Use of steel slag in concrete mixtures

Abstract

The recent unprecedented growth in the building industry in the State of Qatar has created a pressing demand for construction materials. Needs for concrete, being the major construction material has grown with the rapidly growing construction sector. Aggregate generally occupy about 70-80% of the volume of concrete used in buildings. The needs for alternative sources of aggregates are pressing. Steel slag, which is a by-product of steel manufacturing, could be an alternative solution.

This paper presents the results from experimental works completed at Qatar University to check the applicability of using steel slag aggregates in concrete mixes in Qatar. Five trial concrete mixes were prepared.  One concrete mix composing of 100% gabbro coarse aggregates was designated as the control mix. Four other concrete mixes were prepared and they contained 100%, 75%, 50%, and 25% partial replacement of gabbro aggregates with slag aggregates, by weight. The concrete mix was proportioned to have a 28-day compressive strength of 35 MPa. The water-to-cement ratio was kept constant at 0.58 for all of the five mixes. All mixtures were cured for 7, 28, and 90 days.  No admixtures or additives were used in these mixes. The data indicate that steel slag has a promising potential to be used as a partial replacement for conventional aggregates in concrete.

The emphasis of the work in the initial phase of this study was on the feasibility of utilizing steel slag aggregates in concrete, as a total or partial replacement of gabbro aggregate, used in construction in the State of Qatar by studying the properties of fresh and hardened concrete. Tests were conducted on concrete samples made of different aggregates to determine their acceptability for use in concrete. The different mixes were tested to determine compressive strength, splitting tensile strength, flexural strength, air content, and bulk density. Laboratory results, obtained in the six months research project, indicated that steel slag alone or in combination with other virgin raw materials such as gabbro, sand, and others could find uses in road construction applications in the State of Qatar.