Compression and Deformation Performance of Concrete Containing Postconsumer Plastics

Postconsumer plastic chips that cannot be processed for useful applications may end up in a landfill. This constitutes an environmental problem and is considered an additional burden on the already tight landfill space. In this research, plastic chips were used as partial replacement of coarse aggregates in concrete mixtures. The testing program was organized to study the effect of adding plastic aggregates to the concrete in order to reduce the density and gain superior deformation qualities. In this study, plastic aggregates replaced 5, 10, and 15% by mass of coarse aggregates. A total of 198 concrete cubes were made to examine the effect of plastic content and water/cement ratio on the mechanical properties of concrete. The cubes were tested in compression at 1, 7, 14, 21, and 28 days where measurements of deformation were made. The measured load and deformation were used to calculate stress, strain, and modulus of elasticity as related to different plastic content and water/cement ratio. Test results were used to optimize mix design and to establish mathematical relationships between plastic content in the mix and the strength and deformation characteristics of the hardened concrete. Furthermore, digital imaging was employed to scan cross sections of cubes with plastic aggregates to study the orientation of plastic chips in the cube, and to correlate the area of plastics to the increase in durability or the decrease in strength. Test results demonstrated that plastic aggregates are viable in providing the concrete with a high degree of deformability as compared with regular concrete. This characteristic makes the concrete useful in situations where it will be subjected to harsh weather, such as expansion or contraction, or freeze and thaw.