Mechanism and crack research of sodium silicate-slag-basalt fiber ternary synergistic solidification of silty clay

To address the engineering challenges of poor mechanical properties and easy shrinkage and cracking of silty clay, this study developed a ternary composite solidification system composed of sodium silicate (SS), slag (SL) and basalt fiber (BF) based on the concept of green and sustainable development. Unconfined compressive strength (UCS) tests were conducted using the center composite rotational design (CCRD), a multivariate nonlinear regression model of material ratio and compressive strength was constructed, and the synergistic curing mechanism among the three components was revealed. The results show that the optimal mix ratio of the composite solidified silt is 7.763% SS, 9.955% SL, and 0.295% BF, with a 7-day UCS value reaching approximately 157 kPa, an increase of 214% compared to the undisturbed silt. Combined with quantitative PCAS crack identification and PIV displacement vector analysis, it was found that the alkali-induced effect of SS dissolved the active components in SL and generated C-S-H gel and ettringite, significantly reducing the crack ratio by filling pores. BF, with its three-dimensional network distribution, formed a "bridging-reinforcing" effect, effectively inhibiting the propagation of microcracks. As the solidification effect intensified, the failure mode of the sample changed from the brittle shear localization of pure silt to ductile expansion deformation, with a significant increase in shear band thickness and a greatly enhanced energy dissipation capacity. This study provides a scientific basis for the development of green geotechnical materials in the Yellow River Delta region.