# Expansive Soil Stabilization with Time, Cement, and Silica Fume
## 1 Introduction
By utilizing the technique of stabilization of soil, which is a general term for any physical, chemical, or biological method, or any combination of these methods, used to enhance or change the specific characteristics of natural soil to make it usable for the intended engineering work, the risk posed by such soils can be reduced [PERSON] et al. (2018). The moisture content of the soil changes as a result of precipitation or evapotranspiration in tandem with the climatic or seasonal changes in the region, known as the active zone or seasonal zone, which is sufficiently close to the ground surface. With the depth of the active zone, the major portion of the soil zone that experiences swelling phenomena increases [PERSON] et al. (2018). The geography, climate, soil type and soil structure all have an impact on the depth of the active zone (depth of desiccation), which typically ranges between 1 and 4 m [PERSON] et al. (2018). To analyze the features and behavior of this type of soil under circumstances that are comparable to those observed in the field, a variety of methodologies have been utilized to quantify the potential magnitude of swell in clay. [PERSON] (2018) presented a simple laboratory test that is used to determine the magnitude of swelling pressure in soils, which is the \"oedometer test\". According to ASTM D 4546 [PERSON] (2018), the sample is added to the oedometer cell with a modest surcharge of 6.9 kN/m\({}^{2}\), and water is then added to cause the soil sample to expand, which allows the volume to be measured until equilibrium is attained. It is possible to express the amount of free swell as a ratio:  
\[S_{w(free)}(\%)=\frac{\Delta H}{H}\times 100 \tag{1}\]  
where:  
\(S_{W(free)}\): free swell as a percentage;  
\(\Delta H\): change in height of swell due to saturation;  
\(H\): original height of the specimen. According to [PERSON] et al. [PERSON] et al. (2018), if fine-grained clay soil passes through a 75 mm screen at least 25% of the time, has more than 0.3% sulfate, has a plasticity index above 10 and contains more than 1% organic material, stabilization is required. Before it may be used as a sub-base, sub-grade or base for the construction of highways, bridges and many structures, expansive soil needs to be stabilized. The main goals of stabilizing the soil are to make the natural soil more rigid and hard and to lessen its flexibility and tendency for shrinkage and swelling [14]. According to [PERSON] et al. [14], stabilized expansive clay soil has a higher bearing capacity when a heavy load is placed on it. For expansive soils to have a lower likelihood of expanding, soil stability is essential [15]. Chemical stabilization seeks to offer additives that decrease and increase for both the liquid limit and plastic limit, respectively, as well as decreasing the plasticity index as a result of the liquid and plastic limits. As a result, the stabilized soil becomes more compressible, which improves the workability of the soil, the water content and the maximum dry density. The shear strength of soils treated with cement is increased, but the liquid limit, plasticity index and swelling potential are all reduced [16]. Since only a tiny amount of cement is needed, stabilizing granular soils using cement has proven to be more effective and cost-effective. According to research, it is difficult to treat soils with a plastic index (PI) > 30 with cement; for this reason, lime is added before mixing to maintain the soil's workability. This study also demonstrated that when the cement concentration is increased from 0 to 12%, the unconfined compressive strength (UCS) improves, and the soil flexibility decreases, changing from 57.81% to 27.57%. With the use of the F1 ionic stabilizer, the basic physical parameters and shear strength parameters of this reinforced expanding clay were examined from an engineering standpoint [17]. The expansive clay soil's water sensitivity, compaction properties and shear strength were all greatly enhanced by the F1 ionic soil stabilizer.