Environmentally Friendly Binders from Calcium Carbide Residue and Silica Fume and Feasibility for Soft Clay Stabilization

Abstract

Abstract This study demonstrates the use of calcium carbide residue (CCR) and silica fume (SF), both of industrial waste, as green binders instead of ordinary Portland cement (OPC). A series of raw material fractions was designed based on the molar ratio derived from the pozzolanic reaction and the chemical composition of the raw materials. The Ca/SiO2 molar ratio (C/S ratio) ranged from 1.85 to 0.65. The chemical composition, phase evolution and microstructure of the raw materials and hydrated pastes were characterized by energy dispersive X-ray fluorescence, X-ray diffraction, thermogravimetric analysis and scanning electron microscopy/energy dispersive X-ray spectroscopy. The results show that the fraction of raw materials significantly influences the cementitious formation and compressive strength of specimens. The sample with the highest compressive strength over a long period had a C/S ratio of 1.55, which is related to the C-S-H content in the pastes. The CCR-SF mixture demonstrates promising potential as a stabilizer for enhancing the strength of soft Bangkok clay, particularly in the context of long-term observation. The addition of 30 wt.% of this mixture results in a substantial improvement, with the stabilized clay achieving an unconfined compressive strength that is 84% higher compared to the use of a 10 wt.% OPC stabilizer.