Recycled Expanded Polystyrene as Lightweight Aggregate for Environmentally Sustainable Cement Conglomerates

Abstract

In the present work the rheological, thermo-mechanical, microstructural, and wetting characteristics of cement mortars with recycled expanded polystyrene (EPS) were analyzed. The samples were prepared after partial/total replacement of the conventional sand aggregate with EPS having different grain size and size distribution. Lightness and thermal insulation were relevant features for all the bare EPS composites, despite the mechanical strengths. Specifically, EPS based mortars were characterized by higher thermal insulation with respect to the sand reference due to the lower specific mass of the specimens mainly associated with the low density of the aggregates and also to the spaces at the EPS/cement paste interfaces. Interesting results in terms of low thermal conductivity and high mechanical resistances were obtained in the case of sand-EPS mixtures although characterized by only 50% in volume of the organic aggregate. Moreover, sand-based mortars showed hydrophilicity (low WCA) and high water penetration, whereas the presence of EPS in the cement composites led to a reduction of the absorption of water especially on the bulk of the composites. Specifically, mortars with EPS in the 2–4 mm and 4–6 mm bead size range showed the best results in term of hydrophobicity (high WCA) and no water penetration in the inner surface, due to low surface energy of the organic aggregate together with a good particle distribution. This was indicative of cohesion between the ligand and the polystyrene as observed in the microstructural detections. Such a property is likely to be correlated to the observed good workability of this type of mortar and to its low tendency to segregation compared to the other EPS containing specimens. These lightweight thermo-insulating composites can be considered environmentally sustainable materials because they are prepared with no pre-treated secondary raw materials and can be used for indoor applications.

Assessment of cement concrete partially replaced with polystyrene and plantain peel ash

“…The presence of voids and loose packing of the elements resulted in weaker bonding observed between the elements, and hence corresponding decrease in compressive strength. This trend is similar to that observed in previous research [20]. Figure 7 shows the scanning electron micrograph (SEM) of the sample with 90% OPC and 10% PPA/POL.…”

Lightweight Cement Conglomerates Based on End-of-Life Tire Rubber: Effect of the Grain Size, Dosage and Addition of Perlite on the Physical and Mechanical Properties

“…The sand replacement with tire rubber determined the formation of voids in the composite ( Figure 5C) at the organic/inorganic interface due to the unfavorable adhesion of the aggregate to the cement paste [49][50][51][52][53][54], with a decrease of the specific mass and increase of the porosity of the samples with respect to the references ( Table 1). The hydrophobic tire rubber with its organic compounds can explain the poor adhesion to the inorganic and hydrophilic cement matrix, on the contrary to what was observed with the sand in the reference sample with a good adhesion of this aggregate to the cement paste [55].…”

“…Th sults were totally ascribed to the hydrophobic nature of the organic aggregate in the higher porosity with respect to the reference and the bare perlite samples. The and the bulk of the bare perlite samples showed a fast water absorption and a hydr behavior ( Figures 13B and 14B) due to the hydrophilic porous domains of the in aggregate and of the cement paste, a result also observed in the case of the referen mortars [23,55]. In the case of the rubber/perlite sample (P/TRF), the water absorpti significantly lower than the perlite and reference samples but higher than the TR m (≈20% on the side surface, ≈20% on the fracture surface), thanks to the opposite con…”

Novel Bioderived Composites from Wastes

“…In the papers by Petrella and coworkers [12,13], recycled materials, such as end-of-life tire rubber (TR), porous glass (PG) and expanded polystyrene (EPS) were used as aggregates for the production of unconventional cement mortars. A cheap and environmentally safe process was employed, since no pre-treatment of the renewable aggregates was carried out.…”

“…For that purpose, six papers were related to the preparation of innovative composite materials. Specifically, five papers reported the reuse of end-of-life tire rubber, porous glass, expanded polystyrene, slags, fly ashes and sheep's wool fibers for the preparation of cement conglomerates [12][13][14][15][16], while the last one reported the reuse of amorphous silica nanoparticles for the preparation of composites with natural rubber [17]. Moreover, five papers were related to the treatment of wastes for environmental applications.…”