Effect of cooling water temperature and space between cooling pipes of post-cooling system on temperature and thermal stress in mass concrete

Hydration heat trapped in concrete can cause cracks due to thermal stress caused by temperature gradient inside the concrete. The trapped heat can be removed by using a post-cooling system, where the concrete is cooled by running water through pipes embedded in it. However, post cooling may cause thermal stresses owing to the temperature gradient in the region adjacent to the cooling pipe. In this study, the thermal stress and temperature gradient caused by the space between the cooling pipes and cooling water temperatures of the post-cooling system are investigated numerically. Based on the concrete type, thermal properties and dimension of post cooling components used in this study, it was found that, compared to cooling water temperature, the space between the cooling pipes had a stronger effect on the distribution of temperature and thermal stress in the concrete. The increase in cooling water temperature tend to increase concrete temperature and decrease thermal stress especially in region next to cooling pipe, while the increase in distance between cooling pipe tend to increase both of concrete temperature and thermals thermal stress near the cooling pipes. To reduce the risk of concrete cracking due to post cooling, it is not enough just to adjust the temperature of the cooling water and space between cooling pipes. The cooling water temperature, space between cooling pipe and convection coefficient from surface of cooling pipes to cooling water need to be set to obtain a temperature distribution which result a thermal stress which lower than tensile ultimate strength of the concrete.