Mechanical Performance of Steel- Slag and Lime-Modified Asphalt Mixture: A Response Surface Approach

The Response Surface Methodology (RSM) is a collection of methods used to create various experiment designs, determine relationships between experimental variables and responses, and use these relationships to identify the ideal conditions. This study uses RSM to forecast the mechanical characteristics of mixtures modified with steel slag and lime. Using the Box Behnken Design (BBD) method for the mix proportion, steel slag (0–100%), lime (0–4%), and bitumen content (4–8%) were considered independent variables, while the responses were the resilient modulus, indirect tensile strength, flexural stiffness, and compressive strength. Analysis of variance showed that the steel slag was the most influencing factor for the flexural stiffness property of the steel-slag and lime-modified asphalt mixtures. Also, the regression coefficient (R2) of 0.9214, 0.8380, 0.7412, and 0.8266 was obtained for the stiffness, Mr, compressive strength, and ITS, respectively. Some interaction effects on the responses were found between the steel slag and lime. The optimization findings show that 25.01% steel slag, 2.43% lime, and 5.51% bitumen content are the best values to satisfy the design criteria. The optimized mixture design will offer a cost-effective and environmentally friendly solution, promoting resource conservation and sustainable development in the construction industry.