Stabilisation of expansive soil using alkali-activated binder produced with un-calcinated precursor

Expansive soil, prone to significant swelling and shrinking with changing moisture content, poses challenges for construction projects. It causes damages to foundations, pavements, and basement walls resulting in long-term maintenance issues and economic losses. Traditional solutions, particularly using calcium-based binders like lime or cement, have limitations due to their high calcium composition, energy-intensive and high carbon footprint production. Recent studies have introduced alkali-activated or geopolymer binders derived from precursors like fly ash (FA) and metakaolin (MK), known for their strength enhancement and swelling control properties. However, these precursors still require high-temperature calcination, and some, like FA, still contain high levels of calcium. This study aims to address these issues by developing a low-temperature, low-calcium, and low-carbon footprint alkali-activated binder for expansive soil stabilisation in construction. It is referred to herein as uncalcinated kaolinite-based alkali-activated binder (U-KAB). The precursor of U-KAB is un-calcinated kaolinite, one of the most abundant clay minerals present in nature. Testing on our constituted surrogate soils with consistent swelling potential of 13%, revealed that U-KAB treatment, at a 3.2% dosage, effectively reduced swelling to less than 1%, slightly better than lime-treated samples. This study underscores U-KAB's potential in enhancing the stability of expansive soils, reducing maintenance costs, and contributing to more sustainable construction practices.