Masahiro Ouchi

EFFECT OF SUPERPLASTICIZER ON SELF-COMPACTABILITY OF FRESH CONCRETE

The effect of superplasticizer on the balance between flowability and viscosity of mortar in self-compacting concrete was investigated quantitatively. From experimental results, the ratio of funnel speed to flow area of mortar with a fixed amount of superplasticizer was found to be almost constant, independent of the water-powder ratio. A higher amount of superplasticizer resulted in a lower ratio of funnel speed to flow area. The ratio is proposed as an index for the effect of superplasticizer on mortar flowability and viscosity from the viewpoint of achieving self-compactability. This index is convenient for evaluating the amount of superplasticizer for proper flowability and viscosity of mortar using only one set of experimental results. The relationship between superplasticizer amount and its effect was found to differ depending on the type of powder or superplasticizer. The difference can be indicated quantitatively by the proposed index.

QUANTITATIVE EVALUATION ON THE PARTICLE DISPERSION EFFECT OF A SUPERPLASTICIZER WHEN MIXING TIME IS VARIED

自己充填コンクリート用モルタルの相対フロー面積比と相対漏斗速度比の比を高性能AE減水剤の粒子分散効果の指標として, 練混ぜ時におけるポリカルボン酸系高性能AE減水剤の粒子分散効果を定量的に表した. 練混ぜ水を分割投入して練り混ぜると, 練混ぜ時間の延長によって高性能AE減水剤の粒子分散効果が低下した. この主要因は, セメント粒子の比表面積が水和反応によって練り混ぜるほど増加するためであることを示した. 高性能AE減水剤の吸着量を, 単位セメント重量当たりから単位表面積当たりに置き換えると, 粒子分散効果は単位表面積当たりの吸着量に比例した. 練混ぜ時においても, ポリカルボン酸系高性能AE減水剤の立体障害効果による粒子分散作用を明確に示した.