Research on hydration heat temperature field in mass concrete baseplate of large water conveyance pump station

The temperature field distribution and development of hydration heat of mass concrete at early ages are very important for the safety of structure. Based on the monitored data of a thick concrete baseplate in a deep foundation in Shanghai Qingcaosha Raw Water Engineering, the temperature distribution and development process with temporal variation were studied. It´s found that the cement hydration change greatly in the first 2.5 days and the temperature distribution in the thickness direction is high in the middle and low at both sides with a shape of asymmetrical parabola. It´s also found that the temperature gradient is quite gentle in the middle but steep at both sides. The upper surface of concrete baseplate was influenced by the ambient temperature mostly, so the temperature gradient was most steep and it´s the most dangerous part. The temperature difference between the internal part of the baseplate and the surface experienced a process of increase at first and then decrease. The biggest temperature difference occurred in the initial stage of temperature depression in the middle part when the hydration heat completely released, which was about 3 days after the concrete was cast. So it´s the most dangerous period of concrete in the first 3 days. It´s also proved by the monitored data that concrete curing by water storage can effectively reduce the influence of ambient on the temperature field distribution in the concrete baseplate, which was beneficial to the control of temperature crack. At last, some suggestions were put forward for the control of temperature stress for mass concrete baseplate.