Influence Of Low Temperature On Static And Fatigue Properties Of Lightweight Aggregate Concrete

According to the temperature condition,the research of concrete performance can be divided into three categories: normal temperature,high temperature and low temperature,the performance of concrete at normal temperature is the first aspect of research,at present,the research on the performance of concrete is mainly concentrated in the ambient temperature environment.However,China has a vast territory and a large gap between North and south temperature differences,and the northern cold zone has a low temperature and a large temperature difference.There are few domestic research on the performance of concrete at low temperature.And as a special underground construction,freezing method is undoubtedly the best choice;however,the key to ensure the success of freezing method is to ensure that concrete is protected from disasters under low temperature.Taking LC30 all lightweight concrete(ALWC)and semi lightweight concrete(SLWC)as an example,the static and fatigue properties of concrete under the condition of low temperature curing were tested and studied.The main contents are as follows:(1)The general mechanical properties of all lightweight,semi lightweight and fiber concrete under the condition of normal temperature curing and low temperature curing were tested.The characteristic strength,elastic modulus and stress-strain curve of different ages and different kinds of concrete are analyzed,and the mechanical properties of different temperatures,different ages,different kinds of concrete were compared and analyzed;(2)The strength of light aggregate concrete and normal weight concrete after low temperature is compared,respectively.The freezing performance of lightweight aggregate concrete is better.Under different maintenance systems,the whole light concrete is cured at low temperature and turned to normal temperature,there is a certain increase in strength;(3)The corresponding uniaxial compression fatigue test was carried out for the full light concrete after the low temperature,the S-N curve and ?-N curve were obtained.Compared with the normal temperature curing concrete,the fatigue strain of concrete after low temperature is in accordance with the three stage change law,but its fatigue life is lower;(4)Scanning electron microscope(SEM)was used to scan all light concrete specimens after different low temperatures,the micro morphology,gel pore structure change and distribution were analyzed,and it is compared with the microstructure at normal temperature,the lower the curing temperature,the larger the porosity and the looser the structure.