## 1 Introduction
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Chemical modification remains the most effective method of soil stabilization. Among the available chemical admixtures, the most extensively used for soil stabilization is lime [16]. [PERSON] et al. [1] performed unconfined compressive strength, X-ray diffraction, and scanning electron microscopy tests on gypseous soil (with different gypsum amounts: 5%, 15%, and 25%) to investigate the influence of lime applied at different dosages (0%, 3%, 5%, and 10%) to stabilize sulfate-bearing soil. The results noted that the mechanical properties of soil specimens were not only affected by the curing time, but also depended on the lime dosage. The optimum reduction in strength was detected to be 5%, and the results of micro tests confirmed the ettringite formation and the pozzolanic products. Researchers and engineers are now progressively exploring novel materials that can serve as soil stabilizers to overcome the lime-induced heave problems often encountered in sulfate-bearing soils during the construction of civil structures. Novel methods should be able to repress heave and ettringite formation in sulfate-rich soils. Materials that exhibit pozzolanic properties, such as rice husk ash (RHA) and ground granulated blast-furnace slag (GGBS), are believed to be suitable sulfate soil stabilizers because such materials generally consume lime [17], thereby reducing its availability for the formation of expansive products while improving the strength of the soil [18]. Annually, millions of tons of industrial and agricultural waste are produced globally, creating serious problems such as environmental pollution and the deterioration of the health of many inhabitants of the world [10,19]. Due to this fact, studies are needed to find alternative uses for waste materials for economic purposes. Concurrently, the sources of cement, lime, and other raw materials, especially near large urban centers, are depleting and thus becoming more expensive, in addition to existing transportation costs and environmental restrictions [10]. Considering these facts, waste materials such as RHA and GGBS can be used as alternative raw materials in the production of building materials to reduce the cost of building projects while protecting the environment [9,10,17,19,20,21]. The processes involved in the production of lime and Portland cement (PC) contribute significantly to environmental pollution; for instance, the production of one ton of (PC) leads to the emission of almost 0.95 tons of CO2 and requires almost 5000 MJ of energy to complete [9; 22; 23; 24]; for lime production, these values are ~0.79 tons of CO2 and ~3200 MJ of energy [9]. This calls for the use of waste materials as a complete or partial replacement of conventional binders, as proposed by various researchers [6; 10; 12; 20; 25; 26; 27; 28; 29]. GGBS is a waste product from the iron industry and has been considered a suitable material for soil stabilization [19]. In terms of CO2 emission and energy consumption, only 1300 MJ of energy is required to produce one ton of GGBS, and the process emits only 0.07 tons of CO2 [2; 26]. GGBS can be activated via lime for soil stabilization, as it is a latent hydraulic material [16; 30]. This process involves three basic reactions: the lime-soil reaction, lime-GGBS reaction, and GGBS-soil reaction [30]. Calcium silicate hydrates (CSH), calcium aluminosilicate hydrates (CASH), and calcium aluminate hydrates (CAH) are the major hydration products of lime-GGBS-stabilized soil [6; 24; 26]. GGBS can serve as a partial or complete replacement for cement or lime to prevent or reduce ettrinigite formation in stabilized sulfate soils. The alumina and silica contents of GGBS can quickly react with the calcium content in soil to form a cementitious gel, thereby reducing or preventing ettrinigite formation [6; 15]. GGBS can also reduce water availability and permeability through the formation of a denser cementitious matrix, which improves resistance to both external and internal sulfate attacks [17; 21; 31; 32].