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

Area of Science:

• Geotechnical Engineering
• Materials Science
• Civil Engineering

Background:

• Pre-mixed fluidized solidified soil (PFSS) offers practical advantages like pumpability and rapid setting.
• Excavated loess presents a potential resource for soil solidification.

Purpose of the Study:

• To synthesize PFSS using a novel cement-fly-ash-ground granulated blast furnace slag-carbide slag (CFGC) geopolymer system.
• To investigate the influence of water-solid ratio and CFGC dosage on PFSS fluidity and mechanical properties.
• To characterize the microstructure of the synthesized CFGC-PFSS.

Main Methods:

• Synthesis of PFSS using loess and a CFGC binder.
• Systematic variation of water-solid ratios and CFGC dosages.
• Assessment of fluidity and mechanical strength (flexural and compressive) at 28 days.
• Microstructural analysis of the solidified soil.

Main Results:

• Increasing the water-solid ratio (0.46 to 0.54) enhanced fluidity but reduced 28-day flexural and compressive strengths.
• Increasing CFGC dosage (15% to 25%) improved fluidity and significantly increased 28-day flexural and compressive strengths (1.7x and 1.6x, respectively).
• Microstructural analysis revealed needle-like AFt, C-S-H gel, and C-(A)-S-H gel formation, creating a robust 3D network with soil particles.

Conclusions:

• The CFGC system effectively synthesizes PFSS from excavated loess.
• Optimizing water-solid ratio and CFGC dosage is crucial for balancing fluidity and mechanical performance.
• The formation of a dense, reticular structure of hydration products dictates the strength development in CFGC-PFSS.