Research On The Interface Bonding Properties Of ECC And Insulation Materials Under Conventional And Freeze-thaw Environment

Engineered Cementitious Composites（ECC）is a high-performance cement-based composite material with good toughness,high corrosion resistance,excellent deformation and crack control capabilities,which is very suitable for combining with insulation materials to form a thin-walled"sandwich"structure,and has broad application prospects in the field of enclosure structures.As a sandwich wallboard,in order to prevent quality and safety accidents such as falling off,the bonding strength between the surface layers must be guaranteed.In this thesis,combined with Xuzhou City’s key Research and Development plan"Research on the Stress Mechanism and Degradation of Textile/ECC Wall Materials",the interface bonding performance between ECC and thermal insulation materials under conventional and freeze-thaw environments was studied.The main work and contents are as follows:（1）The mechanical properties of the BFRP reinforcement connectors and ECC surface layer used in the sandwich structure are studied.It was found that the BFRP bar with a diameter of 6mm has higher tensile strength,and the ECC material has good flexural and tensile properties and excellent crack control capability,which is very suitable for being used as a sandwich structure surface layer material.（2）The influence of the type and thickness of insulation materials,the embedding angle of the connector and the production method on the bonding performance of the interface between the ECC and the insulation material under the conventional environment are studied.The results show that the type and thickness of the insulation material have a great influence on the interface bonding performance.The bearing capacity of the XPS specimens is higher than that of the EPS specimens,but the interface bonding performance between the EPS insulation and the ECC surface layer is superior.With the thickness of the insulation layer of the two specimens increases,the bonding effect of the specimens becomes worse.The joining of the connectors obviously improves the ultimate bearing capacity of the specimens.When the angle of the embedded connector is 45°,the shear strength of the specimens is the highest,and the prefabricated specimens is the lowest.（3）The effects of the number of freeze-thaw cycles,the freeze-thaw environment,the type and thickness of insulation materials,the embedding angle of the connector and the production method on the bonding performance of the interface between ECC and the insulation material under the freeze-thaw environment are studied.The test results show that the interface bonding performance of the specimens is greatly reduced in the freeze-thaw environment,and as the number of freeze-thaw cycles increases,the interface adhesion of the specimens becomes worse.Moreover,the Na₂SO₄ solution has a greater impact on the performance of the specimens than the clean water environment.The bearing capacity of the XPS specimens is higher than that of the EPS specimens,but compared to the XPS insulation,the interface bonding performance between the EPS material and the ECC surface layer is higher.The thickness of the insulation layer is reduced,and the bonding effect becomes better.The bearing capacity of the specimens with connectors is generally higher,and the prefabricated specimens is the lowest.（4）Based on the energy aspect,the toughness analysis of the load-slip curve after the peak of the specimen is in good agreement with the test results.The shear bearing capacity of the composite specimens is analyzed,and the formula for the shear bearing capacity under conventional and freeze-thaw environments is obtained.The theoretical value is in good agreement with the actual value.