Pore Solution Resistivity Sensor for Concrete Materials and Structures

The US Department of Transportation (DOT) Federal Highway Administration (FHWA) sponsored a Small Business Innovation Research (SBIR) project for development of a commercially viable concrete pore solution resistivity (PSR) sensor, conducted by the Callentis Consulting Group in collaboration with Penn State University. In line with the Performance Engineered Mixtures (PEM) initiative, a concrete’s Formation Factor is used to assess its transport properties and as an indicator of long-term durability and resilience against ingress of aggressive ions. The Formation Factor has been shown to be an important parameter in service-life models to predict permeability of concrete, and chloride ion penetration that can cause corrosion of concrete and its reinforcing steel. In AASHTO PP 84-20, the Formation Factor is defined as the ratio of the electrical resistivity of the bulk concrete mixture over the resistivity of the concrete pore solution. The AASHTO TP 119 and the equivalent ASTM C1876 standards were developed to measure the bulk concrete resistivity, and AASHTO T 358 to measure surface resistivity of the concrete mixture. However, there are no standard equipment or test methods for non-destructive measurement of the pore solution resistivity, and the only available methods involve labor-intensive laboratory extraction of the pore solution. In-situ measurement of the electrical resistivity of the pore solution along with the resistivity of bulk concrete allows for qualification of concrete mix designs before construction, quality control (QC) and quality acceptance (QA) of concrete batches placed during construction, and service-life prediction of vital concrete infrastructure such as bridges, pavements, and marine structures. Additionally, the PSR sensor can be embedded in structures and used for long-term health monitoring to evaluate changes in the chloride content inside concrete over time. Finally, the sensor’s output can be translated to concrete’s pH and used for evaluation and mitigation of the risk of alkali-silica reaction (ASR) in concrete containing reactive aggregates.

The technology under development in this project is a sensor system that allows in-situ measurement of concrete’s PSR with an accuracy of 15% or better compared to laboratory measurements. The sensor system includes the sensor assembly that is embedded inside concrete and a measuring device to interrogate the sensor. The sensor assembly includes the sensor matrix, attached insulated electronic components, and a placement mechanism. The sensor matrix is made of a custom-designed nano-porous body with an insulating skeleton. The sensor placement mechanism is designed in a way that would be easily embedded in concrete cylinders or structures. The mobile measurement device is a low-cost consumer-level product. The overall sensor system and the simple data post-processing is designed for seamless application by field and lab technicians, ideally along with the bulk or surface resistivity measurements.

The Phase I project explored candidate body (matrix) materials for the sensor, manufacturing techniques, optimum sensor geometry and packaging, and the best methods for reading and measuring the sensor output. Phase I also explored the costs, material availability, manufacturability, scale-up, marketability, technology transfer, and industry implementation of the proposed sensor system. Phase I output was a proof-of-concept report summarizing the above and offering two best prototype designs to be produced and tested in Phase II. The project team has also filed a patent for the developed technology.

Phase II will include the development and demonstration of market-ready prototypes for user testing and commercialization. Phase II will perform further refinement of the technology, design, and fabrication of the sensor prototypes. Phase II will also include experimental verification of the technology, including third-party testing (by the FHWA and several State DOTs), precision and bias evaluation, and development of a user’s guide and draft standard test method to facilitate effective implementation of the PSR sensor.

Patent Pending

The Callentis-PennState team have filed for a patent regarding the developed technology, which is pending. The displayed abstract schematic is showing a sensor embedded in a cylindrical concrete sample that can be used for qualification of concrete mix designs before construction, quality control (QC) and quality acceptance (QA) of concrete batches placed during construction. Another sensor system is designed for embedding inside concrete structures for long-term health monitoring to evaluate changes in the chloride content inside concrete over time.

Abstract schematic of pore solution resistivity sensor
Technology Readiness Levels based on FHWA TRL Guidebook

Technology Readiness Levels (TRL)

About Us

Callentis Consulting Group is a small research, development and consulting company, focused on integrating the latest proven technologies into existing business processes to create growth and opportunity. With extensive background in engineering and computational science, our team offers software and hardware development for a variety of science and technology applications.

Meet the Callentis leadership team.

Andrew Drach, PhD

Founder and President

Dr. Drach has over ten years of experience in numerical modeling techniques, applied statistics, data science, custom software and hardware development, and renewable energy engineering. He has published over 40 peer-reviewed articles, presented at over 20 international conferences, and gave 4 invited talks. He did his postdoctoral training in Computational Engineering and Sciences at the University of Texas at Austin. He holds a PhD in Mechanical Engineering from the University of New Hampshire.

Monika Jociunaite, MS

Creative Director

Mrs. Jociunaite has over ten years of experience in business data analysis, creative communication, data visualization, and user experience design. She has extensive experience working in 5 different countries, and assisting large multinational firms with their regional marketing strategies. She has successfully helped more than 15 companies with the creative design of their product and functionality to offer a seamless user experience. Mrs. Jociunaite holds two bachelors degrees in Economics and Business Administration, and two masters degrees in International Business and Marketing.

Nima Kargah-Ostadi, PhD, PE, PMP

Vice President

Dr. Kargah-Ostadi has over ten years of experience in applied statistics, data science, machine learning, evolutionary computation, and transportation infrastructure asset management. He has published over 15 peer-reviewed articles, and presented at over 20 conferences, workshops, and webinars. He holds a PhD in Civil Engineering and a doctoral minor in Computational Science from Penn State University. He is a registered Professional Engineer and a certified Project Management Professional.

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