Effective Utilization of Sludge in Concrete Using Retarder

As for the effective utilization of sludge water containing cement and fine particles of aggregate, JIS A 5308 permits now the usage under 3 percent as solids for the unit content of cement. This study, in order to utilize the larger quantity of sludge water than that now allowed in the mixing plants, is to obtain the basical data on the properties of fresh concrete and of hardened concrete. Especially, in order to stabilize the quality of sludge by preventing hardening of sludge due to the hydration of cement particles, the effect of setting retarder has been discussed experimentally. From the results of this study, it was clarified that a good quality concrete could be obtained even though the sludge mass of 9% and the sludge age of 3 days, provided that setting retarder was used adequately.