Determining the Optimum Sample Size for Quality Assurance (QA) of Asphalt Mixtures: A Case Study

Acceptance plans for asphalt mixtures use a certain sample size that is often established based on the purpose of sampling, population size, risk, and allowable error evaluation. The rate quality control (QC) higher than assurance (QA) size. test results obtained from QA samples are commonly used to validate QC assist state department transportation (DOT) with payment decisions. However, if insufficient make accurate judgments, probability making incorrect decisions regarding acceptance increases. On other hand, oversampling needlessly consumes both time cost. To identify appropriate testing, balance must be struck between number variables. In this case study, two models were developed using Oregon Department Transportation (ODOT) data determine need work was realized when review ODOT paving projects revealed large variability in lot These ranged 3000 more 100 000 tons commensurate rates. typical standard deviation (STDEV) values content (AC) in-place density determined. show STDEV represented 90 percent projects, needed increase AC lots less 22 tons. also can decreased remain as mixtures. proposed optimum different sizes.