Understanding of EPS beads on mechanical properties and void morphology of a CO2-solidified foam concrete based on solid wastes

Abstract

Two major issues of EPS doped concrete are apparent reduction in compressive strength associated with the presence of EPS-formed artificial defects and ultra-light weight related easy segregation in the mixes, even though the thermal conductivity of composites shows a satisfactory reduction. This paper presents a composite lightweight concrete by introducing EPS into a solid waste (carbide slag and quartz sand tailings) prepared industrial grade γ-C2S-based foam concrete (CFC) to partially replace foam-formed voids. Results show that the partially EPS-substituted CFC with reasonable EPS parameters (Especially 1 mm in diameter and 5 wt% in content) exhibits a notable improvement in compressive strength (24.3%) while accompanied by the reduction in sorptivity, drying shrinkage and thermal conductivity. This is attributed to the fact that the EPS can effectively improve the foam stability by delaying foam drainage velocity due to its hydrophobicity and discrete smooth surface during the pre-curing procedure, which results in a refinement of void morphology and distribution as well as the optimized interfacial transition zone (ITZ). Accompanied by the compact inner surface and optimized ITZ, leading to a lower drying shrinkage, thermal conductivity, and also a reduction in sorptivity due to the increasing of tortuous path for the capillary flow. Moreover, magnesium slag (MS) containing dicalcium silicate mineral phase is also used to prepare MS-based CFC to further reduce costs and achieve the resource utilization of solid waste and a large amount of CO2 storage, which contributes to the sustainable development of CFC.