Mechanical and microstructural properties of one-part geopolymer-solidified soil attacked by Na2SO4

Abstract

In the construction of traffic engineering, a large amount of waste soils was generated. These soils have poor engineering properties, cannot be used as subgrade fill, so they were solidified treatment, commonly used cement curing agent have adverse effects on the environment. One-part geopolymer (OPG), as a green and new type of soil stabilizer, not only provides a new idea for the solidification of engineering waste, but also offers an effective way for the disposal of industrial solid waste, and reduces the consumption of cement. In order to evaluate the durability of geopolymer solidified soil, in this paper, with fly ash (FA) and ground granulated blast furnace slag (GGBS) as raw materials, solid NaOH and Na2SiO3 as solid alkali-activator to prepare OPG, which was used as a solidifier to solidify the waste dredged silt to produce one-part geopolymer-solidified soil (OPGSS). The variation patterns of mass, unconfined compression strength (UCS) and elasticity modulus of OPGSS with attack time under 0%, 5% and 10% Na2SO4 solutions were investigated. The changes in the phase composition, micro-morphology and pore size distribution of OPGSS were characterized by XRD, SEM-EDS and nuclear magnetic resonance (NMR). The results showed that: Under both 5% and 10% Na2SO4 solutions, the UCS of OPGSS decreased in two stages with attack time, and the number of large pores and total pores of OPGSS increased in two stages. The inflection points appeared on day 8 under 5% Na2SO4 solution; the inflection points appeared on day 5 under 10% Na2SO4 solution. This was mainly due to the expansion of corrosion products formed by OPGSS under Na2SO4 attack, which destroyed the microstructure of OPGSS and led to a reduction in the UCS of the OPGSS.