Influence of aggregate type on mortar thermal stability

The contributions of components, especially aggregates, to the fire resista nce of mortar and concrete have been studied. Blast-furnace slag, as a by-p roduct from iron and steel industries, is allowed to cool slowly in air to form dense slag or to cool very rapidly in water to form granulated slag. T he present work aims to study the effect of using crushed air-cooled and wa ter-quenched slags as a fine aggregate for replacement of sand on the mecha nical and chemical properties of mortars exposed to fire at different tempe ratures. Mortar mixes were prepared with three different water cement ratio s (0.4, 0.5, and 0.5) and cured in potable water for 90 days, then kept in laboratory atmosphere conditions For about four months. They were exposed t o fire at temperatures of 300, 400, 500, and 600 degreesC for 2 h soaking t ime followed by rapid cooling in water. Results of this investigation indic ated that the compressive strength of mortars exposed to fire was gradually decreasing with increasing temperature of fire up to 500 degreesC, while i t significantly decreased when temperature reached 600 degreesC. The use of air-cooled slag improved the thermal stability of mortar.