988) estimated that the contribution from concrete to indoor radon ranged from 15 to 105 Bq/m3 (0.4 to 2.8 pCi/L), including 40 Bq/m3 (1.1 pCi/L) for U.S. concrete containing 1 pCi/g of 226Ra.

For perspective on the estimated incremental radon concentration due to tile use, continual exposure (18 h/d) to an indoor radon concentration of 0.0187 pCi/L would result in an annual dose of:

((0.0187) x 0.4) x (WL Y) x (18 x 365) x (WLM) x (500 mrem) = 1.4 mrem (100) x (170) (WL Y) x (WLM) y

This calculation assumes an indoor radon progeny equilibrium factor (F) of 0.4 (U.S. NCRP 1987) and a dose conversion factor of 500 mrem/WLM (working level month) for members (all ages) of the public (ICRP 1993). One WLM is defined as exposure to a radon progeny concentration of 1 WL for 170 h. One WL is the concentra-tion of radon progeny in equilibrium (F = 1.0) with 100 pCi/L of radon.

Despite the conservative assumptions used in the calculations, the resultant radon concentrations and doses are very low. Gamma Radiation

Potential gamma radiation doses were estimated for two types of exposure condi-tions: 1) maximal conditions which assumed large areas of tile use, and extended expo-sure durations; and 2) more typical conditions which assumed more "typical" tile cover-age and exposure durations. The estimates of potential gamma radiation exposure rates for various source geometries were made using the MicroShield computer code (Grove 1994). The estimated exposure rates and resultant annual doses are shown in Tables 28 and 29, respectively.

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As shown in Table 28, the floor and roof were each assumed to be 10 m x 10 m

and to be completely covered with tiles in order to represent maximal exposure condi-tions. The exposure rates were calculated at the center of the room and at a more likely

average off-center location (2 m from one edge) for the floor and roof to show the effect of receptor location within the room. The more typical conditions assumed tile use in the kitchen, bathroom and house entranceway (Chapman 1999). The dimensions of these rooms were arbitrarily chosen, but are felt to be conservative, i.e., unlikely to underesti-mate tile usage in typical residences.

Table 28. Estimated Exposures from Ceramic Tiles Fabricated Using Phosphogypsum.

Distance Exposure Rate

Source Geometry (cm) (microR/h) Maximal conditions

Floor: 10 m x 10 m x 0.76 cm

- center 100 4.6 20 8.1

- off-center 100 4.1 (2m from one edge) 20 7.6

Roof: 10 m x 10 m x 1.0 cm

- center 200 3.8 280 2.8

- off-center 200 3.3 (2m from one edge) 280 2.4

More Typical Conditions

Kitchen Floor: 5 m x 5 m x 0.76 cm

- center 100 2.9 20 6.7

Entrance Hall/Bathroom Floor: 3 m x 3 m x 0.76 cm

- center 100 1.8 20 5.5

Bathroom Wall: 2 m x 3 m x 0.76 cm

- center 50 2.8

For adults, the receptor-source distance was assumed to be 1 m for the floor and 2 m for the roof (based on an assumed floor-roof distance of 3 m). For children, a smaller receptor-source distance of 20 cm to the floor was used; the corresponding distance to the

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roof was 280 cm. No shielding was assumed between the receptors and roof tiles. A distance of 50 cm was used for the bathroom wall for both the adult and child. As shown in Table 28, the exposure rates depended somewhat on distance from the tiles, especially

for the smaller sources.

The physical properties of the ceramic tiles were based on 100% SiO2 in the Mi-croShield runs (the tiles will actually be 75% SiO2). However, using another material (e.g., 100% gypsum at the same 2.6 g/cm3 density) had essentially no effect (< 2%) on the estimated exposure rates. Build-up in air due to scattering was assumed in the Mi-croShield calculations.

The exposure rates are directly proportional to the 226Ra concentration in the tiles. Because there is little self-shielding of gamma radiation by the thin tiles, the exposure rates are also almost directly proportional to the thickness of the tiles. The results in Table 28 can therefore be prorated to different combinations of 226Ra concentration and tile thickness if required.

The exposure rates were combined with assumed exposure durations to estimate annual doses, as shown in Table 29. For maximal conditions, the assumed 18 h/day exposure time is comparable to the 16.4 h/day for indoor residential exposure recom-mended by the (U.S. EPA 1997, pp. 15-187) for risk assessments. The exposure dura-tions in the kitchen, bathroom and entrance hall for the more typical areas of tile use were considered realistic, slightly conservative estimates. In all cases, the resultant doses are directly proportional to the assumed exposure duration. The exposure-to-dose conversion factors for exposure to environmental gamma radiation from 238U series radionuclides (i.e., 226Ra and progeny) (Table 29, Note b) were based on recommendations of the U.S. NCRP (1987) and UNSCEAR (1993).

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Table 29. Estimated Annual Doses Due to Ceramic Tiles Fabricated

Using Phosphogypsum.

Exposure Rate a Duration Annual Dose b Exposure sources (micro R/h) (h/d) (mrem/y) Maximal conditions 10 m x 10 m floor: adult 4.6 18 18.1

(off-center) child 8.1 18 37.3 plus roof: adult 7.4 18 29.2

child 10.0 18 46.0 More typical conditions

kitchen: adult 2.9 8 5.1 child 6.7 4 6.8

bathroom: adult 4.6 1 1.0 child 8.3 1 2.1

entrance hall: adult 1.8 0.25 0.1 child 5.5 0.25 0.4

total: adult 6.2 child 9.3 Notes: a. Exposure rates based on Table 1. b. Exposure dose conversion = 0.6 rem/R adult, 0.7 rem/R child.

Considering the maximal exposure conditions, the calculations indicate maximal

annual doses of less than 50 mrem/y if both the floor and roof are entirely covered with tiles. Because of the conservative nature of the calculations (i.e., area of tile coverage), these may be considered as bounding, upper limits. For example, O'Brien (1997) esti-mated that continual exposure in a 5 m x 5 m x 3 m room in which the walls and ceiling are lined with 1 cm thick PG plaster-board containing 0.4 Bq/g (10.8 pCi/g) of 226Ra would lead to a dose of 13 mrem/y. If this estimate is pro-rated to the parameters used in this analysis (18 h/d and 23.9 pCi/g 226Ra), the annual dose would be 22 mrem/y. This supports the notion that the dose estimates in Table 29 for maximal conditions are conservative. It should be noted that gamma radiation doses from "background" building materials are comparable to the maximal dose estimates shown in Table 29. Indoor levels due to building materials have been observed experimentally to be of the order on 40 mrem/y (UNSCEAR 1988).

O'Brien et al. (1998) estimated the annual dose for continual exposure to tiles glazed with zircon-containing material (with up to 80 pCi/g or more of 226Ra in the glaze) to be about 37 mrem/y in the center of a 3 in x 3 in x 3 in room. O'Brien et al. (1998) also suggested that most members of the public would be exposed to such tiles only 2 to 3% of a full year, and actual exposures would be correspondingly lower. In the present study, exposures under more typical conditions indicate doses of less than 10 mrem/y (Table 29). The doses estimated for the child are larger than those for the adult primarily because of the smaller receptor-source distance (20 cm versus 100 cm). The exposure-to-

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dose conversion factor is also larger for children (by about 17%) because of less self-shielding provided by their smaller bodies.

Risk Conclusions

These screening-level calculations indicate that indoor radon levels resulting from tile use would not likely be significant under realistic exposure conditions. This is a result of the very low radon emanation from the ceramic tiles.

The calculations suggest that gamma radiation doses would not be elevated under typical conditions of tile use and exposure. Direct measurement of exposure rates from fabricated tiles can be used to assess the validity of the estimates. In addition, for com-parative purposes, estimates of exposures from other types of tiles could be undertaken based on a literature survey of the radioactivity content of the tiles.

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CONCLUSIONS AND RECOMMENDATIONS

In a previously funded project, it was shown on a laboratory scale that glass could be readily made from gypsum and tailings sand that are currently waste products. The scope of this current project was to determine if a glass or glass-ceramic product made from gypsum and tailings sand could be marketed. The other task was to complete a preliminary risk assessment for a selected product. The conclusions made during this research were:

A very wide range of products could be produced using the readily available gyp-sum and tailings sand, particularly if a glass were subsequently heat-treated to form a strong, chemically durable glass-ceramic. The credible range of products included rolled and imprinted flat glass, container glass, abrasion-and chemical-resistant floor and wall tiles, roof tiles, abrasives, cookware, bakeware, tableware and flat cooktops. When the glass is quenched and ground to small size (50 to 75 micron particles), the glass powder can be raw material for conventional ceramics fabrication of an even more diverse range of ceramic type materials. Fiber glass, rock wool and fibrous wollastonite is yet another class of products that can be manufactured. One patent discloses that cement can be made by blowing sufficiently small fibers to obtain dicalcium silicate in a stabilized beta phase, thereby eliminating the capital and operating costs of grinding the raw materials and the cement clinker.

Manufacture of a diversity of different products using a vitrification process ap-pears to be capable of achieving the Institute’s goal of using 15% of the otherwise waste gypsum but would understandably require many years and capital investments on the order of $2 to $5 billion to realize new industries with annual gross sales of $2 to $4 billion.

Competitive cost advantage of up to 20% of cost could be realized by maximizing the use of gypsum and tailings sand. Compositions high in calcia (up to 40 wt %) and silica are commonly cited to produce attractive products with wollastonite crystals. Wollastonite is visually attractive because it yields a very white product and is used in ceramics for this purpose.

The product believed to be attractive for the first production plant was one that makes floor and wall tile. Consistent white tiles could be made that are strong, abrasion-resistant and uniform throughout. Tiles could have calcia content of 25 wt% and possibly more. Different colors could be obtained with conventional oxide colorant additives. The wholesale value for this product appears to be adequate for even a relatively small plant (25 to 100 tons per day). Florida is one of the largest consumers of floor and wall tile in the nation so shipping costs would also be competitive.

Samples of product tiles, which was beyond the scope of this project, are required to achieve commitments for wholesale or retailing agreements.

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The preliminary risk assessment indicated that radon exposure was insignificant.

Gamma radiation exposure was calculated to be acceptable for maximum anticipated use of floor and wall tile. Maximal use of high-gypsum-containing tile that included the

entire roof and floor was more questionable. Recommendations

The next project phase should focus additional emphasis on making a sufficient number of product tiles to enable testing and marketing. Representative sample tiles could then potentially lead to meaningful discussions with wholesalers and retailers.

The next project phase should also consider making a room or “model house” for measurement of radon and gamma exposures that may be required to obtain regulatory approval for the use of gypsum in these products.

At some point in the phosphate mining process, the gypsum is not phosphogyp-sum and presumably is not regulated as phosphogypsum. This would be the desired location for providing gypsum for a vitrification plant and should avoid some of the confounding aspects of the regulations. This is true and is used in other mining opera-tions and should be applicable here. This presumption should be clarified because if true it would enable a more tractable business plan essential for obtaining capital to construct a gypsum-to-glass-products plant. If this presumption is not true, a clear regulatory path for use of phosphogypsum needs to be identified. Without a well defined regulatory path, use of phosphogypsum is very unlikely.

To mitigate some of the challenges and concerns with phosphogypsum such as radon and gamma exposures, perhaps the first vitrification plant could use Northern Florida gypsum or other sources of gypsum that are lower in radium concentration. This may ease the regulatory barriers and allow one to assess the risks for central Florida gypsum.

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REFERENCES

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