Study On The Utilization Of Recycled Clay Brick In Internal Curing Concrete

The water-cement ratio is relatively low and adding silica fume superfine mineral admixture,so high performance concrete internal relative humidity decreased rapidly in the early cement hydration reaction,and it is tend to dry,resulting in the shrinkage of concrete,even crack.The traditional external curing method can not completely solve the problem of concrete drying,shrinkage,and cracking,while the internal curing material mixed with prewetting treatment can effectively alleviate the self desiccation of concrete and reduce the autogenous shrinkage.On the basis of the principle of internal curing of water saturated lightweight aggregate,it is found that the recycled clay brick has the potential to be used as the internal curing material.And at the same time,it provides the new methods for the recycle of waste clay brick.This paper determinated and analyzed the basic physical properties of recycled brick,to replace part of fine aggregate of mixing recycled brick and study the influence of recycled brick on the workability,shrinkage cracking,mechanical performance and durability.At the same time,it also studied the mixing recycled brick and super absorbent polymer(SAP)effect on internal curing of concrete,and provide a scientific evidence for the use of internal curing materials of waste brick slag.The main achievements of this paper are as follows:(1)We can draw a conclusion that the waste brick slag has the potential to be used as the internal curing material after the analysis of the basic physical properties,microstructure and water absorption rate of recycled brick.The influence of fine aggregate on properties of concrete replace the recycled brick were studied,It showed that water saturated into concrete after increasing the fluidity of concrete with recycled brick.With recycled brick increasing,cement mortar self shrinkage and dry shrinkage rate are decreased gradually,but also improve resistance of crack.(2)The effect of recycled brick on compressive strength of concrete has been studied.When the proportion of the recycled brick is less than 30%,the late strength of concrete is almostly the same as that of the reference concrete.When the ratio of waste brick slag is 20%,the 90 d strength exceeds the basic concrete.In addition,the effect of recycled brick residue on the later strength of concrete with low water-cement ratio is more obvious,it can promote the influence of pozzolanic effect of silica fume.With the decrease of the particle size of recycled brick,the strength of concrete decreases gradually,and the strength of recycled brick concrete with single particle size is lower than that of the recycled brick concrete with mixed particle size.Mix SAP and recycled brick can improve the adverse effect of the strength of SAP.(3)The effect of recycled brick on the carbonation resistance of concrete has been studied.The results show that the carbonation resistance of concrete is not affected when the amount of recycled brick is not more than 30%.The influence of recycled brick on the carbonation resistance of concrete with low water-cement ratio is more obvious,but the influence of different dosage of silica fume concrete is more consistent,which may enlarge the carbonation depth by about 3 times.The carbonation depth of the recycled brick concrete with mixed particle size is higher than that of the single particle size.Mix SAP recycled brick can improve the adverse effect of the carbonation resistance of SAP.(4)When the amount of recycled brick is 10%,the electric flux is lowed by about 25.3% compared with the basic concrete.After more than 10%,with the increase of the dosage,the electric flux increases.The higher the water-cement ratio is,the smaller the influence of recycled brick on the electric flux of concrete.After mixing the waste brick slag,with the increase of the proportion of silica fume,the influence of recycled brick on the electric flux of concrete is not obvious.In addition,the influence of the particle size of recycled brick on the concrete electric flux is not significant,but the electric flux of the recycled brick concrete with mixed particle size is higher than that of the single particle size.At the same time,the electric flux of concrete with mixing SAP and recycled brick is increased compared with that of single SAP concrete.From these factors,we can know that under the premise of no obvious influence on the strength and durability of concrete,the waste brick slag can effectively reduce the early shrinkage of concrete and improve the crack resistance.It is feasible to use the recycled brick as the internal curing material.