Influence Mechanism of Silica Fume on Cement-Soil with Blast Ferronickel Slag

Blast ferronickel slag is a both sustainable and environment-friendly material with low pozzolanic activity. The effect of silica fume on the unconfined compressive strength of cement-soil with blast ferronickel slag is studied, and the effect of the replacement rate of blast ferronickel slag and silica fume on the strength and failure pattern are analyzed. Scanning Electron Microscope and X-ray Diffractometer are used to explore the mechanism of the effect of silica fume on the properties of cement-soil with blast ferronickel slag. The results show that the strength of cement-soil with the increase of silica fume content increases, which is attributed to the fact that silica fume promotes cement hydration reaction and secondary pozzolanic reaction to produce C-S-H gel coating the surface of soil particles, and the particles without hydration reaction are reduced. Moreover, the soil particles, blast ferronickel slag and silica fume are packed by gel between the large soil particles to improve the compactness and strength of cement-soil. The best dosage of silica fume is 10%. However, excessive dosage of silica fume consumes Ca(OH)₂ and affects the secondary pozzolanic reaction of silica fume. When the dosage increases to 30%, the strength of cement-soil decreases by 3.6%.