Strength and hygroscopic behavior of biopolymer-treated silty sand under remodeling and dry-wet cycles

The soil construction materials are usually subjected to repeated remodeling in engineering applications, such as subgrade or foundation filling. However, the mechanical behavior of biopolymer-solidified soils (BSS) after remodeling is still unclear. This study used two biopolymers, xanthan gum (XG) and guar gum (GG), as representatives to improve the mechanical properties of silty sand dredged from the Yellow River. The unconfined compressive strength (UCS), hygroscopicity, and microstructure properties of BSS were analyzed through a series of experiments considering the remodeling cycles (including dry-wet cycles). Results showed that when the biopolymer content reached 1%, both XG and GG solidified soils exhibited good self-healing ability of strength and microstructure under remodeling cycles. The mechanical properties and durability of XG under remodeling cycles are obviously better than those of GG. Moreover, the hygroscopicity of BSS gradually decreased with an increase in dry-wet cycles. FTIR results indicated that during the first five dry-wet cycles, the properties of hydrophilic groups in XG and GG remained stable, and the hydrolysis degree of XG and GG molecular chains further increased, which confirms the strength improvement of BSS during the remodeling cycles.