Practical application of CS-CG Stabilised soil in subgrade construction

To enhance the water stability and bearing capacity of the Shandong Ming Dong Expressway's soaked subgrade, carbide slag (CS) and coal gangue powder (CG) were used as stabilisers. Stabiliser dosages of 5%, 10%, and 15%, with the CS:CG ratios of 0:100, 30:70, 50:50, 70:30, and 100:0, were tested. The study evaluated the performance of CS-CG stabilised soil through unconfined compressive strength (UCS) tests at 7 and 28 days, six dry-wet cycles, a 30-day water immersion test, pH test, swell rate test, XRD, SEM, and MIP analyses. A UCS prediction model for CS-CG stabilised soil under dry-wet cycles was established. Results showed that CS-CG-10%-(70:30) achieved a UCS of 5.87 MPa after 28 days, decreasing to 4.77 MPa after six dry-wet cycles, indicating excellent bearing capacity and water stability. Increasing CS content improved UCS after 30 days' immersion, reaching 5.74 MPa for CS-CG-10%-(70:30). The CS-CG mix produced hydration products like C-(A)-S-H gel, Ca(OH)2 crystals, and ettringite, enhancing pore structure and UCS. More dry-wet cycles increased hydration products and pore diameter, causing an initial UCS drop before stabilisation. The UCS prediction model using the Exp3p2 (Y=e(AX2+BX+C)) equation offers higher accuracy, supporting strength prediction. The study found that CS-CG stabilised soil behaves similarly to cement-stabilised soil in settlement.