Y. Ohama Disposal and Recycling of Organic and Polymeric Construction Materials 1995

Disposal and Recycling of Organic and Polymeric ConstructionMaterials

Disposal and Recycling of Organic andPolymeric Construction Materials

Proceedings of the International RILEM WorkshopTokyo

2628 March 1995

EDITED BY

Y.OhamaDepartment of Architecture,

College of Engineering,Nihon University, Koriyama,

Japan

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1995 RILEM

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Workshop.

Contents

Workshop organization vi

Preface viii

PART ONE PLASTICS-BASED MATERIALS 1

1 Mechanical properties of polymer mortar made from recycled PET-basedunsaturated polyester resinY.S.SOH, H.S.PARK and D.S.LEE

2

2 Properties of plain and reinforced polyester concretes made with recycled PETK.S.REBEIZ and D.W.FOWLER

9

3 A new kind of hybrid recycled polymer mortarY.BAO, D.P.WHITNEY and D.W.FOWLER

22

4 Utilization of waste plastics as aggregate in asphalt mixtureM.YAMADA

33

5 The behavior of Portland cement concrete with the incorporation of waste plasticfillersD.SANDER, D.W.FOWLER and R.L.CARRASQUILLO

43

6 Polymer granulates for masonry mortars and outdoor plasterH.R.SASSE, O.LEHMKMPER and R.KWASNY-ECHTERHAGEN

54

7 Polymer modified lightweight cement mortar using plastics wasteY.HAYASHI, R.NANIWA, H.IIBACHI, K.HADA and T.YAMAZAKI

62

PART TWO FRP-BASED MATERIALS 71

8 Updating recycling technologies for thermoset composites in JapanT.KITAMURA

72

9 Environment-conscious materials design of lightweight precast concretecomponents with recyclable FRP rebarsT.FUKUSHIMA, K.YANAGI and T.MAEDA

81

10 Recycling of plastics wastes from electronic parts production processesM.IJI and S.YOKOYAMA

91

11 Preparation and properties of lightweight high-strength mortars containing FRPfine powder as aggregateA.KOJIMA and S.FURUKAWA

99

12 Properties of autoclaved cement paste containing scrap FRP powderM.WAKASUGI and A.SUGIURA

110

13 Recycling of FRP as a cementitious compositeK.YAMADA and H.MIHASHI

116

14 Properties of artificial woods using FRP powderK.DEMURA, Y.OHAMA and T.SATOH

127

PART THREE RUBBER-BASED MATERIALS 136

15 Noise abatement by panels of recycled vehicle tiresM.MOTAVALLI, M.FARSHAD and P.FLELER

137

16 Construction materials using powdered rubber made of vehicle tiresR.YAMAMOTO

143

17 Punching resistance of mats made of recycled PVC and rubber in undergroundconstructionP.FLELER, M.FARSHAD and A.ROLLER

150

PART FOUR WOOD-BASED MATERIALS 156

18 Newly developed wood-chip concrete with recycled timbersY.KASAI, M.KAWAMURA, J.D.ZHOU and K.MACHIDA

157

19 Particleboards made from recycled woodS.SUZUKI

168

20 Development of formwork material made of scrap lumberT.ONO, S.ONO, T.KUMANO, T.SANO and Y.MUKAWA

177

PART FIVE PAPER-BASED MATERIALS 185

21 Ecology boards using recycled paper resources for concrete formsK.KURIHARA, S.TAKATA, Y.TOMIMURA and S.HOSOYA

186

22 Recycling of used paper as a building materialH.MIHASHI, K.KIRIKOSHI, S.ARIKAWA, T.YAMAMOTO and T.NARITA

194

23 Use of paper sludge ash in concrete productsY.S.SOH, S.Y.SOH and D.S.LEE

203

PART SIX OTHERS 209

24 Investigation on deterioration of recycled hot-mixed asphalt concrete pavement anda trial re-recycling of asphalt concreteT.YOSHIKANE

210

25 Reuse of carpet industrial waste for concrete reinforcementY.WANG

222

Author index 230

Subject index 231

v

Workshop organization

Sponsoring OrganizationInternational Union of Testing and Research Laboratories for Materials and Structures (RILEM)Architectural Institute of Japan (AIJ)Japan Technology Transfer Association (JTTAS)International Advisory Committee

Professor. K.Kamimura Utsunomiya University, Japan (Chairman)Professor A.M.Brandt Polish Academy of Sciences, PolandProfessor D.W.Fowler University of Texas at Austin, U.S.A.Dr. H.W.Fritz Eidgenssische Materialprfungs-und Forschungsanstalt, SwitzerlandDr. T.Kawano Maeta Concrete Industry Ltd., JapanProfessor K.Kishitani Nihon University, JapanProfessor W.Koyanagi Gifu University, JapanProfessor S.Nagataki Tokyo Institute of Technology, JapanProfessor K.Okada Fukuyama University, JapanDr. S.Okamoto Building Research Institute, JapanDr. A.M.Paillere Laboratoire Central des Ponts et Chaussees, FranceProfessor H.W.Reinhardt Universitt Stuttgart, GermanyProfessor F.Sandrolini Universita di Bologna, ItalyProfessor H.R.Sasse Rheinisch-Westflische Technische Hochschule Aachen, GermanyProfessor R.N.Swamy University of Sheffield, United Kingdom

Organizing Committee

Professor Y.Ohama Nihon University (Chairman)Professor H.Mihashi Tohoku University (Secretary)Dr. K.Demura Nihon University (Secretary)Professor T.Arima University of TokyoDr. T.Fukushima Building Research InstituteProfessor Y.Kasai Nihon UniversityMr. A.Kawamura Kumagaigumi Co., LtdProfessor A.Kojima Gunma College of TechnologyMr. S.Kurihara Japan Reinforced Plastics SocietyProfessor A.Moriyoshi Hokkaido UniversityMr. N.Nishiyama Nishimatsu Construction Co., LtdProfessor F.Oishi Kanagawa UniversityDr. M.Sawaide Shimizu CorporationDr. A.Shirai Tokyo Kasei Gakuin UniversityMr. M.Wakasugi Sumitomo Osaka Cement Co., Ltd

Professor M.Yamada Osaka City University

RILEM Subcommittee of Architectural Institute of Japan (AIJ)

Professor Y.Ohama Nihon University (Chairman)Professor H.Mihashi Tohoku University (Secretary)Professor T.Arima University of TokyoDr. K.Demura Nihon UniversityDr. T.Fukushima Building Research InstituteMr. T.Kaminosono Building Research InstituteProfessor Y.Kasai Nihon UniversityProfessor T.Kuwahara Hokkaigakuen UniversityProfessor R.Naniwa Kogakuin UniversityProfessor T.Soshiroda Shibaura Institute of TechnologyDr. H.Tamura General Building Research Corporation of JapanMr. K.Tobinai Mitsubishi Materials CorporationProfessor F.Tomosawa University of TokyoMr. K.Yanagi Japan Testing Center for Construction Materials

vii

Preface

In recent years, various polymers have been widely used as construction materials, and the disposal and recycling oforganic (polymeric) construction materials has become a serious problem in the construction industry. Theconstruction industry is one of the major consumers of the polymers, and is considered to be a significant potentialcustomer for recycled polymers. Accordingly, there is a pressing need for the construction industry to developecologically safe disposal systems and effective recycling systems for the organic (polymeric) constructionmaterials.

Against such a background, the RILEM Workshop on Disposal and Recycling of Organic (Polymeric)Construction Materials is to be held in Tokyo, Japan on 2628 March 1995, and is co-sponsored by the InternationalUnion of Testing and Research Laboratories for Materials and Structures (RILEM), the Architectural Institute ofJapan (AIJ) and Japan Technology Transfer Association (JTTAS) under the auspices of the American ConcreteInstitute (ACI), the American Society for Testing and Materials (ASTM), the Gypsum Board Association of Japan,the Japan Cement Association, the Japan Concrete Institute, the Japan Fiberboard and Particleboard ManufacturersAssociation, the Japan Housing and Wood Technology Center, the Materials Research Society (USA), the MaterialsResearch Society of Japan, the Plastic Waste Management Institute (Japan), the Slate Association of Japan, the JapanReinforced Plastics Society, the Japan Society of Civil Engineers, the Japan Society of Waste Management Experts,the Japan Wood Research Society, the Society of Gypsum & Lime (Japan), the Society of Materials Science, Japan,the Society of Polymer Science, Japan, and the Society of Rubber Industry, Japan. Financial support was provided bythe TOSTEM Foundation for Construction Materials Industry Promotion, AIJ and JTTAS.

The main objectives of this Workshop are to collect recent information about the disposal and recycling of organic(polymeric) construction materials, and develop new ideas to further improve the ecologically safe disposal systemsand effective recycling systems for organic (polymeric) construction materials.

The main topics of the Workshop are as follows:

1. Disposal and recycling of organic (polymeric) construction materials using plastics, rubber, asphalt, wood andpaper.

2. Development of construction materials using waste organic (polymeric) materials from the other industries.

This Proceedings volume brings together the papers which will be presented at the Workshop. I believe that thevolume will be of interest for the manufacturers, users and researchers of organic (polymeric) construction materials.

On behalf of the Organizing Committee, I would like to thank all the authors of the papers included here for theirco-operation. I wish to acknowledge the national and international organizations or institutions which supported theWorkshop. I would also like to express my sincere appreciation to the members of the International AdvisoryCommittee for their useful advice and suggestions.

Yoshihiko OhamaKoriyama, Japan

January 1995

PART ONE

PLASTICS-BASED MATERIALS

1MECHANICAL PROPERTIES OF POLYMER MORTAR MADEFROM RECYCLED PET-BASED UNSATURATED POLYESTER

RESINY.S.SOH and H.S.PARK

Department of Architectural Engineering, College of Engineering, Chonbuk National University,Chonju, Korea

D.S.LEEDepartment of Chemical Technology, College of Engineering, Chonbuk National University,

Chonju, Korea

Abstract

Unsaturated polyester (UPE) resins made from recycled poly ethylene terephthalate (PET) were prepared andthe properties of the polymer mortar prepared with PET-modified UPE resin as well as those of the cured resinitself were investigated. It was found that the degree of unsaturation of the resins was the most importantproperty affecting the thermal and mechanical properties. The cured unsaturated polyester resin or polymermortar made with resins of higher degree of unsaturation showed higher glass transition temperatures,compressive strength, or higher flexural modulus and lower flexural strength, compared with those made withresins of lower degree of unsaturation. Such properties were interpreted in terms of unsaturation, crosslinkdensity, and chain flexibility of the resin molecules.

Keywords: mechanical properties, polymer mortar, unsaturated polyester resin, recycled PET, degree ofunsaturation, glass transition temperature.

1Introduction

Polymer concretes show excellent mechanical properties and chemical resistance compared with conventionalcement concretes. Polymer concretes can be cured quickly by the use of curing agents. Thus, the applications ofpolymer concretes are being increased. One of the popular polymers for polymer concretes is unsaturated polyester(UPE) resin. The properties of UPE resin can be modified by changing its molecular features. For the synthesis of theresin, phthalic anhydride or isophthalic acid as well as maleic anhydride can be employed to modify the mechanicalproperties or hydrothermal resistance. Terephthalic acid which is also used for the synthesis of poly ethyleneterephthalate (PET) enhances the thermal resistance of the cured UPE resin. However, the synthesis of unsaturatedpolyester resin from terephthalic acid is difficult. One method to synthesize unsaturated polyester from terephthalicacid is the use of recycled PET.

PET is useful polymer used for fiber, film, and plastic containers such as carbonated beverage bottles. Recently,the recycling of polymers such as PET after use is attracting the attention of many researchers aware ofenvironmental problems and wishing to find ways to save earth resources. Previous studies showed that unsaturatedpolyester resins can be economically prepared from recycled PET and the resins may be useful for resin concretes(14). However, there is little information on the molecular features of the UPE resins. Thus, we synthesized variousUPE resins from PET. Especially, the PET content, chain flexibility and degree of unsaturation of the resins weresystematically varied and the effects of those variables on the mechanical properties of the cured resins and polymermortars made therefrom were studied.

Disposal and Recycling of Organic and Polymeric Construction Materials. Edited by Y.Ohama. RILEM.Published by E & FN Spon, 26 Boundary Row, London SE1 8HN, UK. ISBN 0 419 20550 0.

2Experimental program

Carbonated beverage bottles made of PET, high density polyethylene (HDPE) base cup, and labels were collected,washed, and crushed into small fragments by using a crusher. The fragments of crushed PET bottles include PET,HDPE, and various labels from which PET fragments can be easily separated by density difference in water. ThePET collected was dried in vacuum oven. Glycolyses of the PET were carried out using propylene glycol (PG) ordipropylene glycol (DPG) at 200C for 8 hours. For the glycolyses of the PET, zinc acetate(0.05% by weight of thePET) was added as a catalyst. Unsaturated polyester resins were prepared by condensation polymerization at 200Cusing the products of glycolyses and dibasic acids such as maleic anhydride and adipic acid. The resins were thendiluted with styrene to make 44% (by weight) styrene solution after the polymerizations and hydroquinone(0.5% byweight of the resin) was added as an inhibitor. Variables in the syntheses of the UPE were the type of glycol, the PETcontent, the molecular weight of the resin, and the degree of unsaturation of the UPE. In Table 1, recipes of UPEresin from recycled PET are given. Hydroxyl values of the resin were measured to check the number average molecularweight of the resin.

In order to cure the resin, methyl ethyl ketone peroxide(MEKPO), 1 wt.% of the resin, was added as an initiatorand cobalt acetate, 0.5 wt.% of the resin, was also added as an accelerator of the cure. Glass transition temperatures(Tgs) of the cured resins were measured by employing differential scanning calorimeter (DSC: DuPont Thermalanalyzer 2000). About 10 mgs of samples were heated in DSC in nitrogene gas environment at 10C/min to measureTgs of the samples. Mechanical properties of the cured resin were measured by employing universal testing machineat room temperature (25C). Polymer mortars (PM) were prepared with the UPE resins, calcium carbonate, andaggregates. Mix formulations of the polymer mortar is given Table 2. Mechanical properties of the polymer mortarwere also measured by employing universal testing machine.

Table 1. Recipes (by molar ratios) for preparation of unsaturated polyester resin from recycled PETSample Code Recycled-PET Propylene glycol Dipropylene glycol Maleic anhydride Adipic acid

A-1 1.4 1.4 - 1.0 -A-2 1.2 1.4 - 1.0 -A-3 1.0 1.4 - 1.0 -A-4 0.8 1.4 - 1.0 -A-5 0.6 1.4 - 1.0 -B-1 1.2 1.2 - 1.0 -B-2 1.0 1.2 - 1.0 -B-3 0.8 1.2 - 1.0 -C-1 1.2 1.1 - 1.0 -C-2 1.0 1.1 - 1.0 -C-3 0.8 1.1 - 1.0 -D-1 1.2 - 1.2 1.0 -D-2 1.0 - 1.2 1.0 -D-3 0.8 - 1.2 1.0 -B-31 0.8 1.2 - 0.95 0.05B-32 0.8 1.2 - 0.90 0.10B-33 0.8 1.2 - 0.85 0.15B-34 0.8 1.2 - 0.80 0.20

Table 2. Mix formulation for polymer mortar

Material Weight ratios

Unsaturated polyester resin 15Calcium carbonate 15Aggregate 70

MECHANICAL PROPERTIES OF POLYMER MORTAR 3

3Results and Discussion

In Table 3, the hydroxyl values and the number average molecular weights of the resins are summarized. Numberaverage molecular weights of the resins were found to be dependent on the stoichiometry of the reactants as weexpected to be.

In Fig.1, Tgs of the cured resins depending on the PET content of the reins are shown. It is observed that Tgs ofthe resins decrease as the PET contents of the resins are increased. Even though the introduction of PET is expectedto increase chain rigidity of the resin molecules, it results in decrease of unsaturation and crosslink density of theresin. Thus, the decrease of the Tg as PET content is increased in the resin is attributable to the decreased crosslinkdensity. It is of interest to note that Tg of the resin made from glycolyses products using PG is higher than that of theresin made from glycolyses products using DPG. It is also observed that the higher are the molecular weights of theresin, the higher, Tgs of the cured resin. It seems that Tgs of the cure resins are determined mainly by unsaturationof the resin.

Table 3. Hydroxyl values and number average molecular weights of the UPE resins prepared

Sample Code Hydroxyl value (mg KOH/g) Number average molecular weightA-1 95.02 1178.76A-2 97.05 1154.10A-3 110.10 1017.26A-4 122.51 914.20A-5 146.64 763.8B-1 76.08 1472.13B-2 75.58 1481.87B-3 75.43 1484.82C-1 55.09 2033.04C-2 50.05 2237.76C-3 72.07 1553.90D-1 64.21 1744.28D-2 63.65 1759.60D-3 66.59 1582.80B-31 80.75 1387.08B-32 87.96 1273.30B-33 81.39 1376.05B-34 77.65 1442.37

In Fig. 2 and Fig. 3, flexural strength and flexural modulus of the cured resin depending on the PET content areshown. It is observed that flexural modulus of the cured resin made from glycolyses product using PG is higher than

Fig. 1. Tgs of the cured UPE resins depending on the PET content in the resin: A-series; B-series; C-series; ( )D-series.

4 SOH, PARK AND LEE

that of the cured resin made from glycolyses products using DPG, while flexural strength of the cured resin showedopposite trend. It is speculated that the cured resins made from glycolyses products using DPG have more flexiblechain and flexural modulus are low compared with the cured resin made from glycolyses products using PG.However, ultimate strength of the cured resin made from glycolyses products using DPG is superior to the curedresin made from glycolyses products using PG due to possibly higher ultimate strain. It is of interest to note thatflexural strength of the cured resin made from glycolyses products using PG decrease as PET content in the resin isincreased. As we noted in Fig. 1, higher PET content implies lower unsaturation of the resin and lower crosslinkdensity of the cured resin. Thus, the decrease of flexural strength with PET content may be attributable to lowerunsaturation and lower crosslink density.

In Fig. 4 and Fig. 5, flexural modulus and flexural strength of the cured resin depending on the adipic acid contentare shown. It is found that flexural modulus of the cured resin decreased as the adipic acid content in the resin wasincreased. Introduction of adipic acid instead of maleic anhydride implies decrease of unsaturation of the resin. Itseems that the decrease of flexural modulus resulted from decreased crosslink density due to lower unsaturation. It isof interest to note that flexural strength, on the contrary, tends to increase as the adipic acid content is increased. It isspeculated that the cured resins of higher adipic acid content have more flexible chain and the flexural modulus arelow compared with that of the cured resin of lower adipic acid content relatively. But, ultimate strength of the curedresin of higher adipic acid content is superior to the cured resin of lower adipic acid content due to possibly higherultimate strain.

In Fig. 6 and 7, changes of compressive strength and flexural strength of PM depending on styrene monomer(SM)of the various resins are given. It is observed that the mechanical properties of the PMs were not affected by the SMcontents so much. However, it is of interest to note that the compressive strength of PM prepared with the UPE madefrom recycled PET using DPG is lower than that of PM prepared with the UPE resin made from recycled PET usingPG while the flexural strength of PM prepared with the UPE made from recycled PET using DPG is higher than thatof PM prepared with the UPE resin made from recycled PET using PG. It is speculated that the UPE resin moleculemade from PET using DPG is more flexible than the UPE resin molecule made from PET and PG and the

Fig. 2. Flexural modulus (FM) of the cured UPE resins depending on the PET content in the resin: B-series; D-series.

Fig. 3. Flexural strength (FS) of the cured UPE resins depending on the PET content in the resin: B-series; D-series.


phenomena observed in Fig.6 and 7 are due to the different molecular flexibilities and crosslink densities of theresins as in Fig. 5.

In Fig. 8, changes of compressive strength of the PM depending on the adipic acid content in the resin are given. Itis observed that the compressive strength of the PM decreased as the adipic acid content is increased. The increase ofadipic acid in the UPE resin results in the decrease of the degree of unsaturation of the resin. The decrease ofcompressive strength of PM as the adipic acid content is increased is attributable to the decrease of crosslink densityof the resin because of the decreased degree of unsaturation. In Fig. 9, changes of flexural strength of the PMdepending on the adipic acid content in the resin are given. It is observed that the flexural strength of the PMincreased as the adipic acid content is increased. The increase of flexural strength of PM as the adipic acid content isincreased is also attributable to the decrease of crosslink density of the resin, increased molecular flexibility, andpossibly increased ultimate strain.

Fig. 4. Flexural modulus(FM) of the cured UPE resins depending on the adipic acid (AA) content in the resin.

Fig. 5. Flexural strength(FS) of the cured UPE resins depending on the adipic acid (AA) content in the resin.

Fig. 6. Compressive strength (CS) of the PM from different UPE depending on the styrene monomer (SM) content in the resin: B-1; B-2; B-3; D-1; ( ) D-2; D-3.

6 SOH, PARK AND LEE

4Conclusion

Various UPE resins based on recycled poly ethylene terephthalate(PET) were prepared and the properties of thepolymer mortar made with the UPE as well as those of the cured resin itself were investigated. It was found thatdegree of unsaturation of the resins was the most important property affecting thermal and mechanical properties ofthe cured resin and PM. The cured unsaturated polyester resin or polymer mortar made from resins of higherunsaturation, i.e., less PET content or adipic acid content in the resin, showed higher glass transition temperatures,

Fig. 7. Flexural strength (FS) of the PM from different UPE depending on the styrene monomer (SM) content in the resin: B-1; B-2; B-3; D-1; ( ) D-2; D-3.

Fig. 8. Compressive strength (CS) of the PM depending on the adipic acid (AA) content in the resin of different SM content (wt.%):40; 44; 48.

Fig. 9. Flexural strength (FS) of the PM depending on the adipic acid (AA) content in the resin of different SM content (wt.%):40; 44; 48.


compressive strength, or higher flexural modulus and lower flexural strength. Such properties could be interpreted interms of unsaturation, crosslink density, and chain flexibility of the resin molecules.

5References

1. Pearson, W., Emerging Technologies in Plastics Recycling, Andrews, G.D. and Subramanian, P.M. (1992), Edt., Chapter1, ACS Symposium Series 513, ACS, Washington D.C.

2. Rebeiz, K.S., Iyer, V.S., Fowler, D.W. and Paul, D.R. (1990), Proceedings of 48th Annual Technical Conference(ANTEC90).

3. Schneider, J.B., Ehrig, R.J., Brownell,G.L. and Kosmack, D.A. (1990), Proceedings of 48th Annual Technical Conference(ANTEC90).

4. Rebeiz, K.S., Fowler, D.W. and Paul, D.R., (1992), Emerging Technologies in Plastics Recycling, Andrews,G.D. andSubramanian, P.M. Edt., Chapter 1, ACS Symposium Series 513, ACS, Washington D.C.

8 SOH, PARK AND LEE

2PROPERTIES OF PLAIN AND REINFORCED POLYESTER

CONCRETES MADE WITH RECYCLED PETK.S.REBEIZ

Department of Civil and Environmental Engineering, Lafayette College, Easton, Pennsylvania,USA

D.W.FOWLERDepartment of Civil Engineering, The University of Texas at Austin, Austin, USA

Abstract

Recycled poly (ethylene terephthalate), PET, plastic waste can be used to produce unsaturated polyester resins.The PET waste is typically found in used beverage bottles that are collected after use in many localities.Research at the University of Texas investigated the use of suitable unsaturated polyester resins based on recycledPET for the production of polymer concrete (PC) materials. The properties and structural behavior ofunreinforced and steel-reinforced PC materials using resins based on recycled PET were found to becomparable to those obtained with PC materials using virgin resins. Resins based on recycled PET can alsorelatively easily be altered to achieve a wide variety of properties and performances in the PC. Anexperimental design also showed that the effect of the level of PET in the resin did not adversely affect theneat resin and the PC mechanical properties. Resins based on recycled PET help in decreasing the cost of PCproducts, saving energy, and alleviating an environmental problem posed by plastics waste.

Keywords: Polymer concrete, polyester, polyethylene, recycled materials

1Introduction

The high cost of resins used in the production of polymer concrete (PC) makes the material expensive relative to cement-based materials. Not surprisingly, a recent survey ranked lower cost resins as the most important future need for PC[1]. Recently, some work has been done on the production of unsaturated polyester resins based on recycled poly(ethylene terephthalate), PET [2]. The PET wastes are typically found in used beverage bottles, and many states havepassed legislation to collect and recycle these bottles. If specially formulated, the unsaturated polyester could be usedin the production of PC [3].

Unsaturated polyesters based on recycled PET might be a potentially lower source cost of resins for producinguseful PC based-products. A main advantage of recycling PET in PC is that the PET materials do not have to bepurified, including removal of colors, to the same extent as other PET recycling applications (such as carpets andfiberfills), which should facilitate the recycling operation and minimize its cost. The recycling of PET in PC couldalso help save energy and allow the long term disposal of the PET waste, an important advantage in recyclingapplications. The objective of this paper is therefore to report on investigations of the important properties and behaviorof PC using resins based on recycled PET.


2Materials

PET consists of repeating ethylene glycol and terephthalic acid molecules connected together through ester linkages.For the production of unsaturated polyester, the PET molecules are converted into low molecular weight oligomersby glycolysis in the presence of a transesterification catalyst. These oligomers are then reacted with unsaturateddibasic acids or anhydrides to form unsaturated polyester resins [3]. A variety of other chemicals may also be usedduring the production process to give the resin some specific properties such as flexibility or rigidity.

Phthalic anhydride or isophthalic acid is typically used in the formulation of conventional unsaturated polyester.Virgin terephthalic acid is not usually used in the production of unsaturated polyester because it is expensive andpossesses a high melting point, which presents difficulties in synthesis. Conversely, recycled PET is effective inincorporating terephthalic functionality into the backbone of a polyester resin [4] [5]. Terephthalic-based polyestersexhibit more linear properties than isophthalic or orthophthalic-based polyesters when the polymerization reactionwith typical glycols and acids occurs because of the location of the carboxyl groups on the benzene ring of phthalicacid. Terephthalic, isophthalic, and orthophthalic-based polyesters have their carboxyl groups in the para, meta, andortho position of the benzene ring, respectively. The degree of linearity, in descending order, results from the para, meta,and ortho-based structures. Therefore, the more linear molecular structure of terephthalic-based polyester resins, ascompared to isophthalic or orthophthalic based-polyesters, allows the cross-linking reaction to be more accessiblewhen free radical polymerization takes place upon final curing, thus producing a more uniformed and structuredcross-linking matrix with a higher degree of strength, stiffness, and toughness. Another advantage of using recycledPET in making unsaturated polyesters, as compared to using virgin materials, is that it takes about 50% shorterprocessing time to produce a polyester resin with a certain molecular weight and acid number [3].

The experimental unsaturated polyester resins used in this study were supplied by several chemical companiessince the PET chemical conversion into unsaturated polyester could not be done at the University of Texaslaboratories. These resins were prepolymers with high viscosity. They were therefore diluted with styrene to reducetheir viscosity and allow their further cure to a solid (polymer) upon the addition of suitable free radical initiators andpromoters. The typical styrene content varied between 30 to 40% of the total resin weight, and viscosities were in therange of 100 to 1000 cps.

3Mix Design

The PC mix design, optimized for workability, strength, and economy, was 10% resin, 45% pea gravel (3/8-in./10-mm), 32% sand (fineness modulus of 3.25), and 13% fly ash (type F). The gravel and sand were oven-dried for aminimum of 24 hours at 260F (127C) to reduce their moisture content to less than 0.5% by weight, thus ensuringgood adhesion between the polymer matrix and the aggregates. Fly ash was already obtained dry from the supplierand therefore did not need to be oven-dried. The use of fly ash greatly improved the workability of the fresh mix andthe strength of the hardened material. It also helped produce PC specimens with very smooth surfaces. One percent,by weight of resin, of methyl ethyl ketone peroxide initiator (9% active oxygen) and 0.1%, by weight of resin, of cobaltnaphthenate promoter (12% solution) were added to the resin immediately prior to its mixing with inorganicaggregates. The PC mixing procedure followed the Polymer Concrete Test Method 1.0 of the Society of PlasticsIndustry [6]. The age at testing of the specimens was three days, unless otherwise specified, although the specimenscould have been tested much sooner.

4Testing

The compression test used 3-in.6-in. (7.6-cm15.2-cm) cylinders. The specimens were tested in a hydraulic loadmachine at a constant loading rate of 10,000 lbs/min (4,500 kg/min). Electrical strain gages were bonded to thespecimens and connected to an automated data acquisition system in a full-bridge configuration. Flexural specimensused 2-in.2-in.12-in. (5.1-cm5.1-cm30.5-cm) beams. The beams were loaded in third-point loading, at auniform rate of 500 lbs/min (230 kg/min).

Bond strength between PC overlays and portland cement concrete substrate was measured using the pull-out testmethod [7]. The tensile bond test is illustrated in Fig. 1. Specimens were thin overlays, about 1/2-in. (1.3-cm) thick,cast directly (without the use of a primer) on sandblasted portland cement concrete slabs. Circular grooves (4-in./10.8-cm diameter) were cored through the overlays and into the portland cement concrete substrate. Circular steel disks

10 REBEIZ AND FOWLER

were then bonded to the sandblasted overlay at the cored locations using a strong epoxy. The disks were then pulledout in direct tension to determine the type and magnitude of the bond failure. The mix design used in making theportland cement concrete substrate was designed to achieve a compressive strength of 5000 psi (34.5 MPa) with theuse of air entraining agents.

The Duponts method was used to measure shrinkage strains [3]. Specimens consisted of 3-in.3-in.12-in. (7.6-cm7.6-cm30.5-cm) beams cast in Teflon-lined molds. The molds were wrapped in a plastic sheet to reduce theeffect of ambient temperature changes on the plastic shrinkage readings. Immediately after mixing and placing thematerials in the molds, the shrinkage measuring device was carefully inserted into the fresh PC mix to recordshrinkage strains for different time intervals. The shrinkage device consists of a horizontal rod to which tworemovable angles were attached. One angle was fixed while the other was free to move on roller bearings. A directcurrent differential transformer, attached to the rod, was used to record the longitudinal displacement induced byshrinkage. PC peak exotherms were measured by inserting thermocouples inside the shrinkage specimens andconnecting them to a digital temperature indicator.

The thermal expansion test used 3-in.6-in. (7.6-cm15.2-cm) cylinders. Electrical strain gages werelongitudinally bonded to the specimens at mid-height and on opposite sides using a special epoxy system insensitiveto high temperatures (other epoxy systems showed improper behavior beyond 130F (54.4C)). The strain gageswere then connected to a switch and balance unit in a full-bridge configuration. A piece of fused quartz with a knowncoefficient of thermal expansion was used as the compensating arm of the full-bridge circuit. The specimens weresubjected to thermal cycles beginning at room temperature. The temperature was increased to 162F (72.2C),decreased to 10F, and then returned to room temperature. Strain and temperature readings were taken inincrements of 10F (5.6C). For each of the increments, the specimens were left at a constant temperature for aminimum of eight hours to ensure thermal stabilization before the strain and temperature readings were taken.Thermocouples, attached to the surface of the specimens and connected to a digital temperature indicator, were usedto monitor specimen temperatures.

Creep specimens consisted of 3-in.6-in. (7.6-cm15.2-cm) cylinders tested in uniaxial compression using ahydraulic spring-loaded creep frame. During testing, cylinders were aligned on top of each others to ensure uniformstress in all of them. Electrical gages were bonded to the specimens at mid-height using epoxy and then connected toan automated data acquisition system in a full-bridge configuration. Electrical strain gages were also attached todummy or control specimens that were left unloaded to correct for non-creep related deformations such as shrinkageof the adhesive used to attach the strain gages, springs decompression in the loading frame, or ambient temperaturechanges. Since temperature changes of plus or minus 2F (1.1C) could significantly affect the creep readings, thespecimens were enclosed in an insulating Styrofoam box to ensure that the temperature was maintained at 75F (23.9C) throughout the testing period.

Rectangular beams, reinforced in tension with longitudinal steel bars, were tested for their flexural behavior. Atypical reinforced flexural beam is shown in Fig. 2. The reinforcing steels were Grade 60 deformed bars conformingto ASTM Standard A615. The beams were simply supported and two equal concentrated loads were applied at thethird points of the span. The shear span-to-depth ratio was 4.0. The two outer portions of the flexural beams wereover-reinforced with vertical closed stirrups to prevent a shear mode failure. Vertical stirrups were #3 Grade 60deformed steel bars spaced 3-in. (7.6-cm) apart (high strength wire was used to securely tie the stirrups). Each stirrupwas rectangular in shape and was closed by welding its ends together. Electrical strain gages were bonded to thereinforcing steel and to the PC at various levels and connected to a data acquisition system. The vertical deflection ofthe beams was measured using linear transducers. The beams were loaded to failure with strains and deflectionsrecorded for each load level.

5Properties of PC Using Resins Based on Recycled PET

The PC mechanical properties using various unsaturated polyester resins based on recycled PET are shown inFigs. 3 to 6. Each value in these figures represents the average value of two specimens. The different PC systemswere made with different resins using different formulations. The wide range of properties encountered with PCusing resins based on recycled PET enable these materials to be used in various applications where differentproperties are desirable. For example, PC with high strength and modulus can be used in making precast machinebase components. Conversely, PC with low modulus and good bond strength to portland cement concrete can beused in the repair of pavements and bridges. The properties of PC made with resins using recycled PET arecomparable to those obtained with PC using virgin materials and tested under the same conditions at the University ofTexas.

PLAIN AND REINFORCED POLYESTER CONCRETES 11

The failure of PC in compression was violent. Compression cylinders would shatter violently and the remainingcore of the cylinders had either a cone shape or a near vertical failure surface. Flexural beam specimens also failed ina violent manner as a tensile crack developed in the zone of maximum moment near mid-depth. The specimens werebroken into almost two identical pieces and the failure surface was near vertical. The tensile bond strength betweenthe PC overlays and the portland cement concrete substrate was found to be strongly dependent on the type of resinused. In overlay or repair applications, it is usually desirable to have tensile bond failures occurring in the portlandcement concrete substrate rather than at the interface between the two materials.

A typical stress-strain curve in compression for two PC systems, one using a flexible resin and the other using arigid resin, is shown in Fig. 7. PC made with a flexible resin exhibits lower modulus, higher ductility, and moretoughness than the PC made with a rigid resin. In precast components, PC should be based on rigid resins. In overlayapplications, PC should be based on flexible resins capable of stretching when subjected to large thermal ormechanical movements. The stress-strain behavior and the ultimate compressive strength of PC using resin based onrecycled PET are comparable to those obtained with PC using virgin resins [8]. It can also be observed that theultimate compressive strain of PC is much larger than the one corresponding to portland cement concrete.

A typical shrinkage and exotherm curve for PC is shown in Fig. 8. Most of the shrinkage strains in PC took placewithin the first eight hours after mixing and stopped after 24 hours. It is also noted in the figure that most of theshrinkage took place after the occurrence of the peak exotherm. Shrinkage is important in many PC applications. Inprecast components, low shrinkage is important because excessive shrinkage strains may significantly affect thedimension of these structures, thus making their demolding, assembly, or use more difficult. In overlay applications,relatively low shrinkage is desirable because studies have reported that excessive shrinkage strains may causedelamination between the overlay and the substrate [9] [10].

A typical thermal expansion curve for PC is shown in Fig. 9. The thermal expansion is important when PC is usedin conjunction with other materials such as steel or portland cement concrete since the coefficient of thermalexpansions of PC is at least twice as high as those corresponding to steel or cement concrete. Hence, changes intemperature in the composite structure will create shear stresses at the interface between the two materials that mayeventually cause deterioration in the structure.

A common problem encountered with PC systems used in precast components is excessive creep deformationunder service conditions. Creep takes place in PC as the result of molecular movement in the viscoelastic resinbinder. Therefore, variations in time and temperature significantly affect the PC creep behavior. A typical PC creepcompliance (or strain per uniaxial unit sustained stress) and Poissons ratio are plotted versus time in Fig. 10. Thestress intensity ratio (which is the ratio of the applied compressive stress to the ultimate compressive strength) usedin this test was 20%. A stress intensity ratio of 20% was chosen to avoid complications resulting from nonlinearviscoelastic behavior and because PC is usually designed with a high safety factor. The application of larger loadlevels would also have been more difficult because of the high strength of PC [11]. Previous creep studies with PCdetermined that excessive creep deformation and catastrophic failure often occur when the creep stress intensity ratioexceeds about 50% [12]. More than 20% of the final creep for PC took place within one day and more than 90% ofthe final creep took place within six days. The specific creep (which is the creep strain divided by the sustainedstress) for PC was 199.0 /ksi (1372 /MPa) after 95 days, which is comparable to what was observed with otherPC systems using virgin resins [13]. The PC creep strain is higher than the one corresponding to portland cementconcrete. It should be noted however that different conditions affect the creep behavior of polymer composites andcement-based materials. The creep behavior of polymer composites is sensitive to temperature variations while thecreep behavior of cement-based materials is sensitive to humidity changes. It is also noted in Fig. 10 that thePoissons ratio of PC, measured during the compressive creep stress, increased by about 26% during the three monthtest period. This time dependency of the PC Poissons ratio needs to be taken into consideration in the analysis ofstructural elements.

6Effect of Level of PET on Strength Properties

A D-optimal experimental design was developed to determine the effect of recycled PET as a raw component inunsaturated polyester resins [14]. This study was done on several resins made with the same basic formulation butwith the percent PET and glycol type as the only variables. The three different glycols that were used in the digestionprocess of the recycled PET were ethylene glycol, diethylene glycol, and a combination of ethylene anddiethylene glycol. These three different glycols will be referred to as glycols 1, 2, and 3 respectively. Unsaturatedpolyester resins were synthesized with a low PET concentration of 15% by weight and a high PET concentration of


40% by weight of the alkyd portion portion of the resin. The D-optimal experimental design consisted of eightunsaturated polyester resin preparations with two replicates.

The effects of recycled PET on the tensile and flexural strengths of the neat resins (cured resins without the use ofaggregates) are shown in Figs. 11 and 12, respectively. The neat resins were produced and tested according to ASTMprocedures [15]. The tensile strength of the neat resin increases with increasing amount of PET for glycols 1 and 2,while it remains almost constant for glycol 3. The tensile strength of resins using glycol 3 is the highest, followed byresins using glycols 1 and 2, respectively. The flexural strength of all neat resins increases with increasing amounts ofPET. The flexural strength of resins using glycol 3 is highest, followed by resins using glycol 1, and then resins usingglycol 2.

The effects of percent PET and glycol type on the PC compressive and flexural strengths are shown in Figs. 13and 14, respectively. The compressive strength of PC using resins made with glycols 1 and 2 increases significantlywith increasing PET, while it increases very slightly for PC using resins made with glycol 3. The compressivestrength of PC made with resins using glycol 3 is the highest, followed by PC made with resins using glycol 1, andthen PC made with resins using glycol 2. The flexural strength of PC made with resins using glycols 1 and 3increases with increasing PET, while it decreases for PC made with resins using glycol 2. At a low PETconcentration of 15%, all systems are comparable in flexural strength. At a high PET concentration of 40%, theflexural strength of PC made with resins using glycol 1 is the highest, followed by PC made with resins using glycol3, and then PC made with resins using glycol 2.

Fig. 1. Pull-out Bond Test

Fig. 2. Reinforced PC Flexural Beam


7Flexural Behavior of Reinforced PC

The effect of the tensile steel reinforcement ratio, , on the load-deflection and moment-curvature responses of PCbeams is shown in Fig. 15. The moment was computed from the applied loads by statics while the correspondingcurvature was calculated from the strain distributions. It is noticed that the load-deflection and moment-curvatureresponses are very similar in terms of shape. In the first stage of loading, a linear relationship existed between themoment (or load) and curvature (or deflection). This proportional limit stage ended with the formation of a majorvertical flexural crack and the resulting change in slope and decrease in stiffness.

The cracking patterns for steel-reinforced flexural PC beams were similar and generally typical to those observedin steel-reinforced portland cement concrete. However, PC exhibited more cracks that were more uniformly spacedthan what would be observed with portland cement concrete with the same reinforcement ratio, thus indicating alarger bond strength between PC and steel than between portland cement concrete and steel. The first noticeablecracks were flexural cracks that originated in the tension zone at mid-span between the two point loads andpropagated vertically toward the compression zone with increasing loads. The second type of cracks observed in thebeams were flexural-shear cracks that originated in the shear span. The initiation of cracks depended on the tensilesteel reinforcement ratio. The lower the steel ratio, the earlier the visible crack occurred at a lower load. As thereinforcement ratio increased, the number and spacing of cracks decreased.

Fig. 3. PC Compressive Strength

Fig. 4. PC Flexural Strength


Variation of strain over the compression region up to failure for the beams was found to be almost perfectly linear.Failure occurred when the ultimate compressive strain in the PC reached a value of at least 0.005. As the beamsfailed, the compressive concrete piece separated as a V-shape, a phenomenon already observed before with othersteel-reinforced PC systems.

The ultimate flexural strength of steel-reinforced PC using resins based on recycled PET was also compared withother steel-reinforced concrete systems as shown in Fig. 16. The other concrete systems were portland cementconcrete, unsaturated polyester (virgin resin), methyl methacrylate (MMA), polyesteramide resin (PEAR), epoxy,and vinyl ester. It is observed that the flexural strength of PC using resins based on recycled PET is much higher thanthe one corresponding to portland cement concrete and comparable to those obtained with PC systems using virginmaterials. It should be noted that a large portion of the PC internal moment at failure is resisted by the tensile stressesin the concrete, unlike what would be happening with steel-reinforced portland cement concrete.

Fig. 5. PC Compressive Modulus of Elasticity

Fig. 6. PC Tensile Bond Strength


8Conclusions

Resins based on recycled PET can relatively easily be altered to achieve a wide variety of properties andperformances. Resins with high strength and stiffness can be formulated for precast applications, while resins withlow modulus, high elongation at break, and good bond strength to portland cement concrete can be formulated foroverlay applications. The properties of PC materials using resins based on recycled PET are very comparable tothose obtained with PC materials using virgin resins. Potential applications of PC using resins based on recycled PETcan include thin overlays on bridges and floors, repairing concrete bridges and pavements, and the production ofmany precast products such as containers for hazardous wastes, floor drains, electric insulators, bases for large metal-working machines, and building panels.

The effect of the level of PET in the resin did not adversely affect the neat resin and the PC properties. Resinsusing a maximum amount of recycled PET and impurities are desirable because they did not adversely affect thematerials properties while they helped decrease the cost of PC based-products, thus making them more competitive.As more localities are instituting recycling programs, the supply of recycled PET is expected to increase and,consequently, the price of resins based on recycled PET is expected to decrease.

The use of steel bars can be very effective in increasing the strength of PC materials. Compared to steel-reinforcedportland cement concrete, the material is much stronger and more ductile. PC also requires less reinforcement coverfor the tensile reinforcing steel than portland cement concrete because of its inherent high flexural strength, lowpermeability, and excellent chemical resistance. The flexural strength of steel-reinforced PC using resins based onrecycled PET was found to be comparable to other PC systems using virgin resins.

Fig. 7. Typical PC Stress-Strain Curve in Compression

Fig. 8. Typical PC Shrinkage and Exotherm versus Time Curves


Field applications and continuous monitoring of PC materials using resins based on recycled PET would reallydetermine the long term behaviors of these materials under field conditions. Special precautions should be taken incases involving large sustained loads because the viscoelastic nature of the resin binder can result in unreasonablyhigh deformations. Special resin formulations, adequate supports, and/or large safety factors would be advisable inthese instances. Trial testing of the materials is also advisable because it would help overcome problems due toerratic cure or batch to batch inconsistencies of the resins. For applications requiring very high strength, a specialmix using strong aggregates and special reinforcements should be formulated. Future progress in physics andchemistry should allow the economical chemical conversion of other plastic wastes into resins that can be usedeffectively in the production of new PC systems with improved properties that will extend their use in engineeringand structural applications even further.

Acknowledgement

The authors acknowledge the support for this research from the Advanced Research Program of the Texas HigherEducation Coordinating Board.

9

Fig. 9. Typical PC Thermal Expansion Curve

Fig. 10. Typical PC Creep Compliance and Poissons Ratio versus Time Curves


References1. D.W.Fowler (1989). Future Trends in Polymer Concrete. ACI SP1168, pp 129 143.2. U.R.Vaidya and V.M.Nadkarni (1987). Unsaturated Polyester Resins from Poly(ethylene terephthalate) Waste. Industrial &

Engineering Chemistry Research, Vol. 26, No. 2, pp. 194198.3. K.S.Rebeiz, D.W.Fowler, and D.R.Paul (1991). Formulating and Evaluating an Unsaturated Polyester Composite made

with Recycled PET. Journal of Materials Education, Vol. 13, No. 5 & 6, pp. 441454.4. J.B.Schneider, R.J.Ehrig, G.L.Brownell, and D.A.Kosmack (1990). Unsaturated Polyesters Containing Recycled PET.

Proceedings of the 48th Annual Technical Conference of the Society of Plastics Engineers, pp. 14621465.5. A.J.DeMaio (1991). Engineering High Performance Thermoset Resins from Poly(ethylene Terephthalate) Thermoplastics.

Proceedings of the 46th Annual Conference of the Composites Institute of the Society of Plastics Institute,pp. 18C/118C/5.

6. Polymer Concrete Test Methods (1987). Composite Institute of the Society of Plastics Industry.7. Use of Epoxy Compounds with Concrete (1979). ACI Committee 503 Report.

Fig. 11. Effect of Level of PET on Tensile Strength of Neat Resins

Fig. 12. Effect of Level of PET on Flexural Strength of Neat Resins


8. C.Vipulanandan, N.Dharmarajan, and E.Ching (1987). Stress-Strain Behaviour of Polymer Concrete Systems. Proceedingsof the Fifth International Congress on Polymers in Concrete, Brighton, England, pp. 165170.

9. A.Al-Negheimish (1988). Bond Strength, Long Term Performance and Temperature Induced Stresses in Polymer Concrete-Portland Cement Concrete Composite Members. Ph.D. Dissertation, The University of Texas.

10. R.Letsch (1987). Polymer Mortar OverlaysMeasurement of Stresses. Proceedings of the Fifth International Congress onPolymers in Concrete, Brighton, England, pp. 119123.

11. K.C.Kyriacou (1991). Accelerated Compression and Flexural Creep Testing of Polymer Concrete. Ph.D. Dissertation, TheUniversity of Texas.

12. M.Hsu and D.W.Fowler (1985). Creep and Fatigue of Polymer Concrete. ACI SP 89, pp. 323341.13. J.Hristova and R.A.Bares (1987). Relation between Creep and Performance of PC. Proceedings of the Fifth International

Congress on Polymers in Concrete, Brighton, England, pp. 99102.14. K.S.Rebeiz (1992). Structural Use of Polymer Composites Using Unsaturated Polyester Resins Based on Recycled Poly

(ethylene Terephthalate). Ph.D. Dissertation, The University of Texas.15. Annual Book of the American Society for Testing Materials (1988).

Fig. 13. Effect of Level of PET on PC Compressive Strength

Fig. 14. Effect of Level of PET on PC Flexural Strength


Fig. 15. Typical PC Moment-Curvature and Load-Deflection Responses


Fig. 16. Ultimate Moment Strength of Various Concrete Systems


3A NEW KIND OF HYBRID RECYCLED POLYMER MORTAR

Y.BAOEast China Hydroelectric Power Investigation & Design Institute, Hangzhou, Zhejiang Province,

ChinaD.P.WHITNEY and D.W.FOWLER

Department of Civil Engineering, The University of Texas at Austin, Austin, USA

Abstract

Polymer mortar is especially suited to applications requiring quick set time, high strength, and lack ofdelamination. Since environmental regulations have become stricter regarding the disposal of the large amountof waste plastic produced, these waste materials have begun to be incorporated in polymer mortar. In this study,tests were performed on a new variety of polymer mortar which combines recycled polyester and polyurethanewith traditional aggregates. The resins studied included RPE (recycled polyethylene), HRPE (a hybrid ofRPE), and RPU (recycled polyurethane). Tests included compressive, tensile, and bond strengths versus theratio of RPU to RPE in the mortar. The results are presented.

Keywords: Polymer concrete, polyester, polyurethane, recycled materials.

1Introduction

A new type of polymer mortar was developed by combining two recycled polymers: recycled polyester and recycledpolyurethane. The technology of recycled polyurethane-modified recycled polyester has made possible materials thatcombine the flexibility, adhesion, and expansion of polyurethane, and the quick set time, high strength and lowercost of polyester. The recycled polymer mortar was obtained by mixing these new hybrids, initiator and promoter,with sand and fly ash. This new kind of recycled polymer mortar has excellent bond and tensile strength,compressive strength and lower shrinkage. It exhibits no delamination when used for overlays on concrete subjectedto thermal cycling. The short set time and the fast strength development make this recycled polymer mortar a usefulmaterial for fast repairs of concrete.

Research was conducted on the method of recycling polyurethane, formulation of recycled polyurethane-modifiedrecycled polyester (RPUMRPE) and their mechanical and chemical resistance properties.

2The Recycling of Rigid Polyurethane Foam [1] [2] [3]

The utilization of plastic products has been a vital development in 20th century technology. Along with more andmore plastic wastes being placed into the environment, the problems of disposal and environmental pollution must beovercome. Plastic waste products are very light; they occupy about 7% of the weight of garbage, but they representabout one-fourth of the total volume which requires a large portion of the landfill. Incineration is another disposalmethod, but locating sites for new incineration facilities has led to considerable public opposition. Consequently theecological disposal of plastic products is presently of great concern.


Use of polyurethane foam has been increasing dramatically and with this increase there has also developed aserious problem in disposing of waste foam products. Various approaches have been developed in an effort to reclaimthe waste foam. Flexible polyurethane waste foam generated in production or recovered after use as packagingmaterials can be recycled by shredding and mixing with a polyurethane binder to make carpet underlay. The rigidfoams are highly cross-linked materials, and at present the disposal methods are landfill and incineration. Neithermethod is acceptable because long-range ecological goals dictate zero pollution as well as conservation of rawmaterials. Therefore efficient recycling methods are mandatory in the years to come.

Three methods of recycling of polyurethane foam have been proposed: hydrolysis, pyrolysis and glycolysis.1. Hydrolysis:

In hydrolysis, a complex mixture of polyol and polyamine is obtained. The method of separation is required, but it isvery difficult and not feasible.

2. Pyrolysis:

This process gives a more complex mixtures of chemical compounds, useful only as gaseous or liquid fuels.3. Glycolysis:

This process can achieve a recovery of scrap foam into a polyol mixture, which can be used to produce polyurethanewithout the need for purification. This method requires low capital investment and is simple enough to cope withvariations in the mix scrap foam. The resulting recycled polyol can be incorporated with polyisocyanate to producerecycled polyurethane which can be used to modify recycled polyester mortar made with either virgin or recycled resins.

The glycolysis method of recycling polyurethane foam consists of heating scrap foam with glycol or polyol,increasing the solubilizing agent at a temperature of 180 to 196C. The scrap polyurethane is chopped into particlesof relatively small size to reduce the reaction time. The addition of the scrap can be made over a period of time. Theperiod of heating will range from about 5 to 8 hours depending upon the nature of the scrap polyurethane and theglycol or polyol employed. The viscosity of the reactant is mainly controlled by the proportion of scrap polyurethaneto glycol, polyol and increasing-solubilizing agent used. When the reaction is completed, the viscosity and hydroxylvalue will be determined. The procedures are shown in Figures 1 and 2.

The hydroxyl number is very important for the synthesis of polyurethane. It is defined as the number of milligramsof potassium hydroxide equivalent to the hydroxyl content of one gram of the sample. The principle of the analyticalmethod is that the hydroxyl group is esterified with a solution of phthalic anhydride in pyridine. The excess reagentis back-titrated with standard sodium hydroxide solution, and a blank is run on the reagents to determine the amountof anhydride consumed. The phenolphthalein is an indicator for the titrate. Because the color of recycled polyol isdark brown, the faint pink endpoint is not clear, so a potentiometric titrate can be applied.

3Recycled Polymer Mortar from Recycled Polyurethane and Polyster (RPUMRPE) [4]

It is well known that polyurethanes are used for their excellent adhesion, abrasion, toughness, flexibility and ease ofapplication. Polyester also has many outstanding characteristics: low-cost, quick set time, high strength and gooddurability. The combined use of polyurethane and polyester has been studied by many investigators [6]. The highreactivity of polyurethane with active hydrogen-containing groups is conveniently used for modifying. The approachprovides a material with very useful properties. The characteristics of polyurethane are eminently demonstrated whenused in the rubbery region which is in contrast to the properties of unsaturated polyester resin, which in generallyused in the glassy region. Polymerized polyurethane-modified polyester has a marked increase in toughness thatcombines flexibility and rigidity and also exhibits a great improvement in bond strength as well as reduced shrinkage,which is very helpful in delamination resistance.

In this work, polyurethane was made from recycled polyol obtained from rigid foam and polyisocyanate. The rawmaterial for the polyester resin was recovered from scrap PET [5], then depolymerized using different amounts ofethylene, propylene glycol into glycolized monomer and oligomer. These glycolized products were reacted withmaleic or terephthalic acid to obtained recycled polyester. The proportion of recycled polyurethane to recycledpolyester was varied ranging from 1:1, 1:2, 1:2.5, and 0:1. The combined resins were then mixed with initiator,

A NEW HYBRID RECYCLED POLYMER MORTAR 23

promoter, sand and flyash to yield recycled polymer mortar. The tensile strengths of the mortar made from thevarious combination of resin are as follows:

Table 1. Tensile Strength of RPUMRPE Mortara

Specimens Tensile Strength, psi (MPa)Ratio of Polyurethane to Polyester Resin

1:1 1:2 1:2.5 0:1

1 1586 (10.93) 1722 (11.88) 1540 (10.62) 1560 (10.76)2 1684 (11.61) 1702 (11.74) 1770 (12.21) 1580 (10.90)3 1540 (10.62) 1715 (11.83) 1704 (11.75)Avg. 1603 (11.06) 1713 (11.81) 1671 (11.52) 1570 (10.83)a Measured at 7 days

This tensile strength was measured using dog bone specimens with a 1 in.1 in. (25 mm25 mm) crosssection.The results of Table 1 show that RPUMRPE mortar exhibits an excellent tensile strength of about 1700 psi (11.72MPa) after 7 days when the ratio (RPU:RPE) ranges from 1:2 to 1:2.5. It can be seen that recycled polyurethaneimproves the tensile strength of the recycled polyester.

4Selection of Initiator and Promoter

Several tests were conducted to identify the best initiator-promoter system. It is well known that expansion occursduring the polymerization of polyurethane. The slower the curing rate, the larger the expansion and the lower thestrength that will result. Rapid curing can result in greater strength because the fast curing time limits the extent ofexpansion so that the mortar is more dense. Table 2 shows the effect of the initiator-promoter on tensile strength andexpansion. Expansion was measured on the increase in length of the specimens which were dog bone shaped.

Table 2. Effects of the initiator and promoter on tensile strength and expansion

Initiator (Cumene hydroperoxide), % 0.29 0.58 0.87 1.16Promoter (Cobalt naphthenate), % 0.12 0.23 0.35 0.47Specimens Tensile strength, psi (MPa)1 1100 (7.59) 1175 (8.10) 1275 (8.79) 1275 (8.79)2 1100 (7.59) 1250 (8.62) 1200 (8.28) 1240 (8.55)3 1080 (7.45) 920 (6.34) 1215 (8.38) 1350 (9.31)Avg. 1093 (7.54) 1115 (7.69) 1230 (8.48) 1288 (8.88)Expansion, % 35.8 18.4 9.5 2.5

The amount of initiator and promoter exhibits a significant effect on curing time as well as strength, and thepromoter has a very definite role (Table 3).

The analogous results can also be seen from effect of benzoyl peroxide and cobalt naphthenate in Table 4.Although the amount of benzoyl peroxide was reduced from 1 to 0.87%, the tensile strength was increased becausethe amount of cobalt naphthenate was increased from 0.23 to 0.34%.

The peroxides were used to compare the effect on expansion and tensile strength: methyl ethyl ketone peroxide,cumene hydroperoxide and benzoyl peroxide. Methyl ethyl ketone peroxide is a popular initiator for low temperature,particularly in conjunction with cobalt naphthenate, since it results in fast curing, less expansion and high tensilestrength. In contrast, benzoyl peroxide starts to decompose free radicals at about 122F, therefore, at roomtemperature and with small quantities of cobalt naphthenate, longer curing time, larger expansion and very lowstrength were obtained as shown in Table 5. If more cobalt naphthenate is used, the greater exothermicreaction raises the temperature, and benzoyl peroxide can also provide fast curing and higher tensile strength.Cumene hydroperoxide is a good initiator at room temperature which can combine with cobalt naphthenate to yieldhigher strength. The results of test are shown as Table 5.

The curves for viscosity vs. time (Figures 1 and 2) show that the cure time can be controlled by initiator andpromoter. The viscosity of polyols changes depending on temperature, particularly below 20C.

24 BAO, WHITNEY AND FOWLER

Table 3. Results of The Amount of Initiator and Promoter on Properties

Cumene hydroperoxide, % 0.5 1 1 1Cobalt naphthenate, % 0.07 0.07 0.15 0.23Expansion, % 41.3 25.9 10 3.1Tensile strength, psi (MPa) 870 (6.00) 916 (6.32) 1102 (7.60) 1553 (10.71)

5Typical Properties of Recycled P Polyurethane Modified Recycled cycled Polyester Mortar

(RPUMRPE)Typical properties of RPUMRPE mortar in comparison to the hybrid recycled polyester (HRPE) mortar and recycledpolyester (RPE) are presented in Table 6. The HRPE is hybrid polymer of recycled polyester and polyurethane whichcomes from F2 hybrid resin part A made by Amoco. The RPE is recycled polyester made by Alpha corporation. Thebond, tensile and compressive strength, modulus of elasticity and shrinkage of these three kinds of polymer mortar weremeasured at 4, 8, 12, and 24 hours respectively.

As shown in Table 6, the RPUMRPE possesses excellent properties. Its bond strength is 2 to 4 times higher thanthat of RPE because of the polarity of polyurethane molecules. Its shrinkage is about half of that of RPE due to theexpansion during the polymerization of polyurethane. The tensile strength is also about 1.5 to 2 times greater thanthat of RPE. This kind of polymer mortar can used for rapid repair materials because the strength cevelopment isvery fast as shown in Table 7 and Figures 10 and 11.

Table 4. The Effect of The Amount of Benzoyl Peroxide and Cobalt Naphthenate

Benzoyl peroxide, % 0.58 1 0.87Cobalt naphthenate, % 0.23 0.23 0.34Expansion, % 12.3 11.8 10.6Tensile strength, psi (MPa) 1040 (7.17) 1326 (9.14) 1416 (9.77)

Table 5. RPUMRPE with Various Catalyst Systemsa

Initiator Promoter Expansion, % Tensile Strength, psi (MPa)1% Methyl ethyl ketone peroxide 0.04% Cobalt naphthenate 4 1476 (10.17)1% Benzoyl peroxide 0.04% Cobalt naphthenate 20.7 153 (1.06)1% Cumene hydroperoxide 0.07% Cobalt naphthenate 25.9 916 (6.32)1% Cumene hydroperoxide 0.15% Cobalt naphthenate 10 1102 (7.60)1% Cumene hydroperoxide 0.23% Cobalt naphthenate 3.1 1533 (10.57)0.58% Benzoyl peroxide 0.23% Cobalt naphthenate 12.3 1040 (7.17)1% Benzoyl peroxide 0.23% Cobalt naphthenate 11.8 1326 (9.14)0.87% Benzoyl peroxide 0.34% Cobalt naphthenate 10.6 1416 (9.77)1% Benzoyl peroxide 0.35% Cobalt naphthenate 2 1505 (10.38)a Measured at 7 days

6Thermal Compatibility Test

For the determination of the thermal compatibility, the ASTM C 88478 test method was followed. A layer ofRPUMRPE mortar was applied to a slab of cured and air dried concrete. After the material cured for one week, thesamples were subjected to five cycles of temperature change. In the first cycle, the specimens were placed in theenvironmental chamber at -63F (21.1 1.7C) for 24 hours and then removed to room temperature at 731.8F(231C) for 24 hours. Three beams with 1/2- to 2 inch (12- to 50-mm) overlays and four slab with 1/2-inch (12-mm)overlays were tested. No delaminations were found in the specimens. The direct shear tests were conducted tomeasure the effect of the thermal cycles. The results are shown in Table 8.

Pull-out tests were also conducted to measure the bond strength between the polymer concrete overlay and theportland cement concrete substrate before and after the thermal compatibility test. The results are shown in Table 9.


According to the ASTM C-884-78, delamination of the polymer mortar layer from the concrete test block or thepresence of horizontal cracks in the concrete near the interface shall constitute failure. It is obvious from these resultsthat the RPUMRPE mortar passes the ASTM C-884-78. After thermal cycling, no delamination was found in thespecimens. The failure in all specimens in the shear and pull out tests occurred within the portland cement concretesubstrate. These results depended on the tensile strength of the concrete substrate.

Table 6. The Comparison of Main Properties of Three Polymer Mortar Within 24 hrs.

PROPERTIES TIME, hrs RPUMRPE HRPE RPE

Bond Strength, psi (MPa) 4 455 (3.14) 94 (0.65) 113 (0.78)8 501 (3.46) 162 (1.12) 153 (1.06)12 528 (3.64) 213 (1.47) 182 (1.26)24 535 (3.69) 327 (2.26) 253 (1.75)Tensile Strength, psi (MPa) 4 1288 (8.88) 163 (1.12) 457 (3.15)8 1378 (9.50) 247 (1.70) 636 (4.39)12 1492 (10.29) 383 (2.64) 791 (5.46)24 1540 (10.62) 780 (5.38) 1027 (7.08)Compressive Strength, psi (MPa) 4 7799 (53.79) 1150 (7.93) 6674 (46.03)8 8026 (55.35) 1681 (11.59) 7213 (49.74)12 8134 (56.10) 2235 (15.41) 8209 (56.61)24 8233 (56.78) 3617 (24.94) 8925 61.55)Modulus of Elasticity, 106 psi (103 MPa) 4 1.89 (13.0) 0.0634 (0.437) 1.58 (10.9)8 2.0 (13.8) 0.086 (0.593) 1.67 (11.5)12 2.12 (14.6) 0.196 (1.35) 1.75 (12.1)24 2.37 (16.3) 0.493 (3.40) 1.83 (12.6)Shrinkage, in./in.103 4 3.00 0.25 5.408 3.15 0.80 5.6512 3.28 1.40 5.7524 3.30 2.25 5.80

Table 7. Strength Gain of RPUMRPE

4 hrs 8 hrs 12 hrs 1 day 7 days 14 days 30 days

Compressivestrength, psi(MPa)

7,799 (53.79) 8,026 (55.35) 8,134 (56.10) 8,233 (56.78) 11,153 (76.92)

11,157 (76.94)

11,407 (78.67)

Percentage of30-daystrength

68 70 71.3 72 97 98 100

Tensilestrength, psi(MPa)

1288 (8.88) 1378 (9.50) 1492 (10.29) 1540 (10.62) 1625 (11.21) 1633 (11.26) 1650 (11.38)

Percentage of30-daystrength

78 83.5 90.4 93.3 98.5 99 100

The compressive strength has 68% of the 30 day strength in 4 hours and tensile strength has 78% within 4 hours.

Table 8. Comparison of Shear Strength from Thermal Compatibility Test

Mortar Type Load to Failure, lbs. (N) Shear Strength, psi (MPa) Failure ModeRPUMRPE (Before Thermal Cycling)Specimen 1 13,000 (58,000) 1035 (7.14) PCCaSpecimen 2 12,500 (55,600) 994 (6.86) PCCSpecimen 3 11,000 (49,000) 875 (6.03) PCCAverage 12,166 (54,114) 968 (6.68)


Mortar Type Load to Failure, lbs. (N) Shear Strength, psi (MPa) Failure Mode(After Thermal Cycling)

Specimen 1 12,000 (53,000) 955 (6.59) PCCSpecimen 2 8,900 (40,000) 709 (4.89) PCCSpecimen 3 11,950 (53,150) 951 (6.56) PCCAverage 10,950 (48,710) 871 (6.01)HRPE (Before Thermal Cycling)Specimen 1 14,700 (65,400) 1169 (8.06) PCCSpecimen 2 9,050 (40,250) 720 (4.97) PCCSpecimen 3 12,900 (57,400) 1026 (7.08) PCCAverage 12,216 (54,337) 972 (6.70)

(After Thermal Cycling)Specimen 1 7,600 (34,000) 605 (4.17) PCCSpecimen 2 14,800 (65,800) 1177 (8.12) PCCSpecimen 3 9,900 (44,000) 788 (5.43) PCCSpecimen 4 11,050 (49,150) 879 (6.06) PCCAverage 10,837 (48,203) 861 (5.94)aPCC=portland cement concrete

Table 9. Results of The Tensile Bond Strength From Thermal Comparability Test of RPUMRPE

Load to failure, lbs. (N) Tensile bond strength, psi (MPa) Failure mode(Before Thermal Cycling)

Specimen 1 3,620 (16,100) 288 (1.99) EpoxyaSpecimen 2 3,600 (16,000) 286 (1.97) PCCbAverage 3,610 (16,050) 287 (1.98)

(After Thermal Cycling)Specimen 1 3490 (15,500) 277 (1.91) PCCSpecimen 2 3520 (15,700) 280 (1.93) PCCAverage 3505 (15,600) 278.5 (1.92)aEpoxy resin was used to bond the circular steel disc to the slab.bPortland Cement Concrete

7The Influence of Foam on Permeability

When polyurethane was polymerized in the presence of moisture, some expansion is inevitable. In order toinvestigate the influence of foam on permeability a rapid chloride ion permeability test was conducted in accordancewith AASHTO T-277. Three resin systems: RPUMRPE-1, RPUMRPE-2, and HRPE were used. The permeabilityresults of 12 slices are shown in Table 8. It can be seen that every specimen is impermeable. After 6 hours, thepermeabilities were the same as at the beginning. Although RPUMRPE-2 contains more isocyanate compound andmore expansion than RPUMRPE-1, it still had excellent impermeability which means the pores are closed, and thewater cannot pass through.

8Overlay

Several overlays from 0.5 to 1.0 inch (12 to 25 mm) in thickness were cast on beams from 16 to 65 inches (406 to1650 mm) long for each polymer mortar. Three polymers mortars, RPUMRPE, HRPE, and RPE, were tested. Theywere demolded after one day, and it was found that RPUMRPE and HRPE overlays showed no delamination, but therecycled polyester (RPE) developed a 0.51-mm crack at the interface of the overlay and beam. After 3 months, theRPE overlay separated from the beam. In contrast, the RPUMRPE and HRPE overlays performed well. Two


RPUMRPE overlays on beams were placed outdoors and subjected to sunlight exposure. After 6 months no changehas been observed.

Other overlays of RPUMRPE from 1 to 2 inches (25 to 50 mm) in thickness were cast on beams. They alsoexhibited no delamination, although the shrinkage stresses increased with increased mortar layer thickness. Thismortar shows good compatibility with concrete substrate.

Table 10. Results of Rapid Chloride Permeability Test of RPUMRPE and HRPE

Data on strain gage channel

Time Time Time

Specimen 0 hr 3.5 hrs 6 hrs

1 0.00002 0.00002 0.000012 0.00001 0.00001 0.000013 0.00001 0.00001 0.000004 0.00001 0.00001 0.000005 0.00001 0.00001 0.000016 0.00001 0.00001 0.000017 0.00001 0.00001 0.000018 0.00001 0.00001 0.000009 0.00002 0.00002 0.0000110 0.00001 0.00001 0.0000211 0.00001 0.00001 0.0000112 0.00001 0.00001 0.00001*14 RPUMRPE-1; 58 RPUMRPE-2; 912 HRPE

9Conclusion

Laboratory tests on recycled polyurethane-modified recycled polyester mortar have shown that this is an effectivematerial for making polymer mortar overlays which combines the advantages of both polyurethane and polyester. Thismortar shows higher bond strength, good tensile and compressive strength, lower shrinkage, and impermeability. The1- to 2-inch (25- to 50-mm) thickness mortar overlay exhibited no delamination. Because of the fast development ofstrength, this mortar can be used for rapid repair of concrete structures.

This has particular significance due to the fact that the materials came from recycled plastic wastes. This not onlyalleviates pollution of the environment, but also reduces the cost of the polymer concrete. These two kinds ofrecycled polymer can complement each other to produce excellent properties.

Fig. 1. Viscosity vs. Time for RPUMRPE With Varied Cobalt Naphthenate

Curve 10.23%; Curve 20.15%; Curve 0.1%


References1. Polyether Diols From Urethane Resin Scrap. Organic and Polymer Waste Reclaiming Encyclopedia, p. 341.2. Osamu Kinoshita. Process for Decomposition of A Polyurethane Resin. U.S.P., Vol. 3, p. 530, p. 632.3. F.F.Furilla, W.A.Odinak. Reclaiming Scrap Polyisocyanate Foam with an Aliphitic Diol and A Dialkanol Amine. U.S.P.,

Vol. 3, p. 440, p. 708.4. K.S.Rebeiz, D.W.Fowler, and D.R.Paul (1991). Making Polymer Concrete with Recycled PET. Plastic Engineering, p. 33.5. U.R.Vaidya and V.M.Nadkarai (1987). Unsaturated Polyester Resin Foam Poly(ethylene terephthalate) Waste-Part 1:

Synthesis and Characterization. Ind. Eng. Chem. Res., Vol. 26, pp. 194198.6. K.H. Hsieh, J.S.Tsai, K.W.Chang (1991). Interpenetrating Polymer Network of Polyurethane and Unsaturated Polyester.

Journal of Materials Science, Vol. 26., pp. 58775882.

Fig. 2: Viscosity vs. Time for RPUMRPE With Varied Amount Cumene Hydroperoxide

Curve 1:1%; Curve 2:0.5%

Fig. 3. Viscosity vs. Temperature for Polyol

Fig. 4. Comparison of Bond Strength of Three Resin Mortars


10

Fig. 5. Comparison of Tensile Strength of Three Resin Mortars

Fig. 6. Comparison of Compressive Strength of Three Resin Mortars

Fig. 7. Comparison of Modulus of Elasticity of Three Resin Mortars


Fig. 8. Comparison of Shrinkage of Three Resin Mortars

Fig. 9. The Initial Expansion and Shrinkage of RPUMRPE

Fig. 10. Compressive Strength Development of RPUMRPE


Fig. 11. Tensile Strength Development of RPUMRPE


4UTILIZATION OF WASTE PLASTICS AS AGGREGATE IN

ASPHALT MIXTUREM.YAMADA

Department of Civil Engineering, Osaka City University, Osaka, Japan

Abstract

This paper proposes a utilization of waste plastics in asphalt pavement. Laboratory tests conducted to examineeffects of substituting crushed plastics for a portion of the aggregate of an asphalt paving mixture.

Six samples of waste plastics were prepared for the tests. Four of them were obtained from a size reductionfacility for industrial plastics recycling. The size of the plastics particles was about 2 to 10mm. The other twowere obtained by being separated from domestic wastes collected in two cities and crushed to produce the sizeof 2 to 5 mm particles. These plastics particles were added to an asphalt mixture in quantities from 5 to 10percent of the aggregate volume.

Marshall properties, dynamic stability. bending strength and strain at failure of the asphalt mixtures witheach of the plastics aggregates were compared with those of a conventional asphalt mixture. Results showedthat dynamic stability of asphalt mixture with a plastics aggregate which softened at the mixing temperaturewas higher than the conventional mixture.

Field tests were also carried out to evaluate the constructability and performance of asphalt mixtures withplastics aggregates.

Keyword: paving material, asphalt mixture, waste plastics, recycling, Marshall test, wheel tracking test.dynamic stability, bending test.

1Introduction

Plastic is used widely for various purposes at home and work from its characteristics: inexpensive. moldable. light,strong, hygienic. colorful. etc. But. most of plastic goods are used only for a short time and then thrown away. Weuse and disuse a large quantity of plastics. The amount of plastics supplied in Japan was about ten mililon tons in1990. The amount of plastics discharged was 3.13 million tons as domestic wastes. 2.44 million tons as industrialwastes. and 5.57 million tons in total.

A part of the industrial plastics wastes (about 27 percent in 1987) were reutilized for productions of solid fuel, oil,gas. monomers and so on, A large quantity of the other plastics wastes were disposed of.

Almost all of domestic wastes, which are filled in land after appropriate treatments or incinerated. But. they areunsuitable for the landfill as being persistency in land. When they are incinerated, the heat of combustion damages anincinerator and harmful gases may be caused.


Recycling is the best alternative. Much of industrial post-consumer plastics can be recycled by some methodsbecause they are sorted. Meanwhile, the range of plastics collected from households is enlarged substantially. It isdifficult to recycle unsorted plastics.

Therefore, new technologies for reutilization of unsorted plastics wastes must be developed. This paper proposed autilization of waste plastics in asphalt pavement [1][2]. Significant amounts of domestic plastic waste collected by aself-governing community will be able to be utilized for construction of roads in the community, if this utilizationtechnology is put to practical use.

2A conception of utilization of waste plastics in asphalt pavement

Crushed waste plastics may be utilized as a base materials in road. But, the utilization is unrecommendable, becausethe characters of plastic do not become effective there. It will be desirable that plastics which is organic are usedtogether with an asphalt which is organic.

Waste plastics will be utilized in an asphalt mixture in two ways as follows.

Dissolution in the asphalt to utilize as a portion of the binder Substitution for the crushed stones or sands of the same size in the mixture

The former may be more supportable than the latter. If a proper quantity of an appropriate plastic is dissolved in anasphalt, properties of the asphalt will be modified to become more suitable for road paving. Maybe, there are somesorts of appropriate plastics like that in the wastes. However. the proportion of the appropriate plastics to the allwaste plastics will is not high. The optimum volume of the plastics dissolved in the asphalt to modify properties ofthe asphalt is not high too. Therefore, the former utilization does not spend much waste plastics and it is not aeffective way for the plastics waste reduction.

The latter may spend comparatively much waste plastics become, because they are utilized as aggregate. If thewaste plastics used as aggregate have a good influence upon the properties of asphalt mixture. the latter is an effectiveway for plastics waste reduction.

The particles of crushed plastics will present one of the following three states in a hot asphalt mixture, whereasphalt. filler and aggregate are mixed at 150 to 170C.

1. Very soft and soluble in the asphalt2. Soft and plastic-deformable, but insoluble in the asphalt3. Almost unchanged and only elastic-deformable, of course insoluble in the asphalt

It is probable that there are the three sorts of plastics in wastes which are discarded from households, and among thethree the most numerous are of the second sort.

Plastics of the first sort are soluble in the asphalt at hot-mixing and have the effect of raising the viscosity of theasphalt. But. too high viscosity of the asphalt binder may produce bad effects on the workability at construction andthe flexibility of the asphalt mixture in pavement.

Plastics of the second sort are insoluble in the asphalt and have little effect on the properties of the asphalt, butthey may have some effects on the mechanical properties of the asphalt mixture. The particles of the plastics becomesoft and plastic at hot-mixing for making the asphalt mixture and deform at compaction, in between the aggregateparticles. They become back to hard and elastic upon cooling. The elastic particles in between the aggregate particleswill restrict the movement of the aggregate particles, and consequently the resistance to permanent deformation ofthe asphalt mixture will become higher.

As plastics of the third sort are like aggregate particles, the addition of them will have little influence on themechanical properties of the asphalt mixture, if the percentage of the addition is not too high. When the particles ofplastics are too much or large-sized, the strength of the asphalt mixture will drop. because the particles of plastics aresofter than the particles of the aggregates at even low temperature.

The effect of the second sort plastics is worth notice. It is expected that the effect will avail the improvement ofasphalt mixtures and the utilization of plastics wastes.

34 YAMADA

3Plastics samples and experimental procedures

3.1Plastics samples tested in this study

Six samples of waste plastics were prepared for this study. Four of them were obtained from a size reduction facilityfor industrial plastics recycling. The size of the plastics particles was about 2 to 10 mm. The other two were obtainedby being separated from domestic wastes collected in two cities (see Fig. 1) and crushed to produce the size of 2 to 5mm particles. The sort and properties of them are them are shown in Table 1.

3. 2Making of asphalt mixtures with the waste plastics

The type of asphalt mixture used in this study was a densegraded asphalt mixture, which is one of typical asphaltmixtures in Japan, and the maximum particle size of the aggregates was 13 mm. The asphalt mixture is composed ofasphalt binder, filler and aggregates.

As the asphalt binder, a straight asphalt which complies with the quality requirements specified in JIS K 2207, havinga penetration grade of 60 to 80, was used.

As the filler, a mineral powder produced by crushing a lime stones was used.As the aggregates, crushed sand stones and a river-mouth sand, and crushed waste plastics were used. The plastics

aggregates were substituted for a portion of the aggregates of the same size as them, in quantities from 0 to 20percent of the tatal aggeregate volume.

The design asphlt contents of the asphalt mixtures with the waste plastics were determined by the procedure in theManual for Asphalt Pavement by Japan Road Association where is applied to the conventional asphalt mixtures.

Mixing of the asphalt mixture materials was conducted for 3 minutes at 152 to 157C in a mixer. Compaction ofthe asphalt mixture into a mold was conducted at 140 to 144C with the Marshall test rammer or a roller compactor.

Table 1. Plastic samples tested in this

Documents

Y. Ohama Disposal and Recycling of Organic and Polymeric Construction Materials 1995