Effect of Mechanical Loading on the Fire Behavior of compressed Earth Bricks

Earthen materials, with their interesting thermal-hydro-mechanical properties and their low carbon footprint, are increasingly considered for construction in industry. Nevertheless, their fire behavior remains poorly understood, hindering their widespread use. This study focuses on the influence of mechanical loading on the fire behavior of earth bricks. Recognizing that mechanical characteristics can impact fire response, two sets of compressed bricks with similar compressive strengths were manufactured: unstabilized earth bricks compacted at 50 MPa and cement-stabilized earth bricks compacted to Proctor level with 3.5% cement. These bricks, equalized at 75% relative humidity, underwent ISO 834-1 standard fire exposure from a mobile gas furnace while concurrently enduring various mechanical loading ranging from 0 to 2.5 MPa. Results unveiled that unstabilized earth bricks exhibited more pronounced thermal instability throughout the fire exposure, irrespective of loading. In contrast, cement-stabilized bricks displayed reduced susceptibility to thermal instability, primarily when subjected to mechanical loads. For both materials, loading increased the risk of instability during fire. It influenced crack closure/opening, affecting internal pore pressure, vapor permeation, and, consequently, material stability or instability. This underscores the relationship between mechanical loading and fire behavior of earthen materials, emphasizing its importance in evaluating their fire behavior.