Effect of Heat Curing Methods on Temperature Profile and Strength Gain of Wall Concrete subjected to Severely Low Temperature Condition

극저온 조건에서 보온 양생방법이 벽체 콘크리트의 온도이력 및 강도발현에 미치는 영향

This study is to investigate the effect of heat curing method on the temperature history and early strength development of the concrete applied for a nuclear power plant structure exposed to severe environment, up to $-20^{\circ}C$. Various types of insulating methods (namely conventional form, insulating form, heating mat and heating cable) were compared to find the optimum measure for developing the required strength in such harsh environment. Thermo-couples were implemented in 6 positions in the concrete specimens and one position outside. Test results showed that under exposure of $-20^{\circ}C$, for the use of the conventional form, the average temperature inside of the concrete dramatically dropped to under $-15^{\circ}C$, whereas the application of other forms maintained the concrete temperature of over $0^{\circ}C$: the application of heating cable was the highest followed by that of heating mat and insulating form. For maturity development of these concretes, the control concrete with the conventional form could not achieved the required level, $64\;^{\circ}D{\cdot}D$, but other concretes achieved the required level within 3 days. Again, the application of heating cable in this analysis was the most effective. This study compared the experimental results with a logistic model and found that the results were slightly higher for the concretes exposed to $-10^{\circ}C$ and similar for the concrete exposed to $-20^{\circ}C$, compared to the results obtained from the model.