Determine Relationship between IDT based on NCHRP Report 789 IDT Test Protocol and MOR for CSM Pavement Layers

The Mississippi Department of Transportation (MDOT) is active in the implementation of the Mechanistic-Empirical Pavement Design Guide (MEPDG) procedure for designing both new and rehabilitated flexible and semi rigid pavements. This design procedure is available in a software program AASHTOWare Pavement ME Design (Pavement ME). The cementitious stabilized material (CSM) layer(s) in a semi rigid pavement structure are typically constructed using either portland cement or hydrated lime, and historically were also constructed using blends of hydrated lime and fly ash (LFA). One of the material characterization inputs to Pavement ME for CSMs is modulus of rupture (MOR). MOR test protocol requires testing beam samples which can be fabricated in the laboratory but not practically extracted from an existing pavement structure. However, CSM cores may be obtained from existing pavement structures and processed to provide indirect tensile strength (IDT) test samples. IDT test results can be used to estimate MOR via a conversion factor. MDOT State Study (SS) No. 263 is being conducted to sample/test multiple pavement test sections throughout Mississippi to provide requisite information for use in locally calibrating the models included in the MEPDG to Mississippi climate, traffic, and pavement construction materials. To date, SS No. 263 has tested all CSM pavement layers including IDT testing in accordance with the IDT test protocol included in National Cooperative Highway Research Program (NCHRP) Report 789 (IDTNCHRP). An MOR test procedure for CSM is being developed at Mississippi State University (MSU) via ongoing MDOT SS No. 276 (MORMSU). A research study using laboratory derived test data is required to develop one or more conversion factors relating IDTNCHRP to MORMSU.