Analysis of compressive strength, durability properties, and micromechanisms of solidified loess using industrial solid waste: Slag–white mud–calcium carbide residue

Abstract

Traditional lime-solidified loess presents the issue of high carbon dioxide emissions. This paper presents the development of a kind of cementitious material using industrial solid waste: slag–white mud–CCR (calcium carbide residue). The slag mainly contains CaO, SiO2, and Al2O3, with a 10.6 pH value. The white mud and CCR mainly contain CaCO3 and Ca(OH)2, respectively. We further assessed the efficacy of slag–white mud–CCR in solidified loess and employed SEM and TG/DTG to explore their micromechanisms. The pH value of the CB4 sample (slag–white mud–CCR with the lowest CCR content) was 42.3 % higher than that of pure loess. Considering the 3-day and 28-day compressive strength and the material costs, the optimal mortar mixture ratio was found to be slag–white mud–CCR = 60:32:8, and this mixture was used to solidify loess. The unconfined compressive strength of 15 % slag–white mud–CCR-solidified loess is almost 5.0 times and 6.0 times higher than that of lime-solidified loess at 7 and 28 days of curing age, respectively. The durability of the solidified loess after freeze–thaw and wet–dry cycles was significantly improved compared with that of lime- or slag-solidified loess. Specifically, 10 % and 15 % slag–white mud–CCR-solidified loess maintained a high compressive strength after eight freeze–thaw and wet–dry cycles. SEM and TG/DTG analyses of the mortar and solidified loess confirmed the formation of hydration products of C–S–H- and C-A-(S)–H-type gels. The compressive strength results were obtained using a dual mechanism: the cementation of loess particles through the formation of hydration products and their subsequent filling action.