A water reducing agent P, an agent for extremely stiff consistency and lean mix concrete R, an agent for lean mix concrete Y and an air entraining agent V were used as the admixtures. The consistency and compaction characteristic of extremely stiff consistency and lean mix concretes with these admixtures were investigated by comparison. The VC value of the concrete decreased linearly with increasing unit admixture content. The decrement degree of VC value was about 5 to 10 seconds per 1kg/m3 of admixture content and it was almost the same for all the admixtures. The flow value of mortar comprised in the concrete increased with increasing unit admixture content. The increment degree of flow value for the mortar with admixture R or Y was considerably higher than that of mortar with P or V. The flow values of mortars with admixture R, Y, P and V were 160, 140, 117 and 116, respectively, for the concrete with the VC value 20 seconds. The optimum compaction periods to obtain the efficient compaction degree of concrete with admixture R, Y, P and V were 120, 160, 190 and 270 seconds, respectively, for the VC value 20 seconds. The VC values of the concretes with admixture Y, R, P and V changed from 20 seconds to 30, 38, 51 and 51 seconds, respectively, at the elapsed time after mixing 90 minutes.
