Investigation of desiccation cracking in unsaturated clays improved by recycled micro-concrete particles

Soil improvement techniques can effectively improve the structural properties of soil, suppress soil cracking, and have a wide range of applications. This study found by mathematical derivation that the fractal dimension (D) of crack networks should be consistent and that D has advantages in characterizing soil cracks. In this paper, we study the laws of change in water content, suction, D, and crack ratio of clay improved with different contents of micro-concrete particles. Research showed that: (1) during the process of crack development, the trend of various parameters for all samples is basically the same over time. As water content decreases and suction increases, D and crack ratio continue to increase. When there is no shift in the water content, the remaining parameters gradually stabilize and eventually reach their maximum values. (2) Compared with untreated clay, clay mixed with micro-concrete particles has a later formation time for cracks at all levels, a higher residual water content and suction, and a decrease in the maximum values of D and crack ratio. (3) In both sets of samples, the residual water content of samples with 5% waste content micro-particles increased by 195% and 230%, respectively, and the maximum D and crack ratio decreased by 8.38%, 28.38%, and 8.84%, 24.41%, respectively, compared to untreated clay. The results show that micro-concrete particles can improve the structural properties of clay, with 5% micro-concrete particles having the best effect in inhibiting clay drying and cracking.