Hybrid Fiber Reinforced HPC at Elevated Temperatures - Analysis of Thermal Properties

Hybrid fiber reinforcement, based on a combination of steel and polymer fibers, is generally accepted by concrete community as a functional solution preventing spalling. For fire safety and effective structural design, knowledge of concrete properties retained after temperature exposure as well as of material parameters accessed directly at high temperatures is of the particular importance for civil engineers and practitioners. On this account, temperature dependent specific heat capacity of hybrid fiber reinforced high performance concrete is investigated in the paper using the inverse analysis of sample response to elevated temperatures. For the measurement, a novel non-adiabatic method was developed and used in the temperature range from 25 degrees C to 1000 degrees C. Except temperature dependent specific heat capacity, basic physical properties were accessed for samples thermally treated for 2 hours at the temperatures of 200 degrees C, 400 degrees C, 600 degrees C, 800 degrees C, and 1000 degrees C respectively. The acquired specific heat capacity exhibited a high dependence on temperature and several structural changes that concrete underwent at elevated temperatures. Similarly, the material parameters accessed after thermal load clearly pointed to the concrete damage and crucial temperatures affecting concrete performance and durability.