NRRA: Enhanced Entrained Air Void System Characterization for Durable Highway Concrete

Status:  Complete
Report Date:  09/16/2022


The air void system in concrete provides a strong influence on the behavior of cementitious materials in both the fresh and hardened state, especially as it relates to freeze-thaw resistance and de-icer scaling. The most common test procedure to characterize the air void system is American Society of Mechanical Engineers (ASTM) C457, which involves microscopic determination of the air content, paste content, air-void size distribution, and spatial dispersion of a sawn concrete sample. This procedure is reliant on the user to make hundreds of critical decisions per sample, which requires a lot of time, and is subject to human error. Additionally, ASTM C457 Procedure C requires significant sample preparation, including lapping, polishing, and dying which is laborious and time consuming. Due to this drawback, most state agencies do not perform this test and generally only rely on fresh air content values. Therefore, there is a need to develop a method to fully characterize the air void system in hardened concrete that is more reliable, less time consuming, cost effective, and easy to complete. This project will research an alternative test procedure to characterize the entrained air void system for hardened concrete. The procedure utilizes a microscope with onboard counting and measuring software to make sophisticated measurements of a prepared sawn or drilled core sample. Additional focus will be placed on minimizing the sample preparation required in ASTM C457 Procedure C. The new procedure and hardware will be developed to be robust (long-lasting), and easily implemented across state agencies.

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