# Influence of Five Additives on No Loading Swelling Potential of Red Clay
## 1 Introduction  
Red clay is widely distributed in southern China. It has good engineering mechanical properties under the condition of low water content, but the clay will expand and contract under the conditions of water absorption and loss. When red clay is used as a foundation, it will deform due to the dry-wet cycle, which will have an adverse impact on the upper pavement and other structures [1]. With the construction of infrastructure and the expansion of urban areas in recent years, engineering construction increasingly needs to be carried out in areas covered with red clay. Reducing the influence of red clay swelling and shrinkage has become a common problem in engineering construction. At present, the method of replacing foundation soil with other soil is often used to eliminate the influence of expansive soil. However, the replacement method not only has the problem of high cost, but also has the problem of environmental protection; that is, the excavated earthwork is difficult to dispose of. The use of additives to modify the engineering properties of soil can fully take advantage of the role of in situ soil as much as possible, reduce the excavation and disposalof soil, and achieve the dual benefits of reducing expenses and protecting the environment. The use of additives to modify the swelling properties of expansive soil mainly considers two aspects: one is to reduce the hydrophilicity of clay particles in soil by cation exchange, and the other is to bond soil particles by the pozzolanic reaction to increase the resistance of soil expansion. Lime is one of the most commonly used additives to modify expansive soil. [PERSON] et al. studied the modification effect of lime, pozzolana, and their combination on the expansibility of black cotton soil in Kenya using the liquid plastic limit test, California bearing ratio (CBR) test, and Unconfined Compressive Strength (UCS) test. Combined with the analysis of pH, electrical conductivity (EC), XRD, and transmission electron microscope (TEM) test results, lime was found to significantly modify the physical and mechanical properties of black cotton soil. Pozzolana was also found to modify the physical and mechanical properties of black cotton soil to a certain extent, but it is not as effective as lime. The combination of lime and pozzolan to modify the physical and mechanical properties of black cotton soil can achieve better results than adding one of them alone [2]. [PERSON] et al. studied the treatment of bentonite by lime under high-temperature curing conditions and found that a certain amount of lime is used to destroy the silicate layer of bentonite and form different hydrates, whereas more than this quantity of lime results in a pozzolanic reaction to produce hydrated calcium aluminate (CAH) and hydrated calcium silicate (CSH), and a high temperature can greatly accelerate the rate of pozzolanic reaction [3]. Blast furnace slag (BFS) is a nonmetallic by-product obtained during the manufacturing process of cast iron. It consists primarily of silicates, aluminosilicates, and calcium aluminosilicates [4]. Different forms of slag products are manufactured depending on the method used to cool the molten slag. These products include air-cooled BFS, expanded or foamed slag, pelletized slag, and granulated blast furnace slag (GBFS). When crushed or ground into very fine particles, blast furnace slag has cementitious properties [5]. [PERSON] studied the unconfined compression strength of the olive-GGBS treated soil, and the experimental results showed that ground granulated blast furnace slag (GGBS) has soluble calcium, which can generate CSH gel to improve soil properties [6]. Cement is widely used in soil modification and solidification because of its large output, low cost, and small side effects on the environment.