Abstract: Sludge is a kind of soil with very poor engineering properties and difficult to solidify rapidly. Through unconfined compressive strength test, consolidated drained triaxial test, micro test and mercury intrusion test, the strength development law of sludge solidified by composite rapid soil stabilizer (CRSS) and the influence of the content of soil stabilizer on the strength are studied, and the micro mechanism of strength development is preliminarily discussed. The results show that the strength of CRSS-solidified sludge increases logarithmically with the curing age, the early strength develops rapidly, and the unconfined compressive strength can reach 3 MPa after curing for 1 h; with the increase of stabilizer content, the triaxial shear stress-strain curve of solidified sludge gradually develops from strain hardening type to strain softening type, and the failure deviatoric stress and cohesion increase linearly. The microstructure shows that the hydration products of stabilizer can cement soil particles, fill soil pores and enhance the integrity of soil. The mercury intrusion test results further reveal the mechanism that the cohesion of solidified sludge increases linearly with the increase of the content of stabilizer through the connection of the most probable pore size. CRSS-solidified sludge has significant advantages of fast hardening and high strength, which provides a theoretical basis for the application of rapid solidification of sludge.

Key words: composite rapid soil stabilizer, rapid solidification of sludge, compressive strength, micro mechanism