Study on solidification modification and engineering characteristics of solid waste-based cementitious materials on pile spoil

Abstract In view of the problem of difficult treatment of pile spoil in infrastructure construction, the solid waste-based cementitious material was designed and used as the solidifier for pile spoil. The modification of solidifier on pile spoil was studied from the aspects of physical and chemical characteristics, microstructure, and engineering characteristics. The results show that the solid waste-based cementitious material, primarily composed of granulated blast furnace slag (GBFS) powder, steel slag powder, steel slag dust, and desulfurization gypsum, exhibits excellent synergistic hydration effects. Under the action of alkaline solution, a large amount of Ca 2+ , [SiO 4 ] 4− , [AlO 4 ] 5− and SO 4 2− are released from the system, to form C-S–H, Ca(OH) 2 , N-A-S–H, AFt, and other hydration products through a series of chemical reaction processes. With a slag/(steel slag) ratio of 6:3, the cementitious material S631 shows superior hydration and hardening performance, achieving compressive strengths of 15.9 MPa, 25.7 MPa, and 49.8 MPa at 3, 7, and 28 days, respectively. Solid waste-based cementitious material S631 was further used as solidifier to treat the pile spoil. The solidified pile spoil begins to harden within about 5 to 16 h and loses its plasticity between 67.5 and 84.1 h. The higher the dosage of solidifier, the quicker the hardening rate, with the spoil containing 10% solidifier reaching unconfined compressive strengths of 0.68 MPa and 1.13 MPa at 7 and 28 days, respectively. The active silicoaluminate minerals of the solidifier produce C-S–H gels and other products through solution-precipitation reaction, which connects the mineral particles of pile spoil. Macroscopically, it is manifested as the hardening of the solidified soil and the generation of strength. In terms of engineering characteristics, the use of solidifier reduces the liquid and plastic limits of pile spoil while increasing its plasticity index, optimum moisture content, and maximum dry density. In the experiments of simulating the influence of compaction degree and wheel loading rate on the strength of engineering soil in actual roadbed engineering, the solidified soil has shown better strength performance, indicating that the solidifier improved and optimized the engineering characteristics of the pile spoil.