Effect of fire and cooling mode on the properties of slag mortars

When building materials are subjected to fire and exposed to slow or rapid cooling, some changes may occur in their characteristics; such as phase transformation, weight loss, aggregate-cement bond, etc., which directly affect its chemical resistivity and mechanical properties. In the present investigation, two types of slag - air-cooled (ACS) and water-quenched slag (WQS) - were used as a fine aggregate in slag mortars. The properties of these slag mortars were compared with the sand one. Three different water-to-cement (w/c) ratios were used: 0.4, 0.5, and 0.6. All mortar samples were prepared and cured in tap water for 90 days, then kept in laboratory atmosphere for about 4 months. The tests were carried out by subjecting the samples to a temperature of 600degreesC for 2 h, then cooling by three different methods: water, air, and furnace cooling. The results indicated that all mortars exposed to fire irrespective of cooling method suffered a significant depression in compressive strength. However, a remarkable reduction in compressive strength was observed for mortars cooled in air rather than those cooled in furnace or in water. ACS mortars exhibited a relatively higher thermal stability than others. (C) 2001 Elsevier Science Ltd. All rights reserved.