Brian Mazzeo

Two- and four-electrode, wide-bandwidth, dielectric spectrometer for conductive liquids: Theory, limitations, and experiment

Dielectric spectroscopy is used to measure the dielectric properties of liquids. Two-electrode measurements are common but have resolution difficulties because of electrode polarization and small measured phase angles, particularly for solutions with high ionic content. Four-electrode measurements have been used in previous attempts to overcome these problems. The electrical responses of two- and four-electrode dielectric cells are derived with appropriate circuit analysis to yield expressions for the measured phase angle. The theory demonstrates that an ideal four-electrode measurement cannot resolve the permittivity of the liquid and that polarization effects will still be present in the measured characteristics. A two- and four-electrode experimental cell with a bandwidth of 100 Hz to 40 MHz was constructed and used to measure the electrical properties of water and salt solutions. Electrode polarization and conductivity effects are present in both two- and four-electrode measurements. Parasitic impedan...

Observation of protein-protein interaction by dielectric relaxation spectroscopy of protein solutions for biosensor application

Dielectric spectroscopy was used to measure the dielectric relaxation of bovine serum albumin, Protein A, and rabbit IgG in solution. Measurements were performed with an impedance analyzer and dielectric cell. Protein additions to bulk solution were measured by differential dielectric relaxation spectroscopy, presented as a method to measure the individual contributions of proteins to relaxation phenomena and reduce effects of electrode polarization. Relaxation characteristics of the proteins individually and as a complex were observed. Frequency shifts in the relaxation characteristics indicate binding. This illustrates the potential use of bulk solution dielectric relaxation as the principle of operation for a biosensor.

Rapid Multichannel Impact-Echo Scanning of Concrete Bridge Decks from a Continuously Moving Platform

Impact-echo testing is a non-destructive evaluation technique for determining the presence of defects in reinforced concrete bridge decks based on the acoustic response of the bridge deck when struck by an impactor. In this work, we build on our prior research with a single-channel impactor to demonstrate a seven-channel impact-echo scanning system with independent control of the impactors. This system is towed by a vehicle and integrated with distance measurement for registering the locations of the impacts along a bridge deck. The entire impact and recording system is computer-controlled. Because of a winch system and hinged frame construction of the apparatus, setup, measurement, and take-down of the apparatus can be achieved in a matter of minutes. Signal processing of the impact responses is performed on site and can produce a map of delaminations immediately after data acquisition. This map can then be used to guide other testing and/or can be referenced with the results of other testing techniques ...

Vertical Impedance Testing for Assessing Protection from Chloride-Based Deicing Salts Provided by an Asphalt Overlay System on a Concrete Bridge Deck

In cold regions, chloride-based deicing salts are commonly applied to roads and bridges during winter to melt ice. The objective of this work was to demonstrate the utility of a new technology, vertical impedance testing, for assessing the condition of concrete bridge decks treated with membranes and asphalt overlays to reduce chloride-induced corrosion of the reinforcing steel. The vertical nature of the impedance testing allows interrogation of all layers from the deck surface down to the reinforcing steel, specifically permitting evaluation of the protection against chlorides provided by any deck surface treatments, the full depth of the concrete cover, and any rebar coatings. Spatial variations in vertical impedance measurements on a bridge deck in Wendover, Utah, were compared to the occurrence of cracking in the asphalt overlay, half-cell potential values, and chloride concentrations measured at specific locations before deck rehabilitation. The data were also compared to the occurrence of actual deck repairs completed after the asphalt overlay and membrane were removed. The impedance data were well aligned with the distress and half-cell potential data and were used as a basis for strategically selecting locations for coring and chloride concentration sampling, which enabled further interpretation of the impedance data. Of the 29 patches corresponding to delaminations identified by the contractor, nine were positioned at locations originally characterized by cracking of the asphalt overlay surface, 18 were positioned at locations characterized by low impedance magnitude, and eight were positioned at locations characterized by uncertain half-cell potential classifications. The vertical impedance testing method therefore shows great promise as a tool for evaluating the protection against chlorides provided by an asphalt overlay system. Furthermore, contour plots of impedance magnitude may possibly be used to estimate the scope of work, including the location and extent of deck repairs, that may be required during deck rehabilitation.

Algorithms for highway-speed acoustic impact-echo evaluation of concrete bridge decks

A new acoustic impact-echo testing device has been developed for detecting and mapping delaminations in concrete bridge decks at highway speeds. The apparatus produces nearly continuous acoustic excitation of concrete bridge decks through rolling mats of chains that are placed around six wheels mounted to a hinged trailer. The wheels approximately span the width of a traffic lane, and the ability to remotely lower and raise the apparatus using a winch system allows continuous data collection without stationary traffic control or exposure of personnel to traffic. Microphones near the wheels are used to record the acoustic response of the bridge deck during testing. In conjunction with the development of this new apparatus, advances in the algorithms required for data analysis were needed. This paper describes the general framework of the algorithms developed for converting differential global positioning system data and multi-channel audio data into maps that can be used in support of engineering decisions about bridge deck maintenance, rehabilitation, and replacement (MR&R). Acquisition of position and audio data is coordinated on a laptop computer through a custom graphical user interface. All of the streams of data are synchronized with the universal computer time so that audio data can be associated with interpolated position information through data post-processing. The audio segments are individually processed according to particular detection algorithms that can adapt to variations in microphone sensitivity or particular chain excitations. Features that are greater than a predetermined threshold, which is held constant throughout the analysis, are then subjected to further analysis and included in a map that shows the results of the testing. Maps of data collected on a bridge deck using the new acoustic impact-echo testing device at different speeds ranging from approximately 10 km/h to 55 km/h indicate that the collected data are reasonably repeatable. Use of the new acoustic impact-echo testing device is expected to enable more informed decisions about MR&R of concrete bridge decks.

Vertical impedance measurements of concrete bridge deck cover condition without a direct electrical connection to the reinforcing steel

Vertical impedance measurements provide significant quantitative information about the ability of concrete cover to slow the penetration of chloride ions that can corrode steel reinforcement in a bridge deck. The primary limitations preventing the widespread adoption of vertical impedance for assessment of concrete bridge decks are (1) the necessity to have a direct electrical connection to the embedded steel reinforcement and (2) the low speeds of data acquisition. This work presents solutions to both limitations. A method using a large-area electrode as a reference electrode for vertical impedance testing is validated using both simulations and measurements in the field.