Development and Performance Evaluation of Geopolymer-Based Fluidized Solidified Soil Using Phosphogypsum and Slag...

Area of Science:

• Materials Science
• Civil Engineering
• Environmental Science

Background:

• Industrial solid waste utilization is crucial for sustainable building materials.
• Challenges exist in achieving effective backfilling quality in confined civil engineering spaces.
• Flowable solidification materials from industrial waste offer solutions for traditional backfilling limitations and resource efficiency.

Purpose of the Study:

• To prepare and evaluate phosphogypsum-based fluidized solidified soil (PFSS) using geopolymers as binders.
• To assess the workability, mechanical strength, and toxic substance leaching of PFSS.
• To investigate the mechanisms of strength formation and heavy metal immobilization in PFSS.

Main Methods:

• Phosphogypsum was utilized to synthesize geopolymers, replacing cement in PFSS formulations.
• Workability, compressive strength, California Bearing Ratio (CBR), and resilient modulus were evaluated.
• Microstructural analyses (hydration, pozzolanic reactions, geopolymerization, carbonation) and heavy metal leaching tests were conducted.

Main Results:

• Optimal PFSS composition: water-to-solid ratio of 0.48-0.50, geopolymer content of 12-18%.
• Achieved performance: fluidity 160-220 mm, 28-day compressive strength 0.86 MPa, CBR 8%, resilient modulus 40 MPa, meeting high-grade highway standards.
• Heavy metal (As, Pb, Cr) leaching concentrations complied with China's Class III groundwater standards.

Conclusions:

• PFSS with optimal composition meets performance requirements for highway backfilling.
• Geopolymerization, hydration, pozzolanic reactions, and carbonation contribute to strength development.
• An interlocking 3D network of C-S-H, C-A-S-H gels, and ettringite (AFt) immobilizes heavy metals through adsorption and chemical bonding.