Effect of Using Plastic and Rubber Wastes as Fine Aggregate on Some Properties of Cement Mortar

Abstract

This research describes the production of lightweight cement mortar using four types of fine aggregates including chopped rubber tires, chopped plastic wastes, a mixture from the previous types by 1:1, and a mixture composed from substitution of 10% from the previous type by natural sand. Theuseofthese wastes has rolein getting rid oftheir hugequantitieswhich constitute a fundamentalenvironmental problembecause of the difficulty of itsdegradation.Four, cement to aggregate ratios have been used. They are1:0.5, 1:0.7, 1:1, and 1:1.2 for each aggregate type mentioned above, with changing w/c ratio and superplasticizer content to have a constant flow of about 23%. Also, the effect of curing samples by different methods, including continuous submerge in water, autoclave curing for 3 hours, and carbonation curing by 50% and 100% CO2 at 75oC for 90 minutes, was studied.The results indicated that it is possible to produce lightweight cement mortar, using any type of aggregates mentioned above, with compressive strength satisfying the requirements of clay brick class C of Iraqi Standard, that used in partitions, for a mix proportion of 1:1, except when using chopped rubber tires that need using mix proportion of 1:0.5 to satisfy the strength requirements, where the use of this aggregate type needs higher w/c ratio and superplasticizer content to get the required flow, which leads to lower strength in comparison with the other types. As for chopped plastic aggregate, although it needs lower water and superplasticizer content to get the required flow and strength, care should be taken to balance betweenthe amount of waterand superplasticizer addedto avoidthe possibility of segregation in it. So it was found that using the mixture of chopped plastic and rubber aggregate give the best properties. Results also indicated that using all aggregate typeswith cement: aggregate mix proportion 1:1 satisfy the flexural strength requirements of American Standards for cellulosic fiber insulating boards, and were with thermal conductivity valueslower than that for brick and concrete having density lower than 2000 kg/m3. The results indicated that partial replacement of 10% mixed waste aggregates by normal sand cause increase in strength but in the same time increase density and thermal conductivity for the produced mortar.Results also indicated that curing by autoclave or curing with 50% or 100% CO2 cause increase in the 7 days strength compared with those cured by water but they show almost the same strength at 28 days age.