Mechanical Properties and Microstructure of Geopolymer-Based PFSS Synthesized from Excavated Loess

Pre-mixed fluidized solidified soil (PFSS) has the advantages of pumpability, convenient construction, and a short setting time. This paper took the excavated loess in Fuzhou as the research object and used cement-fly-ash-ground granulated blast furnace slag-carbide slag as a composite geopolymer system (CFGC) to synthesize PFSS. This study investigated the fluidity and mechanical strength of PFSS under different water-solid ratios and curing agent dosages; finally, the microstructure of the composite geopolymer system-pre-mixed fluidized solidified soil (CFGC-PFSS) was characterized. The results showed that when the water-solid ratio of PFSS increased from 0.46 to 0.54, the fluidity increased by 77 mm, and the flexural strength and compressive strength at 28 d decreased to 450.8 kPa and 1236.5 kPa. When the curing agent dosage increased from 15% to 25%, the fluidity increased by 18.0 mm, and the flexural strength and compressive strength at 28 d increased by 1.7 times and 1.6 times. A large number of needle-like AFt, C-S-H gel, and C-(A)-S-H gel coagulate with soil particles to form a three-dimensional reticular structure, which is the mechanism of the strength formation of PFSS under the action of CFGC.