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.

Evaluation of the Influence of PU/EVA Waste-Based Lightweight Aggregates on the Physical Properties of Alkali-Activated Mortars

“…The fine aggregate (sand) was used in five different granulometries: 2.36; 1.18; 0.60; 0.30 and 0.15 mm according the same granulometric distribution of the samples showed in Table 2. The sand came from Jacuí River -south of Brazil with density 2570 kg/m 3 [7].…”

Performance and applications of lightweight geopolymer and alkali activated composites with incorporation of ceramic, polymeric and lignocellulosic wastes as aggregates: A review

“…PET flakes, b. PET strips [ 56 ]; c. waste PET granules [ 57 ]; d. recycled plastic beads; e. shredded rubber [ 58 ]; f. EPS beads [ 59 ]; g. recycled polystyrene foam [ 60 ]; h. PU/EVA [ 61 ]. …”

“…In order to decrease both the density and the thermal conductivity in concrete, mixtures of polyurethane (PU) and ethylene vinyl acetate (EVA) ( Fig. 2 h) from footwear manufacturing surpluses [ 61 , 75 ] have been added.…”

“…of polyurethane foam (PUR) to the cementing agent produced composites with compressive strength of 7–11 MPa and flexural strength of 1.5–3.6 MPa [ 74 ]. Much lower compressive strengths (1.42 and 3.07 MPa) were reported for composites in which between 10 and 40% vol of sand was replaced with polyurethane (PU) and ethylene-vinyl acetate (EVA) residues [ 61 ].…”

“…For rubber-lightened composites, water absorption ranged between 4.7 and 13% [ 58 , 71 ]. In composites that incorporated PUR, the absorption varied between 10.3 and 12.7% [ 74 ]; while with the addition of PU + EVA it changed from 7.8 to 30.5% [ 61 , 75 , 104 ]. Water absorption increased by more than 14% in composites with incremental substitutions of stone aggregate with PU, PS and PET particles [ 57 , 66 , 75 ].…”