## 1 Introduction
In the future, power demand will keep increasing in China; specifically, the total amount of FA is expected to accumulate to approximately 3 Gt by 2020 [43]. The vast volumes of solid waste will take up large areas of landfill; this condition will destroy ecological environments, pollute water, soil, and the atmosphere, and even cause geological disasters [44; 45]. Thus, the reclamation of FA as sustainable waste is necessary to solve environmental pollution in landfill sites and climate change. Class C FA of cementitious and pozzolanic properties was used in this study. It typically incorporates more than 10% CaO and mainly conduces to the hydration of FA. cementitious materials are formed by the reaction of CaO with the pozzolans (SiO\({}_{2}\), Al\({}_{2}\)O\({}_{3}\), and Fe\({}_{2}\)O\({}_{3}\)), and hydrated calcium silicate gel (C-S-H) or calcium aluminate (C-A-H) gel as a cementitious material can bond inert materials together with the presence of water [46; 47]. Given its pozzolanic properties, FA has been successfully used as an effective agent for chemical and mechanical stabilization of loess through modifying the particle size distribution, enhancement in bonding strength between particles, and destruction of its open structure [48; 49]. Therefore, FA can improve soil density and plasticity and reduce water content and strength performance of loess; thus, FA has been used in treating loess soils by many researchers in recent years [50; 51; 52; 53; 54]. For example, [PERSON] et al. (2003) studied the influence of FA on strength behavior of three different types of soil by using different percentages of FA from 9% to 46% by weight of the soil [55]. [PERSON] (2004) explored the potency of Class C FA as an expansive soil stabilizer, which is effective in improving the plasticity of soils [52]. [PERSON] et al. (2009) examined the engineering properties of class C FA mixed with loess [56]. [PERSON] et al. (2013) analyzed the optimum usage of FA for stabilization of subgrade soil by using genetic algorithm [57]. The above-mentioned studies have investigated the effect of FA on the geotechnical properties of loess, but most of them have focused on FA stabilization methods without investigating curing and comparison between submergence and non-submergence of FA stabilized loess (FASL) samples. Loess has relatively high strength and low compressibility at moisture contents lower than the optimum because of partial cementation by CaCO\({}_{3}\), iron oxide, and clay minerals [58]. If the moisture content goes beyond optimum, then the clay and CaCO\({}_{3}\) can soften, which results in the collapse of the loess soil structure [59]. Thus, loess stabilized by FA requires further critical examination, and practice in various conditions is necessary for loess ground improvement. The augmentation in curing time has also been adopted to increase the strength of the soil and decrease its compressibility [57]. Thus, this work was carried out to investigate the influence of submergence on the stabilization of loess in Shaanxi Province by the addition of FA via laboratory study. This study aimed to investigate the effect of FA on the strength behavior of loess through exploring the Atterberg limits, standard Proctor compaction (SPC), unconfined compressive strength (UCS), and California bearing ratio (CBR) with curing time under non-submergence and submergence conditions and swell potential of CBR during soaking.