Enhanced mechanical, thermal and fire resistance performance of expanded polystyrene-based fiber-reinforced mortar made with limestone-calcined clay cement (LC3)

Lightweight construction materials have received extensive attention due to their better thermal insulation, which helps improve energy efficiency in buildings. This study aimed at developing lightweight, thermally resistive and fire-protective green plastering mortar by adopting the low-carbon LC3 binder. A green and economical ternary blended binder has been prepared by substituting 60 wt% of the ordinary Portland cement with a blend of limestone powder and metakaolin at a ratio of limestone to metakaolin of 1:2 (wt%). The binder has been blended with expanded polystyrene (EPS) beads as fine aggregate with different aggregate contents of 25, 50 and 75 vol. %. Polypropylene microfibers were added at a constant ratio of 0.5% by weight of binder. The compressive and flexural strengths, capillary water absorption, bulk density, thermal conductivity, fire resistance and microstructure of the developed mortars were studied after 28 days of hydration. The newly developed LC3 fiber-reinforced mortar complies with the standard recommended criteria of lightweight and thermal insulation characteristics, with a density as low as 654 kg/m³, a thermal conductivity as low as 0.18 W/mK and an improved compressive strength of 11.89 MPa. The integration of EPS into the fiber-reinforced LC3 binder has distinctly provided an enhanced fire resistance rating; the greatest enhancement of about 125% was attained for the LC3 lightweight mortar with 50 vol. % EPS.