Abstract: Application of cement-solidified mud to filling projects can mitigate the local scarcity of sand and gravel filling material and dispose of significant volumes of dredged mud. Nevertheless, when the dredged mud is at extra-high water content (>300%), the treatment efficiency of pure chemical solidification becomes very low. However, such problems can be effectively solved by treating mud slurry using the physicochemical composite method. As the quicklime has both the effect of flocculant and solidification agent, using quicklime to replace part of the cement may further increase the treatment efficiency. In this paper, the effect law of the replacement ratio of quicklime on physicochemical composite treatment of dredged mud slurries was studied via vane shear tests, and its solidification mechanism was revealed by XRD and FESEM tests. The results show that quicklime significantly impacts on the physicochemical composite treatment effect, and there is an optimal replacement ratio. Under this optimal replacement ratio, the quicklime can exert the dual effects of flocculation and solidification, which effectively increases the earlier and later strength of the treated mud specimens. From the microscopic test results, the treated mud samples at this optimal replacement ratio produce the highest amount of CSH/CAH/CASH, ettringite and other hydrated cementitious materials with the smallest pore gap. Therefore, quicklime can be used to replace part of the cement during the physicochemical composite treatment of dredged mud slurries in the actual project.

Key words: mud slurry, physicochemical composite method, quicklime, undrained shear strength, water content, solidification mechanism