Incorporating Waste Plastic in Cement-Lime Mortar Mixtures

Abstract

The objective of this research was to evaluate the viability of replacing sand with waste polypropylene plastic in standard cement-lime mortar typical of that used for concrete masonry wall construction. The results of this research indicate that, because of the rough surface texture of the plastic particles that resulted from grinding, the amount of water required to achieve a given mortar flow increased as the percentage of plastic increased. As the amount of water increased, corresponding to higher water-cementitious materials ratios, the compressive strength decreased. To compensate for these effects, higher concentrations of cement and comparatively lower concentrations of sand and plastic were required to meet compressive strength specifications. For a baseline mixture design similar to that used for batch 3 in this research, up to 10 percent of the sand by volume can be replaced with plastic. This mixture design not only exceeded the minimum strength required for a Type N mortar, but it also exhibited levels of durability comparable to those of mortar mixtures not comprising plastic in terms of exposures to a freeze-thaw cycle and to fire. Furthermore, the incorporation of plastic decreased the density of the mortar, which may be beneficial in many applications.