Nobukazu Nito

STRENGTH DEVELOPMENT AND SHRINKAGE CRACKING TENDENCY OF CONCRETE WITH BLAST-FURNACE SLAG CEMENT USING HIGH ALITE CLINKER

In order to reduce CO₂ emission on the process of cement production, it is efficient to use blended cement widely for concrete structures instead of ordinary Portland cement. From this point of view, blast-furnace slag cement has been widely used for civil engineering structures in Japan. However, blast-furnace slag cement has rarely been used for reinforced concrete buildings, mainly because strength development of this type of cement is slower at early ages compared to ordinary Portland cement. In this study, in order to improve strength development of blast-furnace slag cement concrete at early ages, a sample of high alite clinker with C₃S content of 72%, by Bogue equation, was manufactured at a commercial cement plant. Strength development and shrinkage cracking tendency of blast-furnace slag cement with slag content of 20% using the high alite clinker were experimentally investigated. Influences of temperature and moisture condition on strength development were also investigated. Tendency of cracking due to dying was investigated with uniaxial restraint tests, in which the drying period until cracking was observed. It was proved from the experimental results that early-age strength development of blast-furnace slag cement was improved by using the high alite cement especially at low temperature. Shrinkage cracking properties was also improved compared with ordinary Portland cement and conventional blast-furnace slag cement type A.高炉セメントを用いたコンクリートの初期材齢における強度発現性の改善を目的とし、エーライト量の大きいセメントを実機プラントで試作した。このセメントに高炉スラグ微粉末を20％混入した高炉セメントを用いたコンクリートの強度発現性および収縮ひび割れ抵抗性について実験により検討した。その結果、高エーライトセメントを用いた高炉セメントは、普通ポルトランドセメントや通常の高炉セメントと比較して、低温時においても強度発現性に優れており、収縮ひび割れ抵抗性の向上も期待できることが明らかとなった。