Study On Mechanical Properties Of Lightweight Aggregate Concrete Based On Experiments And Micromechanics

Lightweight aggregate concrete has the advantages of light weight,high strength,earthquake resistance,thermal insulation and so on,and its application in the construction field is of great significance.According to the absolute volume method,three series of lightweight aggregate concrete was designed by replace sand ratio,ceramic sand ratio and water cement ratio as variables,which has carried on the test to obtain the compressive strength,flexural strength,apparent density,thermal conductivity and modulus of elasticity.The main factors affecting the performance of lightweight aggregate concrete were analyzed.Based on the theory of mesomechanics,a two-phase model of lightweight aggregate concrete was established,and the stressstrain curve,flexural strength and elastic modulus of concrete were simulated,which were compared with the test results This research has the following conclusions:(1)The physical properties of ceramsite were tested,the shale ceramsite was selected as the coarse aggregate of high strength lightweight aggregate.(2)The slump of lightweight aggregate concrete increases with the increase of sand ratio and decreases with the increase of substitution ratio of pottery sand.The compressive strength and flexural strength of lightweight aggregate concrete with 35%sand ratio can be improved.The increase of substitution ratio of ceramic sand decreases the compressive strength and increases the flexural strength of lightweight aggregate concrete.(3)By testing the strength,apparent density and thermal conductivity of lightweight aggregate concrete,the relationship between compressive strength,flexural strength,thermal conductivity and apparent density was obtained.The compressive strength and flexural strength of lightweight aggregate concrete with 35% sand ratio are the highest.The change of the replacement ratio and water-cement ratio of ceramic sand has little effect on the compressive strength,but increasing the replacement ratio of ceramic sand and decreasing the water-cement ratio can improve the flexural strength.There is a strong linear relationship between thermal conductivity and apparent density of ceramsite concrete,and a linear model is established.(4)The mechanical properties of ceramsite concrete are related to the mechanical properties of mortar matrix and the content of ceramsite lightweight aggregate.The compressive strength of ceramsite concrete is largely affected by the compressive strength of mortar matrix and is basically positively correlated with the compressive strength of mortar.When the sand ratio is too small or the water-cement ratio is too low,the compressive performance of ceramsite concrete will be affected by the synergistic action of ceramsite lightweight aggregate and mortar matrix.Mortar and ceramsite aggregate jointly determine the flexural resistance of ceramsite concrete.(5)Based on the concrete plastic damage(CDP)model and the actual test results,the mechanical parameters and constitutive model of mortar material are defined,and the compressive and flexural tests of concrete are simulated.The simulation results show that the ultimate strain of ceramsite concrete is between 0.003 and 0.004,which is greater than that of ordinary concrete,and it has better elastic deformation ability.The simulated damage pattern of ceramsite concrete is roughly similar to the test results,and the variation law of compressive flexural strength and elastic modulus is basically similar to the test results,which indicates the basic reliability of the model.