Chip seal design framework with life-cycle cost analysis for local agencies

Abstract

The paper introduces a systematic framework for local agencies to determine their project’s design based upon McLeod rational methodology in an easy and simple approach. The framework provides an optimum design of material types (aggregate and binder), their required application rates, and estimated performance guaranteeing the lowest life-cycle cost. A prototype is developed using MS Excel with solver Add-In package to illustrate the approach. The prototype offers a simple user-friendly platform to promote the use of “scientific and engineering” concepts to reach an optimum design. The approach could serve as a planning tool since it estimates chip seal projects’ LCC, design lifetime, probability of survival, and estimated performance at the end of the selected analysis period. The prototype consists of four modules that summarise the whole process, which are (1) temporary database, (2) permanent database, (3) systems builder/assessment, and (4) optimisation engine. The first module stores project’s related information and agency preferences. The second module stores construction materials’ alternatives, technical properties, traffic considerations, road factors, cost data, economic data, and performance data. The third module builds different design alternatives and calculates their application rates based upon McLeod performance measures. The fourth module suggests an optimum design identified as the best value option with the lowest long-term cost that satisfies the performance objective. A case study of a chip seal project is presented to show the effectiveness of using such prototype by comparing between the prototype optimum design and the agency design. Findings reveal that the prototype had suggested an alternative design that offered materials cost savings reaching up to 46%. Eight case studies of chip seal projects’ application rates were back-calculated using the tool and compared to the agency empirical rates. Findings showed that there are material variations reaching up to 38%. The use of unnecessary materials does not only affect costs but also affects performance. The prototype can be found very useful to local agencies as it is an easy to develop tool that does not only ensure the project’s design economic value but also assures performance quality.