Abstract
The influence of NaCl on initial strength enhancement effect of concrete using seawater as mixing water is dominant, which is the main component of seawater. The initial hydration of the C3S is promoted by NaCl. Compared with the case of using tap water, it was confirmed that the formed tissue is denser. Previously, self-compacting concrete using sea water and unwashed sea sand for urgent restoration works as well as for construction work at isolated islands and other similar region where fresh water is not sufficient was developed. In this study, strength, drying shrinkage and thermal properties of concrete with sea water and unwashed sea sand are experimentally examined. It is found that initial strength development increased as compared with the control concrete made of tap water and land sand. Drying shrinkage strain and autogenous shrinkage strain of concrete were almost equal or higher than the control concrete, but the improvement of crack resistance was observed. Furthermore, in regard to the thermal properties, the rate of temperature rise due to the accelerated hydration reaction and the coefficient of thermal expansion was slightly larger. Considering these properties, the proposed concrete can possibly be used for un-reinforced concrete application.
