Experimental investigation on waste slurry improvement using vacuum preloading with calcium oxide

Vacuum preloading with the flocculation method has good engineering benefits in treating waste slurry. The related research mainly focuses on the effect of the treatment method on the dehydration effect. However, the mechanism of flocculant’s effect on the vacuum consolidation rate of slurry is not precise. This study aims to explore the mechanism of CaO’s influence on the vacuum consolidation rate of the slurry. First, the waste slurry was pretreated with different percentages of CaO (0 ~ 0.6%). Then, a one-dimensional vacuum consolidation experiment was carried out on the pretreated slurry. Finally, the influence mechanism of different CaO additions on the vacuum consolidation rate of the slurry was explored by analyzing the relationship among PSD, thermal fractal dimension, permeability, and vacuum drainage rate. The results show that the permeability coefficient, cumulative total pore volume, and thermal fractal dimension of slurry increase first and decrease with CaO content. The optimal addition amount of CaO is 0.4%. Furthermore, the larger the thermal fractal dimension of slurry, the larger the cumulative pore volume, the more complex the pore structure, the better the permeability, and the faster the vacuum consolidation rate.