This study discovered that the combination of waste gypsum and fly ash was capable of being used as fine aggregate in concrete. However, results showed that the unit water amount of the concrete with waste gypsum had to be increased to assure the designated workability. In general, if the unit water amount of concrete increases, hardened concrete will have various issues. Therefore, in this study, we try to reduce the unit water amount of this concrete by the high-performance AE (Air Entraining) water reducing agent containing viscosity improver. In order to investigate the effect of the above AE water reducing agent for the reduction of the unit water amount of the concrete with waste gypsum, the workability of above concrete with this agent from slump test and air containing test was examined. Also, compression, tension, and bending, of the concrete with waste gypsum from each strength test was measured. On the basis of the test results, it showed that we are able to assure the workability of fresh concrete with waste gypsum by the above agent used in this study, even if the unit water amount is reduced. Also, it was confirmed that the compressive strength of concrete with waste gypsum is equivalent to the strength of concrete without waste gypsum.
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