Research Record, RR-98

C&T Research Record is published by the Michigan Department of Transportation’s Construction and Technology Division New quality control and assurance standards are being implemented in many industries across the country. The new standards will enable government agencies to base specifications on measured values and statistical principles rather than average measured values alone. Specifications based on measured values and statistical principles more accurately account for variability than those based only on average measured values. As Figure 1 indicates, when asphalt testing is based on measured values alone the mean value can fall within the specification limits even when the curve describing the results includes values that are well outside of the limits. On the other hand, when testing is based on measured values and statistical principles, all values typically fall within the specification limits. quire samples of HMA. Sampling procedures can be simplified if they’re based on one method, but very little data exists on which to base a comparison of the different methods. This issue of Research Record describes a research project that compares results from three of the most common methods, used in Michigan, for sampling HMA behind the paver. The project also determined how the results affect pay adjustment factors on asphalt paving projects. The project, An Analysis of Three Methods of Sampling Hot Mix Asphalt from Behind a Paver, was undertaken by a team headed by Dr. R. Christopher Williams of Michigan Technological University (MTU). Cooperation between the Michigan Department of Transportation (MDOT), the Michigan Asphalt Paving Association (MAPA), and Mathy Construction Co., a private company based in Wisconsin, was an important element that contributed to the successful completion of this project. “MTU acted as a neutral entity between government and private industry,” Dr. Williams explained, “I appreciate the cooperation and participation of everyone involved in this project.”