###### Abstract  
This study aims to optimize the sustainable utilization of excavated soil by incorporating it exclusively as a fine aggregate and cement in the formulation of soil-based controlled low-strength materials. The polycarbonate superplasticizer was introduced to enhance flowability. Various factors, including the cement contents, initial water contents, and curing time, were systematically analyzed for their effects on the fresh properties, mechanical parameters, transverse relaxation time distribution, pore size distribution, porosity, and corrosivity of soil-based controlled low-strength materials. The results indicate that polycarbonate superplasticizer effectively dispersed clay minerals and cement particles, enhancing the flowability. The unconfined compressive strength increased with the rising cement content and decreased with the increasing initial water content. Additionally, the transverse relaxation time distribution curves of the soil-based controlled low-strength materials exhibited two peaks. These curves shifted to smaller transverse relaxation time values with the increasing cement content, while gradually shifting to larger transverse relaxation time values with the increasing initial water content. An increase in the cement content resulted in higher volume percentages of small and mesopores, while extra-large pores and macropores decreased. The addition of the polycarbonate superplasticizer had minimal impact on the pore volume percentage distribution. Furthermore, porosity experienced a decline with the rise in the cement content and curing time, in contrast to a notable increase with a higher initial water content. This investigation provides valuable insights into the engineering properties and microstructural characteristics of soil-based controlled low-strength materials, offering a foundation for sustainable waste management practices in geotechnical applications. also poses environmental threats, particularly in urban areas. To address the disposal of excavated soil, increased attention has been given to its potential use as a partial substitute for fine aggregate in CLSMs. CLSMs incorporating soil are referred to as soil-based CLSMs, soil cement slurry, and ready-mixed soil materials [5]. Various research highlights the successful application of the excavated soil as a constituent in CLSMs [5,6]. For example, the high-plasticity clays could be utilized for the preparation of CLSMs [6]. Flowability is a crucial parameter for evaluating the workability of CLSMs. Both the water content and fine particle content play pivotal roles in the flow value of soil-based CLSMs [7]. Due to the high water absorption capacity of clay fines in soil, soil only partially replaces the fine aggregate in CLSMs, with a small mix proportion of soil in soil-based CLSMs [8]. Specifically, the proportion of excavated soil classified as silty sand should not exceed 30% when substituting for ponded ash in CLSMs [9]. [PERSON] and [PERSON] [10] pointed out that in general, flowability is primarily controlled by the amount of water. They observed an increase in flowability with a higher ratio of water to solid, recommending optimal ratios of 0.5-0.7 for cement to water and 0.7 for water to solid, considering flowability, strength, and bleeding. In cases where the added water was fixed, the proportion of excavated soil increased from 10% to 40%, resulting in a reduction in the flowability of the mixture approximately from 275 mm to 161 mm [9]. However, the water added to enhance flowability often surpasses the requirements for cement hydration, leading to excess water and subsequent strength reduction [10]. The research on using only clayey soils as aggregates in soil-based CLSMs is limited [6,10]. Polycarboxylate superplasticizer (PCE) is widely utilized in concrete engineering for its superior water reducing rate [11]. It effectively absorbs and disperses cement particles, reducing water consumption and enhancing the concrete strength. PCE has been recommended to decrease the water demand of CLSMs [12].