Engineering properties of cementitious composites containing olivine, chromium slag and waste chromium powder

Today's construction sector has entered into a fast and developing industrial formation with the twenty-first century. This development provides benefits from the point of view of civilization, but it creates problems when the negative consequences of industrial waste are taken as a basis. Since the amount of waste material will increase with the increase of the world population, this situation will pose a big problem for the coming years. One of the most environmentally friendly ways to solve this problem is to make these waste materials reusable and evaluate them in different sectors. When we look at the studies in which chromium slag, chromium powder and olivine mineral are used in the literature; they were used in different studies by substituting natural aggregate in volume or replacing it with cement after fine grinding. It has not been found in the literature that these three materials have been used together in concrete in different experimental studies. In the study, 0%, 10% and 20% waste chromium powder, 80%, 90% and 100% chromium slag and 0%, 2.5% and 5% olivine mineral were substituted into the mixture instead of aggregate and binding material. To investigate the effect of these materials on the engineering properties of hardened concrete; unit weight and slump experiment were performed on fresh concrete samples; saturated surface dry bulk density, oven dry bulk density, water absorption percentage by mass, apparent porosity percentage, sodium sulfate resistance, compressive strength, flexural strength experiments and electromagnetic shielding experiments were performed on hardened concrete samples, as well as SEM-EDS and XRD experiments to study the microstructural properties of the samples produced in the study. According to the results of the experiment; as the amount of use of olivine and waste chromium powder in the mixture increases, an increase in the density of fresh concrete, the compressive and flexural strengths of the samples were observed. The best mechanical and physical properties in concrete samples were observed in samples containing olivine mineral and waste chromium powder. In the electromagnetic shielding (EM) experiment conducted on concrete samples, an increase in EM shielding values was observed as a result of an increase in the amount of waste chromium powder and olivine in the concrete. The presence of Fe2O3, Cr2O3 and MnO compounds in the internal structures of waste chromium powder and olivine minerals, which were chemically analyzed by XRF analysis, had a positive effect on shielding values. When a general assessment is made, the use of olivine mineral in concrete between 2.5%-5% by replacing cement, waste chromium powder of 20% and chromium slag of 80% instead of aggregate will positively affect the mechanical, physical properties of concrete and the EM shielding property, which is one of the main objectives of this study. With this study, the consumption of natural resources used both for cement production and as concrete aggregate will be reduced, and the energy consumed for cement production will be saved. By adding olivine and waste chromium powder in different proportions to the concrete, EM shielding feature will be given to the normal concrete and innovation and sustainability will be brought to the construction sector by using it in nuclear power plants, the health sector and places directly exposed to radiation.