Experimental Study On Bond Properties Between Ribbed Bar And Recycled Aggregate Self-compacting Concrete

As a new type of environmentally friendly material,recycled aggregate self-compacting concrete not only has the advantages of good workability and easy pouring of self-compacting concrete,but also can effectively solve construction waste,fly ash and other wastes,responding to the national call for energy saving and emission reduction.The bond properties between steel bar and concrete is the precondition for the structure to bear the load,and it is also an important factor for determining the ductility of the component.To further apply the recycled aggregate self-compacting concrete to the actual project,the bond properties must be studied.There are three parts of the experiment in this paper,the first part of the experiment studied the effect of concrete strength,the diameter of the bar,the bonding length and the thickness of concrete cover on the bond performance of recycled aggregate self-compacting concrete by the center pull out test of 80 specimens.The results show that: the bond strength is approximately proportional to the cube splitting strength.With the increase of the diameter of the steel bar,the bonding length and the thickness of concrete cover,the bond strength increases first and then decreases;The relative thickness of concrete cover of the 16 mm diameter ribbed steel bar in recycled aggregate self-compacting concrete should be set around 4.2.In the second part,the center pull-out test was also adopted.The effect of the content of fly ash and replacement ratio of recycled aggregate on the bond performance was studied through 125 specimens.The results showed that: when the content of fly ash was 30%,the deformation of recycled aggregate self-compacting concrete is better.When the replacement ratio of recycled aggregate is 75%,the recycled aggregate self-compacting concrete has the best bonding performance.Through the regression analysis of experimental data,the calculation formula of the characteristic value of the bond slip curve considering various factors and the basic bond-slip constitutive relationship model are obtained.This paper also studied the variation of the bond stress between recycled aggregate self-compacting concrete and ribbed steel bar along the bonding length by the local bond-slip test of 18 specimens,and the effect of the content of fly ash and replacement ratio of recycled aggregates on the variation law of bond stress.The results show that with the increase of the content of fly ash and replacement ratio of recycled aggregates,the distribution of bond stress on the bonding length becomes more and more uneven.The test also obtained a function of the bonding stress applied to different content of fly ash and replacement ratio of recycled aggregates,and the bond-slip constitutive relationship of recycled aggregate self-compacting concrete considering the bonding position by coupling the bond stress position function with the basic bond-slip constitutive relationship.