ＲＣＣＰ用コンクリートの配合およびワーカビリティー特性に及ぼす各種混和剤の効果

Abstract

In this report, air-entraining, high-range water reducing admixture A, water reducing agent for extremely stiff consistency concrete B, admixture B with viscosity increasing admixture C and normal water reducing agent D were used and each one was added to the concrete for roller compacted pavement having the water cement ratio of 0.37. In order to compare the effect of each admixture on the mixture proportion and workability of concrete, the unit water content and sand percentage were varied and vibrating compaction value measured by a Swedish-type Vebe apparatus, compaction ratio, surface vibrating compaction time to get a fully compacted state and segregation degree taken place by falling were determined. The conclusions were as follows;(1) In the case of a constant unit water content, the minimum vibrating compaction value, minimum surface vibrating compaction time and maximum compaction ratio were obtained at a sand percentage for each admixture but the segregation degree became maximum. This phenomenon was closely related to the fluidity and viscosity of mortar component and mixture proportion such as the ratio of mortar content to coarse aggregate content.(2) In the case of a constant vibrating compaction value and maximum compaction ratio, the sand percentage was least by adding admixture B and the unit water content was least by adding A or C, and the surface vibrating compaction time was least by adding admixture D and the segregation degree was least by adding A or C, respectively.(3) It can be thought that admixture B is effective to improve the abrasion resistance and A or C is of use to reduce the unit cement content and segregation degree. An admixture with viscosity increasing admixture is more effective to reduce the segregation degree.