Study on the interfacial shear performance between engineered cementitious composites and concrete after being subjected to high temperatures

This paper researched the interfacial shear performance between engineered cementitious composites (ECC) and concrete after exposure to high temperatures. A total of 13 groups of 35 Z-shaped specimens were manufactured and subjected to direct shear tests. The test parameters included the maximum temperature experienced by the concrete part, the surface roughness of the substrate concrete, cooling regimes of the concrete part, fibre category of ECC, and interfacial agents. The test results showed that below 400 degrees C, the interfacial shear strength increased with temperature while the interfacial shear strength decreased with increasing temperature above 400 degrees C. Similarly, below 3.5 mm, the interfacial shear strength increased with the surface roughness of the substrate concrete while above 3.5 mm, the interfacial shear strength decreased with increasing surface roughness. Specimens with PE-ECC exhibited better interfacial performance than those with PVA-ECC. The interfacial strength of the specimens decreased if the concrete part was water-cooled or its interface treated with fly ash or cement paste. A mathematical model was proposed to predict the interfacial shear strength of the Z-shaped specimens and a digital image correlation (DIC) technique was utilized to measure the strain field of the specimens.