Experimental study on shear strength of composite cement-solidified peat waste soil

Addressing the poor engineering properties and difficulties in the reuse of peat soil, this study investigated the use of ordinary portland cement (OPC) and composite cement stabilizer (CCS) for its solidification treatment (CCS is made by uniformly mixing 90% OPC and 10% ultra-fine cement). Based on direct shear tests, the study explored the influence of patterns and mechanisms on the shear strength of solidified peat soil. The results indicate that when using OPC to strengthen peat soil, the optimal mixing ratio is approximately 17.5%, at which the cohesion (C) of the sample can reach 44.2 kPa and the internal friction angle (φ) is approximately 30 °, both of which are higher than the shear strength indicators of general cohesive soils. When using CCS to strengthen peat soil, the optimal mixing ratio is 12.5%, at which the C value can reach 41 kPa and the φ value exceeds 20 °, both of which are also greater than the shear strength indicators of general cohesive soils. Under the same conditions, the reinforcement effect of CCS specimens is much greater than that of OPC. Under the same conditions, the shear strength of the 12.5% CCS sample is close to that of the 17.5% OPC sample. CCS can save 28.6% of the cement usage compared to OPC, indirectly reducing CO2 emissions. Therefore, the conclusions of this study provide theoretical guidance for addressing the challenges of peat waste disposal and carbon reduction in engineering.