Abstract: The strength development of solidified soil would be limited by the incompletely hydrated cement particles for the gradually reduced Ca2+ concentrations as the hydration reaction proceeds. Theoretically the unhydrated cement particles would be catalyzed by the active substances in cementitious capillary crystalline waterproofing (CCCW) materials. Using sulfur aluminate cement (SAC) as cementitious material, CCCW as additive, a series of experiments was conducted in a single-mixed or admixed way. The properties of solidified soil including unconfined compressive strength (UCS), water stability, the ability resisting wetting-drying cycles and microstructure were analyzed with X-ray diffraction (XRD) and scanning electron microscope (SEM) characterization. The results show that the UCS of soil solidified by 16% mixture (4% CCCW+12% SAC) is 1.5 times the soil solidified by the same content of SAC and 1.41 MPa higher than the soil solidified by 20% SAC. The average softening coefficient of the soil solidified by 16% mixture (4% CCCW+12% SAC) reaches 0.97 after 2-8 days soaking in water while only 0.73 of the soil solidified by SAC. The UCS of soil solidified with single-mixed gradually decreases with the increase of wetting-drying cycles while wavy development of solidified soil with admixed. The generation amount of AFt increases and the microfractures are repaired in solidified soil by the active substances in CCCW. Two or more soil particles are connected by AFt and a three-dimensional net structure is formed with a significantly increased aspect ratio. It is shown that the properties of soil solidified by SAC including the UCS, water stability, ability resisting wetting and drying cycles are improved due to the application of CCCW.

Key words: solidified soil, cementitious capillary crystalline waterproofing materials (CCCW), unconfined compressive strength, water stability, wetting and drying cycles, microstructure