Abstract
Most of the important properties of hardened concrete are related to the quantity and the characteristics of the various types of materials in the concrete. In this study, iron ore tailings (IOTs), an inert, industrial waste material, was combined with sand in varying proportion as fine aggregate in concrete. Five concrete samples A, B, C, D and E were produced. Sample A served as control while samples B, C, D and E contains IOTs as partial replacement for sand. Physical properties, Energy dispersive x-ray (EDX) spectroscopy and X-ray fluorescence (ERF) of fine aggregates were determined. Slump and compacting factor of the fresh concrete were also determined. The density, compressive strength, flexural strength, ultrasonic pulse velocity and the microstructure of the hardened concrete were also assessed. The outcome of this study reveals that concrete sample with 40 % iron ore tailings (IOTs), is about 3.7 % denser than the control sample. Concrete sample with 30 % iron ore tailings (IOTs), recorded the highest compressive and flexural strengths. Ultrasonic pulse velocity values and the microstructure of the IOTs concrete samples shows that inclusion of Iron ore tailings in normal weight concrete reduces absorption of water in the concrete.

Key words: Fine aggregate; hardened concrete; iron ore tailings; water absorption; ultrasonic pulse velocity; compressive strength; flexural strength; microstructure