Statistical Quality Control and Quality Assurance Evaluation of Structural and Paving Concrete

The variability associated with the production, construction, and testing of structural and paving concrete is discussed. Data from more than 900 projects constructed from 1992 through 1999 representing more than 25,000 lots were evaluated. The data were collected from the Louisiana Department of Transportation and Development’s (DOTD’s) computerized Material Test Data Reporting System. The analysis indicated that ( a) overall price reductions were less than 0.2% for structural concrete and about 0.5% for paving concrete, ( b) the thickness of concrete cores is the major contributor to the overall reduction in the price of paving concrete, ( c) there was good control in the production and testing of structural concrete, and ( d) there was an increase in the nonuniformity of paving concrete acceptance criteria. Recommendations include a need to maintain better control of the variability of paving concrete through the application of control charts or unknown variability in the specification types and a need for continued evaluation for monitoring the overall quality control and quality assurance program of the DOTD.