Experimental study on the behavior of steel tubular columns filled with concrete containing iron filings

Iron filings are industrial by-products that have harmful effects on the environment. To handle this issue, iron filings can be used in concrete production as a substitute for part or all of the sand. This study investigates, the compressive performance of concrete-filled steel tubular columns (CFST) with a circular cross section. The concrete used inside the CFST columns contained 0, 10, 20 and 30% iron filings as replacement of sand with two different water to cement ratios. After fabrication and curing for 28 days, CFST columns, were subjected to compressive axial load and the results were obtained as load-displacement curves and load-bearing capacity of the specimens. The parameters studied in this research include diameter to thickness ratio of steel tubes, water to cement ratio (mixing plan) and different percentages of iron filings as replacement of sand. In order to estimate the compressive strength of concrete, standard cube specimens were prepared and their 28-day compressive strength was measured. The results were extracted as compressive strength of concrete cube samples and stress-strain curves. Also, the effect of water to cement ratio (mixing plan) and percentage of iron filings on the compressive strength and efficiency of concrete cube samples, has been studied. The results show that the addition of iron filings up to 20% of the sand weight increases the compressive strength of concrete and CFST columns to an acceptable level. This also increases the initial stiffness of the samples. Increasing the amount of iron filings from 20% to 30% of the sand weight, showed a decrease in compressive strength of the specimens, according to which it can be concluded that the optimal percentage for the amount of iron filings is 20%.