Explosive Spalling Behavior of Single-Sided Heated Concrete According to Compressive Strength and Heating Rate.

Area of Science:

• Civil Engineering
• Materials Science
• Fire Safety Engineering

Background:

• Concrete spalling, a critical failure mode under fire conditions, poses significant risks to structural integrity.
• Understanding the influence of heating rate and concrete compressive strength on spalling behavior is crucial for fire safety design.

Purpose of the Study:

• To investigate the effects of heating rate and compressive strength (60 and 100 MPa) on the spalling behavior of single-sided heated ring-restrained concrete.
• To analyze the internal vapor pressure and restrained stress development under different heating conditions.

Main Methods:

• Experimental investigation of concrete spalling under controlled heating rates (fast and slow).
• Measurement of internal vapor pressure and restrained stress within concrete specimens.
• Evaluation of concrete compressive strength and its influence on spalling characteristics.

Main Results:

• Spalling was observed in 100 MPa concrete, with distinct behaviors under fast and slow heating rates.
• Fast heating resulted in continuous surface spalling due to widespread moisture clogging and restrained stress.
• Slow heating led to explosive spalling in dense, 100 MPa concrete, attributed to deep-seated moisture clogging and stress accumulation.

Conclusions:

• Heating rate is a critical factor influencing moisture migration and restrained stress, thereby determining the type of concrete spalling.
• The interplay between internal vapor pressure, reduced tensile strength, and restrained stress drives spalling in heated concrete.
• High-strength concrete (100 MPa) exhibits more severe spalling, with the heating rate dictating the failure mechanism (surface vs. explosive).