Mechanical response and micro-mechanism of humus soil solidified by industrial solid waste-cement

To advance the resource utilization of humus soil within the realm of geotechnical engineering, industrial solid waste materials (encompassing biomass fly ash, carbide slag, and phosphogypsum) cooperated with cement was used in this paper to solidify the humus soil. In this paper, humus soil mined from an obsolete simple landfill in Guangdong Province, China was solidified by industrial solid waste-cement. Then mechanical properties, durability and the underlying microscopic mechanisms were investigated by conventional triaxial tests, wet-dry and freeze-thaw cycling tests, scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and mercury intrusion porosimetry (MIP) tests. The results showed that with the increasing of Po-b (i.e., the replacement ratio of cement by industrial solid waste), the relationship between deviatoric stress and axial strain of the samples gradually transitioned from strain softening to strain hardening. The appropriate incorporation of ternary industrial solid waste materials (ranging from 25 % to 50 % for Po-b) was beneficial in slowing down the deterioration rate of industrial solid waste-cement solidified humus soil samples under the action of dry-wet cycles. Furthermore, the cement-solidified humus soil samples exhibited excellent ultimate deviatoric stress and frost resistance. Microstructural analyses showed that a large number of reaction products such as ettringite crystal and C-(A)-S-H gel enhanced the bonding between humus soil particles and filled in the microscopic pores. The research results provide a theoretical foundation for the restoration and reuse of humus soil mined from landfill sites.