Study on the bonding properties of Engineered Cementitious Composites (ECC) and existing concrete exposed to high temperature

This paper researches the bonding properties between the existing concrete and ECC by 66 slant shear and 66 split tensile specimens exposed to 22 °C, 200 °C, 400 °C, 600 °C and 800 °C. The existing concrete was firstly heated from room temperature (22 °C) to 200 °C, 400 °C, 600 °C and 800 °C, and then reinforced by the repairing material (strengthening concrete and ECC) respectively, named as Type A Test. While, another is that existing concrete is firstly reinforced by repairing material, and then the repaired specimens are heated from room temperature (22 °C) to 200 °C, 400 °C, 600 °C and 800 °C, as Type B Test. In Type A Test, when its temperature is below 200 °C, the slant shear strength and the splitting tensile strength increase with the temperature increasing, and the bonding performance is improved. However, when the temperature is above 200 °C, the slant shear and splitting tensile strength gradually decrease and the bonding performance declines with the temperature increasing. In addition, the bonding performance of the existing concrete/ECC is higher than that of the existing concrete/strengthening concrete at the same high temperature. In Type B Test, when its temperature was rose from room temperature to 600 °C, it is beneficial to the bonding performance of the existing concrete/ECC. Furthermore, a serious burst happened in the existing concrete/ strengthening concrete specimens at 600 °C. But no burst happened in existing concrete/ECC specimens even at 800 °C, which ensured the integrity of the repairing system.