Experimental Study On Internal Curing Concrete With Shale Pottery Sand

This project comes from the 2018 project of Shandong Academy of Transportation Sciences: bridge and concrete technical consultation of Beijing Shanghai Expressway Reconstruction and expansion project.In order to improve the strength of concrete,low water binder ratio is usually used.However,the early shrinkage cracking of concrete caused by its low water binder ratio can not be ignored.Researchers propose to introduce internal water source and maintain it from the inside of concrete,which is called internal maintenance.In this paper,shale pottery sand light aggregate is used to replace part of ordinary aggregate,and it is used as internal curing material to study its influence on concrete performance,especially on self shrinkage performance.The main research contents and results are as follows:(1)In this paper,the compressive strength of concrete cured in shale pottery sand is studied.The results show that the effect of internal curing on the strength of concrete is greater than that of the same replacement rate.When the water binder ratio is low,its influence on the strength is small,but on the compressive strength of low-grade concrete.When the water binder ratio is the same,the strength of concrete decreases with the increase of shale sand.When the age reaches 90 days,the compressive strength of concrete with water cement ratio of 0.27 is 5.3%,7.1%,8.7% and 11.0% lower than that of the reference group.(2)In this paper,the autogenous shrinkage test of shale ceramic sand curing concrete is studied.The results show that the self shrinkage of concrete can be improved by adding shale pottery sand,and the greater the content of shale pottery sand,the more obvious the effect of improving the self shrinkage of concrete.The shrinkage reduction effect of pre wet shale pottery sand is better than that of non wet shale pottery sand with the same replacement rate.When the water cement ratio is 0.42,the self shrinkage of concrete with pre wet shale sand is 6.2%,42.3%,67.2% and 79.1% lower than that of the reference group.After adding the pre wet shale pottery sand,the shrinkage reduction effect of low strength concrete is more significant.(3)In this paper,the durability of concrete cured in shale pottery sand is studied.The results show that the chloride penetration resistance of concrete decreases with the increase of the content of dry shale pottery sand.At the age of 90 days,the chloride diffusion coefficient of concrete group with 5%,10%,15%,20% pre wet shale ceramic sand is lower than that of concrete group with dry shale ceramic sand.It shows that the impermeability of pre wet shale ceramic sand concrete is better than that of dry shale ceramic sand concrete.After the concrete is mixed with shale pottery sand,it has a great influence on its frost resistance.The larger the content of shale pottery sand is,the less the number of freeze-thaw cycles is,and the frost resistance of the concrete mixed with pre wet shale pottery sand is worse than that of the concrete mixed with dry shale pottery sand.(4)The microstructure of the concrete cured in shale pottery sand was analyzed.The results show that the internal structure of shale pottery sand and its interface transition zone(ITZ)in concrete are observed by SEM.It is found that the internal pore connectivity of shale pottery sand is high,and the bond between shale pottery sand and concrete cement paste is closer than that of ordinary fine aggregate.