“This noon, the south tower bearing concrete has reached the temperature peak. Now it is time for cooling. Please control the temperature difference between inside and outside and its cooling speed.” According to the monitoring data provided by the mass concrete hydration heat intelligent monitoring system, the monitoring unit can timely issue temperature control instructions, which is an innovative practice of the Dongting Creek Yuan River Bridge of Zhangjiajie-Guanzhuang Expressway and also an epitome of promoting the “intelligent construction”.

Working interface of hydration heat monitoring system for mass concrete of the Bridge

Temperature control and crack prevention of mass concrete is a world-class problem recognized in the field of engineering construction at home and abroad. The hydration reaction of cement in concrete generates heat, causing the temperature of the concrete to rise after pouring, and then slowly cool down to the ambient temperature. “That's why I feel hot when I step barefoot on freshly poured concrete.”The technician explains. If the temperature can not be effectively controlled and the concrete is allowed to expand and shrink with the change of temperature, cracks will inevitably occur, which will seriously affect the integrity and safety of concrete components.

The south main tower of the Bridge is 18.8 meters long, 16.8 meters wide and 6 meters high, requiring 4700 concrete pouring. In order to solve the problem of temperature control and crack prevention from the beginning, the project construction team cooperated with JSTI Group Monitoring and Certification Co., Ltd., to jointly research and develop the intelligent monitoring system for hydration heat of mass concrete. The system automatically collects and monitors important parameters such as concrete temperature, environmental temperature, cooling water temperature and cooling water flow rate, sets the flow rate change threshold and intelligently adjusts the flow rate of cooling water, in order to realize the adaptive flow rate of cooling water, and ensure the accurate control of concrete temperature.

On the second day after the pouring of the first layer of concrete on the left side of the south tower of the bridge, the components were in the overall heating stage. On that night, there was a sudden rainstorm, and the sudden drop in temperature caused the surface temperature of the concrete components to drop rapidly. From monitoring to temperature changes, processing instructions, and accurate and efficient completion of various treatment measures, the entire process takes less than 1 hour.

“Compared to the manual method, the thermal hydration monitoring system greatly reduces the adverse impact of human factors on data collection, and has higher synchronization, continuity and accuracy, and faster processing efficiency.” the person in charge said.

In order to test the feasibility and reliability of the hydration heat monitoring system, the project construction team successfully carried out a full-size temperature control model test of 6m×6m×2.5m super bulk concrete in advance. The system has been put into practical application in the construction of concrete pouring on the left side of the south tower of the bridge, and has achieved the expected effect, which provides a more reliable practical support for the subsequent construction.