Abstract
Authors have been studying for several years as for the effective utilization of sludge water produced in ready mixed concrete plants due to washing of a mixer, agitating truck dram etc. Nowadays, JIS A 5308 permits the usage under 3 percent as solids of sludge for the unit content of cement of new concrete. Recently, it is strongly requested to re-use a further large quantity of sludge water, in order to achieve the zero-emission. Sludge water consists of cement, fine particles of aggregate and water. All materials are one of the constituents of concrete. This study, in order to utilize the larger quantity of sludge water than that now allowed, is to verify the properties of concretes containing sludge which were designed for the identical slump and compressive strength to comparative concrete. From the results of this study, it became clear that as for the sludge concrete containing sludge within the range of 3-15%, there was no problem about the properties of fresh and hardened concrete, that is, slump, bleeding, compressive strength, drying shrinkage, carbonation depth and freezing and showing resistance, etc. In other words, within the range of 15% of sludge solid content, the concrete containing sludge water with setting retarder could obtain good performance as same as comparative concrete. It was also confirmed that the bulk volume of coarse aggregate was available for the design method of concrete mixture.
