Effects of sample crumbling and particle size on accelerated carbonation of alkaline construction sludge treated with paper-sludge ash-based stabilizers

Abstract

Construction sludge generated from underground and pile construction works frequently appears in a liquid state. For its utilization as a construction geomaterial, it can be improved by mixing in cement or lime. The target strength can be achieved relatively easily by adjusting the amount of cement or lime added to the sludge. However, this type of chemical treatment is associated with high alkalinity, which causes environmental concerns associated with alkali leaching. In this study, therefore, the accelerated carbonation of alkaline construction sludge through treatment with a paper-sludge ash-based stabilizer (PSAS) was experimentally attempted to neutralize the pH. The alkaline sludge treated with the PSAS was exposed to pure CO2 gas to accelerate the carbonation. The effects of granulation via crumbling prior to the accelerated carbonation on the pH neutralization period were analyzed from the test results. It was observed that crumbling the sludge prior to the CO2 gas exposure accelerated the pH neutralization. These results suggest that a short pH neutralization period can be achieved by reducing the particle size. Therefore, the effect of the particle size of the PSAS-treated sludge on the pH neutralization period was also investigated. The results showed that the pH neutralization period decreased with an increasing particle size. However, it was also observed that, when the addition ratio of the PSAS was increased, the difference in the pH neutralization period induced by the change in particle size became less significant.