Experimental Study Of Size Effect On Biaxial Compression Behavior Of Concrete And Mortar

The size effect of concrete has always been a focus area of civil engineering research at home and abroad.Concrete as a quasi-brittle material,its strength is not only determined by the material itself,but also affected by the size of concrete specimens.At the same time,a series of studies on the size effect of concrete under the uniaxial force are made,and some results are obtained,which promote the development of the size effect theory.But in the actual project,the concrete in the concrete is not a simple one-way force state,but in a multi-axis stress coupling state.At present,there are few studies on the compression behavior of concrete under the action of biaxial reaction,and there are many factors that affect the compressive performance of concrete.The effect of aggregate component on the size effect of concrete biaxial compression is large,and the related research has not been seen Reported.In view of the shortcomings of the current research,this paper will make some experimental studies on the effect of aggregate composition on the size effect of concrete compression performance.The main contents are as follows:(1)the size effect of the biaxial compression performance of the concrete was systematically studied.Specimens' side length are 100mm,150mm and 200mm using cube specimens.The principal side stress ratios are 0.1,0.2,0.25,0.3 and 0.4,respectively.The experimental results show that the mechanical properties and deformation properties of concrete under biaxial compression have a certain degree of size effect.With the increase of the geometric size,the biaxial compressive strength decreases,and the peak strain and the limit strain increase.When the main side stress ratio is 0.25,the compressive strength,peak strain and ultimate strain of the specimen with a length of 200mm are about 95%,106%and 107%of the length of 100mm specimen respectively.(2)compared with the results of biaxial compression test of different main-side stress concrete specimens,it is found that the main-side stress ratio has a great influence on the size effect of concrete.In the case of biaxial compression,the size effect is gradually weakened with the increase of the principal side stress ratio.For a cube specimen with a length of 150 mm.When the principal side stress ratio is 0.4,the compressive strength of the compressive strength is about 72%of the stress ratio of 0.1.In the case of biaxial compression deformation,when the main stress ratio is in the range of 0?0.3,the size effect decreases with the increase of the stress ratio.When the stress ratio is 0.3,the dimensional response of the peak strain and the limit strain is about 69%and 51%when the stress ratio is 0.1.When the stress ratio is 0.3,the dimensional effect is gradually increased with the stress ratio of 0.3%,and the size effect of the peak strain and ultimate strain is about 1.5and 1.8 when the stress ratio is 0.3.(3)The size effect of the aggregate component on the biaxial compression performance of concrete is great.When the stress ratio is 0.4,the compressive strength,peak strain and ultimate strain of mortar specimen are 61%?62%and 76%respectively.(4)On the basis of the systematic analysis of the statistical size effect theory,based on the experimental data,the values of the parameters in the formula for calculating the compressive strength of the concrete biaxial compression cube are calculated,and critical size and critical strength of biaxial compression under the loading ratio of the concrete cubes is analyzed.