Fundamental study on CO₂ curing conditions for efficiently neutralizing alkali construction sludge treated by paper sludge ash

Abstract

Construction sludge is often modified in the process of generation or intermediate treatment, and the modified sludge often shows high alkalinity. Recently, as one of the methods to reduce the pH of such alkali construction sludge, the modified construction sludge is placed in a pool and aerated with CO₂ gas from the bottom to the top. However, it is difficult to monitor the progress of neutralization of the modified sludge and to predict the completion time.

In this study, we conducted a column-type neutralization test in which CO₂ gas was aired into a cylindrical specimen and simulated the test results to investigate efficient neutralization conditions by predicting the progress of neutralization and completion time. The results showed that the amount of CO₂ input that does not contribute to neutralization could be suppressed by changing the flow rate in the middle of the flow rate for a constant flow rate condition, while keeping the completion time of neutralization the same.