Research On Temperature Crack Control Technology Of Concrete At Early Age

Early-age cracking of concrete structures is a common problem.It is related to early cracking of concrete structures that a large number of civil engineering structures deteriorated until they eventually withdrew from work.Therefore,crack control of early age concrete has attracted much attention.The CIRIA Guideline "Early-age thermal crack control in concrete(C660)provides a method for checking that the reinforcement provided will be sufficient to control early-age.Following the idea of Anti-Early age temperature cracking proposed by CIRIA C660,combined with domestic technical specifications,material properties and construction methods,this paper conducts an experimental study on the Anti-Early age temperature cracking performance of concrete structures from two aspects: temperature field and stress field.The main research work and achievements were as follows.Based on the adiabatic temperature rise experiments of concrete with different mix ratios in China,the adiabatic temperature rise characteristics of concrete with different cement configurations were obtained by analyzing the experimental data.The adiabatic temperature rise characteristic of cement was used to optimize the concrete mix ratio to improve the temperature cracking resistance of concrete structure in early age.The reliability of predicting the actual temperature rise of structures under different working conditions by adiabatic temperature rise data was preliminarily explored,so as to better play the role of adiabatic temperature rise experiment.According to the method given by CIRIA C660,the crack spacing and width of engineering samples were calculated.The method of CIRIA C660 was inconsistent with domestic engineering practice by comparing the calculated and actual values of crack distribution.After further research,the calculation assumption of crack spacing was exploratoryly proposed in combination with the domestic norm system,and the value of the empirical coefficient was given in combination with the engineering sample data.Equivalent model of classical working conditions was studied in the laboratory,and the calculation hypothesis of crack spacing was preliminarily validated by comparing the adjusted calculated values and experimental data.Compared with the adiabatic temperature rise curve of raw material and the temperature rise curve of working condition,the hypothesis of using the adiabatic temperature rise data of material to calculate the temperature difference of inner surface was put forward.The temperature field,stress field and crack distribution of the model are simulated by ANSYS software.Comparing the experimental data with the simulation results,the distribution of temperature field and temperature cracks in early concrete structure were described in detail.The comparison validates the reliability of simulating the temperature cracks of concrete structures in early age by using the life and death option of overlapping elements.