Properties and mechanism of CFBC fly ash-cement based stabilizers for lake sludge

Circulating fluidized bed combustion (CFBC) fly ash was mixed with cement or lime at a different ratio as a stabilizer to stabilize lake sludge. In order to understand the influences of stabilizers on the lake sludge properties, tests unconfined compressive strength, water stability and SEM observation were performed. The experimental results show that with the increase of the curing time, the strength of all the stabilized specimens increase, especially the samples containing cement. The strength of the specimens is decreased with the increasing of the CFBC fly ash/cement ratio, the optimum ratio between CFBC fly ash and cement is 2:3. The water stability of CFBC fly ash-cement based stabilizers is higher than those of cement and lime. Moreover, the lake sludge stabilization mechanism of CFBC fly ash-cement based stabilizers includes gelation and filling of the hydration products, i e, C-S-H gel and the AFt crystal, which act as benders to solidify those particles together and fill in the packing void of the aggregates.