Three Steps Can Improve Your QC
BY Ray Brown, PhD, P.E.
Conducting laboratory tests, analysis of test results and preparation of quality control/quality assurance (QC/QA) reports are all important aspects to ensure a satisfactory asphalt mixture is constructed. Qualified technicians must perform this testing in an acceptable laboratory. Most state departments of transportation (DOTs) have requirements for the technicians, inspectors and QC managers to be certified under a DOT certification program. This helps to ensure the ability of those involved in the work (technicians, inspectors and QC managers) to achieve a satisfactory product.
States also have requirements for certification of these laboratories to ensure that these laboratories are acceptable to conduct this testing. There are three specific areas where projects could be deficient in testing and summarizing data. These three areas include:
1) insufficient analysis of data;
2) lack of adequate visual observations; and
3) insufficient analysis of test data and timely dissemination of the QC/QA report.
Step 1: Analyze Data
The analysis of data for most projects simply involves reporting the test data and providing a comparison of this data to the specification requirements. Comparison of data to specification requirements is important but more analysis is needed to better describe the quality of material. If sufficient analysis is not performed, it is very difficult to adequately describe the overall quality of pavement from the test results in the report.
One method to summarize and analyze the data is to plot the test results on control charts. Some DOTs require control charts be plotted while other DOTs have no requirements for preparing control charts. These charts can be used to summarize the data and to show trends in the data. These control charts are developed electronically and are seldom printed any more.
Typically, individual test results along with running average of test results are plotted to summarize the data and to show trends. The plot of individual test results provides a good summary of all test results that can quickly and easily be observed for all testing. The running average plot is very useful in identifying trends in the data so that adjustments can be made to improve the process as the project progresses. Even if the DOT does not require that control charts be plotted, it is advantageous for the laboratory data to be plotted to help show and understand the overall quality of test results being produced.
Step 2: Observe
Visual observations are an important component of the QC/QA program and can be used along with laboratory test results to provide a good evaluation of the overall quality of construction of asphalt mixture. Many times, visual observations can indicate areas that might need to be further tested.
Testing without visual observations greatly reduces the probability of adequately evaluating the overall quality of a paving project. Visual observations should be made to identify segregated areas, to evaluate quality of longitudinal joints, to evaluate transverse joints adjacent to bridge structures, to identify areas of bleeding, to identify pulling and tearing of the mat, and to identify other problem areas. In many cases additional testing in these observed deficient areas might be helpful in confirming the detected deficiencies. Many problems can be identified by visual observations before they will ever be identified by random sampling and testing.
Segregation is one issue that is almost always found through visual observations and not typically identified by routine sampling and testing. Testing can often quantify the amount of segregation, but these segregated areas must typically be identified visually first.
Step 3: Report Correctly
One deficiency of many projects is the lack of sufficient effort in the preparation of the report of results and the timely dissemination of these testing/inspection reports. Most reports present the test data along with specification requirements but only have limited discussion of the test results and observed deficiencies. The report should state all test properties that are not in spec and discuss actions to be taken as a result of these out-of-spec results. The report should also discuss observations of any deficiencies in the constructed asphalt pavement and steps taken to address these deficiencies. These reports should typically be prepared and disseminated within 24 hours of the time that construction was accomplished unless the specifications state otherwise.
The QC/QA report is not always completed in a timely manner. If prepared properly, the QC/QA report should be useful after completion of construction and after traffic has been applied to identify potential causes of any observed pavement performance problem.
Three best practices have been discussed to help ensure a quality asphalt pavement is constructed. These three steps include improved analysis of data, importance of visual observations, and improved and timely submission of the QC/QA report. Addressing these three steps does not take much additional effort on an individual project but will significantly help improve the overall quality of work.
Ray Brown, PhD, P.E., received his BS and MS degrees in civil engineering at Mississippi State University and his PhD from Texas A&M University. He retired after working for approximately 20 years for the U.S. Army Corps of Engineers and approximately 20 years for the National Center for Asphalt Technology (NCAT). He has honorary titles from Auburn University including Professor Emeritus of Civil Engineering and Director Emeritus of NCAT.