Abstract
Deformation and time dependent behavior of thermal expansion coefficient of hardened cement paste in early ages, namely up to 7 days, are investigated. Binders of these hardened cement pastes are Portland cement, Portland cement containing 30％ or 45％ mass of blast furnace. Water to cement ratios of cement paste samples are 0.40 and 0.55, and temperature conditions are 20℃ constant and temperature history up to 60℃ emulating mass-concrete. As a result, in the case using blast furnace slag and the case of Portland cement with W/B＝0.40, thermal expansion coefficient showed local minimum value around 1 day, and after that it gradually increased. And this time dependent change of thermal expansion coefficient produced temperature strain. The amount of this temperature strain is relatively large, and in the case of W/B＝0.40 and binder of 30％ blast furnace slag, temperature strain occupies more than 80％ of the total shrinkage. This result implies that it is quite important to consider the time dependent behavior of thermal expansion coefficient when the mechanism of autogenous shrinkage under temperature history, cracking mechanism of mass-concrete, and countermeasures for the cracking of concrete with temperature rise due to heat of hydration are discussed.
