Effect Of Broken Brick And Polypropylene Fiber On Mechanics, Impermeability And Frost Resistance Of Concrete

Using waste brick in concrete instead of natural coarse aggregate with equal volume not only makes use of construction waste,but also saves natural resources,which accords with the basic national policy of saving resources and protecting environment in our country at present,conforms to the trend of the times,and becomes the hot spot of scholars to study each other.In this experiment,the effects of broken brick and polypropylene fiber on the mechanical properties,impermeability and frost resistance of concrete were studied.The content of broken brick is 10%,15%,20%,25%,30%,50%,70%,100%,and on the basis of the content of broken brick is 0%,10%,30%,50%,the content of polypropylene fiber is 0,respectively..2kg/m~3,0.5kg/m~3,0.7kg/m~3,1.0kg/m~3,1.2kg/m~3.Additionalwaterconsumptionis considered in mix proportion design.The basic properties of raw materials,the workability of recycled concrete mixtures and the compressive strength,bending strength,split tensile strength,impermeability and frost resistance of hardened cubes were measured.The results show that the apparent density,crushing index and water absorption of broken brick aggregate are larger than those of ordinary gravel.Due to the consideration of additional water consumption,the influence of broken brick on concrete and workability can be ignored.Based on the analysis of the test data,two formulas for predicting the cube compressive strength of recycled brick recycled concrete at any age are obtained,and the functional equations between the relative compressive strength of recycled concrete in 28d,the relative bending strength in 28d,the relative split tensile strength in 28d and the content of broken brick are obtained.The influence of broken brick and polypropylene fiber on impermeability and frost resistance of concrete is summarized.When the content of broken brick is 50%,the seepage height increases by 36.2%,and when the content of broken brick is less than 50%,the impermeability grade is P6,the content of broken brick is 70%,100%,the impermeability grade is P5,P4.Polypropylene fiber can improve the impermeability of concrete.The mass loss rate and relative dynamic elastic modulus of recycled brick concrete are similar to those of ordinary concrete.Broken brick reduces the frost resistance of concrete.Polypropylene fiber can improve the frost resistance of concrete,and delay the failure of cement paste surface layer before aggregate exposure.The increase of mass loss rate and the decrease of relative dynamic elastic modulus can be prevented after aggregate exposure.