Laboratory investigation of microstructure, strength and durability of cemented soil with Nano-SiO2 and basalt fibers in freshwater and seawater environments.

• The incorporation of basalt fibers can improve the compressive strength of nano-SiO 2 cemented soils in both seawater and freshwater environments. • The addition of basalt fibers to nano-SiO 2 can effectively increase the unconfined compressive strength and ductility of cemented soil specimens in both freshwater and seawater environments. • Nano-SiO2 promotes the hydration reaction, leading to the formation of a greater amount of hydration products that encompass the basalt fibers, thereby enhancing the bonding and friction between the basalt fibers and the cemented soil. • Adding nano-SiO 2 to cemented soil blended with basalt fibers increases the optimum fiber content in marine environment to 0.3 %. In freshwater situations, an optimum fiber concentration is 0.6 %. • Seawater can boost soil compressive strength when early hydration products are scarce in cemented soil. However, seawater may diminish soil compressive strength if otherwise. The marine environment exposes cemented soils to a variety of adverse environmental conditions, which could substantially compromise the reliability and durability of foundations constructed on these engineered soils. Some researchers have recently proposed using nanoparticles to effectively strengthen and enhance the structure of cemented soil; however, this may compromise the ductility of cemented soils. Alternatively, some researchers have utilized basalt fibers to promote a stable network within the cemented soil by adding adhesion to the soil matrix, but this frequently results in a reduction in compressive strength. To address these issues, the addition of nanoparticles and basalt fibers to cement-treated soils is proposed as an engineering solution for extending the service life of cemented soils with adequate strength and durability in both freshwater and saltwater environments. This investigation utilized six different Nano-SiO2 concentrations and four different basalt fiber concentrations in the specimens. The specimens were then cured for 28 days in both freshwater and saltwater environments, and unconfined compressive strength tests (UCS), scanning electron microscopy (SEM), and X-ray diffraction (XRD) experiments were performed to evaluate their properties, i.e. the microstructure, strength, and durability of cemented soil. The research results indicate that compared to conventional cemented soils, the improvement ratios after adding the optimal ratio of additives are 21 % (in freshwater environment) and 15 % (in seawater environment) for basalt fiber cemented soil, 196 % and 161 % for Nano-SiO 2 cemented soil, and 257 % and 214 % for Nano-SiO 2 /basalt fiber composite cemented soil. Nano-SiO 2 promotes the hydration reaction to generate more C-S-H, which wraps around the basalt fibers, enhances the bonding of basalt fibers in the cemented soil, effectively improves the mechanical properties and internal structure of the cemented soil, and the improvement effect is not weakened by seawater erosion. [ABSTRACT FROM AUTHOR]