Mechanical Properties and Hydration Characteristics of Weathered Residual Soil of Granite-Based Geopolymer

Geopolymer coatings exhibit outstanding corrosion resistance, high-temperature performance and thermal insulation. This thus holds broad application prospects in anti-corrosion of metals, protection of building structures, and functional coatings. However, the large-scale application of geopolymers is constrained by the availability of precursor materials. In South China, construction waste soil is predominantly composed of weathered residual soil of granite (WRSG), which is rich in silicate and aluminosilicate minerals. This soil can serve as a precursor for geopolymer synthesis upon activation. In this study, geopolymers were prepared using activated WRSG as the precursor material. The mix proportion of the geopolymers was optimized through single-factor experiments. Additionally, the hydration process and products of the geopolymer were characterized. The experimental results show that both high alkali content and low water-to-soil ratio contribute to achieving high compressive strength. The geopolymer has early strength characteristics. Its one-day compressive strength can reach 48% of 28-day value. The hydration products of the geopolymer mainly consist of amorphous sodium–aluminum–silicate–hydrate gel and primary minerals such as quartz and albite. With the increasing age, the content of chemically combined water and gel clusters grows, which densifies the microstructure and elevates the degree of hydration reaction of geopolymers.