不同工业固废协同水泥固化盐渍土无侧限抗压强度及机理研究

Research on Unconfined Compressive Strength and Mechanism of Different Industrial Solid Wastes Cooperate with Cement to Stabilize Saline Soil

选用工业固废代替部分水泥制备低碳混凝土胶凝材料固化盐渍土是减少碳足迹,实现绿色可持续发展的主要途径。采用高炉废渣-水泥(SC)、煤矸石-水泥(GC)和粉煤灰-水泥(FC)3种胶凝材料固化剂固化盐渍土,以固废和固废-水泥总掺量为变量,对比分析固化土在7、14和28 d的无侧限抗压强度。同时通过分析矿物组成、基团化学键变化和微观形貌,揭示固化机理。结果表明:固化剂含量低的GC和FC试样破坏裂缝为贯穿裂缝,固化剂含量高的GC和FC试样破坏裂缝为细裂缝,表明固化剂胶凝效果较好。高炉矿渣-水泥固化剂效果优于煤矸石和粉煤灰。总固化剂掺量为30%的3种固废的水泥替代率可达40%,28 d无侧限强度可达1.0 MPa以上。固废-水泥低碳混凝土材料固化盐渍土中主要包含C-S-H、C-A-S-H、C-N-A-S-H、AFt等矿物,这些矿物以土粒之间的胶结、填充孔隙和包裹土颗粒等机理提升固化土强度。在碱性环境中,盐渍土也可参与固化反应,从而提高整体强度。

Choosing solid waste instead of partial cement to prepare low-carbon concrete stabilizer to stabilize saline soil is the main way to reduce carbon footprint and achieve green and sustainable development.In this study,three types of industrial waste blast furnace slag-cement(SC),coal gangue-cement(GC)and fly ash-cement(FC)are used to stabilize the saline soil,and the content of solid waste and solid waste-cement stabilizer are set as variables to compare and analyze the unconfined compressive strength of the stabilized soil for 7, 14 and 28 days. The stabilization mechanism is revealed by analyzingmineral composition, group chemical bond change and micromorphology. The results show that the failurecracks of GC and FC samples with low stabilizer content are penetrating cracks, while the cracks with highstabilizer content are fine cracks, indicating that the stabilizer effectively cements the soil. The effect ofblast furnace slag-cement stabilizer is better than that of coal gangue and fly ash. The cement replacementrate of three types of waste slag with 30% total stabilizer could reach 40% , and the unconfined strength at28 days can reach over 1. O MPa. The solid waste - cement low-carbon concrete materials mainly containC-S-H, C-A-S-H, C-N-A-S-H, AFt in the stabilized saline soil, which enhance the strengthof the solidified soil by cementing between soil particles, filling pores and wrapping soil particles. Thesaline soil can also participate in the reaction to promote the strength improvement in the alkalineenvironment.