Abstract:

In this study, the effect of high temperature post-air curing conditions on the strength of mortars containing alkali-activated blast furnace slag and fly ash was investigated. For this purpose, alkali-activated mortar samples were produced by replacing 0%, 25%, 50%, 75%, 100% fly ash with blast furnace slag. In the study, sodium metasilicate containing 10% sodium (Na) was used as activator. Samples produced were heat cured at 90°C for 24 hours. After heat curing, the samples were exposed to elevated temperatures at 400, 600 and 800oC. Weight loss, flexural, and compressive strength tests were applied to the first group samples one day after the heat curing, the second group samples one day after the elevated temperature, and the third group samples 28 days after the elevated temperature. While the highest compressive strength before high temperature was obtained at 75.5 MPa in 100% slag samples, the lowest compressive strength was obtained at 44.6 MPa in samples containing 100% fly ash. When the compressive strength values of the samples, which were cured in air for 28 days after high temperature, were compared with the compressive strength values of the samples that were not exposed to high temperature, a maximum of 32%, 64% and 93% loss of compressive strength occurred at 400oC, 600oC and 800oC, respectively. Air curing of the samples for 1 and 28 days after high temperature did not cause a significant change in their compressive strength. The flexural and compressive strength loss occurred immediately after high temperature, and the samples generally preserved their strengths after 28 days of air curing.