Durability of Mortars Made with Recycled Plastic Aggregates: Resistance to Frost Action, Salt Crystallization, and Cyclic Thermal–Moisture Variations

Abstract

This study aimed to investigate the use of polymeric end-of-waste materials, including polyethylene-terephthalate (PET) and other plastic types that have not been comprehensively studied to date, namely, acrylonitrile-butadiene-styrene (ABS), polycarbonate (PC), ABS/PC blend, and polyoxymethylene (POM), to improve the durability of cement mortars. The evaluation of freeze-thaw and salt-crystallization resistance and endurance to cyclic changes in moisture and temperature for plastic aggregate (PA) mortars was carried out by measuring mass loss, compressive strength loss, and macroscopic damage following accelerated weathering testing. The PA mortars were prepared by replacing natural sand (5%, 15%, and 20% by volume) with PAs. The results show that PA mortars are more susceptible to thermal/moisture variations and salt crystallization than to frost action, with 4%–7% mass loss and up to a 31% reduction in strength. The damage caused by frost action is insignificant for plastic aggregate mortars, especially at low replacement levels. The damage to mortars done by salt attacks and moisture/thermal changes could be due to the dimensional instability of the PAs because their thermal expansion coefficients are well over those of the minerals with which they are mixed. The compressive strength of the PA mortars, even after weathering, is well above the minimum strength required for structural lightweight concrete.