Research On Temperature Control Of Mass Concrete Structures

Preventing the concrete crack is very important research topic in design and construction of the mass concrete structures. There are two main deformations during the curing of the mass concrete structures:temperature shrinkage deformation due to failing temperature and hydration shrinkage deformation resulted from the cement hydration action; under the constraint condition, these deformations will produce tensile stresses inside and outside of the mass concrete structures. When the tensile stress in the mass concrete is greater than the concrete tensile-resistant strength, the structural crack will appear. So, in order to avoid greater temperature stresses during the construction of the mass concrete structures and prevent the generation of the cracks or even control the width of the cracks within the certain limitation, some methods of temperature control must be done.In this research, the temperature control, tracking and measuring for temperature variation of the mass concrete at the dragon gate Huanghe long bridge was carried out. The Project has achieved effective control of mass concrete construction through the choice of pouring concrete, the set of cooling pipes, the implementation of conservation measures and thermal-time monitoring throughout the construction process. Practice shows that the temperature control method is effective and some important results are obtained.(1) Firstly, this paper simply introduced the concept of the mass concrete, temperature stress and temperature and the importance of the temperature control. And then, the detailed internal and abroad researches on mass concrete temperature control were introduced.(2) The paper introduces the basic theory of the heart of hydration analysis and considers the main influence factors of mass concrete temperature stress on the basic theory. This paper also analysis the temperature function principle, temperature crack development mechanism, danger, method of crack control in mass concrete and summaries the choose of different calorific indexes in mass concrete.(3) This paper introduces the detailed process what the temperature control about heat of hydration in mass concrete, analyzing and comparing the measured data with evaluation results through the dragon gate Huanghe long bridge project. (4) The three dimensional finite element software MIDAS/Civil was used in this research to simulate the temperature field of the heart of hydration according to the actual layout of the cooling pipes, water flow situation, the boundary conditions, actual construction process factors. This paper got some useful conclusions through the analysis about the data and the calculating results in temperature field.