Effects of mixture proportion and test condition on compressive strength of concrete using coal ashes subject to elevatedtemperature

Abstract

This study investigated the effects of mixture proportion on compressive strength of concrete specimens at elevated temperature obtained by subtituting Portland cement with 15 % fly ash, 5 % silica fume and coal ash as aggregates with particle size up to 5 mm. After casting and curing period, the specimens were exposed to various temperatures (200, 400, 600 and 800 oC) for tow hours. The compressive strength according to temperature level was determined, corresponding to tow cooling methods. The results demonstrated that water-binder ratio of 0.61 and aggregate particle size distribution was calculated using the Andersen’s formula with the calculated value of n = 0.357, the strength of concrete was the highest at a temperature of 800 oC, residual compressive strength above 56 %. Rapid cooling in water caused additional compressive strength losses comprared with slow cooling in air at all test temperature, but the difference was not much, about 3÷9 %.