The National Academies

NCHRP IDEA 20-30/IDEA 229 [Active (IDEA)]

Lab Dielectric Measurement System for Asphalt Mixture Bulk Specific Gravity Determination

  Project Data
Funds: $135,422
Staff Responsibility: Inam Jawed
Research Agency: University of New Hampshire
Principal Investigator: Jo Sias
Effective Date: 1/1/2021
Fiscal Year: 2020

This project will develop a laboratory procedure for determining the bulk specific gravity of compacted asphalt specimens using dielectric constant measurements. Work in Stage 1 will focus on establishing the reliability and standardizing procedure for the Lab Dielectric Measurement System (LDMS), including an evaluation of the impact of specimen geometry, surface condition, and mix design variables on dielectric measurements. A design of experiments approach will be used to develop a material sampling plan for plant-produced asphalt mixtures. A survey will be administered to gather information on aggregate sources and planned mixture production from state DOTs and asphalt mixture producers. Data from previous and ongoing studies using dielectric profiling system (DPS) and LDMS will be collected for inclusion in the overall database. Sampling of plant-produced asphalt mixtures as well as component materials (aggregates, recycled asphalt pavement and binders) and mix design information will be conducted. Test specimens covering a range of densities, geometries, and surface characteristics will be prepared and their dielectric constants and bulk specific gravities measured. Necessary refinements to calibration and measurement procedures will be identified. Correlation curves between laboratory-measured bulk specific gravity and dielectric values will be developed. Statistical analysis will be conducted to evaluate the variability and repeatability of measurements and the significance of mixture properties on dielectric-specific gravity relationship. A draft AASHTO Test Specification will be developed for dielectric measurements of compacted asphalt specimens in the laboratory. In Stage 2, a relationship between dielectric value and bulk specific gravity will be established with the goal of replacing laboratory bulk specific gravity measurements with laboratory dielectric measurements. Component materials, such as aggregates, reclaimed asphalt pavement (RAP), and asphalt binder, sampled in Stage 1 will be tested using the LDMS. The collected data will be used to enhance existing models to develop and refine the relationship between laboratory-measured dielectric values and bulk specific gravities of compacted asphalt specimens.


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