Field implementation of a rational Otta seal mix design for enhanced performance on low-volume roads

Low-volume roads connecting rural communities and agricultural fields face unique challenges due to heavy traffic and constrained budgets for maintenance and rehabilitation. The Otta seal surfacing technique utilizing bituminous material and graded aggregates to create a durable road surface has emerged as a promising solution. This study explores a rational mix design, a modified McLeod method, for Otta seal application considering local material properties, and compares it with existing design guidelines. The study involves constructing test sections following a rational design technique and conventional Overby recommended guidelines. The performance of the test sections was assessed by testing skid resistance, surface roughness, dust generation, and structural stiffness over a two-year period. The test section constructed following the modified McLeod method outperformed sections built per traditional Overby guidelines in terms of cost-effectiveness and overall performance. Specifically, the test section that was constructed using the modified McLeod method exhibited the lowest roughness, dust, and loose aggregate from the surface. Results from life cycle cost analysis (LCCA) highlight the economic benefits of the rational mix design technique, demonstrating the economic advantages of the rational mix design, showcasing lower construction and maintenance costs. By adapting the modified McLeod method to suit the local aggregate materials, engineers can achieve more appropriate and accurate application rates for both aggregates and binders, thereby optimizing the performance of the overall mixture. The study contributes practical insights for optimizing Otta-seal surfacing, emphasizing the significance of using local material properties and rational mix design for enhancing the longevity and cost-effectiveness of low-volume roads in Iowa.