Developing a Decision-Making Model to Determine the Optimal Bitumen Supply Plan for Road Construction Companies

Road construction projects are often projects with a duration of several years, and the implementation of asphalt is one of the last stages of these projects. Until now, most road construction companies supply the needed bitumen at the end of the project mainly by the direct purchase method without using planning tools. Considering the fluctuations in the price of bitumen in Iran and the lack of proportional growth of adjustment indices, this method of supplying bitumen is not considered an optimal method and causes losses to the contractor. In this article, to reduce losses caused by bitumen price fluctuations, the issue of bitumen supply by storage method is raised, which is currently not common in road construction contracting companies. Supplying bitumen by storing it in the warehouse is considered a preventive measure against the loss caused by the price increase, but it will impose storage and re-transportation costs on the contracting companies. Therefore, the challenge arises as to what percentage of the required bitumen is provided by the direct purchase method and how much is provided through storage. The answer to this question involves using a decision-making model based on optimization. In this article, a decision-making model is presented to determine the optimal bitumen supply schedule in road construction contracting companies. To express the importance of using this model, a practical example was examined. In this example, 9 different conditions for bitumen supply required in a contracting company were defined and then the optimal program obtained for these 9 conditions was compared with each other. The results showed that it is possible to reduce losses by using the decision-making model, at least 18% and at most 93%. This shows the importance of using this model in reducing the company's losses.