Study On Hydration Heat And Temperature Control Measures Of Mass Concrete

With the rapid development of China’s economy,the demand for infrastructure construction is increasing day by day.Mass concrete has been widely used in traffic,water conservancy,construction and other fields because of its rich raw materials,convenient construction and strong bearing capacity.At the same time,more and more problems are also accompanied.Due to the large size of mass concrete structure and the rich content of cementitious materials,the hydration heat effect during the curing period is significant.Under the influence of internal and external constraints and external environment,temperature cracks are very easy to appear,and the poor control of temperature cracks leads to the generation of through cracks.Thus,the rigidity and durability of the structure are destroyed,and the normal use of the structure function is affected.Based on the background of Pingnan third bridge,this paper chooses the mass concrete floor of the north bank arch as the analysis object.The temperature field,stress field and influence parameters of mass concrete are analyzed.The main research work of this paper is as follows:Starting from the basic concept of mass concrete,combined with all kinds of data,specifications and literature.The basic definition,cause and harm of temperature crack are expounded.The thermal performance parameters of concrete,including thermal conductivity,specific heat capacity and calculation method of adiabatic temperature rise of concrete,are summarized.The basic theory and finite element method of temperature field and stress field of mass concrete are summarized systematically.According to the situation of the mass concrete floor of the arch base on the North Bank of the third Pingnan bridge,three different temperature control measures are proposed.Midas / civil finite element software is used to carry out numerical modeling and hydration heat analysis in the construction stage of the north bank arch base slab foundation.Study on the distribution of temperature field and stress field and the cracking risk of the base slab in different temperature control measures.According to the field monitoring of the bottom slab,the control parameters affecting the temperature field of mass concrete and the law of hydration heat are found by comparing and analyzing the measured data with the simulation value of the finite element software.At the same time,the accuracy of MIDAS / civil modeling is verified.This paper sums up some temperature control and crack prevention measures adopted in the construction of mass concrete base slab of the north bank arch of mass concrete.Including the optimization of concrete mix proportion(selection of raw materials),structural design and improvement of boundary constraints,reasonable construction measures(reasonable layered pouring,concrete mixing and secondary vibration,control of temperature and pouring temperature),concrete insulation,moisture conservation,and temperature monitoring design and layout,etc.,the temperature control and crack prevention measures are proposed.Through the finite element software MIDAS / civil,the influencing factors of the temperature field of the arch base slab foundation are analyzed numerically,including the temperature of the concrete into the mold,the insulation measures of the concrete,the external environment temperature,the parameters of the cooling water,etc.Study the influence rule and degree of each parameter.