Residual compressive performance of low-carbon masonry units after a standard single-face fire

Abstract

Low-embodied-energy masonry such as CSEB, AAC and EPS blocks is displacing fired clay and dense cement units in tropical construction, yet what remains of these units after a building fire is poorly quantified. Existing data come almost entirely from furnaces that heat every face uniformly, unlike a wall exposed on one side only. This study compared four traditional and four alternative unit types under a gas-fired exposure tracking the ISO 834 standard curve to a peak exposed-face temperature of 600 degrees Celsius. Specimens were oven-dried to constant mass, insulated on every face except one to enforce one-dimensional heat flow, cooled in the furnace and then loaded to failure in compression. Fired clay gained capacity, reaching 138 percent of its unheated strength through secondary sintering, while every other unit lost between 11 and 24 percent. Retention followed continuity of the cross-section rather than material category, hollow units losing about twice as much as their solid counterparts. Three of the four alternatives fell below the minimum strengths of the relevant Sri Lanka Standards, showing that selection on embodied energy grounds must be paired with a post-fire capacity check.