Investigation of the mechanical properties of self-compacting concrete produced using industrial waste

This experimental study aimed to prevent environmental pollution and ensure sustainability by using chromite rust, sintered magnesia, natural magnesia, and boron waste (Tinkal), which are produced in high amounts and are difficult to store, self-compacting concrete (SCC). In the series produced in the SCC with a water/binder ratio of 0.40, sintered magnesia, natural magnesia, and chromite rust waste were replaced by 2%, 4%, and 10% cement by weight in self-compacting concrete. Since the required workability was not achieved with boron waste (Tincal), binary mixtures were prepared with other wastes using 1% instead of cement. Since the MgO content of the materials used in the study was high, the Le Chatelier test was applied to measure the expansion of these wastes. Specific surface area and particle size distributions of the used wastes were determined by BET analysis and laser. As fresh concrete tests in SCC mixtures, L-box, Slump-flow, and V-funnel tests were performed. In hardened concrete tests, Compressive strength, flexural strength, determination of water penetration depth under pressure, capillarity, ultrasonic pulse velocity, weigth of water absorption, freeze-thaw, Na2SO4, and MgSO4 experiments were carried out to evaluate the sample performance. Thermogravimetric analysis (TG), X-ray diffraction (XRD), differential thermal analysis (DTA), mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM-EDX) were used for microstructural analysis in each sample. The results showed that MgO creates more hydration products containing magnesium silicate hydrate (M-S-H) in the concrete and fills the voids. After 90 days of water curing in the SCC, the highest compressive strength was obtained from using 2% natural magnesia with 6.9% compared to the control concrete, and the highest flexural strength was obtained from using 2% natural magnesia with 10.3%. The highest compressive strength after freeze-thaw (300 cycles) is 26% in 2% sintered magnesia, the highest compressive strength after Na2SO4 (3 months) is 43.5% in 10% sintered magnesia, and the highest compressive strength after MgSO4 (3 months) is 26%. It was observed with the use of 10% natural magnesia. If the amount of dust waste increased, porosity, water penetration depth under pressure, and water absorption values of the samples increased. Using magnesia and chromite wastes in SCC has improved the workability.