Determining the Appropriate Amount of Mixed Fine-grained and Coarse-grained Slag Based on the Mechanical Properties of Asphalt Mixtures Using Response Surface Methodology

The use of industrial waste, such as steel slag, in the road construction industry, to reduce the use of stone materials and also the environmental benefits of reusing these materials is very important. Research on the use of steel slag as an alternative to stone materials in asphalt pavements has been carried out for many years due to the improvement of some of the main properties of these mixtures. In these researches, slag in general (including fine-grained and coarse-grained with the same percentage) or coarse-grained has replaced the stone materials. However, since some properties of asphalt mixtures show different effects by changing the fine-grained materials or a different combination of fine-grained and coarse-grained to the simultaneous and equal replacement of fine-grained and coarse-grained, in this research, optimum percentage of using slag materials in fine-grained and coarse-grained size has been investigated using the response surface method. In this regard, different mixing schemes of this substitution have been investigated using modulus of resistance, Marshall resistance, indirect tension and moisture sensitivity tests. Results of the performed experiments and their analysis has determined the type of fine-grained and coarse-grained behavior in asphalt mixtures, and finally, for each experiment, the proposed model has been determined based on the research conditions.