Strength enhancement of cement-based stabilized clays via vacuum-assisted filtration

The performance of the cement-based stabilized clay (CBSC), a kind of typical composite, is controlled by the homogeneity and interactions among the hydration products of the cementitious agents, clay minerals and water. For the shallow lowland ground by hydraulic filling or natural deposition with very high-water content, more cementitious agent was required to realize the designed strength when block solidification, where a higher water content should improve the feasibility and homogeneity but decrease its strength. To overcome this contradiction, a vacuum-assisted filtration technique used in sludge and concrete treatment was extended to remove excessive water within the CBSC for strength enhancement. Experiments including the laboratory and pilot project were conducted to study the efficiency of the filtration method by investigating tailing water volume, strength and microstructure of the CBSC. Results reveal that applying the filtration method can effectively discharge the free water from the CBSC within the initial 12 hrs’ hydration of the cementitious additives, with a reduction in water content by 5.8–24.7 %, accompanied by an increase in the 28-day’s strength by more than 1.7 and 1.6 times in the laboratory and field respectively. Microstructural and chemical analyses also reveal that the strength improvement originates from the enhanced mixing homogeneity facilitated by higher water content and subsequent filtration for cementation development. After the auxiliary filtration process, both the total porosity and water content decrease, and the large pores are transformed into smaller ones.