Preparation and properties of ultra-lightweight EPS concrete based on pre-saturated bentonite

Abstract Water-rich gel of pre-saturated bentonite exhibits multiscale pore structures, which can be used as pore-forming agent to prepare porous concrete without any air entraining agents. In this study, pre-saturated bentonite with solid content of 11.1% was used to prepare ultra-lightweight EPS concrete at various dry density levels (300, 400, 500 and 600 kg/m 3 ). For fresh mixtures (without EPS beads), yield stress increased while apparent viscosity decreased with the increased dosage of pre-saturated bentonite. The slump-flow of fresh mixture (with EPS beads) showed a growth trend, which had negative correlations with apparent viscosity. Meanwhile, the slump-flow was also affected by the wet density change. Thermal insulation of ultra-lightweight EPS concrete was improved by 14–31% compared to that of ordinary foamed concrete at the corresponding density. Thermal conductivities of 0.062–0.129 W·m −1 ·k −1 at dry densities of 300–600 kg/m 3 were observed. Compressive strength decreased at lower density (≤400 kg/m 3 ), but increased at higher density (≥500 kg/m 3 ) with the increase of pre-saturated bentonite. The construction of plentiful multiscale pores by pre-saturated bentonite is the main reason for the lower thermal conductivity, while also can cause an increase in volumetric water absorption.