Optimising the properties of sustainable lightweight mortar containing electronic plastic waste

Abstract CDs and DVDs are a type of electronic plastic waste (EPW) and pose an environmental burden owing to their low biodegradability and the absence of viable large-scale strategies for their disposal. Using EPW as replacement components in construction materials, such as concrete and mortar, offers an alternative, sustainable solution to this problem. Moreover, the paper focused on the feasibility of substituting ordinary Portland cement with waste supplementary cementing materials, namely fly ash (FA) and silica fume (SF). The aim is to find environmentally friendly and economical applications of the FA. This study investigates the physical and mechanical properties of lightweight mortar specimens with varying EPW contents to optimise their composition for practical implementation in construction materials. Water absorption, ultrasonic pulse velocity (UPV), bulk density, compressive strength, and flexural strength were measured at 7, 28, and 90 days. The results demonstrate the potential to produce sustainable, lightweight mortar from EPW and that replacing 50% of the sand weight with EPW optimises mechanical strength for use in lightweight construction materials. The results indicate that mixtures with EPW, 30–50%, reach densities of 1600–1800 kg/m 3 and comply with the lightweight mortars classification in ACI 318 − 19. The higher EPW increased water absorption and reduced UPV, perhaps indicating increased porosity and weaker cohesive interfacial bonding. The mechanical strength has slightly decreased as the EPW content increased. Nevertheless, SF-modified mixtures showed a higher compressive strength at 14.11–32.15 MPa and higher flexural strength at 1.21–3.33 MPa compared to FA mixtures at 9.11–24.15 MPa and 2.00–2.84 MPa, respectively. The durability indicators, such as lower absorption, higher density, and higher UV-based ratings, suggest that SF refinement of structures improves long-term performance compared to FA. The data from the experiments carried out demonstrate that EPW has greater potential for use as a lightweight fine aggregate in mortar and, when combined with SF, as a proper, environmentally friendly alternative to natural sand. This should motivate future research to evaluate the future performance of EPW-modified mortars through separate direct durability tests.