Study on the bonding properties of the interface between ECC and thermal insulation materials under freeze-thaw environment

Through the double-sided shear test of sandwich structure, the freeze–thaw environment, the production method, the insulation material, the presence or absence of connectors and the angle of the embedded connectors on the bonding performance are studied respectively. The results demonstrate that the Na2SO4 solution has a greater impact on the interface bonding performance of the specimens than the clean water environment. As the number of freeze–thaw cycles increases, the bonding effect becomes worse. After freezing and thawing cycles, the average ultimate load of the cast-in-place specimens in the EPS and XPS specimens is 4.3 and 5.7 times that of the precast specimens, respectively. Bearing capacity of XPS specimens is generally higher than that of EPS specimens, but the latter has better bonding performance between the insulation layer and the ECC layer. Increasing the thickness of the insulation layer, the bonding properties of the two kinds of insulation series test pieces become worse. With the addition of the connector, the ultimate bearing capacity of the specimen becomes larger and the shear resistance is improved. Among the specimens with BFRP reinforcement, the specimen with 45°embedded connector angle has the highest bearing capacity, while the specimen with 90°has the largest interfacial slip. The toughness index reflects the energy dissipation capacity and ductility of the specimen in the later bearing process to a certain extent. The specimens with higher toughness index are embedded in the connector. The toughness index of the specimens without connectors is low, and the lowest is the specimen with 5% Na2SO4 solution in freeze–thaw environment.