Evaluation of Asphalt Mixture Production Sampling Frequency for Balanced Mix Design Acceptance using IDEAL-CT and IDEAL-RT

Implementation of balanced mix design (BMD) tests during mixture production is crucial for assuring the quality and consistency of BMD mixtures. However, the BMD system lacks engineered testing frequency protocols and can require extensive sampling, labor, time, and equipment during quality control (QC) and quality assurance (QA). The main goal of this study is to determine appropriate production testing frequencies for IDEAL-CT and IDEAL-RT during BMD mixture production. In this study, eight asphalt mixtures with Superpave aggregate gradations, produced across 21 days and forty-nine sublots were evaluated to capture the variabilities occurring at sublot, day, and mixture-level production. IDEAL-CT and IDEAL-RT tests were performed on these reheated plant-produced and laboratory-compacted (RPMLC) mixtures. From the production variability analysis, the coefficient of variation (CoV) for the corresponding sublot, day, and mixture-level production was determined to be 21.1%, 27.7%, and 30.6% for CT _index , and 5.7%, 7.4%, and 9.6% for RT _index . The study also identified reduced sampling scenarios to capture daily production averages in CT _index and RT _index within 5%, 10%, 15%, and 20% deviation from the actual day average. To confidently determine CT _index and RT _index for a production day, 3S-2R (two replicates each from any three sublots) and 2S-2R (two replicates each from any two sublots) sampling scenarios can be adopted, respectively. Further, the study recommends multiple sublot sampling to determine approximate production day average over single sublot sampling. Overall, the study concludes that it is practically possible for consistent daily BMD mixture productions and incorporation of IDEAL-CT and IDEAL-RT tests during QC&QA.