Residual strength and durability of volcanic ash concrete exposed to high temperature

The strength and durability performance of concretes incorporating 0 to 40% of volcanic ash (VA) as cement replacement (by mass) subjected to high temperatures up to 800 degreesC (1472 degreesF) is described. The strength properties were assessed by unstressed residual compressive strength, while durability was investigated by rapid chloride permeability test (RCPT), mercury intrusion porosimetry (MIP), differential scanning calorimetry (DSC) and crack pattern observations. Volcanic ash concrete (VAC) showed good performance showing higher residual strength, higher chloride resistance and higher resistance against deterioration particularly at temperatures below 600 degreesC (1112 degreesF) compared with the control ordinary portland cement (OPC) concrete. The improved performance of VAC can be attributed to the refinement of pore structure, lowering the presence of free chloride due to Friedel's salt formation and pozzolanic action due to the presence of VA. The deterioration of both strength and durability of VAC increased with the increase of temperature up to 800 degreesC (1472 degreesF) due to substantial reduction in residual strength and an increase in pore volume and pore diameter The serviceability assessment of VAC after a fire should therefore, be based on both strength and durability considerations.