Investigation of the effect of recycled aggregate to fire resistance of geopolimer concrete produced by using blast furnace slag

In this study, geopolymer concrete samples were produced by used blast furnace slag (BFS) activating with alkali activators (Na2SiO3 and NaOH) as binder. In order to examine the effect of the recycled concrete aggregates on the fire resistance of these produced geopolymer concretes, 5 groups of geopolymer concrete mixes with recycled aggregate content of 0%, 25%, 50%, 75% and 100% were prepared. Various properties of geopolymer concrete samples such as compressive strength, ultrasonic pulse velocity (UPV), water absorption rate, capillary permeability and weight change have been examined. The results were supported by visual inspection and microstructure analysis. These values were compared with the test results of samples exposed to high temperatures (100, 200, 400, 600 and 800°C). In addition, three different types of cooling (air, water, oven) have been applied. The experimental results showed that adding recycled concrete aggregate to geopolymer concrete samples at room temperature and after fire reduces compressive strength and UPV values of the samples, and increases the water absorption rate, capillary permeability coefficient and weight change. Keywords: Geopolymer concrete, fire effect, recycled aggregate, blast furnace slag, permeability