Experimental study on size effect of compressive strength of three graded concrete

In order to research the influence of strength grade and slag content on size effect of concrete compressive strength, the cube compressive strength test of 45 groups of three graded concrete specimens was carried out. The specimens include three sizes of 200mm, 250mm and 300mm, five kinds of slag content of 0%, 30%, 40%, 50% and 60%, three strength grades of C15, C20 and C25.The test results show that the compressive strength of three graded concrete has obvious size effect, and the general trend is that the size effect becomes more and more obvious with the increase of the intensity level. However, the effect of slag content on the size effect is not so significant as the intensity level. At last, in combination with Bazant size effect law formula, the critical size and critical strength of three graded concrete with different slag contents and different strength grades were calculated, which can provide reference for the mechanical performance test research and engineering application of slag concrete.