Performance Review of a Quality Control/Quality Assurance Specification for Asphalt Concrete

Abstract

A statistical review of 50 jobs recently completed by using California’s new quality control/quality assurance (QC/QA) specification for asphalt concrete is presented. Performance is contrasted to the quality achieved under method and end-result specifications. A cost analysis is made and issues related to verification are discussed. Improvements to the current specification are proposed. The data present clear evidence that the allowable tolerance of ±0.5 percent for asphalt content is too wide for current practice. Also, an increase in compaction variability for many QC/QA jobs could be controlled by adding an upper specification limit or adopting a two-sided volumetric specification. Although bid amounts did not increase, costs for QC/QA jobs went up approximately 3 percent to pay for bonuses allowed under the specification. Analysis of the contractor’s QC test data indicate that this increase is more than compensated for by projected reductions in future rehabilitation costs. However, a significant lack of agreement between the contractor QC and agency QA testing brings this finding into question. More rigorous verification of contractor-provided test results must be incorporated into the specification and the results analyzed before the cost-effectiveness can be determined.