Investigation of the usage of blast furnace slag and steel slag in diffeferent compositions in concrete production

Slag and other waste materials generated during steel production accumulate in waste areas over time and continue to pose a threat to the environment and human health. In order to eliminate this environmental problem and provide economic gains, there are studies on the utilization of slag in concrete in different ways. In this study, where concrete was produced in two series, completely natural aggregate was used in the first series, while in the second series, granulated blast furnace slag instead of fine aggregate and steel slag instead of coarse aggregate were completely replaced with natural aggregate. However, in both series, a total of 10 different concrete mixtures were prepared by substituting ground blast furnace slag at the rates of 0%, 10%, 20%, 30%, 40% instead of cement. After waiting for standard cure for 28 days, the produced concrete samples were exposed to solutions with 5% magnesium sulfate and 5% sodium sulfate concentration separately for 90 days to examine their strength and durability properties. In addition, in order to make comparisons, the concrete samples obtained from each mixture were left in a group at the standard cure throughout the test period. Ultrasonic sound velocity, concrete test hammer and compressive strength experiments were performed on concrete samples, as well as SEM-EDS and XRD analyzes to examine their microstructural properties. According to the test results, it has been determined that the use of 100% granulated blast furnace slag and steel slag as aggregates in concrete negatively affects the mechanical and physical properties of concrete. On the other hand, as the ground blast furnace slag substitution rate in cement increased, there was a general increase in the performance of both slag aggregate and natural aggregate concretes. When the mechanical properties of samples exposed to sulfate effect and samples kept at standard cure for the same period of time were compared, a greater partial strength increase was observed in samples with slag aggregate than in samples with natural aggregate.