The solidification effect of contaminated soil degrades under wet-dry (W-D) cycles and acid rain. Acidic dry-wet cycle tests for Cr-contaminated soil solidified by alkali-activated granulated blast furnace slag (GGBS) are carried out. Toxic leaching test and accelerated leaching test are performed to study the leaching characteristic and mechanism. Scanning electron microscopy and energy spectrum analysis are used to investigate the microscopic mechanism. The long-term stability is evaluated through the apparent diffusion coefficient. The results show that a few W-D cycles at pH=7 will cause additional hydraulic reaction of GGBS and thus reduce the leaching concentration of total Cr and Cr(VI). Along with W-D cycles more AFt is generated. The expansion of AFt results in micro-fracture and thus more Cr leaching. In acidic W-D cycles

AFt dissolves first

releasing Cr immobilized by ion exchange. With the increasing acidity

C-S-H gels dissolve and more gypsum is generated

resulting in more micro-fractures. Consequently

the encapsulation effect weakens

resulting in more Cr leaching. However

the C-A-S-H gels remain stable. The slopes of the logarithmic curves of cumulative leached fraction versus time range from 0.373 to 0.675. The errors of fitting by a pure-diffusion analytical solution are mainly below 0.5%

indicating that diffusion is the dominant leaching mechanism. However

after 18 W-D cycles at pH=3

the effect of dissolution increases and the diffusion-dominated criteria are not satisfied. The mobility of Cr under neutral

weak acidic

and strong acidic W-D cycles is low

moderate

and high

respectively. It is necessary to take measures to reduce acid rain infiltration and W-D cycles when utilizing solidified soil. This research provides a reference for evaluating the long-term stability of solidified contaminated soil.