Unlike the conducted studies in the field of reinforcing the asphaltic mixture, this research has used the multi-criteria decision-making method to determine the optimal percentage of the asphalt mix, which was reinforced with rubber powder and carbon fibers. After adding different percentages of two kinds of additives, i.e. rubber powder and carbon fibers conjointly, conducting Marshall Tests, analyzing the data and plotting the needed diagrams, it was observed that adding these two additives leads to a change in the results of Marshall Tests. Analyzing the diagrams, the optimal percentages for combining the rubber powder with carbon fibers were obtained, 15% and 0.5%, respectively having the best effect on the asphalt mix. Subsequently, the extra cost caused by adding the additives to the asphalt was evaluated by conducting an economic analysis. Then, six Mar-shall Parameters were used as six indices in the concordance analysis method, which is a multi-criterion decision-making method. Ultimately, the superior alternatives were proposed according to the results of the ranking. Ac-cording to the results, the suggested alternatives differed from the estimated alternative and the concordance analysis method proposed better alternatives.

In this article by adding different percentages of carbon fiber with high strength and doing the necessary Marshall tests, it was observed that the Marshall Resistance and its Flow increased. Due to their armed properties, the carbon fibers have a positive effect on Marshall Resistance. According to the results, in-creasing the percentage of fibers, reduces the resistance, so that the resistance of the sample containing 1.5% of carbon fiber is almost 32% more than the resistance of the sample without fiber. According to the results, the increased resistance compared to the previous researches and other fibers stems from the kind of fiber used in it and its high resistance. After increasing the fiber percentage to 3, a 12% decrease in the resistance was seen. On the other hand, by changing the percentage of the fibers added to the aggregates, the Flow will change, so that the sample containing 3% of fiber is almost 189% more Flow than the base sample. The economic analysis was used for a three-lane road. The results showed that economically speaking, due to their high price, these types of fibers are recommended to be used in restricted and optimal areas.