Influence of cooling methods on high-temperature residual mechanical characterization of strain-hardening cementitious composites

Residual strength tests are commonly used to characterize the high-temperature mechanical properties of concrete materials. In these tests, the specimens are heated to a target temperature in a furnace and then cooled down to room temperature, followed by mechanical testing at room temperature. This research investigates the influence of the cooling method on the residual strength of Strain Hardening Cementitious Composites (SHCC) after exposure to 400°C and 600°C. Two types of cooling methods — furnace-cooling (within a closed furnace) and water-cooling (immersed in a water tank) — were adopted. Four different SHCC previously investigated by the authors for high-temperature residual mechanical and bond behavior with steel were studied. Two different specimen sizes were tested under uniaxial compression and flexure to characterize the residual compressive strength and modulus of rupture. The effect of the cooling method was prominent for the normalized residual modulus of rupture at 400°C, but not at 600°C. The cooling method had no effect on the normalized residual compressive strength of any material at either of the two temperatures, except one of the SHCC (PVA-SC) at 400°C. Specimen size also had no effect on the normalized residual compressive strength and modulus of rupture irrespective of the cooling method.