Preliminary study on the mechanical properties of muddy soil solidified by phosphoric acid-activated geopolymer

In many civil engineering, soft soil is typically stabilized by Ordinary Portland Cement (OPC) and lime, both of which are energy-intensive and emit significant amounts of CO2 during production. Phosphoric acid-activated geopolymer (PAG) is an eco-friendly cementing material, offering great potential as a replacement for traditional curing agents. In this study, the feasibility of using two types of PAG as curing agents was investigated for stabilizing muddy soil. The effects of phosphate-activated metakaolin geopolymer (PAMG) and phosphate-activated fly ash geopolymer (PAFG) on the mechanical properties and microstructure of PAG-stabilized soil were investigated, through compressive strength tests, shear strength tests, x-ray diffraction (XRD), and scanning electron microscopy (SEM). The results indicated that the compressive strength and cohesive force of PAMG-solidified soil showed a nearly increasing trend, while the internal friction angle increased at first, and then almost remained unchanged, with the increase of PAMG content. The compressive strength and cohesive force of PAFG-solidified soil increased initially and then decreased, and the internal friction angle increased as a whole with the rise in PAFG content. The microstructural analysis confirmed that the PAMG and PAFG gels formed in the solidified soil not only filled the intergranular pores but also cemented the soil particles together to form a dense structure. This study shows that the strength of PAG solidified soil could meet the requirements of pavement base material, and it is an effective curing agent. It is meaningful to further explore it in response to the dual carbon strategy.