An experimental study on the thermal properties of concrete under the load ratio condition in a fire

When a fire occurs, the strength of the concrete structure deteriorates due to temperature rise under the condition of constant load. The deterioration in strength causes the change in axial load ratio, so the structure is deformed. In this study, loaded heating test of concrete lining was conducted to realize the condition of an actual fire outbreak in a tunnel where heating and loading affect the structure simultaneously. The shape of the specimens was planned in compliance with the standard for small scale test prescribed in the EFNARC and 24 MPa, 40 MPa and 50MPa were used to analyze the thermal properties associated with different concrete strengths. Constant loading condition was provided based on the load ratios equivalent to 20 % and 40 % of the sectional stress in the concrete and the MHC fire scenario was selected to realize the thermal impact on the concrete by rapid temperature rise. Under each load ratio, more cracks were observed in higher strength and spalling occurred in 50MPa. In terms of fire damage range, 50mm points from heated surface of the 200mm lining did not satisfy the ITA standard for concrete lining upon a fire.