EFFECT OF CEMENT ADMIXTURE ON CHARACTERISTICS OF CONCRETE

Ordinary portland cement using of less than 5％ of cement admixture has been being manifested by JIS R 5210. In the future, from the viewpoint of reducing environmental load, increases of cement admixture might be considered. However, there have been few studies on concrete using cement admixture. It is necessary to investigate the influence of cement admixture. The authors carried out a study about characteristics of concrete with different placing and curing temperature. Limestone powder and ground granulated blast-furnace slag were used as cement admixture. Cement admixture were increased from less than 5％ to 15％. As the result, the concrete using cement admixture showed similar consistency and strength comparable to ordinary portland cement at each temperature. The concrete used ground granulated blast-furnace slag replaced to 5％ to 10％ ordinary portland cement showed high carbonation rate coefficient and low diffusion coefficient of chloride ion. On the other hand, the concrete used limestone powder replaced to 15％ ordinary portland cement showed similar carbonation rate coefficient and diffusion coefficient of chloride ion comparable to ordinary portland cement. Effect of cement admixture on drying shrinkage and autogenous shrinkage of concrete were small.現行では5％以下となっている普通ポルトランドセメントの少量混合成分を15％まで増加した場合のコンクリートの諸性状を検討した。石灰石微粉末と高炉スラグ微粉末を15％まで混合した混合成分増量セメントは、コンクリートの打設温度、養生温度が変化しても、流動性、強度発現は普通ポルトランドセメントと同等であった。混合成分増量セメントは、普通ポルトランドセメントに比べて中性化抵抗性はやや劣り、塩化物イオン拡散係数は石灰石微粉末のみを増加した場合はほぼ同等となり、高炉スラグ微粉末を増加した場合は小さくなった。