Investigation of Stripping in Minnesota Class 7 (RAP) and Full-Depth Reclamation Base Materials

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Date Created
2009
Report Number
2009-05
Description
This research investigates the effect of RAP content, freeze-thaw and severe moisture conditions on the structural capacity of the pavement base layer. The investigated material included one source of 100% RAP, one source of virgin aggregate, and three full depth reclamation samples where RAP was mixed with virgin aggregate/soil and was in use as a base layer. RAP was blended in the lab with the virgin aggregate at 50% and 75% RAP content. RAP was coarser than virgin aggregate and it had a higher percentage loss in the Micro-Deval test. The resilient modulus (MR) was measured following the National Cooperative Highway Research Program 1-28A test protocol. The MR for all RAP material was higher than that of the virgin aggregate. The resilient modulus of RAP material was found to be dependent on confining pressure. There was no clear loss of the modulus due to freeze-thaw conditioning for the tested RAP. Decreasing the moisture content increased the resilient modulus for RAP material. Maximum deviator stress in the shear test was reduced after freeze-thaw (F-T) conditioning for RAP/aggregate blends at a low confining pressure, but the effect of F-T on the maximum deviator stress was not clear at a higher confining pressure.

Best-Value Based on Performance

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Date Created
2008
Report Number
2008-40
Description
The Best-Value procurement strategy is gaining interest from federal and state agencies. The strategy increases the value added to the project for each dollar added. This report discusses a new concept of Best-Value, that is; a rational and flexible model based on expected performance. The model flexibility is obvious in the selection of parameters, to be included in the contractor selection process, and in the determination of the parameter's weights. The model rationality will be achieved through relating all awarded score to the agency's expected performance. The establishment of the Best-Value model calls the past record of the contractor work for the agency as an indicator of qualification trend. Contractor Best-Value will be the base in selecting the most appropriate contractor that has the best qualifications for a given project. Data are collected from groups of experts in the Minnesota Department of Transportation and processed through the analytic hierarchy process (AHP) to establish the parameter weights. While this research assists DOTs in selecting the best contractor, the shared results are relevant to both academics and practitioners. A computer software "MnCAST" has been developed to help implementing the developed Best-Value system.