Proper quality control during embankment construction is critical to ensure long-term performance. Currently, the Iowa Department of Transportation (DOT) uses a specification that involves moisture control or moisture and density control as part of the quality control (QC) and quality assurance (QA) process. A review of other state DOT specifications revealed that a majority of them also were similar to the Iowa DOT specifications, although some differences existed in terms of what the limits are. Recent testing by Iowa State University researchers has revealed that embankments are frequently constructed outside the moisture and density control limits, even though the QC/QA testing data showed otherwise. To further evaluate this issue, this study was undertaken to evaluate QC/QA operations on 27 active earthwork construction projects in Iowa. As one aspect of the study, dynamic cone penetrometer (DCP) was used to measure the strength/stiffness properties of compacted fill materials, and the compacted layer thicknesses.

The overall goal of this project is assess the current state-of-the-practice of earthwork construction QC/QA practices in the State of Iowa, in reference to the state-of-the-practice by other state agencies, and develop recommendations for better practices.

Field testing indicated that 17 out of the 22 field projects with 20 to 100% of the moisture and density test results outside the QC/QA acceptance limits. This is a problem that should be addressed by improved process control procedures. DCP is one test method that can help address the problem. An approach to set target values for DCP testing in reference to moisture and density is provided in this thesis. The target values can be implemented in-situ, in lieu for moisture and density testing, to rapidly assess problem areas.