Rheological and mechanical performances of ultralightweight expanded polystyrene concrete: Synergistic effect of accelerator and multiscale fibers

The balance among desired mechanical properties, homogeneity, and lightweight is crucial to concrete with ultralight aggregates. The mix designs considering the packing of expanded polystyrene beads (EPS) and rheological regulation are studied to realise an ultralight EPS concrete (with an oven-dry density lower than 800 kg/m 3 ) with desired specific strength and reduced drying shrinkage values. The synergistic effects between the early-age strength accelerators (calcium sulphoaluminate cement, calcium chloride) and multiscale fibers (macro polyvinyl alcohol (PVA) fibers and cellulose nanofibrils (CNF)) on the early-age properties and mechanical properties of EPS concrete are investigated. The formation of the AFt phase induced by calcium sulphoaluminate cement at the 2 hours of hydration is the main reason for those contrary change laws between yield stress and drying shrinkage values of EPS concrete. The excellent anti-drying shrinkage performance of ultralight EPS concrete is attributed to the synergistic effects among the CNF, AFt, and PVA fibers. • PCE-SPs promote hydration of sulphoaluminate cement, resulting in massive production of Ettringite. • Synergistic effects of Ettringite and PVA fibers regulate the rheology of ultralight EPS concrete. • Specific compressive strength of EPS concrete with oven-dry density of 700 kg/m 3 ranges 8–10 kN•m/kg. • The maximum drying shrinkage of ultralight EPS concrete at 28-day-age reduces about 36 %. • Thermal conductivity of the ultralight EPS concrete with PVA fibers reduces by more than 20 %.