# Research and Application of Slag-Nanosilica Stabilizer for Silt Subgrade
## 1 Introduction  
Economic development and urban construction in China's coastal areas have brought about the accumulation of silting waste soil. According to official statistics, from 1950 to the end of 2015, Zhejiang Province of China excavated 272,800 h\(\mathrm{m}^{2}\) of silt [1]. The silt not only occupies a large amount of land resources and causes huge economic losses but also has practical engineering shortcomings, such as high moisture content, poor mechanical properties, and low comprehensive durability [2], which brings potential safety hazards to the construction project and people's lives. The commonly used methods for treating silt include soil displacement method [3], pile foundation method, structure optimization method [4], ocean dumping [5], etc. However, in the face of the accumulation of large tons of silt, the above methods are not perfect in the implementation process; there are great safety risks, and they are not enough to deal with all the silt. Therefore, the treatment of silt in coastal areas has become a problem that urgently needs to be solved. The application of stabilizer in soil has a long history [6]. Cement was first used as a stabilizer in the United States in the early 20 th century to mix with soil to form road material. In the 1940s, an American engineer grinded shells and mixed them with cement to stabilize soft clay soil, achieving certain results [7]. Since then, comprehensive stabilizer based on cement, lime, lime-lime or cement-lime has been developed [8]. From the 1970s, the research on soil stabilizer began to mature and the classification of stabilizer appeared, which was gradually applied to different fields [9, 10]. In recent years, studies on cement-based soil stabilizer have become more significant. For example, [PERSON] [11] developedEPS, a new soil stabilizer, to excite ordinary Portland cement and stabilize silt in Tokyo, Japan, and found that EPS has good stimulation and economic applicability. [PERSON] [12] used cement and lime to stabilize soft clay soil and found the optimal amount of lime through a series of mix ratio design. The test results also effectively showed that cement and lime could significantly improve the mechanical properties of soft clay soil. However, there are serious environmental pollution problems in the production process of ordinary Portland cement, which not only emit a large amount of CO\({}_{2}\) but also discharge dust, CO, SO\({}_{2}\), fluoride, and other gases into nature in the whole cement production line, causing obvious pollution to the air environment [13; 14]. Therefore, it is of great significance to develop a green, environmentally friendly, and economic soil stabilizer [15]. Many scholars have devoted themselves to the research of new economic and environmentally friendly soil stabilizers to make up for the defects of traditional soil stabilizers. [PERSON] [16] strengthened soft soil in the Pekan area and used the Eades-Grim pH method to determine the optimal lime content. It was found that 4% lime content could raise the pH value of the soil to 12, and the strength of the stabilized soil could reach a higher level. It was proposed that the treatment of stabilized silt by lime could be used for highway construction. [PERSON] [17] assessed the potential of using binders to stabilize expansive soil consisting of fly ash and blast furnace slag. It was found that the addition of a small amount of lime could further improve soil properties by increasing the pozzolanic activity of the binder. In addition, mineralogical and morphological studies of stabilized soil samples with optimum binder content showed that the reactions between silt and binder formed hydration particles and gel compounds. Therefore, without considering economic factors, the use of fly ash as binder to stabilize expansive soil is suitable for sustainable construction. According to the research and analysis of [PERSON] [18] and [PERSON] et al.