Experimental Research On Shrinkage Deformation Properties Of High Strength Lightweight Aggregate Concrete

Lightweight aggregate concrete is considered to be one of the most promising materials in the 21 st century due to its stable performance,economy and environmental protection.The research on high-strength and high-performance lightweight aggregate concrete is the key to expanding the engineering application of lightweight aggregate concrete.However,due to the characteristics of light weight and low strength of the aggregate,high-strength lightweight aggregate concrete has a high brittleness,and the shrinkage deformation of the concrete has a more significant impact on the generation and expansion of micro-cracks.Therefore,it is necessary to conduct in-depth and systematic research on the shrinkage deformation properties of high-strength lightweight aggregate concrete.This paper takes LC45 high-strength lightweight aggregate concrete as the research object.By changing the sand ratio,the content of light aggregate,the pre-wetting time of the light aggregate,and the particle size of the light aggregate,the drying shrinkage of the high-strength light aggregate concrete and the influence of the internal temperature and humidity on the macroscopic shrinkage and deformation of the concrete were experimentally researched and theoretical analysis.The main research contents and conclusions are as follows:(1)The mix ratio of LC45 high-strength light-weight aggregate concrete was obtained through the trial mix of concrete.Based on this mix ratio,considering the changes of four factors,such as the amount of light aggregate and pre-wetting time,the working performance parameters and some mechanical indexes of the corresponding high-strength light-weight aggregate concrete are obtained.(2)The single-factor variable test method was used to study the effects of sand rate,light aggregate content,light aggregate pre-wetting time and light aggregate particle size on drying shrinkage of high-strength light aggregate concrete within 0d～130d and obtained the development law of concrete shrinkage deformation.The regression equations of concrete shrinkage and sand ratio,pre-wetting time of lightweight aggregate and particle size of lightweight aggregate were established respectively.Based on the aforementioned mechanical indicators,the correlation between the shrinkage strain and the compressive strength of highstrength lightweight aggregate concrete was explored,and it was found that there was a good linear relationship between the two.(3)Using the concrete temperature and humidity detector,the dynamic monitoring of the internal temperature and humidity changes of the high-strength lightweight aggregate concrete was carried out,and the influence of the changes of the four factors of the lightweight aggregate on the internal temperature and humidity changes of the concrete was obtained.It is found that when all the coarse aggregates are light aggregates,the decreasing rate of concrete temperature and the increasing rate of shrinkage strain keep the same trend.An exponential regression equation between shrinkage strain and humidity of high-strength lightweight aggregate concrete is established.(4)The applicability of six commonly used ordinary concrete shrinkage prediction models to high-strength lightweight aggregate concrete is analyzed.The ACI209 model was revised by introducing the strength influence coefficient.A prediction model that can accurately calculate the shrinkage of high-strength lightweight aggregate concrete is obtained.