Investigation of Using Steel Slag on Concrete as a Partial Replacement of Fine Aggregate with Admixture

Abstract

Concrete is an essential construction material for various infrastructure projects worldwide, including buildings, bridges, roads, and dams. It is produced by combining cement, water, fine aggregate, coarse aggregate, and admixtures (if needed) in precise ratios. However, the sourcing of fine aggregate from natural resources is limited and can lead to supply scarcity. To address this issue, alternative materials such as steel slag, a byproduct of steel manufacturing industries, can be used as a replacement for fine aggregate. Steel slag has a greater hardness than sand and can be an effective substitute. This research aims to investigate using steel slag replacement in normal-strength concrete by incorporating Admixture, which enhances the workability and strength of concrete. This study involves experimental laboratory tests of concrete-making materials, including fine aggregate, steel slag, and coarse aggregate. The chemical composition of steel slag was also analyzed to assess its suitability as a replacement for fine aggregate. The concrete mix design for C-25 concrete followed the ACI mix design procedure. The percentage replacement of fine aggregate by steel slag ranged from 0% to 60% in increments of 10% by weight. The workability of fresh concrete was determined by measuring the slump height. A total of 105 specimens were prepared, including concrete cubes at the age of 7th, 14th, and 28th days, as well as concrete cylinders for the 7th and 28th days of curing. Generally, Seven concrete mixes were prepared, including a control mix used as a reference. The laboratory findings show that the workability of concrete decreases as the percentage of steel slag replacement increases. However, the test results show that the compressive strength of concrete containing Admixture improves when fine aggregate is replaced with steel slag up to 60% at 28 days of curing, with an increase of 9.88%. The ratio between two successive replacements between 10% and 20% of steel slag replacement achieves a maximum of 3.16%, which then decreases onwards. The split tensile strength gradually increases in all mixes from the reference mix up to the 60% replacement of fine aggregate with steel slag, showing a 6.78% increase at 28 days of curing. Therefore, this study suggests that partial replacement of fine aggregate with steel slag and Admixture can improve the strength of concrete. Further studies are recommended to determine the maximum and optimum replacement of steel slag as a fine aggregate in concrete incorporating Admixture.