Evaluation of the Mechanical and Environmental Behavior of Alkali-Activated Mortars Containing PU/EVA-Based Waste

Abstract

The objective of this study is to evaluate the use of polyurethane (PU) coated textile wastes processed with ethylene-vinyl acetate (EVA) as lightweight aggregates in fly ash-based and alkali-activated metakaolin mortars, targeting the development of non-structural elements for civil construction. The PU/EVA waste was processed in three different proportions: 30/70, 50/50 and 70/30. Reference mortars were prepared using a 1:2 (fly ash + metakaolin: conventional construction sand) ratio, by mass. The PU/EVA-waste-containing mortars were prepared via partial replacement of natural sand with the waste in percentages of 10%, 20%, 30% and 40%, relative to the volume of the sand. The activators used in all mortars were NaOH and Na2SiO3. The mortars were cured at 80 °C for 21 hours and subsequently removed from the molds and maintained at room temperature until testing was conducted for compressive strength (at ages of 7, 28 and 91 days), leaching (7 days) and solubilization (7 days). Based on the results for compressive strength, the optimum PU/EVA content was 50% for a sand-to-waste replacement percentage of 40%. At an age of 28 days these mortars reached strengths greater than 2.5 MPa which, from a mechanical standpoint, allows for the production of non-structural elements for civil construction like sealing blocks, side walls or finish mortars. From an environmental perspective, no hazardous substances were detected in the leaching and solubilized extracts in any of the PU/EVA waste containing mortars.