Experimental Research On Concrete Elastic Modulus Based On Capillary Tension Theory

The problem of concrete cracking has always plagued many scientific research and engineering construction personnel.With the improvement of the mechanical properties of concrete and the progress of structural design,how to accurately calculate the constrained tensile stress of concrete has become a problem that cannot be ignored.To calculate the constrained stress,in addition to measuring its constrained strain,it is necessary to obtain an accurate elastic modulus value of the concrete relative to the constrained stress..Aiming at the problem that the confinement stress of concrete cannot be accurately calculated,starting from the capillary stress theory in the shrinkage mechanism of concrete,this paper obtains the relative elastic modulus Et based on the capillary stress theory,and at the same time,obtains the relative elastic modulus Et based on the theory of constrained cracking.Through the experiment,the concrete shrinkage data of different strength grades and different ages and the observation data of concrete cracking under different constrained conditions are obtained.From this,the relative elastic modulus E_tand E_t-cof concrete are calculated and co MPared and analyzed.Finally,E_tis used to calculate the confinement stress of concrete and predict the cracking time,which is co MPared with the real cracking time to verify its effectiveness.The main research content and conclusions of the thesis are as follows:（1）The shrinkage and restrained cracking experiments of concrete under different mix ratios and different restraint conditions are carried out.Through the analysis of the test data,it can be obtained:1)The free shrinkage of the specimens with different mix ratios is significantly different;2)The steel plate is different from the concrete.The restraining effect is obvious,which can directly reduce the early autogenous shrinkage of concrete;3)Under the premise of basically unchanged other conditions,the smaller the water-cement ratio of concrete,the faster the cracks develop after the concrete cracks,and the width and length of the cracks formed are larger..（2）Calculate the two relative elastic moduli through the data obtained from the experiment,and co MPare and analyze the results.The results show that there is a positive correlation,and both increase slowly with time.（3）Finally,the relative elastic modulus Et based on the capillary stress theory is used to calculate the constrained stress,and the cracking time is estimated.Co MPared with the actual initial cracking time,the error is basically within 15%.Explains the accuracy of this calculation method.