Fresh and hardened properties of high strength self-compacting concrete using by-product ferronickel slag fine aggregate

Concrete nowadays is the most frequently used building material all over the world. This is causing a tremendous pressure on the supply of its constituents like natural sand which is traditionally used as the fine aggregate. Therefore, it is essential to search for alternative materials in order to meet the increasing demand of concrete and improve the sustainability of concrete industry. This study investigated the effect of using by-product ferronickel slag (FNS) as a partial replacement of natural sand in high strength self-compacting concrete (SCC). Utilization of by-product FNS will also lessen the risk of environmental pollution. Results show that concrete containing up to 40% FNS fine aggregate met all the recommended criteria of EFNARC for SCC without any segregation in the flow and J-ring tests, and no blockage in the L-box and V-funnel tests. The increase of FNS to 60% resulted in significant segregation and reduced flowability due to the larger size, angular shape and higher density of FNS as compared to sand. The 28-day uncompacted compressive strength of concrete with 40% FNS was 66 MPa, which was almost same as that for the vibrated concrete of same mixture, confirming the achievement of self-compaction property. Tensile strength could be conservatively predicted from compressive strength by using the ACI318 and AS3600 equations. The volume of permeable voids and water absorption of the SCC using up to 60% FNS were in the category of "Excellent" and "Low" as per the VicRoads specifications. Sorptivity values were far less than the recommended value of 27.11 x 10(-3) mm/s(0.5). The charge passed in the rapid chloride permeability test was less than 1000 Coulombs. Therefore, FNS content up to 40% was found as an environmentally friendly substitute of natural sand for the production of high strength SCC of good durability.