Study on Compressive Strength and Microstructure of Slag–Calcium Carbide Residue Solidified Mud Under Wetting–Drying Cycles

The high water content and viscosity make construction mud extremely difficult to manage, causing land occupation and environmental pollution problems. This research aims to investigate the durability of ground granulated blast furnace slag (S) and calcium carbide residue (CCR), two industrial by-products, solidified waste mud under wetting–drying cycles, and assess its serviceability as subgrade material. The tests of unconfined compressive strength (UCS), mass loss, and scanning electron microscope (SEM) were carried out to analyze mechanical and microstructural characterization of solidified mud. The optimal binder content and S:CCR ratio in terms of UCS values were found at 25% and 8:2, respectively. The maximum compressive strength at 7 days reached 3.73 MPa. There was a logarithm function between the development of compressive strength and curing time. The hydration reaction still occurred during the wetting–drying cycles; thus, UCS value first fluctuated and then gradually decreased with the progression of wetting–drying cycles. SEM images showed that the effect of the wetting–drying cycles on the solidified mud was manifested by the increase of pore and the decrease of hydration products. It was found that S-CCR is an environmentally friendly binder for bored pile mud solidification, which facilitates the reduction of a large number of waste by-products and waste mud from landfills.