Effect of Cementitious Material Composition on the Performance of Low-Carbon Foamed Lightweight Soil

Abstract

This study simulated the production process of low-carbon foamed lightweight soil (LCFLS) prepared using prefabricated foam technology in real engineering conditions. The preparation and properties of LCFLS with a wet density of 600 kg/m3 were systematically investigated. The effects of different mix designs of large dosing granulated blast furnace slag and fly ash on the properties of LCFLS were investigated. The workability, rheological properties, and mechanical properties of LCFLS were studied. XRD, TG–DTG, and SEM were used to analyze the hydration mechanism of LCFLS. The results showed that fly ash could improve the flowability of LCFLS, while excessive fly ash could lead to foam and slurry delamination. Granulated blast furnace slag improved the mechanical properties of LCFLS, while excess granulated blast furnace slag caused the foam to break and merge, affecting the soil’s homogeneity. The higher the dynamic yield stress of the freshly mixed slurry, the better the homogeneity, and the smaller and more evenly distributed pore sizes formed after hardening. The main hydration products of LCFLS were C-S-H gel and CH, with small amounts of the carbonation products CaCO3, Hc, and Mc. The LCFLS prepared with 30% cement, 30% fly ash, and 40% granulated blast furnace slag had a flowability of 170–180 mm, with slight differences between wet and quasi-dry densities. The rheological properties of the slurry following the Bingham model showed a dynamic yield stress of 9.41 Pa, an average pore size after hardening of around 300 μm, and compressive strengths at 7 d and 28 d reaching 0.92 MPa and 2.04 MPa, respectively.