The Pavement Mechanistic Empirical Design (PMED) was developed by AASHTO as the standard for rigid pavement design and performance analysis, and as the most advanced tool, it has transformed the pavement design process.
Many state DOTs are in the process of implementing PMED into their pavement design processes and are characterizing local concrete materials in this process. NCDOT is also planning to incorporate PMED into the design process for rigid pavements. The NCDOT conducted a research project completed in 2016 as an initial step to conduct the characterization of concrete materials (FHWA Report No. NC/2015-03) which provided a database of concrete material inputs incorporating Piedmont, Coastal, and Mountain coarse aggregates along with a manufactured sand and a natural sand. Although this project provided a range of useful inputs, it is understood that there are differences in aggregates from other areas of North Carolina, including areas where rigid pavements are anticipated to be constructed. These areas, including the Charlotte area, the Greensboro/Winston-Salem area, the Boone/Blowing Rock area, and the Morganton/Lenoir area, may have quarries that will be potential candidates for use in future concrete paving mixtures. Based on the NC geologic map, there may be some geologic differences that translate into thermal performance changes between these aggregates and the aggregates which were tested in the earlier project. So, there is a need to characterize the concrete paving mixes prepared with these coarse aggregates and potentially other variables to obtain a more detailed catalog of PMED inputs for rigid pavement design, and subsequently, to evaluate the effects of the obtained material inputs on the design and performance analysis of rigid pavements.
The need for this work is amplified as NCDOT is undertaking new rigid pavement projects including re- construction/widening of I-26 (costing $531 million) and I-540 expressway project (costing $2.2 billion) and many more rigid pavement projects to come in the future. With an accurately established material database to support PMED inputs, the pavement designers will have the opportunity to understand the predicted performance of rigid pavement designs and potentially select the best suited materials and/or mixture characteristics for a specific project.
This proposed research project will result in an enhanced database/catalog of Level 1 mechanical and thermal inputs for PMED design process. The products of this research will be directly implementable by pavement designers, allowing greater confidence in the design and predicted performance of rigid pavements designed using PMED software. The evaluation of various design variables including material inputs, climate, traffic, and geometric properties with regards to the design thickness and predicted performance of rigid pavements will provide a knowledge base to the pavement designers about the impact of these parameters on the rigid pavement design. This will improve the reliability of rigid pavements to provide long lasting service lives with low maintenance.
Prior research has also shown the changes in CTE of paving concrete with age progression and there is a need to conduct long-term testing of concrete paving mixes being used in North Carolina to evaluate the changes in CTE values of these mixes with age progression. This will be a step forward towards improved rigid pavement design and constructing pavements that can perform well throughout the designed service life.