Investigation of the effects of elevated temperatures and cooling conditions on the waste andesite dust-based geopolymer mortars

In this thesis, mortar mixtures were manufactured by activating andesite stone cutting waste with sodium silicate. The sodium silicate content in the mixtures was determined to contain 6%, 8% and 10% Na2O by weight of waste andesite dust. The produced mixtures were subjected to thermal curing at 3 different temperatures, 60 ºC, 75 ºC and 90 ºC, and in 2 different periods, 8 hours and 24 hours. Basalt sand is used in mortar mixes due to its heat resistance. Flexural and compressive strength tests of 1, 28 and 56 days were carried out on the specimens obtained from the mortar mixtures. The effects of Na2O content, thermal curing temperature and time on the strength values of the mortars were investigated. Mortar samples produced with 8 hours of thermal curing were exposed separately to 400 ºC, 600 ºC and 800 ºC. The specimens, which were kept for 1 hour at 400 ºC, 600 ºC and 800 ºC, were exposed to 3 different cooling conditions: slow in air, fast in air and in water. Flexural and compressive strength tests were carried out on the cooled mortars and the effects of high temperature and cooling conditions on the strength values of the mortars were evaluated. In addition, the changes in the microstructures of the mortars were investigated by performing XRD and SEM/EDX analyses on the selected mortars. Rapid cooling of the mortars with water significantly decreased the strength values of the mortars.