# Improving Geotechnical Properties of Expansive Subgrade Using Sugar Cane Molasses and Cement
## 1 Introduction  
Expansive soils, also known as swelling soils, are a significant geotechnical challenge worldwide. These soils undergo dramatic volume changes due to fluctuations in moisture content, which cause them to expand when wet and contract when dry. This cyclical expansion and contraction lead to a variety of structural problems, particularly affecting infrastructure like roads, pavements, and low-rise buildings. The primary factor contributing to this behavior is the presence of clay minerals, particularly montmorillonite, which have a high shrink-swell potential. The excessive volume changes associated with these soils are responsible for severe damage to the engineering properties of buildings and roads, leading to costly repairs and, in some cases, structural failure [1]. The presence of expansive soils is especially problematic in regions with arid and semi-arid climates, where moisture fluctuations are more pronounced. Countries like Ethiopia, Kenya, China, India, the USA, and Australia are notably affected by expansive soils, as these areas experience significant seasonal changes in moisture levels. These changes cause repeated cycles of swelling and shrinkage, which impose stress on infrastructure built on or in these soils [2]. The moisture-driven swelling mechanism of expansive soils is primarily attributed to the mineral composition of the soil, particularly its high content of montmorillonite. This mineral has a layered structure, which allows water molecules to enter and cause swelling. When the soil dries, the water molecules leave, causing the soil to contract. This process leads to significant geotechnical problems, including differentialsettlement, foundation instability, and the cracking of walls and pavements [3]. Given these challenges, it is essential to either remove and replace expansive soils or improve their properties through stabilization techniques. The most common stabilization techniques involve mechanical compaction and the use of various calcium-rich chemical additives, such as lime or cement, which react with the soil to enhance its engineering properties. However, the selection of the appropriate stabilization method depends on several factors, including the type of soil, the project requirements, and the economic feasibility of the stabilization technique [4]. Cement stabilization is a widely used method for improving the properties of expansive soils. Portland cement, when mixed with expansive clay soils, reacts with water and the minerals in the soil to form cementitious compounds. These compounds bind the soil particles together, reducing the plasticity and swelling potential of the soil. Additionally, cement stabilization increases the soil's strength, making it more suitable for construction purposes [5]. Research by [PERSON] et al. [6] has demonstrated that varying the cement content in expansive clay soils can lead to significant improvements in their geotechnical properties. Specifically, they found that the liquid limit (LL) decreased, the plastic limit (PL) increased, and the plasticity index (PI) decreased with increasing cement content up to a certain point, beyond which the effects became less pronounced. However, cement stabilization has several notable drawbacks. One of the primary issues is the high cost associated with the large quantities of cement required for stabilization, making it economically unfeasible in many regions, particularly in developing countries. Additionally, soils stabilized with cement are prone to shrinkage cracks due to the rapid setting time of the cement, which can make it difficult to achieve proper compaction during construction. These shrinkage cracks compromise the integrity of the stabilized soil and may lead to structural issues in the future [7]. As a result, alternative methods of stabilization that are both cost-effective and environmentally sustainable are being explored. One such alternative is the use of sugar cane molasses, a byproduct of the sugar manufacturing process.