EVALUATION OF IRON TAILINGS AS AGGREGATE REPLACEMENT FOR ENGINEERING APPLICATIONS

Abstract

This study evaluated the suitability of iron tailings as aggregate replacement for engineering applications. Stockpiling of waste tailings cannot continue in mines, therefore recycling into blocks for usage in engineering applications are desirable hence this investigation. The physical properties (specific gravity, bulk density, moisture content, particle size and fineness modulus) and mechanical properties (compressive strength, compaction factor, flexural strength of iron tailings concrete were determined and relative density). Iron tailings collected from Itakpe tailings dump and the physio-chemical properties of the water used to cure the concrete cubes and beams (alkalinity, pH and hardness) were determined to find suitable usage of these iron tailings in engineering applications. World Health Organization (WHO, 2008) standard methods for the examination of water and wastewater were used to analyse water used for the curing of the concrete cubes and beams to ascertain its toxicity. Workability of concrete made with iron tailings was perfect with 85 mm (High workability) while concrete made with 50% replacement had a workability of 160 mm which was higher than the 98 mm workability of the control. The chemical analysis shows that toxic elements analysed for were either not detectable in the iron tailing or were in very negligible quantity. The particle size distribution indicated clearly that the iron tailings have high medium coarse granules with less proportion of fines thus making cracks rarely possible. The sharp sand has a high medium and coarse grain matrix, which makes high concrete strength and compaction feasible, 100% replacement gave a high compaction factor of 0.97 compared to the control value of 0.96. The Uniaxial Compressive Strength of 75 and 100% replacement had compressive strength of 140.5 and 153.2 MPa respectively which was greater than 0% (113 MPa) after 28 days of curing. The beams made with 15, 25 and 75% replacement had a high bending stress of 13.0, 9.2, 9.2 MPa compared to 0% (7.9 MPa) at 7days. 15 and 75% replacement had 16.3 and 12.9 respectively while the 0% (12.3 MPa) at 14 days. 75 and 100% replacement had a bending stress of 13.4 and 14.7 MPa which was higher than 0% (13.1 MPa). 28-day (75 and 100% replacement had bending stresses of 18.0 and 16.9 MPa while 0% (15.8 MPa). The pH (12.05-12.43) and Alkalinity tests indicated that the curing water was highly alkaline. The Iron tailings is suitable for fine aggregate replacement up to 75% without altering the mechanical properties of such concrete negatively.