Study of Ultra-High Performance Concrete Mechanical Behavior under High Temperatures

Area of Science:

• Materials Science
• Civil Engineering
• Structural Engineering

Background:

• High temperatures pose risks to concrete, causing strength loss and explosive spalling, especially in Ultra-High Performance Concrete (UHPC).
• Polymeric fibers can mitigate some issues but may affect mechanical properties and workability.
• Understanding fiber effects on UHPC at elevated temperatures is crucial for structural safety.

Purpose of the Study:

• To evaluate the physical and mechanical properties of UHPC with metallic and PVA fibers under high temperatures.
• To determine the optimal fiber mixture for enhanced high-temperature performance.
• To assess the effectiveness of PVA fibers in preventing explosive spalling.

Main Methods:

• A 2^3 central composite factorial design was employed to study UHPC mixtures.
• Physical properties (consistency) and mechanical properties (compressive strength, elasticity modulus) were measured.
• Specimens were exposed to high temperatures to assess performance degradation.

Main Results:

• Both compressive strength and elasticity modulus decreased significantly above 300 °C.
• PVA fibers, despite reducing fluidity, lessened the loss of compressive strength post-heating.
• An optimal mixture of 1.65% steel fiber and 0.50% PVA fiber yielded the highest compressive strength at room and high temperatures.

Conclusions:

• UHPC with a specific combination of steel and PVA fibers exhibits improved strength retention at high temperatures.
• PVA fibers are effective in mitigating strength loss but do not prevent explosive spalling at the tested concentrations.
• Further research is needed to fully address explosive spalling in fiber-reinforced UHPC at high temperatures.