Identifying incompatible combinations of concrete materials - III.pdf

PCA R&D SN2897c

Identifying Incompatible Combinations of Concrete Materials: Volume III—

Additional Appendices

by P.C. Taylor; V.C. Johansen; L. A. Graf; R. L. Kozikowski; J. Z. Zemajtis, and C. F. Ferraris

Published by the Portland Cement Association in 2008 without copyright.

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Table of Contents

VOLUME III – Additional Appendices

INTRODUCTION TO VOLUME III ................................................................................................ 1 KEYWORDS ................................................................................................................................. 1 ABSTRACT ................................................................................................................................... 1 REFERENCE ................................................................................................................................ 1 ACKNOWLEDGEMENTS ............................................................................................................. 2 REFERENCES ............................................................................................................................. 2 APPENDIX G – CALORIMETRY GRAPHS .................................................................................. 3 APPENDIX H – PORE SOLUTION CHEMISTRY REPORT......................................................... 9 APPENDIX I – RING SHRINKAGE GRAPHS ............................................................................ 57 APPENDIX J – FOAM DRAINAGE GRAPHS ............................................................................. 62 APPENDIX K – PORE SOLUTION ANALYSES RAW DATA ..................................................... 68

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INTRODUCTION TO VOLUME III

KEYWORDS admixture, ASTM C1581, incompatibility, calorimetry, foam drainage, pore solution chemistry. ring shrinkage

ABSTRACT Unexpected interactions between otherwise acceptable ingredients in portland cement concrete are becoming increasingly common as cementitious systems become more and more complex and demands on the systems are more rigorous. Such incompatibilities are exhibited as: early stiffening or excessive retardation, uncontrolled early-age cracking, unstable or unacceptable air-void systems.

A number of test methods have been reviewed to assess their usefulness in detecting incompatibility early, thus preventing problems in pavements in the field. A protocol has been developed to allow product manufacturers, concrete producers, contractors and owners to monitor their materials and concrete systems. The protocol is phased to allow relatively simple field tests to provide early warnings of potential problems, and central laboratory tests to support and confirm the field work. This is the last of three volumes. The initial two volumes in this series have been published under the following titles:

• FHWA HRT-06-079, Identifying Incompatible Combinations of Concrete Materials: Volume I–Final Report (Taylor et al. 2006a).

• FHWA HRT-06-080, Identifying Incompatible Combinations of Concrete Materials: Volume II–Test Protocol (Taylor et al. 2006b).

This document contains detailed charts and tables portraying data collected during the development of the protocols. Included are isothermal conduction calorimetry graphs, pore solution chemistry (including a report with additional explanation), ASTM C1581 ring shrinkage data, and foam drainage test data.

REFERENCE Taylor, P.C.; Johansen, V.C.; Graf, L.A.; Kozikowski, R.L.; Zemajtis, J.Z.; and Ferraris, C.F., Identifying Incompatible Combinations of Concrete aterials: Volume III—Additional Appendices, R&D SN2897c, Portland Cement Association, Skokie, Illinois, USA, 2008, 89 pages.

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ACKNOWLEDGEMENTS

The research reported in this paper (PCA R&D SN2897c) was conducted by CTLGroup with the sponsorship of the Portland Cement Association (PCA Project Index No. 03-10) and the Federal Highway Administration (Contract No. DTFH61-03-X-00102). The contents of this report reflect the views of the authors, who are responsible for the facts and accuracy of the data presented. The contents do not necessarily reflect the views of the Portland Cement Association or the Federal Highway Administration.

In addition, the authors wish to acknowledge the work of the following people in completing the work described in this report: Katie Amelio, Pat Berry, Barb Betke, Javed Bhatty, Fred Blaul, Phil Brindisi, Roberto Celestin, Rachel Detwiler, Luis Duval, Ken MacLeod, Greg Miller, Max Peltz, W. Agata Pyc, Brian Szczerowski, Shiraz Tayabji, and John Winpigler.

REFERENCES

Taylor, P.C., Johansen, V.C.; Graf, L. A.; Kozikowski, R. L.; Zemajtis, J. Z.; and Ferraris, C.F., Identifying Incompatible Combinations of Concrete Materials: Volume I—Final Report, FHWA-HRT-06-079, Federal Highway Administration, Maclean, VA, USA, August, 2006a, 162 pages, http://www.fhwa.dot.gov/pavement/concrete/pubs/06079/.

Taylor, P.C., Johansen, V.C.; Graf, L. A.; Kozikowski, R. L.; Zemajtis, J. Z.; and Ferraris, C.F.,

Identifying Incompatible Combinations of Concrete Materials: Volume II—Test Protocol, FHWA-HRT-06-080, Federal Highway Administration, Maclean, VA, USA, August, 2006b, 86 pages., http://www.fhwa.dot.gov/pavement/concrete/pubs/06080/.

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APPENDIX G – CALORIMETRY GRAPHS

Introduction. Isothermal conduction calorimetry was selected as a technique to monitor the cement hydration process. The calorimetry testing was performed using a differential heat flow calorimeter designed to monitor the heat of cement hydration as a function of time. The conduction calorimetry analyses were performed using 5.0 g (0.18 oz) of a selected sample and a w/c or w/cm of 0.50. Tests were performed for 24 h at 25 ± 1°C (77 ± 2 °F). Chapter 2 of Volume I—Final Report contains detailed discussion of the calorimetry testing. Sample Designation. In summary, each of six cement samples (1 to 6) was blended with Class C fly ash (C), Class F fly ash (F), and Slag (S) to produce 18 cementitious materials. In addition, 4 selected cement control samples were used consisting of ordinary portland cement (P). Other variables included admixture type and dosage, and curing temperature. Four rounds of testing were performed. In round one, the 24 samples were mixed with a single dose of admixture (A). In round two, selected samples were mixed varying admixture type (B) and dose (DA), resulting in a total of 15 mixes.

Figure G.1. Round 1 – Cement 1

FHWA Incompatibility Study - Conduction CalorimetryHydration Profile

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Figure G.2. Round 1 - Cement 2



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Figure G.7. Round 2A - Cement 2


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Figure G.8. Round 2A - Cement 4 and Cement 5

Figure G.9. Round 2B - Cement 1 and Cement 6


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Figure G.10. Round 2B - Cement 2, Cement 4, and Cement 5


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APPENDIX H – PORE SOLUTION CHEMISTRY REPORT

Test Methods

Introduction

The methods employed for extracting pore solution out of cement paste were similar to those applied in research studies done elsewhere. Depending on the initial time of set for the different mixes, extractions were done on either plastic-state or hardened-state paste. Mixing procedure for the paste was adapted from that described in report “Development of an Early Stiffening Test” (Tang 1997). This method of mixing cement paste was also used for the “mini-slump” testing. Chemical analysis of the pore solution collected was conducted for sodium, potassium, calcium, and sulfate ion, as well as pH measurement. In order to obtain the desired amount of liquid for chemical analysis, trial extraction tests were conducted prior to extractions.

The scope of work for pore solution extraction and analysis followed that for mini-slump, calorimetry, and all other tests performed under Task 2.1.1. In summary, each of 6 cement samples (1 to 6) was blended with class C fly ash (C), class F fly ash (F), and slag (S) to produce 18 cementitious materials. In addition, 4 selected cement control samples were also used consisting of ordinary portland cement (P). Other variables included admixture type and dosage, and curing temperature. Samples were mixed with water at w/cm ratio of 0.50 to produce paste and extract solution either in plastic or hardened state, at 5, 10, 30, 60, 360, and 1440 minutes after mixing.

Four rounds of testing were performed. In round one, the 24 samples were mixed with a single dose of admixture (A). In round two, selected samples were mixed varying admixture type (B) and dose (DA), resulting in a total of 15 mixes. In round three, selected samples were mixed to look at the effect of high temperature (32°C or 90°F), resulting in another group of 8 mixes in total. Similarly, in round four selected samples were mixed to look at the effect of low temperature (10°C or 50°F), 8 mixes total.

Paste Mixing

Paste was mixed in a Waring Blender™ mixer at 10,000 rpm for 90 seconds counting from the time that all cement and admixture were added to the water. Mixing proportions used were 500 g of cementitious material, 250 ml of water, and varied amounts of WRA admixture. Admixtures were measured and emptied into the mixer using 5-ml plastic syringes and dosed at single and double dosages recommended by the manufacturer. Lignin-based WRA admixture “A” was dosed at 1.62 ml and 3.25 ml per 500 grams of cementitious material. Sugar-based WRA admixture “B” was dosed at 0.81 ml per 500 g of cementitious material. A 0.50 water/cementitious material ratio was used in all paste mixes.

Because of the different effects on paste consistency experienced on initial time of set and early stiffening by using different extraction conditions such as time after mixing, combination of materials, mixing temperature, etc., the solution extractions were performed either in plastic state where the sample was poured into disposable centrifuge tubes, or in hardened state where samples were cast in small cylinder molds.

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Extractions During Plastic-State

An Analytical Centrifuge machine was used for extraction of solution before cement paste reached initial set. The centrifuge machine, manufactured by Clay Adams and equipped with a 115 volt-, 1.5 amp-, 60 Hz-motor, had a total capacity of 6 tubes. Plastic centrifuge tubes with gradation scale with a total capacity of 15 ml were used.

Minimum extraction times were previously determined in order to obtain between 10 and 15 ml of solution. Extraction times of 1 min. for very fluid paste and 3 min. for less fluid paste were used. Paste was placed inside each of 6 centrifuge tubes with the help of a funnel, and in cases where the paste would not flow easily, using a vibrating table. For paste mixes not reaching initial set yet but showing significant stiffening at 6 hours after mixing, 12 tubes were filled in with paste to obtain the desired amount of liquid.

For most mixes pore solution at ages of 5, 10, 30, and 60 minutes after mixing were centrifuged. Even some extractions at 6 and 24 hours were also performed using the centrifuge method, when temperature of the paste was kept at 10ºC (50°F).

Extractions During Hardened-State

An extraction method for squeezing solution out of hardened cement paste was adopted from previous research studies at Purdue University (Barneyback 1987). A press die manufactured of steel and designed to receive loads of up to 1335 kN (300 kips), “squeezed” the pore liquid by applying pressure to the paste specimen through a piston cylinder, and collecting the liquid via grooves in a base platen that removed the liquid and carried it out into tube receptacles using a flexible piece of tube flushed with nitrogen gas. Specimens used for this extraction technique were discs cast in 50-mm (2-in.) diameter by 19-mm (¾-in.) high cylinders that were able to provide a tight seal. An illustration of the press die set is shown in Fig. H.1, showing on the left side photo the paste specimen and the cylindrical chamber before introducing the disc and applying the pressure. Prior to testing, trial extractions were done in order to determine the approximate volume of hardened paste necessary to obtain 10 to 15 ml (0.34 to 0.51 fl oz) of solution. Normally 4 or 5 disc specimens were required to obtain the desired volume of liquid.

For most mixes, solution extraction at ages of 24 hours after mixing was done using the press die. Even some extractions at 6 hours were performed using the press die method, when temperature of the paste was kept at 32ºC (90°F) and the paste had hardened enough to prevent the use the centrifuge method.

Chemical Analysis

Pore solution samples were submitted to the chemical laboratory for analysis. After the extraction, samples were sealed and kept in the refrigerator until the next morning before analysis. After refrigeration samples were allowed to reach room temperature and pH was measured and solutions acidified to minimize potential changes in chemical composition due mainly to carbonation upon prolonged exposure to air. Samples were analyzed within the next 24 hours for sulfate, calcium, sodium, and potassium concentration. Sulfate analyses were done according to ASTM C114 wet method for chemical analysis, determined by the gravimetric

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method after precipitation with reagent-grade barium chloride. Calcium, sodium, and potassium analyses were done using Atomic Absorption Flame Emission Spectroscopy (AAS) using Varian spectrometer model SpectrAA 800. Sample preparation in most cases did not require more than 10 times dilution of the original volume, and in no case exceeded 100 times. Concentrations were calculated in mg/L of solution and used in ppm for data reduction and analysis.

Figure H.1. Die set for squeezing pore solution out of hardened cement paste specimens.

Reproducibility of Results

Additional selected paste samples were produced in one repetition to evaluate the reproducibility of the entire method of mixing, extracting, and analyzing the pore solution samples. Samples 2CA and 2CB at 21°C (70°F), 1CA at 32°C (90°F), and 1CB at 10°C (50°F), were randomly selected to repeat mixing of the paste, extracting of the pore solution at all six different times, and subsequent analyzing pore solutions for chemical composition. The results of the two determinations, along with their average value were plotted in the graphs shown in Appendix K.

The reproducibility was evaluated by computing the standard deviation and the average of each pair of data values determined, and then by calculating the coefficient of variation (COV) in percentage dividing the standard deviation by the average. Then, the maximum and minimum COVs over the whole range of six times of extraction and four repeat samples were determined,

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as well as the average COV over the same data range, for each ionic species and pH. The resulting COV parameters are shown in Table H1.

Table H.1. Coefficient of Variation (COV)* Parameters for Repeat Samples

pH SO42- Ca2+ Na+ K+

MAX. 4.6% 55.6% 60.9% 56.0% 29.4%

MIN. 0.1% 0.4% 0.8% 0.5% 0.7%

AVG. 0.8% 10.2% 16.7% 11.8% 9.7% *COV = coefficient of variation = standard deviation / average

From Table H.1, the standard deviation of each pair of pH data determined for all the repeat samples at all six times of extraction, ranged from 0.1% to 4.6% of the corresponding mean value for that pair of data. The same analysis was applied to the sulfate ion content, where the standard deviation ranged from 0.4% to 55.6% and averaged 10.2% of the corresponding mean value. It can be seen from Table H.1 that while variability is larger for ionic concentration methods than for pH, the overall average coefficient of variation for chemical analysis is around 12%, which may be considered fair for such a labor-intensive methodology and number of persons involved in each determination.

Results and Discussion

Appendix K shows graphs containing the results of chemical analysis done for each system under each round of testing described before. Sample notation used throughout this section and in the graphs has been given before. Concentration and pH results are shown for the different ionic species analyzed, i.e. sulfate, calcium, sodium, and potassium, for the different times of extraction tested. The concentration data is plotted on a primary y-axis, from 0 to 20,000 ppm, whereas pH values are plotted on a secondary y-axis from 12 to 14. Both concentration and pH are plotted vs. time of extraction or time after mixing, in minutes in the x-axis on logarithmic scale.

The data was analyzed in two portions, the raw ionic concentration data (trends) and the resulting calculated saturation factors for gypsum, calcium hydroxide, and syngenite. The data is preceded by an introduction section, which provides a basic explanation of cement hydration principles and pore solution chemistry.

Introduction

When portland cement enters in contact with water it hydrates, meaning that the cement particles dissolve and chemically react in water. The reactants of this chemical dissolution are cement particles and water. In Type I cements, particles are mainly (above 95% by mass) clinker grains.

Clinker grains are composite particles of the so-called four “cement phases” and other solidified melts from the kiln. These grains consist of the phases C3S and C2S, held together by C3A and C4AF that solidify from the kiln melt. Sulfate and alkalies that are part of the clinker reactions in the cement kiln and originate from raw materials and fuel used, also form solid compounds upon

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clinker cooling. These compounds are different varieties of alkali sulfates, the most commonly found being potassium sulfate (K2SO4). These compounds are usually found in cements that show a high alkali content in their chemical analysis.

Other particles present in cement are gypsum, plaster (resulting from gypsum dehydration in the cement mill), anhydrite, mineral additions (fly ash, slag), and contaminants. Some of this particulate matter is not soluble in water, like quartz and other silico-aluminate clays. Gypsum and plaster are both soluble in water, and plaster dissolves more easily than gypsum.

From the dissolution reactions of all these particles that comprise portland cement, the products of the chemical dissolution are simply the ionic species derived from all these compounds. For example: Gypsum (CaSO4•2H2O) dissolves in water to produce calcium ion (Ca2+) and sulfate ion (SO4

2-); plaster (CaSO4•½ H2O) dissolves in water to produce the same ionic species as gypsum; potassium sulfate (K2SO4) produces potassium ion (K+) and sulfate ion. Calcium silicates from clinker grains dissolve partially to produce solid “gel” calcium-silicate hydrate (C-S-H), calcium ion (Ca2+) and hydroxyl ion (OH-). Chemical admixtures used in concrete mixtures also contribute to calcium ion concentration, as they are soluble in water.

The plus or minus sign shown as super indices on the chemical element symbol indicates the electrical charge of the ion. Essentially this means that the molecular matter is dissociated into ions, and each ion will tend to find another ion of opposite charge to achieve electrical neutrality. When there are enough pairs of ions, the solid reforms from the aqueous dissolution in the form of solid crystal or “phase.”

As cement particles hydrate the mixing water or the water surrounding the particles becomes an aqueous solution of various ionic species. This explains the term “pore solution” to designate the water that remains in the porous concrete microstructure after it hardens. Fig. H.2 illustrates cement particles in close proximity to each other surrounded by water, such as in concrete mixtures where water/cement ratios normally range from 0.35 to 0.45. The water surrounding cement particles starts to dissolve the solids at different rates, depending on their rate of dissolution, which in turn is a function of temperature. The resulting ionic species become more and more concentrated and start to interact between each other and with the solid phases. Ionic electrical neutrality must be attained, so in order to balance the electrical charge, as more negative charge ions are incorporated into solution, more positive charge ions will also be incorporated and vice-versa. Eventually, solid products of reaction will “precipitate” or form from the pore solution, such as calcium hydroxide and ettringite phases.

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Figure H.2. Schematic representation of portland cement solid phases and their ionic species in aqueous dissolution right after cement enters in contact with water.

As cement hydration progresses with time, the trends in ionic concentrations observed are based on the following typical portland cement hydration processes:

1. During the first 30-minute period high levels of sulfate in solution denote dissolution of alkali sulfates, plaster, gypsum, and anhydrite.

2. This high level of sulfate ion in solution stays almost unchanged as a result of precipitation of gypsum from plaster, syngenite, and formation of ettringite.

3. At 6 hours of hydration there should be:

a. Significant decrease of sulfate ion in solution resulting from the reaction of sulfate and C3A to form the maximum amount of ettringite in the paste.

b. Increase of potassium ion in solution (and subsequent increase in pH), which results from releasing of potassium ion in solution.

c. Slight decrease of calcium ion concentration is the result of precipitation of solid calcium hydroxide during the onset of C3S acceleratory hydration (usually observed as a second peak in a calorimeter heat curve).

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4. By 24 hours, sulfate and calcium ion concentration decrease significantly, whereas potassium and sodium ion increase. Formation of calcium hydroxide, calcium silicate hydrate, and the conversion of ettringite to monosulfoaluminate take place.

The chemical composition of concrete pore solution has been the subject of several studies on the hydration of portland cement (Tang, et al. 1988; Gartner, et al. 1985; Rothstein, et al. 2002). Until recently, not many measurements have been reported of the ionic concentration of solutions when supplementary cementitious materials (SCM) are used in the concrete mix. As shown on various graphs in Appendix K, sulfate ion concentration is high right after mixing and remains at a high level until after 6 hours or later, decreasing until it reaches very low concentration at 24 hours. Potassium and sodium ion concentrations will start at some point (depending on the alkali content of the cement and other SCM added) and will increase as time progresses and cement grains react more with water. Calcium ion concentration follows the same trend as sulfate, being highest at the beginning and slowly decreasing until becoming negligible after 24 hours of hydration. Of these four ionic species, sulfate and potassium usually show higher relative concentration levels than sodium and calcium right after mixing. The pH of the solution increases with time, normally moving in the range from 13 to 13.5 during the first 24 hours.

These are the general trends seen in the pore solution data analyzed during this study. However, there are variations within different cementitious materials used, dosage and type of admixture used, and mixing/curing temperatures used. The following sections discuss the particular effects observed of the variables tested on the pore solution concentration of the ionic species monitored at different times of hydration.

Round 1 - Effect of Chemical Composition of Cementitious Materials

In round 1 of testing, sulfate ion concentrations during the first 6 hours for pastes made with cement sample 2 and its combinations (i.e. P, C, F, and S) are about twice as high at approximately 16,000 ppm than those for paste made with cements 1, 3, 4, and 6, at less than 8,000 ppm. Sulfate ion concentrations are also high for paste made with cement 5 and some of its combinations. This is a direct effect of cement composition. Fig. H.3 illustrates the relative proportions of C3A, alkalies, and SO3 in all 6 cement samples. ASTM C150 specification provides for additional sulfate content when the C3A content exceeds 8%. Cements 2, 3, 4, and 5 are above 8%, while 1 and 6 are below, so sulfate contents are at the expected levels. The alkali contents are highest in samples 2 and 5, while at normal levels (below 0.6% Na2Oeq., according to ASTM limits) in all the rest.

Based on Differential Scanning Calorimetry (DSC) analysis results shown in Table H.3, reasonable assumptions can be made on sulfate distribution (clinker sulfate vs. gypsum sulfate) that lead to calculations showing that indeed cements 2 and 5 contain the highest amount of clinker sulfate, or alkali sulfate, as shown in Fig. H.4 (where data is sorted by gypsum content). Of all sulfate-bearing phases in cement, alkali sulfates contained in clinker (mainly K2SO4) are the most readily soluble in water, followed by syngenite (K2Ca2(SO4)2•H2O), hemihydrate or plaster, and gypsum, in that order. Based on this sulfate-bearing phase solubility, sulfate ion concentrations in pore solution are in agreement with cement composition: samples 2 and 5 are expected to reach highest levels because of both the higher total sulfate content and the higher

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alkali sulfate content. While cement 2 has no syngenite present, it has a bigger proportion of plaster to gypsum than cement 5. Fig. H.5 shows sulfate ion concentration of pore solutions extracted from paste made with cement samples 1 through 6 without supplementary cementitious materials and single dose of admixture A.

Table H.2. Chemical composition of cements and supplementary cementitious materials with calculated Bogue compounds where applicable (weight % of sample)

Sample ID (Cement Sample No., SCM): 1 2 3 4 5 6 Slag Class C

Fly ash Class F Fly ash

Oxide XRF Analysis

SiO2 20.51 19.06 20.29 19.48 19.22 20.83 37.6 32.26 52.56

Al2O3 4.46 6.03 5.48 5.95 5.56 4.20 7.95 17.38 20.26

Fe2O3 3.19 2.13 2.8 2.68 2.66 3.3 0.87 6.06 11.46

CaO 63.43 62.45 65.59 64.42 61.63 62.55 38.91 26.8 4.29

MgO 2.99 2.67 1.02 0.85 2.34 3.23 10.87 7.87 1.00

Total SO3 2.72 3.87 2.63 3.32 4.42 2.75 2.49 2.65 0.64

Na2O 0.13 0.23 0.19 0.18 0.27 0.13 0.33 2.03 1.32

K2O 0.65 1.25 0.3 0.53 0.99 0.65 0.37 0.35 1.92

L.O.I. (950oC) 1.44 1.23 0.9 1.41 2.11 1.45 -0.99 0.24 4.22

Total 99.99 99.82 99.86 99.88 99.99 100.24 99.84 98.47 99.1

Alkalies as Na2Oeq. 0.56 1.06 0.38 0.53 0.92 0.56 0.58 2.26 2.58

Calculated Compounds per ASTM C150-02a.

C3S 60 55 65 61 51 56

C2S 13 13 9 10 17 18

C3A 6 12 10 11 10 6 11

C4AF 10 6 9 8 8 10 * Determined by X-ray diffraction (XRD)

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Table H.3. DSC results for cement samples showing Gypsum, Plaster, and Syngenite amounts (weight % of sample) Sample ID: 1 2 3 4 5 6 Gypsum 0.6 0.2 0.2 2.1 3.7 1.1 Plaster 0.4 2.6 2.8 2.0 0.9 1.9 Syngenite 1.1 0.0 0.0 0.0 0.4 1.0 Gypsum/Plaster ratio 1.50 0.08 0.07 1.05 4.11 0.58

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Of the SCMs used, class C fly ash and slag are the type of materials that could usually make important contributions to sulfate ion concentration in solution. The class C fly ash and slag contained 2.65% and 2.49% SO3 respectively, although the form of sulfate differed substantially from the form of sulfate in cement. X-ray diffraction (XRD) coupled with selective chemical dissolution methods performed as part of Task 2.1.1, reported class C fly ash containing about 4% by mass of calcium sulfate. This amount of calcium sulfate represents 2.36% of the total percent SO3 obtained by XRF analysis (2.65%, see Table H.2 above), or 89%. This calcium sulfate is relatively soluble in water due to its fine particle size, since it forms in the coal-fired power generation process during cooling of the flue gas, and is captured in the electrostatic precipitators of as part of the fly ash. This means that a significant portion of the sulfate present in the ash (89%) is relatively soluble and contributes to sulfate ion concentration in pore solution in a relatively short period of time.

As for the distribution of sulfate in the slag, it is mostly part of the amorphous structure of the slag and not immediately soluble in water. The amount of slag replacement by cement (40%, twice as much as that for the ashes) does have some impact on sulfate ion and other ionic concentrations just by the account of a dilution effect of the contribution from the cement components.

Particularly high concentrations of sulfate ion are observed in pore solutions made with cement 2 (2P) and cement 2 combined with fly ash C (2C) up to 6 hours after mixing. Sulfate concentration in pore solution declines drastically as expected for all cement systems treated at 21ºC (70ºF) after 6 hours.

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n (p

pm)

23°C 1 P A23°C 2 P A23°C 3 P A23°C 4 P A23°C 5 P A23°C 6 P A

Figure H.5. Sulfate ion concentration in pore solutions extracted from paste made with all cements without SCM and admixture A, at 21ºC (70°F). Alkali ion concentration (potassium more than sodium) was also observed to be high in pastes made with cements 2 and 5 and their combinations, somewhat less for combinations with slag and class F fly ash, reflecting mainly the cement amount they replaced (i.e. alkali sulfate). Fly ash replacement levels were only 20% for both class C and F, whereas slag replacement level

19

was 40%. Alkali content of the SCMs may not contribute directly to sodium or potassium ion concentration in solution because the form of alkali is not readily soluble in water. Note from Table H.2 that the total equivalent alkali content of both fly ashes and the slag were not only comparable with total equivalent alkali in the cement samples, but even twice as much. However, the nature of this alkali in SCMs is different from that of a water-soluble form; therefore their contribution to ionic concentration was very limited.

As explained before, pH is a direct function of the hydrogen [H+] and hydroxyl [OH-] ion concentration in solution. Because of the greater affinity of OH- for Na+ and K+ than for Ca2+, more than any other ion present in hydrated cement pore solution, potassium and sodium ions greatly affect hydroxyl ion concentration. As the potassium and/or sodium ionic concentration increases, the hydroxyl ion concentration will increase, thus increasing the pH of the pore solution. This increase on hydroxyl ion occurs simultaneously to the reaction of calcium hydroxide formation, from calcium [Ca2+] and hydroxyl [OH-] ions in solution, consuming hydroxyl ions from solution and competing with other reactions. However, an overall increasing effect in pH should be noticeable in systems with high amount of alkali ion in solution, i.e. cements 2 and 5 with high contents of alkali sulfate in cement. As shown in Fig. H.6, the pH for pastes made with cement samples 2, 5, and 6 is noticeably higher (approx. 13.3 to 13.7) than that measured in pastes made with all other cementitious materials. Looking at sulfate-phase distribution in cement samples (Fig. H.4), pH values for cements 2 and 5 are easily explained again by a very high, very soluble alkali sulfate content. In cement 6, perhaps the high pH measured results from a combination of alkali sulfate content and the cement’s high content of readily soluble syngenite, a potassium-bearing phase. Fig.H.7 shows potassium and sodium ion concentration for the same pore solutions. Again, pore solution pH is highest for those solutions, made with cement samples 2, 5, and 6 showing highest concentration of alkali ion.

pH

12.4

12.6

12.8

13.0

13.2

13.4

13.6

13.8

1 10 100 1000 10000Time after mixing (min)

pH

70F 1 P A70F 2 P A70F 3 P A70F 4 P A70F 5 P A70F 6 P A

Figure H.6. Measured pH of pore solution made with cement samples 1 to 6 and admixture A at 21°C (70°F).

20

Figure H.7. Alkali ionic concentration of pore solution of pastes made with different cement samples (admixture A and 21°C (70°F)).

Regarding calcium ion concentration, there seemed to be an additive effect when combining class C fly ash and cement sample 3 that resulted in higher concentrations. Fig. H.8 shows calcium ion concentration in pore solutions extracted from pastes made with samples 1CA, 2CA, 3CA, 4CA, 5CA, and 6CA, using single dose of admixture A and curing at room temperature. It is apparent there was a sustained higher calcium ion concentration for pore solution extracted from paste sample 3CA. To a lesser degree, a higher concentration of calcium ion was also observed when comparing pore solutions extracted from pastes made with other SCMs and cement 3, as shown in Fig. H.9, where the effect of the class C ash in calcium ion concentration is apparent. As seen in Table H2, cement sample 3 has a higher Bogue C3S content (65%) mainly due to its higher CaO (65.6%) content.

It is interesting to note here that reported as part of Task 2.1.1, conduction calorimetry data related to C3S hydration, as well as 24-hour mortar cube compressive strength data from specimens made with samples 3CA, 3FA, and 3SA at 21°C (70°F), seem to show some positive correlation between enhanced hydration properties and calcium ion concentration in pore solution.

70F 1 P A

70F 2 P A

70F 3 P A

70F 4 P A

70F 5 P A

70F 6 P A

Na+ ion

0

500

1000

1500

2000

2500

3000

1 10 100 1000 10000


K+ ion

0

4000

8000

12000

16000

20000

1 10 100 1000 10000


Ioni

c co

ncen

trat

ion

(ppm

)

21

Ca2+ ion

0

500

1000

1500

2000

2500

1 10 100 1000 10000


Ioni

c co

ncen

trat

ion

(ppm

)

70F 1 C A70F 2 C A70F 3 C A70F 4 C A70F 5 C A70F 6 C A

Figure H.8. Calcium ion concentration in pore solutions extracted from paste made with all 6 different cement samples and class C fly ash (admixture A, 21°C (70°F)).

Ca2+ ion

0

500

1000

1500

2000

2500

1 10 100 1000 10000


Ioni

c co

ncen

trat

ion

(ppm

)

70F 3 C A

70F 3 F A

70F 3 P A

70F 3 S A

Figure H.9. Calcium ion concentration in pore solutions extracted from paste made with cement 3 and all SCMs including control paste (admixture A, 21°C (70°F)).

This observation hints perhaps to the importance of proper balance between sulfate and calcium ion in pore solution, because in the case of cement 3PA, sulfate ion concentration (see Fig. H.5) is at a relatively low level, pointing to the safe assumption of a well-controlled aluminate reaction to form a very stable hydration product (ettringite), thereby reducing the potential for false set or flash set. This may be further substantiated by the analysis of the data using activities and ionic activity products to determine the corresponding saturation factors of gypsum, calcium hydroxide, and ettringite. Note that cement 3 is low in clinker alkali sulfate and unusually high in hemihydrate (plaster) proportion to gypsum (see Fig. H.4). This means that plaster relatively quick dissolution in water brings both sulfate and calcium ion into solution while little additional sulfate is brought from the more-soluble alkali sulfate, which in turn contributes with only

22

limited amounts of calcium ion into solution. These contrasts with pore solution data of paste made with cements 2 and 5, for example, where alkali sulfate concentrations are much higher.

The drastic drop in calcium ion concentration between 6 and 24 hours observed in most pore solutions (see Fig. H.8) has a direct relationship to the sudden increase of hydroxyl ion concentration by 24 hours indirectly measured as pH (see Fig. H.6). This sudden drop in calcium ion is partly due to calcium hydroxide formation as reviewed before, but also due to the so-called “common ion effect” by which calcium ion solubility is suppressed because of the presence of more alkali ion in solution competing for the increasing hydroxyl ion. The increase in alkali ion between 6 and 24 hours is apparent from Fig. H.7, and is more pronounced in pore solutions made with cement samples 2 and 5, containing the very soluble alkali sulfate. To illustrate this typical part of the cement hydration process, the following two chemical equations depict these competing reactions:

Na+ + K+ + 2OH- ↔ NaOH + KOH

Ca2+ + 2OH- ↔ Ca(OH)2

Because Ca(OH)2 is much less soluble than NaOH or KOH, the final outcome is that Ca(OH)2 precipitates as hexagonal crystals, while Na+, K+, and OH- remain in solution making for the high pH environment of portland cement hardened paste.

Round 2 - Effect of chemical admixture type and dosage

It is known that chemical admixtures used in concrete will affect the pore solution chemistry, especially the ionic concentrations of calcium and alkali. Even at the very small dosages typical of this type of admixtures (in the range from 0.1 to 0.4 ml per 100 g of cementitious material), the effect of these concentrated substances is to significantly increase ionic concentration and therefore contribute to ionic balance and influence the saturation condition for the different products of reaction (i.e. gypsum, calcium hydroxide, ettringite, etc.).

The effect on calcium ion concentration comparing between paste samples made with admixture A, with double dosage of admixture A, and with admixture B is apparent from Figs. H.10 to H.14. In these figures, the calcium ion concentration of pore solution is shown for samples made with selected cementitious samples 2C, 2P, 4P, and 5P. These four samples were selected after round one of testing because they exhibited strong tendency to early stiffening problems, and to test the effect (commonly referred as “admixture compatibility”) that a different dose and type of admixture would have on these problems. Early stiffening properties were measured by conduction calorimetry, the mini-slump test, setting time, and other tests as reported in other sections of this report under Task 2.1.1. Also, cementitious samples 1P, 1C, and 6P were selected to test the effect that a single dosage of a sugar-based admixture would have, if any, on early stiffening properties. These later samples did not show tendency to early stiffening, but were taken as a reference of “normal” performance. All these tests were performed at room temperature, 21ºC (70oF).

The relative effect on Ca2+ ion is shown on Figs. H.10 to H.13. In Fig. H.11, the apparent sudden drop in concentration at 10 min. and 30 min. for samples 2PDA and 2P respectively, are considered outlier data points. The effects of admixture in Ca2+ ion are more marked in the

23

period of time starting right after mixing to up to 360 minutes (6 hrs). On Figs. H.10 and H.11, the concentration is highest for pore solutions containing double dosage of admixture A (DA), intermediate for pore solutions containing single dosage of admixtures A and B (A, B), and lowest for pore solutions containing no admixture (control). This is the case for samples made with cementitious materials 2P and 2C, while for those made with 5P (Fig. H.13) the concentration is only slightly changed by the dose and or type of admixture. In the case of sample 4P (Fig. H.12), it is noticeable that the addition of more admixture A, or the use admixture B, seemed to have a decreasing effect on calcium ion concentration relative to the use of a single dose of admixture A.

Ca2+

0

200

400

600

800

1000

1200

1400

1 10 100 1000 10000


Ioni

c co

ncen

tratio

n (p

pm)

70F 2 C A70F 2 C

70F 2 C DA70F 2 C B

Figure H.10. Calcium ion concentration for pore solutions made from cement sample 2C and varying dose and type of admixture, at 21°C (70°F).

24

Ca2+

0

200

400

600

800

1000

1200

1400

1 10 100 1000 10000


Ioni

c co

ncen

trat

ion

(ppm

)

70F 2 P A

70F 2 P

70F 2 P DA

70F 2 P B

Figure H.11. Calcium ion concentration for pore solutions made from cement sample 2P and varying dose and type of admixture, 21°C (70°F).

Ca2+

0

200

400

600

800

1000

1200

1400

1 10 100 1000 10000


Ioni

c co

ncen

trat

ion

(ppm

)

70F 4 P A70F 4 P

70F 4 P DA70F 4 P B

Figure H.12. Calcium ion concentration for pore solutions made from cement sample 4P and varying dose and type of admixture, 21°C (70°F).

25

Ca2+

0

200

400

600

800

1000

1200

1400

1 10 100 1000 10000


Ioni

c co

ncen

trat

ion

(ppm

)

70F 5 P A70F 5 P70F 5 P DA70F 5 P B

Figure H.13. Calcium ion concentration for pore solutions made from cement sample 5P and varying dose and type of admixture, 21°C (70°F). Fig. H.14 shows calcium ion concentration with time of hydration for samples 1P, 1C, and 6P. As explained before, these samples were considered as reference regarding early stiffening behavior when tested prior to the second round, because of the normal performance they exhibited. In these solutions, it can be seen from Fig. H.14 that ionic concentration starts high at around 1000 ppm and goes down by 10 minutes to around 600 ppm. This is similar to what it is observed in Figs. H.10 and H.11 for samples 2C and 2P respectively, except perhaps that calcium ion seems to remain at higher concentration for longer period of time when admixtures have been used. A reference threshold concentration for Ca2+ would be around 1080 ppm, which represents the calcium ion concentration of a saturated pure calcium hydroxide solution at 23ºC (73ºF), indicating that higher than this there would be precipitation of calcium hydroxide in that simplified scenario. It is important to note that precipitation of calcium hydroxide is also governed by hydroxyl ion concentration and that both concentrations are a function of other ionic concentrations, such as alkalies.

26

Ca2+

0

200

400

600

800

1000

1200

1400

1 10 100 1000 10000


Ioni

c co

ncen

trat

ion

(ppm

)

70F 1 C A

70F 1 C B

70F 1 P A

70F 1 P B

70F 6 P A

70F 6 P B

Figure H.14. Calcium ion concentration for pore solutions made from cement samples 1C, 1P, and 6P, and varying type of admixture, at 21ºC (70°F). Although cement 1 had a higher C3S/C2S ratio, both cement samples 1 and 6 were very similar in chemical composition. Their total percent SO3 was at the same level, however, sulfate distribution was different. The cement samples had the same alkali sulfate content, about the same syngenite content, but gypsum to plaster ratios were different. Plaster was higher than gypsum in sample 6, while it was lower than gypsum in cement 1. In addition, it was reported that cement 1 contained significant amounts of natural anhydrite, analyzed by XRD. Natural-occurring anhydrite is far less soluble than gypsum, plaster, syngenite, or alkali sulfate.

Round 3 and 4 - Effect of Temperature

By testing pore solution chemistry at 32°C (90°F) and 10°C (50°F), the objectives were to address the effects on mixes showing early stiffening, normal stiffening, and mixes that were slow in reaching initial setting time. Mixing and curing paste specimens at 32°C (90°F) was applied to those mixes showing strong tendency to early stiffening for looking at possible aggravating effects, and to those mixes exhibiting normal behavior. Mixing and curing paste specimens at 10°C (50°F) was applied to mixes showing a tendency for early stiffening but to a lesser degree, looking at possible retardation effects, and also applied to those mixes exhibiting normal behavior as in the 32°C (90°F) treatment.

Mixing and curing at 10°C (50°F) shows a marked effect on sulfate ion concentration compared to room temperature. For the group of paste mixes showing early stiffening (2CA, 2CDA, 2FA, and 1CB) sulfate ion concentration remained relatively high after 6 hours (360 min) at 50°F, contrasting with the observed drop in concentration after 6 hours at room temperature. This is in effect retardation of hydration reactions because of lower temperature. Fig. H.15 shows an example of this trend in sulfate ion, where data at 10°C (50°F) and 21°C (70°F) for sample 1CB is plotted on the right side of the figure.

Furthermore, on the left side of Fig. H.15, the same temperature comparison is shown but for sample 1CA, which is only different to 1CB in the type of admixture used, and was considered

27

as normal stiffening behavior. It is clearly seen here that the lower temperature does not seem to have the same effect on sulfate ion concentration observed before. Therefore, the particular combination of admixture A with these cementitious materials indeed does not seem to represent a risk of retardation because of lower temperature. When saturation factors for gypsum and syngenite are considered in the analysis to interpret stiffening characteristics, as explained and shown in the following sections, the variation in ionic concentrations of pore solutions take a more practical meaning.

The effect of low temperature on sulfate ion concentration observed for the group described above (2CA, 2CDA, 2FA, and 1CB) is not observed for samples in the group of mixes exhibiting normal stiffening rates (1PA, 1PB, 1CA, and 6PA), except for sample 6PA, where sulfate ion concentration remains relatively high after 6 hours (360 min) at 10°C (50°F).

Figure H.15. Effect of low temperature and type of admixture on sulfate ion concentration for "slow" mixes

Comparing with mixes at 21°C (70°F), when mixing and curing at 32°C (90°F), sulfate ion concentration tended to drop earlier than 6 hours after mixing, only after 1 hour, as seen in the example shown in Fig. H.16. This behavior was observed for all samples in the group that were selected for testing at 32°C (90°F), i.e. 2PA, 5PA, 5P, and 5PB. The group exhibiting normal stiffening rates was also tested at 32°C (90°F) as a reference. From this group, the effect on sulfate ion concentration was also to drop earlier, only after 1 hour after mixing, but to a lesser degree and starting from a much lower initial sulfate ion concentration. Sample 1PB is shown in Fig.H.16 as an example of this reference group. In terms of saturation factors, the implication of sulfate ion concentrations dropping from 6000 ppm to around 2000 ppm is likely less significant when compared to concentrations dropping from 16000 ppm to also around 2000 ppm. This means that the level of pore solution super saturation with respect to sulfate-bearing phases like gypsum and syngenite is much higher at concentrations around 16000 ppm, therefore creating more potential for precipitation of these phases that would consequently increase early stiffening problems.

SO42- ion

0

2000

4000

6000

8000

10000

1 10 100 1000 10000


Ioni

c co

ncen

trat

ion

(ppm

)

50F 1 C B

70F 1 C B

SO42- ion

0

2000

4000

6000

8000

10000

1 10 100 1000 10000


Ioni

c co

ncen

trat

ion

(ppm

)

50F 1 C A

70F 1 C A

28

0

4000

8000

12000

16000

20000

1 10 100 1000 10000


Ioni

c co

ncen

tratio

n (p

pm)

70F 1 P B

90F 1 P B

70F 2 P A

90F 2 P A

Figure H.16. Sulfate ion concentration as a function of time after mixing for pastes 1 and 2 with admixtures A and B at two temperatures 21ºC (70ºF) and 32ºC (90ºF).

Aside from the individual ionic concentration of the chemical ionic species, calculations can be made to take into consideration the interactions that these ions have with each other in aqueous solution, what is known as ionic activity. This ionic activity can be used to calculate the ion activity products for each phases of interest, such as gypsum, calcium hydroxide, syngenite, etc. The ion activity products (IAP) are calculated based on the measured ionic concentration using ionic activities, by multiplying ionic activities of the species present in the phase.

In the following section, the analysis of pore solution data is made based on the calculation of IAPs and the findings are summarized based on the saturation factors for gypsum, syngenite, and calcium hydroxide.

Ion Activity Product and Saturation Factor

Introduction

The pore solution chemistry was examined in terms of the ion activity product, IAP. The activity of each species (ai) is given by;

ai = ciγi

where ci is concentration and γi is activity coefficient of a given species i.

In the following paragraphs, activities of a species are given by it chemical symbol in rounded parentheses and its concentration in square parentheses e.g. (Ca2+) and [Ca2+]. In order to determine the activity coefficients, the ion strength, I, has to be determined. This is calculated from the concentrations of the solution by the following equation;

I = 0.5Σzi2ci

29

where zi is the charge of a given species, and ci its concentration. From this the activity coefficient (γi) can be calculated by Davies equation:

log γi = -Azi2 (√I/(1+√I)-0.3I))

where A is Debye-Huckel solvent parameter (equal to 0.5).

The (OH-) activity is determined from the pH of the pore solution:

pH = log10(10-14/(OH-))

and is assumed to be equal to its concentration, which was applied as a first approximation for the concentration to obtain ionic strength and from these the activity coefficients. These values were used to recalculate the OH- concentration from the relation (OH-)/γOH. The calculations were repeated in a second iteration and again in a third iteration of the ion strength and activity coefficients. The results indicated that two iterations are sufficient and the values did not significantly change on the third iterations. Speciation was not considered.

The IAP was calculated for calcium hydroxide, gypsum and syngenite from the activity of each species:

IAPCH = (Ca2+)(OH-)2

IAPgyp = (Ca2+)(SO42-)

IAPsyng = (K+)2(Ca2+)(SO42-)2

Refer to Fig. H.17 for a summary of the ion activity product concept.

30

Ion Activity Product, IAP

For CH in water at equilibrium (25 oC) the solution is saturated and the IAP: (Ca++)(OH-)2 is a constant, KCH=9*10-6

For gypsum, (Ca++)(SO4--), the constant is

KGyp=2.6*10-5

For syngenite, (K+)2(Ca2+)(SO42-)2, the

constant is Ksyng=13.6*10-8

If the value of IAP is smaller than the saturated value, e.g. KCH, the crystal will dissolve, if it is larger the crystal will grow.

Ca(OH)2

Ca++ OH-

Ca++ OH-OH-

OH-

Figure H.17. Summary of ion activity product concept.

The IAP was further used to determine the saturation factor (SF) as a measure of the degree of saturation:

SF = (IAP/Ksp)

Where Ksp is the value of the IAP at saturation. SF = 1 indicates saturation, SF > 1 indicates supersaturation, and SF < 1 indicates under-saturation. The Ksp values used are 9 x10-6 Mole3 for calcium hydroxide, (2.547+2.258 I) x10-5 Mole2 for gypsum, and (13.9I-0.3) x10-8 Mole5 for syngenite (Gartner et al., 1985).

As an example of the meaning of SF, consider a gypsum crystal introduced into a solution with SFgypsum<1. It would dissolve immediately since the solution is under-saturated with respect to gypsum; and in a solution with SFgypsum>1 it would grow because of the super-saturation. Applying this to hydrating cement paste or mortar it would be expected that SFgypsum would be larger than or equal to 1 in the first part of the hydration reactions after mixing cement and water. The presence of hemi-hydrate and/or alkali sulfates would add to the sulfate concentration in addition to that from the gypsum, and hydrating calcium silicates will contribute calcium ions to the solution, so the IAPgypsum = (Ca2+)(SO4

2-) could be high resulting in a SFgypsum>1. In such situations there is a potential for precipitation of gypsum leading to change in rheology of the paste (false setting, etc.). This is depending on the rate with which the aluminate phase reacts in forming ettringite. Later, as the aluminate phase reacts, and the sulfate is consumed, the SFgypsum will decrease to below 1 at which time there is no more gypsum present.

31

For cements with high potassium and sulfate content the SFsyngenite may be larger than one in the pore solution early after mixing and result in a potential for precipitation of syngenite. This will compete with the aluminate phase for the sulfate and as result calcium aluminate hydrates may form instead of ettringite causing changes in stiffening behavior.

During the first part of hydration the calcium ion concentration in general increases in the pore solution and calcium hydroxide, CH, does not precipitate until later. It is therefore to be expected that SFCH is larger than one. This is the case and in the literature is reported that it stays above one for a long time (Gartner, et al. 1985).

Pore Solution Chemistry for 2P, 2C, 4P, and 5P, Rounds 1 and 2

The following section shows results from analyses of pore solution from systems without admixture hydrated at room temperature, 21°C (70 °F).

Gypsum (CaSO4.2H2O):

The SF for all systems are shown in Fig. H.18 and cross the value 1 between 360 and 1440 minutes indicating gypsum is consumed at this time (the point at 30 minutes for 2P is likely caused by an outlier data point for Ca2+).

The SF for system 4P is the lowest ~2.3 compared to ~6.5 for the others. Hence a greater potential for precipitation of gypsum and relative faster setting or changed workability for these systems.

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1 10 100 1000 10000

Time after mixing minutes

IAP

(gyp

)/sol

ubilit

y pr

oduc

t

Gyp. Sat. Fac 2P 2ndGyp. Sat. Fac 2C 2ndGyp. Sat. Fac 4P 2ndGyp. Sat. Fac 5P 2nd

Figure H.18. Saturation factor for gypsum as a function of time for pastes made with portland cements 2, 4, and 5, and cement 2 with class C fly ash. No chemical admixtures were used in these specimens.

32

00.020.040.060.08

0.10.120.140.160.18

0.2

1 10 100 1000 10000Time after mixing minutes

(SO

4--)

mol

e/lit

er 2P2C4P5P

Figure H.19. Sulfate ion concentrations in pore solutions of pastes made with portland cements 2, 4, and 5, and cement 2 with class C fly ash. No chemical admixtures were used in these specimens.

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

1 10 100 1000 10000


Ca+

+ m

ol/li

ter

2P2C4P5P

Figure H.20. Calcium ion concentration in pore solutions of pastes made with portland cements 2, 4, and 5, and cement 2 with class C fly ash. No chemical admixtures were used in these specimens. Note the low value at 30 minutes for the paste made with cement 2 is a likely outlier.

Syngenite (K2Ca(SO4)2):

As detailed in Fig. H.21, the SF for system 4P is around 1 for the first 10 minutes after mixing and then becomes smaller than 1, indicating no syngenite is formed as opposed to the other systems where the SF is around 10, which in turn indicates large potential for syngenite precipitation with possible change in workability relative to 4P. Between 360 and 1440 minutes the SF for all systems falls to low values caused by the decrease in sulfate concentration.

33

1.00E-06

1.00E-05

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1 10 100 1000 10000


IAP

(syn

g.)/s

olub

ility

pro

duct

Syng Sat.fac.2P 2nSyng Sat.fac. 2C ndSyng Sat.fac. 4P 2ndSyng Sat.fac. 5P 2nd

Figure H.21. Saturation factors for syngenite in pore solutions of pastes made with portland cements 2, 4, and 5, and cement 2 with class C fly ash. No chemical admixtures were used in these specimens.

00.10.20.30.40.50.60.70.80.9

1


(K+)

mol

e/lit

er

2P2C4P5P

Figure H.22. Potassium concentration as a function of time for in pore solutions of pastes made with portland cements 2, 4, and 5, and cement 2 with class C fly ash. No chemical admixtures were used in these specimens.

Calcium hydroxide (Ca(OH)2):

The SF values (Fig. H.23) are from 2.5 to about 10 at ten minutes and increase to about 26 for 2C and 5P at 360 minutes. Except for system 2P the SF values decrease between 360 and 1440 minutes. At this time calcium hydroxide is known to be present in hydrating cement systems so the reason for SF>1 is that Ca2+ still is produced by the on-going hydration and the (OH-) is high (see Fig. H.20).

34

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1.00E+03

1 10 100 1000 10000

time after mixing minutes

IAP

(Ca(

OH

)2)/s

olub

ility

prod

uct

Sat. Fac CH 2P 2nd

Sat. Fac CH 2C 2nd

Sat. Fac CH 4P 2nd

Sat. Fac CH 5P 2nd

Figure H.23. Saturation factors for calcium hydroxide in pore solutions of pastes made with portland cements 2, 4, and 5, and cement 2 with class C fly ash. No chemical admixtures were used in these specimens.

0

0.2

0.4

0.6

0.8

1

1.2

1.4


(OH

-) m

ol/li

ter

2P2C4P5P

Figure H.24. Hydroxyl (OH-) ion concentration in pore solutions of pastes made with portland cements 2, 4, and 5, and cement 2 with class C fly ash. No chemical admixtures were used in these specimens. Pore solution chemistry for 2P, 2C, 4P, and 5P with admixture A, rounds 1 and 2

Gypsum:

The addition of the water reducer A, as single, A, and double dosage, DA, causes SFgyp to increase for all systems except cement 4. The relative position of the plots are the same at all dosages, and between 360 and 1440 minutes the value decreases to below 1, indicating gypsum is no longer present in the systems. If a given system had shown tendency for early stiffening or other quick setting symptoms, the increase in SFgyp by addition of admixture A might indicate an strengthening of this effect.

35

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1 10 100 1000 10000


IAP

(gyp

)/sol

ubili

ty p

rodu

ct

Gyp. Sat. Fac 2P 2ndGyp. Sat. Fac 2C 2ndGyp. Sat. Fac 4P 2ndGyp. Sat. Fac 5P 2nd

Figure H.25. Saturation factors for gypsum in pore solutions of pastes made with portland cements 2, 4, and 5, and cement 2 with class C fly ash. No chemical admixtures were used in these specimens. Note the low value at 30 minutes for the paste made with cement 2 is a likely outlier.

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1 10 100 1000 10000


IAP

(gyp

)/sol

ubilit

y pr

oduc

t

Gyp. Sat. Fac. 2PAGyp. Sat. Fac. 2CAGyp. Sat. Fac. 4PAGyp. Sat. Fac. 5PA

Figure H.26. Saturation factors for gypsum in pore solutions of pastes made with portland cements 2, 4, and 5, and cement 2 with class C fly ash, and single dosage of admixture A.

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1 10 100 1000 10000


IAP

(gyp

)/sol

ubili

ty p

rodu

ct

Gyp. Sat. Fac. 2PDA 2ndGyp. Sat. Fac. 2CDA 2ndGyp. Sat. Fac.4PDA 2ndGyp. Sat. Fac.5PDA 2nd

36

Figure H.27. Saturation factors for gypsum in pore solutions of pastes made with portland cements 2, 4, and 5, and cement 2 with class C fly ash, and double dosage of admixture A.

The sulfate concentration is not changed by the addition of admixture A (see Figs. H.29 and H.30), the increase in SFgyp is caused by increase in the Ca2+ concentration (see Figs. H.20, H.31 and H.32).

0

0.05

0.1

0.15

0.2


(SO

4--)

mol

e/lit

er

2P2C4P5P

Figure H.28. Sulfate ion concentration in pore solutions of pastes made with portland cements 2, 4, and 5, and cement 2 with class C fly ash. No chemical admixtures were used in these specimens.

00.020.040.060.08

0.10.120.140.160.18

0.2


(SO

4--)

mol

e/lit

er 2PA2CA4PA5PA

Figure H.29. Sulfate ion concentration in pore solutions of pastes made with portland cements 2, 4, and 5, and cement 2 with class C fly ash, and single dosage of admixture A.

37

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2


(SO

4--)

mol

e/lit

er

2PDA2CDA4PDA5PDA

Figure H.30. Sulfate ion concentration in pore solutions of pastes made with portland cements 2, 4, and 5, and cement 2 with class C fly ash, and double dosage of admixture A.

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035


(Ca+

+) m

ole/

liter

2PA

2CA

4PA

5PA

Figure H.31. Calcium ion concentration in pore solutions of pastes made with portland cements 2, 4, and 5, and cement 2 with class C fly ash, and single dosage of admixture A.

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035


(Ca+

+) M

ole/

liter

2PDA2CDA4PDA5PDA

Figure H.32. Calcium ion concentration in pore solutions of pastes made with portland cements 2, 4, and 5, and cement 2 with class C fly ash, and double dosage of admixture A.

38

It is interesting to note that the Ca2+ concentration for cement 5 does not change with addition of admixture A, where it increases by addition of A and then decreases to the original level by double addition of A (DA) for cement 4. (The variation in the Ca2+ concentration at 10 and 30 minutes for system 2P is due to outlier data points.)

Syngenite:

For cement 4 the effect of adding admixture A as single or double dosage is to decrease the SFsyn, it is however below 1 indicating no syngenite is present. For the other systems the SFsyn changes from 21 to 5 to 15 at 10 minutes by addition of a single dosage, and increases to about 27 by double dosage.

1.00E-06

1.00E-05

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1 10 100 1000 10000


IAP

(syn

g.)/s

olub

ility

prod

uct

Syng Sat.fac.2P 2nSyng Sat.fac. 2C ndSyng Sat.fac. 4P 2ndSyng Sat.fac. 5P 2nd

Figure H.33. Saturation factors for syngenite in pastes made with portland cements 2, 4, and 5, and cement 2 with class C fly ash. No chemical admixtures were used in these specimens.

1.00E-06

1.00E-05

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1 10 100 1000 10000


IAP

(syn

g)/s

olub

ility

pro

duct

Syng.Sat.fac.4PASyng.Sat.fac. 5PASyng.Sat.fac. 2PASyng.Sat.fac. 2CA

Figure H.34. Saturation factors for syngenite in pastes made with portland cements 2, 4, and 5, and cement 2 with class C fly ash, and single dosage of admixture A.

39

1.00E-06

1.00E-05

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1 10 100 1000 10000


iap(

syng

)/sol

ubilit

y pr

oduc

tSyng Sat.fac. 2PDA 2ndSyng Sat.fac. 2CDA 2ndSyng Sat.fac. 4PDA 2ndSyng Sat.fac. 5PDA 2nd

Figure H.35. Saturation factors for syngenite in pastes made with portland cements 2, 4, and 5, and cement 2 with class C fly ash, and double dosage of admixture A.

Thus, relative to cement 4, these systems might have a tendency for early stiffening which, based on the potential for precipitation of syngenite, compared to systems with no addition may be less pronounced with addition a single dosage, and stronger with double dosage.

Calcium Hydroxide:

By adding admixture A the SFCH increases for all systems of which cement 4 has the lowest SF-values. The Ca2+ concentrations generally decrease and the increase in SF-values is caused by the continued increase in OH- concentration.

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1.00E+03

1 10 100 1000 10000


IAP

(Ca(

OH

)2)/s

olub

ility

prod

uct

Sat. Fac CH 2P 2nd

Sat. Fac CH 2C 2nd

Sat. Fac CH 4P 2nd

Sat. Fac CH 5P 2nd

Figure H.36. Saturation factors for calcium hydroxide in pastes made with portland cements 2, 4, and 5, and cement 2 with class C fly ash. No chemical admixtures were used in these specimens.

40

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1.00E+03

1 10 100 1000 10000


IAP

(CH

)7so

lubi

lita

prod

uct

Sat. Fac CH 2PA

Sat. Fac CH 2CA

Sat. Fac CH 4PA

Sat. Fac CH 5PA

Figure H.37. Saturation factors for calcium hydroxide in pastes made with portland cements 2, 4, and 5, and cement 2 with class C fly ash, and single dosage of admixture A.

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1.00E+03

1 10 100 1000 10000


IAP

(CH

)/sol

ubili

ty p

rodu

ct

Sat. Fac CH 2PDA 2ndSat. Fac CH 2CDA 2ndSat. Fac CH 4PDA 2ndSat. Fac CH 5PDA 2nd

Figure H.38. Saturation factors for calcium hydroxide in pastes made with portland cements 2, 4, and 5, and cement 2 with class C fly ash, and double dosage of admixture A.

0

0.2

0.4

0.6

0.8

1

1.2

1.4


(OH

-) m

ol/li

ter

2P2C4P5P

Figure H.39. Hydroxyl ion concentration in pore solutions of pastes made with portland cements 2, 4, and 5, and cement 2 with class C fly ash. No chemical admixtures were used in these specimens.

41

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1 10 100 1000 10000


(OH

-) m

ol/li

ter

2PA2CA4PA5PA

Figure H.40. Hydroxyl ion concentration in pore solutions of pastes made with portland cements 2, 4, and 5, and cement 2 with class C fly ash, and single dosage of admixture A.

0

0.2

0.4

0.6

0.8

1

1.2

1.4


(OH

-) M

ole/

liter

2PDA2CDA4PDA5PDA

Figure H.41. Hydroxyl ion concentration in pore solutions of pastes made with portland cements 2, 4, and 5, and cement 2 with class C fly ash, and double dosage of admixture A.

Pore Solution Chemistry for 2P, 2C, 4P, and 5P with Admixture B, Rounds 1 and 2

The variations of SF-values for systems with addition of water reducer B are similar to those with addition of a single dosage A.

Pore Solution Chemistry for Selected Systems Hydrated at 90 oF, Round 31

Based on rounds 1 and 2 four systems considered "Fast" and four systems considered "Normal" with respect to workability were selected for testing at 32°C (90°F). The "Fast" systems were 2PA, 5PA, 5PB and 5P; the "Normal" systems were 1PA, 1CA, 1PB and 6PA.

1 The SF values at 32ºC (90ºF) and 10ºC (50ºF) are calculated using the room temperature value of the ion activity product at saturation for the relevant compound.

42

Gypsum & Syngenite:

For the period up to about 60 minutes for the systems treated at 32°C (90°F) and to 360 minutes for systems treated at 21°C (70°F), the SF values are generally highest for the "fast" systems. For the "fast" systems SFgyp >5 and for the "normal" systems SFgyp <3, and the temperature increase has only small effect on the saturation factor. The SFsyn for the "fast" systems is around 10, whereas it is ~1 or smaller for the "normal" systems. This reflects the general high potential for the "fast" systems to precipitate gypsum and syngenite during the first period of hydration. Comparing the two systems the difference in SFgyp might be an indicator of whether a system will exhibit changes in workability in a negative way.

The effect of temperature is the earlier drop in SF values for the systems treated at 32°C (90°F) compared to those treated at 21°C (70°F) which is reflecting the higher hydration rates caused by the higher temperature. The hydration of C3A forming AFt (and AFm) is accelerated by the temperature increase, and as a result the sulfate of the pore solution is depleted earlier.

1.00E-03

1.00E-02

1.00E-01

1.00E+00

1.00E+01

1 10 100 1000 10000


IAP

(gyp

)/sol

ubili

ty p

rodu

ct

Gyp. Sat. Fac. 2PAGyp. Sat. Fac. 5PAGyp. Sat. Fac 5P 2ndGyp. Sat. Fac. 5PBGyp. Sat. Fac 2PA 3rdGyp. Sat. Fac 5PA 3rdGyp. Sat. Fac 5P 3rdGyp. Sat. Fac 5PB 3rd

70

90

Figure H.42. Saturation factors for gypsum in pore solutions of “fast” pastes treated at 21°C (70°F) and 32°C(90°F).

1.00E-03

1.00E-02

1.00E-01

1.00E+00

1.00E+01

1 10 100 1000 10000


IAP

(gyp

)/sol

ubili

ty p

rodu

ct

Gyp. Sat. Fac 1PAGyp. Sat. Fac 1CAGyp. Sat. Fac. 6PAGyp. Sat. Fac. 1PB 2ndGyp. Sat. Fac. 1PA 3rdGyp. Sat. Fac. 1CA 3rdGyp. Sat. Fac.1PB 3rdGyp. Sat. Fac.6PA 3rd

90 F

70 F

43

Figure H.43. Saturation factors for gypsum in pore solutions of “normal” pastes treated at 21°C (70°F) and 32°C(90°F).

1.00E-05

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1 10 100 1000 10000


IAP

((sy

ng)/s

olub

ility

pro

duct

Syng.Sat.fac. 2PASyng.Sat.fac. 5PASyng Sat.fac. 5P 2ndSyng Sat.fac. 5PB 2ndSyng. Sat.fac.2PA 3rdSyng. Sat.fac. 5PA 3rdSyng. Sat.fac. 5P 3rdSyng. Sat.fac. 5PB 3rd

90 70

Figure H.44. Saturation factors for syngenite in pore solutions of “fast” pastes treated at 21°C (70°F) and 32°C(90°F).

1.00E-05

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1 10 100 1000 10000


IAP

(syn

g)/s

olub

ility

prod

uct

Syng.Sat.fac.1PASyng.Sat.fac. 1CASyng.Sat.fac. 6PASyng Sat.fac.1PB 2ndSyng. Sat.fac. 1PA 3rdSyng. Sat.fac. 1CA 3rdSyng. Sat.fac. 1PB 3rdSyng. Sat.fac. 6PA 3rd

90 F

70 F

Figure H.45. Saturation factors for syngenite in pore solutions of “normal” pastes treated at 21°C (70°F) and 32°C(90°F).

Calcium Hydroxide:

The SFCH for the "fast" systems increases as a result of the temperature change from 21 to 32°C (70 to 90°F). For 21°C (70°F) at 5 minutes the values are from 5 to 15 and increases slowly to between 13 and 30 at 360 minutes, where after they decrease to between 9 and 20 (the value for 5P may be an outlier result). By increasing the temperature to 32°C (90°F) the SF values all increase.

For the "normal" systems the SF values for 1PA and 1CA two increase and decrease for 6PA and 1PB and as a result all the SF-values are in a relative narrow band at 32°C (90°F).

44

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1.00E+03

1 10 100 1000 10000


IAP

(CH

)/sol

ubili

ty p

rodu

ct

Sat. Fac CH 2PASat. Fac CH 5PASat. Fac CH 5P 2ndSat. Fac CH 5PB 2ndSat. Fac CH 2PA 3rdSat. Fac CH 5PA 3rdSat. Fac CH 5P 3rdSat. Fac CH 5PB 3rd

Arrows indicate direction from 70 to 90 deg F

Figure H.46. Saturation factors for calcium hydroxide in pore solutions of “fast” pastes treated at 21°C (70°F) and 32°C(90°F).

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1.00E+03

1 10 100 1000 10000


IAP

(CH

)/sol

ubili

ty p

rodu

ct

Sat. Fac CH 1PASat. Fac CH 1CASat. Fac CH 6PASat. Fac CH 1PB 2ndSat. Fac CH 1PA 3rdSat. Fac CH 1CA 3rdSat. Fac CH 1PB 3rdSat. Fac CH 6PA 3rd

Arrows indicate direction from 70 to 90 deg F

Figure H.47. Saturation factors for calcium hydroxide in pore solutions of “normal” pastes treated at 21°C (70°F) and 32°C(90°F). Pore Solution Chemistry for Selected Systems Hydrated at 50 °F, Round 4

Four systems, 2CA, 2FA, 2CDA, 1B considered “slow”, were selected together with the "normal" systems for testing at 10°C (50°F).

Gypsum:

"Slow" systems: Up to 360 minutes the SFgyp for 1CB at 21°C (70°F) is around 2. The remainder of the systems have SF-values from around 5 to 13. After 360 minutes all the 21°C (70°F) treated samples decrease sharply, whereas the 10°C (50°F) treated systems only decrease slightly

45

and stay larger than SF=1. This is reflecting the retardation in hydration reactions due to the lower temperature.

"Normal" systems: The SF-values are generally lower than for the "slow" systems, except for two: 1CA and 6PA treated at 10°C (50°F), all the other values are within a narrow interval and at level with 1CB described above. Only 6PA treated at 10°C (50°F) has SFgyp>1 after 360 minutes.

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1 10 100 1000 10000

Time aftwer mixing minutes

IAP

(gyp

)/sol

.pro

d.

Gyp. Sat. Fac 2CA 4thGyp. Sat. Fac 2FA 4thGyp. Sat. Fac2CDA 4thGyp. Sat. Fac1CB 4thGyp. Sat. Fac. 2CAGyp. Sat. Fac. 2FAGyp. Sat. Fac. 2CDA 2ndGyp. Sat. Fac. 1CB 2nd

50 F

70 F

Figure H.48. Saturation factors for gypsum in pore solutions of “slow” pastes treated at 21°C (70°F) and 10°C(50°F).

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1 10 100 1000 10000


IAP

(gyp

)/sol

. pro

d.

Gyp. Sat. Fac. 1PA 4thGyp. Sat. Fac. 1CA 4thGyp. Sat. Fac.1PB 4thGyp. Sat. Fac.6PA4thGyp. Sat. Fac 1PAGyp. Sat. Fac 1CAGyp. Sat. Fac. 6PAGyp. Sat. Fac. 1PB 2nd

Figure H.49. Saturation factors for gypsum in pore solutions of “normal” pastes treated at 21°C (70°F) and 10°C(50°F).

Syngenite:

"Fast" systems: The SF-values are in a band from around 4 to around 10. An exception is 1CB treated at both temperatures with SFsyn < 1 indicating no syngenite can form. The other exception is system 2CDA treated at 21°C (70°F) with SF-values around 30. After 360 minutes all values decrease to below 1.

46

1.00E-06

1.00E-05

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1 10 100 1000 10000


IAP(

syn)

/sol

. pro

d.

Syng. Sat.fac.2CA 4thSyng. Sat.fac. 2FA 4thSyng. Sat.fac.2CDA 4thSyng. Sat.fac. 1CB 4thSyng.Sat.fac. 2CASyng.Sat.fac. 2FASyng Sat.fac. 2CDA 2ndSyng Sat.fac. 1CB 2nd

50 F

70 F

Figure H.50. Saturation factors for gypsum in pore solutions of “slow” pastes treated at 21°C (70°F) and 10°C(50°F).

1.00E-06

1.00E-05

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1 10 100 1000 10000


IAP

(syn

)/sol

. pro

d.

Syng. Sat.fac. 1PA 4thSyng. Sat.fac. 1CA 4thSyng. Sat.fac. 1PB 4thSyng. Sat.fac. 6PA 4thSyng.Sat.fac.1PASyng.Sat.fac. 1CASyng Sat.fac.1PB 2ndSyng.Sat.fac. 6PA

50 F

70 F

Figure H.51. Saturation factors for syngenite in pore solutions of “normal” pastes treated at 21°C (70°F) and 10°C(50°F).

Calcium Hydroxide:

"Slow" systems: The SFCH in general increases for the “slow” systems as temperature changes from 21 to 10°C (70 to 50°F). Contrary to the 21°C (70°F) treated systems, the 10°C (50°F) treated systems do not show any decrease in SF-values after 360 minutes. This could be caused by the lower rate of hydration reactions.

"Normal" systems: The situation is a bit more complicated for these systems. For two systems, 1PA, and 1CA, the level of SF-values increases, and for 6PA and 1PB it decreases.

47

1.00E-02

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1.00E+03

1 10 100 1000 10000


IAP

(CH

)/sol

. pro

d.

Sat. Fac CH 1PA 4thSat. Fac CH 1CA 4thSat. Fac CH 1PB4thSat. Fac CH 6PA 4thSat. Fac CH 1PASat. Fac CH 1CASat. Fac CH 6PASat. Fac CH 1PB 2nd

Arrows indicate 70 - 50 oF

Figure H.52. Saturation factors for calcium hydroxide in pore solutions of “normal” pastes treated at 21°C (70°F) and 10°C(50°F).

1.00E-02

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1.00E+03

1 10 100 1000 10000


IAP

(CH

)/sol

.pro

d.

Sat. Fac CH 2CA 4thSat. Fac CH 2FA 4thSat. Fac CH 2CDA 4thSat. Fac CH 1CB 4thSat. Fac CH 2CASat. Fac CH 2FASat. Fac CH 2CDA 2ndSat. Fac CH 1CB 2nd

50 F

70 F

Figure H.53. Saturation factors for calcium hydroxide in pore solutions of “slow” pastes treated at 21°C (70°F) and 10°C(50°F).

Pore Solution Chemistry for the "Normal" Systems Treated at 50, 70 and 90oF

In the following section the SF-values for the systems 1PA, 1CA, 1PB and 6PA treated at 10, 21 and 32°C (50, 70 and 90°F) are compared.

Gypsum:

The SFgyp for all systems treated at 32°C (90°F) decreases after 60 minutes compared to systems treated at the other temperatures where the SFgyp decreases after 360 minutes. This is caused by the accelerated hydration reactions due to increased temperature.

For 1CA and 6PA the SFgyp values are about the same at 5 minutes for all temperatures. Then they decrease for the 21°C and 32°C (70°F and 90°F) treated systems but stay the same or increase for the 10°C (50°F) treated systems until about 60 minutes from when they slowly decrease. This behavior could be explained by the retardation in hydration reactions at 10°C

48

(50°F); and the slight increase for 1CA could be caused by sulfate containing phases still dissolving. The two other systems show a similar behavior, however to a much smaller effect.

The higher values of the SFgyp for the 10°C (50°F) treated systems indicate a higher potential for precipitation of gypsum at early times after mixing relative to the systems treated at higher temperatures. The same effect that slows the hydration reaction down may possibly also slow down the nucleation and/or growth of gypsum crystals, and as result no change in the workability may be observed.

1.00E-03

1.00E-02

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1 10 100 1000 10000


IAP(

gyp)

/sol

. pro

d.

Gyp. Sat. Fac 1PAGyp. Sat. Fac. 1PA 3rdGyp. Sat. Fac. 1PA 4th

70 F

50 F

90 F

Figure H.54. Saturation factors for gypsum in pore solutions of pastes made with cement 1 and single dose of admixture A, treated at 10°C(50°F), 21°C (70°F), and 32°C (90°F).

1.00E-03

1.00E-02

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1 10 100 1000 10000


IAP

(gyp

)/sol

. pro

d.

Gyp. Sat. Fac 1CAGyp. Sat. Fac. 1CA 3rdGyp. Sat. Fac. 1CA 4th

70 F

50 F

90 F

Figure H.55. Saturation factors for gypsum in pore solutions of pastes made with cement 1, single dose of admixture A, and class C fly ash, treated at 10°C(50°F), 21°C (70°F), and 32°C (90°F).

49

1.00E-03

1.00E-02

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1 10 100 1000 10000


IAP

(gyp

)/sol

. pro

d.

Gyp. Sat. Fac. 6PAGyp. Sat. Fac.6PA 3rdGyp. Sat. Fac.6PA4th

70 F

50 F

90 F

Figure H.56. Saturation factors for gypsum in pore solutions of pastes made with cement 6 and single dose of admixture A, treated at 10°C(50°F), 21°C (70°F), and 32°C (90°F).

1.00E-03

1.00E-02

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1 10 100 1000 10000


IAP

(gyp

)/sol

. pro

d.

Gyp. Sat. Fac. 1PB 2ndGyp. Sat. Fac.1PB 3rdGyp. Sat. Fac.1PB 4th

70 F 50 F90 F

Figure H.57. Saturation factors for gypsum in pore solutions of pastes made with cement 1, single dose of admixture B and treated at 10°C(50°F), 21°C (70°F), and 32°C (90°F).

Syngenite:

All the SFsyng values are around 1, which means that syngenite as crystalline phase cannot exist in these systems.

Calcium Hydroxide:

No clear trend is seen for the SFCH values. For 1PA, the SFCH for the 10°C (50°F) treated system is around 10 times higher than for the 21°C (70°F) treated system, and for the 32°C (90°F) treated system it is about 5 times higher. For 1CA the 10°C (50°F) as well as 32°C (90°F) values of SFCH are between 10 and 15 times larger than the 21°C (70°F) values.

50

For 1PB the 21°C (70°F) values are the highest. The 32°C (90°F) values are about 0.5 times the 21°C (70°F) values, and the 10°C (50°F) values are about 0.1 times the 21°C (70°F) values. The system 1PA is somewhat similar to 1PB, the 21°C (70°F) values are the highest.

1.00E-02

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1.00E+03

1 10 100 1000 10000


IAP

(CH

/sol

ubili

ty p

rodu

ct

Sat. Fac CH 1PASat. Fac CH 1PA 3rdSat. Fac CH 1PA 4th

70 F

90 F

50 F

Figure H.58. Saturation factors for calcium hydroxide in pore solutions of pastes made with cement 1, single dose of admixture A and treated at 10°C(50°F), 21°C (70°F), and 32°C (90°F).

1.00E-02

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1.00E+03

1 10 100 1000 10000


IAP(

CH

)/sol

. pro

d.

Sat. Fac CH 1CASat. Fac CH 1CA 3rdSat. Fac CH 1CA 4th

70 F

90 F50 F

Figure H.59. Saturation factors for calcium hydroxide in pore solutions of pastes made with cement 1, class c fly ash, single dose of admixture A, and treated at 10°C(50°F), 21°C (70°F), and 32°C (90°F).

51

1.00E-02

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1.00E+03

1 10 100 1000 10000


IAP

(CH

)/sol

. pro

d.

Sat. Fac CH 6PASat. Fac CH 6PA 3rdSat. Fac CH 6PA 4th

70 F

90 F

50 F

Figure H.60. Saturation factors for calcium hydroxide in pore solutions of pastes made with cement 6, single dose of admixture A and treated at 10°C(50°F), 21°C (70°F), and 32°C (90°F).

1.00E-02

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1.00E+03

1 10 100 1000 10000


IAP

(CH

)/sol

. pro

d.

Sat. Fac CH 1PB 2ndSat. Fac CH 1PB 3rdSat. Fac CH 1PB4th

70 F

50 F90 F

Figure H.61. Saturation factors for calcium hydroxide in pore solutions of pastes made with cement 1, single dose of admixture B and treated at 10°C(50°F), 21°C (70°F), and 32°C (90°F).

52

Summary

Based on the results from analysis of pore solutions, the pore solution chemistry was examined for a selected number of cementitious systems without and with chemical admixtures and at different temperatures. In most cases the systems were examined at 21°C (70°F). Systems considered "fast" in regards to their stiffening characteristics were studied at 21°C and 32°C (70°F and 90°F). Systems considered "slow" were studied at 21°C and 10°C (70°F and 50°F). In both cases they were compared with the same set considered "normal".

The setting or stiffening behavior of hydrating portland cement or cements with SCMs during the first ~10 minutes after mixing cement and water, is generally attributed to the reactions involving the C3A and the sulfate from the added gypsum and from alkali sulfates in the clinker. In cases when the system is not in "balance" with respect to these reactions changes in rheology of the mixture may result, and the mixture may exhibit "early stiffening," "false setting" or "flash setting." The false setting is related to precipitation of gypsum due to a high concentration of sulfate in the pore solution. Flash setting is the result of too little sulfate available in the pore solution and caused by formation of C3A hydrates instead of ettringite, which is the normal hydration product.

Early after mixing, the concentration of the constituent ions in pore solution varies according to the specific cement. For example for cements high in alkali sulfates the concentration of sulfate ions as well as alkali ions will be high. At the same time the hydration of the C3S will contribute calcium ions as well as hydroxyl ions to the pore solution. In special cases where the concentration of sulfate and calcium ions are high, the pore solution can be super-saturated with respect to for example gypsum, and this may cause gypsum to precipitate. The criteria for this is whether the so-called solubility product for gypsum is higher than corresponding to gypsum in equilibrium with the pore solution, which in this case is said to be saturated with respect to gypsum. The solubility product of gypsum is calculated according to Kgyp = [Ca2+][SO4

2-], where [Ca2+] and [SO4

2-] are the concentrations of calcium ions and sulfate ions respectively in the pore solution. Solubility products for other compounds can be calculated in similar ways, and for saturated solutions the solubility product at a given temperature are constants specific for the considered compound. Strictly taken, “activity” should be used instead of “concentration”. Activity is another measure of concentrations, which takes the presence of other ionic constituents of the pore solution into consideration, and ion activity product, IAP, is used instead of solubility product. For gypsum it is

IAPgyp = (Ca2+)(SO4

2-),

where (Ca2+) and (SO42-) respectively are the activities of the calcium ions and the sulfate ions of

the pore solution, and these can be calculated from the total composition of the pore solution.

One way to characterize the pore solution regarding possible super-saturation with respect to for example gypsum or other constituents is to define the saturation factor, SF, as the ratio between the actual IAPgyp of the pore solution and the corresponding value for the saturated condition.

53

SF values larger than 1 indicate super-saturation, SF=1 corresponds to the saturated solution, and for SF smaller than 1 the solution is under-saturated. A crystal cannot exist in a solution with SF<1, it is not stable and will dissolve. In a solution with SF>1 it will grow, it cannot dissolve.

For the selected systems the saturation factors for gypsum (CaSO4•2H2O), SFgyp, syngenite (K2Ca(SO4)2•H2O), SFsyn, and calcium hydroxide (Ca(OH)2), SFCH, were studied. Syngenite is a potassium-calcium-sulfate that can precipitate in systems with cements with high sulfate and potassium concentrations.

For cement pastes of grey and white portland cement it is known from the literature (Gartner, et al. 1985, Rothstein, et al. 2002) that SFgyp and SFsyn can be larger than one for up to about 10 hours or later and SFCH is larger than 1 for up to 28 days or more. The super-saturation of gypsum is related to the dehydration of gypsum to hemihydrate (plaster of Paris) in commercial cements during grinding. The plaster is much more soluble than gypsum and can deliver sulfate to the pore solution faster than it can be consumed by the reaction with C3A phase. Extra sources of sulfate like alkali sulfates can contribute to the super-saturation situation as well. The reason for the prolonged super saturation with respect to calcium hydroxide is probably the continued hydration of C3S and C2S.

Water reducers are in many ways similar to retarders. Taylor (1991) makes references to work showing that calcium ion concentration and hydroxyl ion concentrations increase in pore solution when such chemical admixtures are used. The mechanism is probably that they modify the reaction products by being adsorbed, and allow the calcium ion concentration in solution to be higher than in pore solutions with the unmodified hydration product.

For the 4 systems 2P, 2C, 4P, and 5P (no admixture) considered "early", in terms of their stiffening behavior at 21°C (70°F), the SFgyp values for 2P, 2C, and 5P were similar ~6.5 and for 4P it was ~2.5 without any significant change up to 360 minutes. After this time all values decreased to below 1, signaling all gypsum had been consumed. During the period from mixing until 360 minutes the SFgyp values indicate super-saturation and hence a potential for precipitation of gypsum with possible effect on the workability. The super-saturation in 4P is lower than in the other systems and it would be expected that this system would show less early stiffening compared to the others.

With regards to the SFsyn system 4P again is the lowest: around 1 up to 10 minutes and then for later times smaller than 1, indicating no presence of syngenite. This makes sense since cement 4P is low in potassium. The other systems all have SFsyn higher than 10 indicating potential for precipitation of syngenite, which can cause same effects as precipitation of gypsum. Since it is a sulfate-bearing phase, it might compete with the C3A for the sulfate ion in the pore solution and cause flash set (Taylor 1991).

Regarding calcium hydroxide the SFCH values for 4P again is the lowest of the set, with values from 2.5 increasing to about 10 at 360 minutes after which time it decreases but maintain values >1. The other systems have values from around 9 increasing to 26 at 360 minutes. As mentioned above the pore solution is expected to be super-saturated by calcium hydroxide for some time after mixing. But the individual differences in super-saturation cannot be explained at this time. The reasons can be many: Different reactivity of the clinker minerals of the cement contributing

54

calcium ions and hydroxyl ions at different rate to the pore solution, effect of alkalies on the calcium ion concentration, different ratios between calcium and silica in the calcium-silicate-hydrate formed during the early hydration process.

Addition of water reducers A and B (single (A) and double dosage (DA) of A and single dosage of B) generally resulted in increase of the hydroxyl ion concentration of the pore solution for all systems and in calcium ion concentration except for 4PA and 4PDA. The SFgyp for 4PA and 4PDA was not changed significantly, but for the other systems it increased with increasing addition of water reducer A. Addition of B had similar effect as addition of a single dosage A. This indicates increasing tendency for early setting with increasing addition of water reducer. For SFsyn the addition of water reducers had similar effects.

For SFCH the addition of water reducer had an effect for all systems: the SFCH increased with increasing addition. The increases in SF values are in line with the findings reported in literature referred to above. However the effect of the super-saturation with respect to calcium hydroxide on the early stiffening behavior is not understood.

One set considered "Fast": 2PA, 5PA, 5PB and 5P, and a set considered "Normal": 1PA, 1CA, 1PB and 6PA at 21°C (70°F), were additionally tested at 32°C (90ºF). Up to 60 minutes after mixing the "fast" systems have higher SFgyp and SFsyn values than the "normal.” The "fast" have SFgyp>5 and the "normal" <3. Changing the temperature from 21 to 32°C (70 to 90°F) has only small effect on the level of individual SF values until about 60 minutes after mixing. Then the SFgyp and SFsyn values decrease to smaller than 1 for the 32°C (90ºF) treated systems. This indicates

• The "fast" systems have higher potential for precipitation of gypsum and syngenite with the possible effects on workability and early stiffening behavior,

• The higher temperature accelerates hydration of C3A and hence the consumption of gypsum at a much earlier time. This will for both the "fast" and "formal" set lead to shorter setting time in general.

The SFsyn values for the "normal" systems are around or below 1 in all cases indicating the non-existence of syngenite and hence no negative effect of this phase on the rheology. For the SFCH no clear tendency was observed other than that of the "fast" systems increased at 32°C (90°F) relative to 21°C (70°F).

Four systems considered "slow" at 21ºC (70ºF): 2CA, 2FA, 2CDA, and 1B together with "normal" systems mentioned above were tested at 10°C (50°F). Regarding the gypsum the SFgyp values for the "slow" systems with the exception of 1CB were around 10 to 14 and the "normal” systems slightly lower. The effect of decreasing the temperature from 21ºC to 10°C (70 ºF to 50ºF) was a slight increase in SF values for the "slow" as well as the "normal" set up to 360 minutes after mixing. With the exception of 6PA, after this time the SFgyp values for the "normal" systems decreased to less than 1, indicating total consumption of gypsum; but the SFgyp values for the "slow" system treated at 10°C (50°F) remained almost un-changed at their levels larger than one indicating that gypsum still was present at 1440 minutes after mixing. For the "slow" set the SFsyn behavior was similar. The values for the system 1CB indicated no existence

55

of syngenite either at 21°C or 10°C (70°F or 50°F), which was also the case for the "normal" systems. No clear trend could be observed regarding calcium hydroxide.

Based on the study of saturation factors with respect to gypsum, syngenite and calcium hydroxide the following findings can be summarized:

• Addition of water reducers results in an increase in the saturation factors for gypsum, syngenite, and calcium hydroxide in the systems studied.

• For "fast" systems treated at 32°C (90oF), the saturation factors for gypsum and syngenite were not affected until after 60 minutes after mixing comparing to those of samples treated at 21°C (70oF). After 60 minutes the 32°C (90oF) saturation factors decreased to below one, indicating total consumption of gypsum. When treated at 21°C (70oF) this change took place after 360 minutes after mixing.

• Treating "slow" systems at 10°C (50oF) had only minor effect on the saturation factors for gypsum and syngenite up to 360 minutes after mixing when compared to samples treated at 21°C (70oF). After 360 minutes the saturation factors decreased to below 1 for samples treated at 21°C (70oF) indicating the presence of gypsum at least up to 1440 minutes after mixing.

• Comparison of "fast" and "normal" systems showed that the levels of gypsum saturation factors were highest for the "fast." The difference in saturation factor values might be an indicator of whether a system could be considered “fast” or “normal”. However when comparing "normal" with "slow" systems the gypsum saturation factors for the "slow" are slightly higher than for the “normal.” Based on the present study it is not possible to characterize early stiffening behavior based solely on pore solution chemistry.

REFERENCES

Barneyback, Jr., R. S.; Alkali-Silica Reaction in Portland Cement Concrete, Ph.D. Thesis, Purdue University, 1987, 256 pages.

Tang, F. J. and Bhattacharja, S.; Development of an Early Stiffening Test, RP346, Portland Cement Association, Skokie, Illinois, 1997, 94 pages.

Gartner, E. M.; Tang, F. J.; and Weiss, Stuart J.; “Saturation Factors for Calcium Hydroxide and Calcium Sulfates in Fresh Portland Cement Pastes,” Journal of the American Ceramic Society, Vol. 68, No. 12, 1985, pages 667 to 673.

Rothstein, D.; Thomas, J.; Christensen, B. J.; Jennings, H. M.; “Solubility behavior of Ca-, S-, Al-, and Si-bearing solid phases in Portland cement pore solutions as a function of hydration time,” Cement and Concrete Research, Vol. 32, 2002, pages 1663 to 1671.

56

Tang, F. J.; Gartner, E. M.; “Influence of Sulphate Source on Portland Cement Hydration,” Advances in Cement Research, Vol. 1, No. 2, April 1988, pages 67 to 74.

57

APPENDIX I – RING SHRINKAGE GRAPHS

Introduction: Detailed information on the ring shrinkage tests is found on pages 20 and 98 of Volume I of this series:

Taylor, P.C., Johansen, V.C.; Graf, L. A.; Kozikowski, R. L.; Zemajtis, J. Z.; and Ferraris, C.F.; Identifying Incompatible Combinations of Concrete Materials: Volume I—Final Report, FHWA-HRT-06-079, Federal Highway Administration, Maclean, VA, USA, August, 2006, 162 pages, http://www.fhwa.dot.gov/pavement/concrete/pubs/06079/.

58

Figure I.1. Plots of Strain Gage Data for 5 Samples From Mix WRA1

Figure I.2. Plots of Strain Gage Data for 5 Samples From Mix WRA2

-60.0

-40.0

-20.0

0.0

8/31/04 9/2/04 9/4/04 9/6/04 9/8/04 9/10/04 9/12/04 9/14/04Date, time

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in, m

illio

nths

12345

#2

-60.0

-40.0

-20.0

0.0

9/20/04 9/22/04 9/24/04 9/26/04 9/28/04 9/30/04 10/2/04 10/4/04 10/6/04 10/8/04 10/10/04Date, time

Stra

in, m

illio

nths

12345

#1

59

Figure I.3. Plots of Strain Gage Data for 5 Samples From Mix FA1

Figure I.4. Plots of Strain Gage Data for 5 Samples From Mix FA2

-60

-40

-20

0

10/4/04 10/6/04 10/8/04 10/10/04 10/12/04 10/14/04 10/16/04 10/18/04 10/20/04 10/22/04 10/24/04Date, time

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#3

-60

-40

-20

0

10/11/04 10/13/04 10/15/04 10/17/04 10/19/04 10/21/04 10/23/04 10/25/04 10/27/04 10/29/04Date, time

Stra

in, m

illio

nths

1234

#4

60

Figure I.5. Plots of Strain Gage Data for 5 Samples From Mix 25FA90


-60.0

-40.0

-20.0

0.0

11/9/04

11/11/04

11/13/04

11/15/04

11/17/04

11/19/04

11/21/04

11/23/04

11/25/04

11/27/04

11/29/04

12/1/04

12/3/04

12/5/04

12/7/04

12/9/04

Date, time

Stra

in, m

illio

nths

12345

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-40

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0

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#6

61



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#8

62

APPENDIX J – FOAM DRAINAGE GRAPHS

Introduction: Detailed information on the foam drainage tests in this program is found on pages 118 to120 of Volume I of this series:

Taylor, P.C., Johansen, V.C.; Graf, L. A.; Kozikowski, R. L.; Zemajtis, J. Z.; and Ferraris, C.F.; Identifying Incompatible Combinations of Concrete Materials: Volume I—Final Report, FHWA-HRT-06-079, Federal Highway Administration, Maclean, VA, USA, August, 2006, 162 pages, http://www.fhwa.dot.gov/pavement/concrete/pubs/06079/.

63

Figure J.1. Admixture A

Figure J.2. Admixture B

Admixture B

0

50

100

150

200

250

300

350

0:00:00 0:10:00 0:20:00 0:30:00 0:40:00 0:50:00 1:00:00 1:10:00

Time, hr:min:sec

Wat

er D

rain

age,

ml

AEAAEA+CAEA+WRAEA+C+WR+C-ASH"AEA+C+WR+F-ASH"

Admixture A

0

50

100

150

200

250

300

350

0:00:00 0:10:00 0:20:00 0:30:00 0:40:00 0:50:00 1:00:00 1:10:00

Time, hr:min:sec

Wat

er D

rain

age,

ml


64

Figure J.3. Admixture C

Figure J.4. Admixture D

Admixture C

0

50

100

150

200

250

300

350

0:00:00 0:10:00 0:20:00 0:30:00 0:40:00 0:50:00 1:00:00 1:10:00

Time, hr:min:sec

Wat

er D

rain

age,

ml


Admixture D

0

50

100

150

200

250

300

350

0:00:00 0:10:00 0:20:00 0:30:00 0:40:00 0:50:00 1:00:00 1:10:00Time, hr:min:sec

Wat

er D

rain

age,

ml


65

Figure J.5. Admixture E

Figure J.6. Admixture F

Admixture F

0

50

100

150

200

250

300

350

0:00:00 0:10:00 0:20:00 0:30:00 0:40:00 0:50:00 1:00:00 1:10:00

Time, hr:min:sec

Wat

er D

rain

age,

ml


Admixture E

0

50

100

150

200

250

300

0:00:00 0:10:00 0:20:00 0:30:00 0:40:00 0:50:00 1:00:00 1:10:00

Time, hr:min:sec

Wat

er D

rain

age,

ml


66

Figure J.7. Admixture G

Figure J.8. Admixture H

Admixture H

0

50

100

150

200

250

300

350

0:00:00 0:10:00 0:20:00 0:30:00 0:40:00 0:50:00 1:00:00 1:10:00Time, hr:min:sec

Wat

er D

rain

age,

ml


Admixture G

0

50

100

150

200

250

300

350

0:00:00 0:10:00 0:20:00 0:30:00 0:40:00 0:50:00 1:00:00 1:10:00Time, hr:min:sec

Wat

er D

rain

age,

ml


67

Figure J.9. Admixture I

Figure J.10. Admixture J

Admixture J

0

50

100

150

200

250

300

350

0 0.006945

0.01389 0.020835

0.02778 0.034725

0.04167 0.048615

Time, hr:min:sec

Wat

er D

rain

age,

ml


Admixture I

0

50

100

150

200

250

300

0:00:00 0:10:00 0:20:00 0:30:00 0:40:00 0:50:00 1:00:00 1:10:00Time, hr:min:sec

Wat

er D

rain

age,

ml


68

APPENDIX K – PORE SOLUTION ANALYSES RAW DATA

69

Task 2.1.1 Pore Solution Analysis Round 1 Cement 1

Time after casting, minutes

Con

cent

ratio

n, p

pm

pH

SO4= Ca++ Na+ K+ pH

Sample 1PA

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0Sample 1CA

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0

Sample 1FA

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0Sample 1SA

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0

70


Con

cent

ratio

n, p

pm

pH


SO4= Ca++ Na+ K+ pH

Sample 2PA

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0Sample 2CA

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0

Sample 2FA

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0Sample 2SA

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0

71


Con

cent

ratio

n, p

pm

pH


SO4= Ca++ Na+ K+ pH

Sample 3PA

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0Sample 3CA

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0

Sample 3FA

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0Sample 3SA

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0

72


Con

cent

ratio

n, p

pm

pH


SO4= Ca++ Na+ K+ pH

Sample 4PA

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0Sample 4CA

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0

Sample 4FA

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0Sample 4SA

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0

73


Con

cent

ratio

n, p

pm

pH


SO4= Ca++ Na+ K+ pH

Sample 5PA

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0Sample 5CA

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0

Sample 5FA

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0Sample 5SA

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0

74


Con

cent

ratio

n, p

pm

pH


SO4= Ca++ Na+ K+ pH

Sample 6PA

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0Sample 6CA

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0

Sample 6FA

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0Sample 6SA

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0

75

Task 2.1.1 Pore Solution Analysis Round 2


Con

cent

ratio

n, p

pm

pH

SO4= Ca++ Na+ K+ pH

Sample 2P

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0Sample 2C

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0

Sample 4P

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0Sample 5P

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0

76


Con

cent

ratio

n, p

pm

pH


SO4= Ca++ Na+ K+ pH

Sample 2PDA

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0Sample 2CDA

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0

Sample 4PDA

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0Sample 5PDA

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0

77


Con

cent

ratio

n, p

pm

pH


SO4= Ca++ Na+ K+ pH

Sample 2PB

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0Sample 2CB

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0

Sample 4PB

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0Sample 5PB

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0

78


Con

cent

ratio

n, p

pm

pH


SO4= Ca++ Na+ K+ pH

Sample 1PB

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0Sample 1CB

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0

Sample 6PB

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0

79



Con

cent

ratio

n, p

pm

pH

SO4= Ca++ Na+ K+ pH

Sample 2PA @ 90°F

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0Sample 5PA @ 90°F

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0

Sample 5P @ 90°F

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0Sample 5PB @ 90°F

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0

80


Con

cent

ratio

n, p

pm

pH


SO4= Ca++ Na+ K+ pH

Sample 1PA @ 90°F

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0Sample 1CA @ 90°F

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0

Sample 1PB @ 90°F

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5


0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0

81



Con

cent

ratio

n, p

pm

pH

SO4= Ca++ Na+ K+ pH

Sample 2CA @ 50°F

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0Sample 2FA @ 50°F

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0

Sample 2CDA @ 50°F

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0Sample 1CB @ 50°F

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0

82


Con

cent

ratio

n, p

pm

pH


SO4= Ca++ Na+ K+ pH

Sample 1PA @ 50°F

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0Sample 1CA @ 50°F

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0

Sample 1PB @ 50°F

0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5


0

4000

8000

12000

16000

20000

1 10 100 1000 1000012.0

12.5

13.0

13.5

14.0

83

Task 2.1.1 Pore Solution Analysis Reproducibility

pH

Time after mixing, minutes

pH

Repeat 2Repeat 1 Average

Sample 2CA - Round 1

13.0

13.2

13.4

13.6

13.8

14.0

1 10 100 1000 10000

Sample 2CB - Round 2

13.0

13.2

13.4

13.6

13.8

14.0

1 10 100 1000 10000


13.0

13.2

13.4

13.6

13.8

14.0

1 10 100 1000 10000

Sample 2FA - Round 4

13.0

13.2

13.4

13.6

13.8

14.0

1 10 100 1000 10000

84


SO4=

SO4= c

once

ntra

tion,

ppm


Repeat 1 Average Repeat 2


0

4000

8000

12000

16000

20000

1 10 100 1000 10000


0

4000

8000

12000

16000

20000

1 10 100 1000 10000


0

4000

8000

12000

16000

20000

1 10 100 1000 10000


0

4000

8000

12000

16000

20000

1 10 100 1000 10000

85


Ca++


Ca++

con

cent

ratio

n, p

pm



0

500

1000

1500

2000

1 10 100 1000 10000


0

500

1000

1500

2000

1 10 100 1000 10000


0

500

1000

1500

2000

1 10 100 1000 10000


0

500

1000

1500

2000

1 10 100 1000 10000

86


Na+

Na+ c

once

ntra

tion,

ppm




0

500

1000

1500

2000

2500

3000

3500

1 10 100 1000 10000


0

500

1000

1500

2000

2500

3000

3500

1 10 100 1000 10000


0

500

1000

1500

2000

2500

3000

3500

1 10 100 1000 10000


0

500

1000

1500

2000

2500

3000

3500

1 10 100 1000 10000

87


K+

K+ c

once

ntra

tion,

ppm




0

4000

8000

12000

16000

20000

1 10 100 1000 10000


0

4000

8000

12000

16000

20000

1 10 100 1000 10000


0

4000

8000

12000

16000

20000

1 10 100 1000 10000


0

4000

8000

12000

16000

20000

1 10 100 1000 10000

Documents

Identifying incompatible combinations of concrete materials - III.pdf