The National Academies

NCHRP IDEA 20-30/IDEA 126 [Completed (IDEA)]

Developing Time Domain Reflectometry (TDR) Instrument for Fresh Concrete and Early Stage Concrete
[ NCHRP 20-30 (NCHRP-IDEA) ]

  Project Data
Staff Responsibility: Dr. Inam Jawed

This project developed a new instrument based on Time Domain Reflectometry (TDR) for measuring properties of fresh and early age concrete as an alternative to traditional quality control methods that rely heavily on the slump value and compressive strength and do not always produce durable concrete. Work in the initial stage focused on the design and development of a prototype sensor system for use on fresh and early age concrete. An experimental program systematically evaluated the sensor system’s ability to measure the performance properties of concrete. The program tested several representative concrete specimens used in highway pavement, bridge, and industrial and residential structures. TDR signals were collected on concrete specimens subjected to different curing conditions, including early freezing, and the results were correlated with data obtained by standard test methods. The results indicated that the TDR sensor system could reliably measure or estimate concrete properties, such as free water content, density, air void content, initial and final setting times, and mechanical strength. New test results also showed promise of advancing this technology to estimate the thermal properties of concrete, such as the thermal conductivity and heat capacity. Experiments were conducted on several types of soils to verify the testing methodology with promising results. The technology was found not only suitable to measure the physical and thermal properties of materials at common temperature but also works non-destructively under freezing-thawing cycles. The system was refined to measure the thermal properties in non-intrusive fashion. The work on thermal properties of construction materials also led to the idea of smart coatings with modulated optimal properties for effective solar energy management. The researchers received a U.S. patent on the technology and have filed for a new patent on a flat strip design, in addition to submitting several invention disclosures to the University for review.

The contractor's report is available.

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