Use of system dynamics for proper conservation and recycling of aggregates for sustainable road construction

• System dynamics can be used to understand the effects of road construction on natural resources.
• Exponential effect of increase in depletion of natural aggregates on cost and emissions.
• Significant effect of use of local non-local and recycled aggregates on availability, costs and emissions.
• Optimization possible for the best overall effect on road quality, costs and the environment.
• Need for the consideration of system dynamics modeling and simulation for road development policy makers.

A significant amount of mineral aggregates are used in constructing, rehabilitating and maintaining roads. As local (nearby) quarries get exhausted, aggregates need to be hauled from sources that are at ever-greater distances. Hence, over time the cost of trucking as well as the amount of emissions generated by trucking increases with a decrease of local natural aggregate stocks. The objectives of this study are to construct and utilize a system dynamics model of the depletion of a stock of natural aggregates due to pavement construction and maintenance, and determine the effect of using local and nonlocal aggregates, recycling and project cancellation (slowing growth) on the paving of roads. Long-term simulations are carried out with available aggregate stock, trucking distance and cost data. The quality of roads and a sustainability score, based on engineering, economic and environmental factors (emissions) are evaluated for different scenarios. An optimal combination of the use of local and nonlocal recycled aggregates, recycling and project cancellation is recommended. The proposed system dynamics model could be utilized by agencies to plan for the proper utilization of aggregate resources for road development and maintenance/rehabilitation projects.