The Efficiency of Steel Slag and Recycled Concrete Aggregate on the Strength Properties of Concrete

Experimental work was carried out to study the effect of using steel slag (SS) and recycled concrete aggregate (RCA) as replacements for the natural aggregate in concrete. Waste materials, such as SS, which is a by-product generated during the production of steel and concrete rubble, which is produced by demolition activities, are dumped in landfill. These waste materials are considered non-degradable and have a negative impact on the environment. They have become such attributes for possible replacements for natural aggregates in the production of concrete. In the present work, SS and RCA were physically and chemically characterized. The next step of the work plan, SS was employed as a partial replacement for (sand) fine aggregate and also RCA was applied as a partial replacement for (gravel) coarse aggregate. The proportions of SS and RCA were calculated based on the criterion of particle size after performing sieve analysis according to the American Concrete Institute standards. These two replacement materials were used to replace the natural aggregate in M40-grade concrete by proportions of 0%, 15%, 25%, 35%, and 45% by weight and the performance of the resulting mixes was compared against that of the original M40-grade concrete. In the comparison, the concrete mixes were examined for the mechanical properties -compressive strength, flexural strength, and split tensile strength. The results showed by introducing SS into the concrete containing RCA caused an increment in the mechanical properties. In addition, the best result was produced with a mix consisting of 25% steel slag and 15% recycled concrete aggregate.