Experimental investigation of structural lightweight mortars containing waste PET aggregates

Abstract The present study investigates the effect of Fly ash (FA) on the strength characteristics of lightweight mortars that utilize recycled Polyethylene Terephthalate (PET) aggregates. The experimental work specifically examined three different sets of mortar samples: one made exclusively with Ordinary Portland Cement (OPC) as a binding agent and the other two incorporating both OPC and varying percentages of FA (50 and 15% with admixture). The waste PET bottles used as aggregates in mortar mixes ranged in size from 0.150 mm to 2.36 mm. The mixtures had a water-binder (w/b) ratio of 0.45 and a PET-binder (PET/binder) ratio of 0.50. The study assessed various parameters, including dry unit weight, compressive strength, flexural tensile strength, and carbonation depth values. The study investigates the incorporation of FA at replacement levels up to 50% in lightweight mortars made from waste PET, resulting in a reduction in both compressive and flexural strength. Moreover, the use of PET aggregates contributed to a decrease in cracking in the specimens and exhibited more ductile failure modes. Mortars containing FA had greater carbonation depth than OPC mortars. Furthermore, mortars that utilize recycled PET aggregates as a partial replacement for natural aggregate show advantages of reduced weight (up to 20%) and enhanced water absorption (up to 30%), making them a promising choice for the production of sustainable construction materials with both environmental and economic benefits.