Resistance of cement-based composites with different contents to high temperature and behavior after high temperature

Concrete is a building material that we often see around us. Although concrete is a durable building material, decreases in the strength of concrete occur when it is exposed to factors that will cause the deterioration of concrete. Due to factors such as high temperature, sulfate effect, freeze-thaw, acid and salt, deterioration of the structure of concrete can be observed. In this context, studies are still ongoing today in order to minimize the negative effects. These studies are important both for sustainability and for obtaining more durable concrete with developing technology. For these reasons, in this study, the behaviors of concrete in the face of high temperatures that cause the deterioration of concrete, the importance of cooling types after high temperatures and the effect of curing after high temperatures on sample behavior were investigated. In this context, the concrete production, the water / cement ratio is determined as 0.5 and the cement dosage is 400 kg / m3, has been carried out in such a way that there are 5 different sets of 5 mixtures. 1. control samples were produced in the set. In the second, third and fourth sets, respectively, fly ash, blast furnace slag and silica fume were added at a rate of 15% by weight of the cement and production was completed. Samples containing polypropylene fiber are 5. it was added to the set as 5 per thousand of the total concrete volume. room temperature test hammer, ultrasonic sound speed (UPV), water absorption, capillarity, abrasion and pressure resistance experiments were performed on the samples whose 28-day curing periods were completed. In order to examine the behavior of concrete samples against and after high temperature, the samples were subjected to 4 different temperatures (200°C, 400°C, 600°C and 800°C) for 2 hours. After high temperature application, the samples were cooled by 2 different methods such as spraying and self-cooling, and their compressive strength was measured. The effects of concrete samples exposed to high temperature on their compressive strength were investigated by exposing them to 2 different spheres (water and air cures) for another 28 days. According to the findings obtained, resistance losses increased in all mixtures with increasing temperature. When the results were evaluated, the loss of compressive strength was higher especially in the samples cooled by spraying method compared to the samples cooled in air. Again, one of the important results obtained as a result of the study is that the polypropylene fiber, fly ash, silica fume and blast furnace slag added to the mixture reduced the losses mentioned above. In addition, it shows that water curing on concretes that have cooled down after high temperatures can compensate for some of the strength losses caused by high temperatures.