Study On Shrinkage And Creep Performance Of Lightweight Aggregate Concrete Based On Aggregate Performance

Lightweight aggregate concrete has the material characteristics of light weight,energy saving and economy.Its application in long-span bridge structure can effectively reduce the cross-section size of concrete structure members,reduce the dead weight of the structure,and achieve remarkable economic benefits.Compared with ordinary aggregate,the elastic modulus of light aggregate is lower and the constraint ability of cement mortar is weak.However,the internal curing effect brought by the water absorption and return characteristics of light aggregate is beneficial to improve the compactness of cement mortar in the interface transition zone.It can be seen that the addition of light aggregate has both positive and negative effects on concrete creep.At present,the domestic and foreign researches on lightweight aggregate concrete can explain the influence of a certain phase property change on creep through microscopic tests,but the research data on shrinkage and creep property of concrete based on the physical and mechanical properties of lightweight aggregate are scarce.In view of this,the shrinkage and creep performance of lightweight aggregate concrete based on aggregate performance will be studied in this project,and the influence of low elastic modulus of lightweight aggregate and internal curing effect on shrinkage and creep performance of concrete will be analyzed from the micro level.In this paper,several commonly used different types of light aggregate were selected,including pulverized coal ash ceramsite,shale ceramsite,non-firing ceramsite and cloud concrete stone ceramsite.light aggregate concrete was prepared on the premise that cement mortar ratio and volume amount of coarse aggregate were not changed,and the 180-day shrinkage and creep performance tests of different types of light aggregate concrete were carried out.Scanning electron microscopy(SEM),X-ray energy spectrum analysis(EDX)and microhardness tests were used to study the influence of aggregate properties on the microstructure,calcium-silicon ratio and microhardness of cement mortar in the interface transition zone,and to reveal the correlation between the interface transition zone properties and the shrinkage and creep of lightweight aggregate concrete from the microscopic level.The influence mechanism of aggregate properties on shrinkage and creep properties of lightweight aggregate concrete is explained.The results show that increasing the aggregate water absorption rate is beneficial to improve the early shrinkage of lightweight aggregate concrete,and increasing the elastic modulus of lightweight aggregate is beneficial to inhibit the late shrinkage of concrete.High water absorption in curing effect of lightweight aggregate release water makes aggregate forms around a more compact interface transition zone,its thickness and hardness are higher than the corresponding cement mortar,cement mortar to matrix deformation of the constraint function,improve the interfacial transition zone volume accounted for the inhibition of lightweight aggregate concrete creep is able to enhance the ability of;The creep of concrete prepared by light aggregate with high water absorption and low elastic modulus develops rapidly.The positive effect caused by interface strengthening is difficult to be reflected,while the weakening effect caused by low elastic modulus of aggregate has a significant effect.In this paper,the influence of aggregate physical and mechanical properties on concrete creep behavior is analyzed,and the creep mechanism of lightweight aggregate concrete is revealed from the micro level,which provides technical support for improving the creep theory and calculation model of lightweight aggregate concrete,and is conducive to promoting the engineering application of lightweight aggregate concrete.