Development of sustainable concrete using iron ore tailings as sand replacement

Abstract

The increasing demands for iron ore worldwide have resulted in the generation of billion tonnes of iron ore tailings (IOT) which were found in all the iron ore mining industries. Rapid increase in consumption of river sand due to the increased in construction activities over exploited the riverbeds. This has led to a range of problems which include: depletion of natural sand, increased riverbed depth, water table lowering, intrusion of salinity and destruction of river embankment. This study explored the possibility of using IOT as a replacement for natural river sand in concrete production. Laboratory investigations were conducted to evaluate the characterization of IOT materials in terms of microstructure, physical and chemical properties. Leaching behaviour of IOT materials was also determined. Furthermore, mix design and the evaluation of the fresh and hardened properties of the IOT concrete were executed. Series of concrete were prepared with IOT at a replacement level of 25%, 50%, 75% and 100%, using water to cement ratio (w/c) of 0.40 and 0.60. Fresh properties of mixtures in terms of concrete slumps and density were studied. The hardened properties examined are mechanical strengths, deformation characteristics, durability properties and corrosion measurement. Corrosion rate were evaluated using linear polarization techniques. Finally, microstructural tests in terms of X-ray Diffraction (XRD), Field emission scanning microscopy (FESEM), Fourier Transform Infrared Spectroscopy (FTIR) and Thermo gravimetric analysis (TGA) were concurrently conducted on control and IOT concrete in order to determine the interaction and effect of the IOT material that brings about the performance of the concrete. A correlation coefficient using fitted linear regression analysis was performed on compressive strength to evaluate the significant level of concretes containing IOT. Results showed that IOT affect mixture workability negatively. However, the inclusion of super plasticiser showed tremendous influence in increasing the workability and reduced this drawback. At 50% replacement, the compressive strength of the concrete at 28 days was 65.6 and 37.7 MPa for 0.40 and 0.60 w/c ratio, respectively, which shows an improvement of 9% and 12% over the concrete with river sand. Concrete with IOT indicates a good resistance to carbonation compared to control specimen. Linear polarization resistance (LPR) results indicates that, corrosion rates of 0.02 mm/year for IOT concretes were the same with control at 0.60 w/c ratio while 0.01 mm/year was observed for control at 0.40 w/c ratio. Considering all these test results, 50% river sand replacement with IOT resulted in concrete of excellent strength and adequate durability performance except for exposure to acid attack. However, it has the quality to be used as partial replacement of sand.