Development of sustainable geopolymer with excavation soil powder as precursor: Cementitious properties and thermal-activated modification

One of the focal and challenging issues in the research on sustainable building materials pertains to the recycling of construction excavation soil. This paper developed the sustainable geopolymer containing waste soil powder (WSP) from the construction excavation soil as a precursor. The WSP contains a large number of inert components, while more active components were generated in 600–1200 °C thermoactivated WSP. Substituting WSP for metakaolin (MK) negatively impacts the alkali-activated polymerization reaction of MK-based geopolymer paste, but the geopolymer paste containing thermal-activated WSP has better micro-properties than the geopolymer paste containing un-treated WSP. Mixing WSP raises the drying shrinkage of geopolymer mortar, while the drying shrinkage is reduced with the addition of 600–800 °C thermal-activated WSP. The maximum drying shrinkage of geopolymer mortar with 75 % 800°C-activated WSP is 36.6 % lower than that of plain geopolymer mortar. Substituting WSP for MK causes a reduction in the strength and permeability resistance of geopolymer mortar. At the constant replacement rate of WSP, the geopolymer mortar containing thermal-activated WSP has better strength and permeability resistance than the geopolymer mortar containing un-treated WSP. At 100 % replacement rate of WSP, the sustainable geopolymer mortar made with 1200 °C thermal-activated WSP still has good compressive strength (36.38 MPa). The waste soil-concrete powder (WSPC) also serves as an alternative precursor for sustainable geopolymer materials. Substituting WSPC for 100 % MK in geopolymer is feasible, and the geopolymer made with 800 °C thermal-activated WSPC is much greater than the geopolymer made with un-treated WSPC. Optimizing WSP/WSPC substitution rate and thermal activation temperature can achieve the sustainable geopolymer materials with good performance.