Influence of Silica Fume and Additives on Unconfined Compressive Strength of Cement-Stabilized Marine Soft Clay

This study presents results on the influence of silica fume (SF) and additives on the unconfined compressive strength (UCS) of ordinary portland cement (OPC)-stabilized salt-rich marine soft clay. The effects of additives including sodium hydroxide (SH), calcium chloride (CC), weed ash (WA), eggshell powder (EP), weed ash (WA)/calcium chloride (CC), weed ash (WA)/eggshell powder (EP) and sodium hydroxide (SH)/calcium chloride (CC) on the engineering properties of salt-rich marine soft clay are investigated and evaluated. The influencing factors included in this paper are the type of additive, the additive dose, the proportion of each additive, and the curing time. The results of the investigation reveal that a single additive of sodium hydroxide or weed ash are more effective than using other additives. By adding sodium hydroxide or weed ash, the strength (at 28 days) of marine soft clay can be increased by 102.10% or 90.70%, respectively, over that without additives. However, with the addition of an increasing amount of calcium chloride, the strength of the stabilized soil slowly decreases. The influence of EP on the strength of marine soft clay is not significant. Compared with the effect of a single additive of sodium hydroxide or weed ash, the selected composite additives-namely, weed ash/calcium chloride, weed ash/EP, and sodium hydroxide/calcium chloride-could not achieve a higher strength. Based on an orthogonal experiment, the OPC-based composite stabilizer with the best stabilization performance is selected. Compared with OPC, the composite stabilizer is more effective and eco-friendly. The investigation results show that the strength of the 5.00% OPC and composite stabilizer could exceed the strength of the clay with only 10.00% OPC. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) tests are conducted to reveal the influence and stabilization mechanisms.