Study on the performance of collapsible loess subgrade improved by steel slag

Steel slag has the potential to replace cement and lime as a cementitious material to eliminate the collapsibility of loess. In this content, the physical and mechanical properties (compaction, compressive strength and shear strength) and engineering properties (California bearing ratio, permeability and collapsibility) of steel slag improved collapsible loess (SSICL) were analyzed by adjusting the steel slag-loess ratio (SS/L). The results show that the maximum dry density (MDD) of the mixture increases and the optimum moisture content (OMC) decreases with increasing steel slag content. Improved compressive strength can be achieved by increasing the SS/L ratio and curing period, and the 7-day strength of SSICL with SS/L ratio of 15 % meets the specification requirement of 0.5 MPa. The internal friction angle increases with increasing SS/L ratio, while the cohesion has the opposite trend. The permeability coefficient of SSICL with different SS/L ratios ranges from 1.14 x 10-6 cm/s to 7.59 x 10-6 cm/s, only when SS/L ratio of 15 % was used did the permeability continue to decrease with increasing curing period. The CBR and immersion expansion rate obtained in the study range are much higher than the specification requirement of 8 % and lower than the specification limit of 2 %, respectively. The results also show that the collapsibility of SSICL was completely eliminated within the study range. Finally, the optimal steel slag content of 15 % was proposed and the field test was carried out, which proves the feasibility of the proposed steel slag for improving collapsible loess subgrade.