Constitutive relationships for ultra-high-performance concrete at elevated temperatures

Area of Science:

• Materials Science
• Civil Engineering
• Structural Engineering

Background:

• Ultra-high-performance concrete (UHPC) offers superior mechanical properties but is susceptible to high-temperature degradation.
• Spalling and strength loss are critical concerns for UHPC structures exposed to fire or elevated temperatures.

Purpose of the Study:

• To establish reliable predictive relationships for UHPC mechanical properties at high temperatures.
• To model compressive, tensile, and flexural strengths, modulus of elasticity, peak strain, and stress-strain curves.
• To evaluate UHPC performance with different fiber reinforcements (none, steel, polypropylene, hybrid).

Main Methods:

• Development of bilinear and trilinear equations for strength predictions.
• Linear and exponential combinations for modulus of elasticity and peak strain.
• Validation of proposed relationships against experimental data and existing models.

Main Results:

• Proposed equations model strength reduction and stress-strain behavior at high temperatures.
• The models generally capture UHPC behavior, with variations noted for specific fiber types (e.g., PPF).
• Discrepancies highlight the need for further refinement, especially for polypropylene fiber reinforced UHPC.

Conclusions:

• The study provides a foundation for predicting high-temperature UHPC performance.
• Further research is recommended to enhance model accuracy, including varying specimen parameters and heating conditions.
• Refined constitutive relationships are crucial for safe UHPC design in elevated temperature environments.