Studies on Processed Granulated Blast Furnace Slag as Fine Aggregate in Mortars and Concrete

Abstract

Fine aggregate is essential for the preparation of mortar and concrete. There are attempts to find alternatives to the river sand as the natural sources for fine aggregates are dwindling. Currently, sand mining from river bed has been banned in several countries including India. Different industrial by-products and non-organic solid wastes are being explored to meet the growing need for fine aggregates. The steel industries produce huge quantities of slag, especially blast furnace and steel slag. The main focus of the investigations was on exploring the feasibility of using the granulated blast furnace slag (GBS) as a substitute for river sand in the mortars and the concrete. The GBS sourced from a local steel industry caused difficulty in handling (sharp edges and flaky/needle-shaped particles) and leading to poor workability for the mortar and the concrete. Therefore, the processed GBS designated as PGBS was used in the experimental investigations. The experimental investigations were focused on (i) characterising the properties of PGBS (ii) exploring the characteristics of the mortar and the masonry using PGBS as fine aggregate, and (iii) investigating the influence of PGBS on mechanical and durability characteristics of the concrete. The characteristics of the mortars (using PGBS aggregates) investigated include workability, water retentivity, strength, and stress-strain characteristics. The hydration products in the mortars with PGBS and river sand were quantified using thermogravimetric techniques (TGA). The impact of PGBS inclusion in mortars on the masonry flexure bond strength and compressive strength were investigated. Similarly, the characteristics of the concrete (in the fresh and hardened state) were investigated by replacing the river sand with PGBS (25, 50, 75 and 100%). The workability, shrinkage, compressive strength, tensile strength, rebar bond strength, stress-strain characteristics and the durability of the concrete were examined.