These projects examined the potential for using electrical testing on concrete as a potential surrogate for obtaining information on ion and fluid transport. Electrical measurements are particularly attractive for use in quality control as they are easy to perform, are performed rapidly, and can be directly related to fluid transport. This work describes how electrical resistance measurements should be corrected for geometry to obtain a geometry independent resistivity or conductivity. Further, this work reviews and discusses several factors that influence the resistivity that is measured including porosity, pore connectivity, the role of temperature on degree of hydration (activation energy), temperature effects on conduction, ionic leaching, and the role of temperature and leaching on porosity. The goal of this work is to provide an overview of the main factors that should be considered when conducting electrical property testing, when using electrical properties for quality control/quality assurance, or if using these materials for acceptance. As a part of this project a series of testing devices were purchased and provided to the INDOT district testing labs for the purpose of providing training and providing information on the variability associated with testing. A round robin study has shown that a coefficient of variation of 4.36 % was obtained leading to a within laboratory precision of 12.8 % and a multi-laboratory precision of 36.0 %. This work has shown that temperature can dramatically influence the resistivity. The work has shown that in general for a standard 100 mm x 200 mm test cylinder, the ratio of surface resistivity to uniaxial resistivity, specifically the factor discussed in Section 5.1, is 1.9 for a homogenous material; however if the material is heterogeneous (due to drying or leaching) this value changes. This project has also illustrated the importance of ionic leaching. It was shown that accelerated curing requires temperature correction as well as control of ionic leaching. A direct correlation is discussed between electrical resistivity and the rapid chloride permeability test. At the current time, resistivity tests show promise in a quality control program, as a method of monitoring the variation associated with production. If used in this way, a trial batch could be used to develop target values, similar to that which is currently done with the maturity method. It is anticipated that an agency could eventually have the potential to use resistivity for mixture qualification; however, additional work is needed to correlate the resistivity with performance

The objective of this project was to evaluate the transport properties of concrete pavement in the state of Indiana using common testing procedures. Specifically this work evaluated the absorption of water, the absorption of deicing solutions, and electrical conductivity. A series of concrete paving mixtures were tested to provide a range of values that were typical for the state of Indiana. While similar mixture proportions were used for the mixtures in Indiana differences in the magnitude of water absorbed occurred. A series of mortars were tested to illustrate the effect of curing conditions, water to cement ratio, and paste volume. It was observed that a long duration of drying was needed to obtain equilibrium. Samples dried to a lower relative humidity showed a greater volume of water absorbed. It was observed that drying at 105C resulted in substantial anomalies in water absorption, as such this method is not recommended. It was observed that when samples were tested using deicing solutions or samples were tested that were previously exposed to deicing solutions the water absorption could be influenced. The electrical conductivity work was performed as a potential method to develop the understanding of rapid test techniques for quality control. The research used a modified parallel law to relate the electrical conductivity to the pore volume, pore solution conductivity and the tortuosity through the pore network. The influence water addition was able to be determined using electrical conductivity. In addition, the pore solution was observed to be approximately linearly related to the degree of hydration. It is critical that a correction be applied to samples tested at different temperatures. An activation energy of conduction was observed that was approximately 10 kL/mol irrespective of water to cement ratio. In addition to the measurement of transport properties, the relative humidity was assessed for concrete exposed to different exposure conditions. The samples considered in this investigation included a sample stored at 50% relative humidity, covered concrete, a concrete with an exposed vertical surface, a concrete on a drainable base, a concrete on a non-drainable base, and concrete that was submerged. The samples showed that for practical field samples the relative humidity in the concrete was always above 80% for the samples tested. The samples that were exposed to precipitation events demonstrated higher relative humidities.

Electrical resistivity measurements are increasingly being used as measurements for concrete acceptance in practice. It has been shown that these measurements are sensitive to temperature. This paper examines the influence of temperature on electrical resistivity measurements in concrete. Two temperature correction approaches that are commonly used by researchers and practitioners were evaluated: a linear temperature correction approach (α) and an activation energy–based temperature correction approach (Ea-cond). These approaches were compared with each other and their predictive capabilities were assessed using measured data from various concrete mixtures. It was found that for cases of low temperature sensitivity (low values of α or Ea-cond), the predictions obtained with α and with Ea-cond were similar. However, the Ea-cond approach was found to provide more accurate corrections (lower error) than corrections using α for measurements conducted at lower temperatures and for systems with higher temperature sensitivities (high values of α or Ea-cond). For saturated concrete specimens, both the linear (α) and activation energy (Ea-cond) approaches are acceptable, whereas the use of the Ea-cond approach provides better predictive capabilities in sealed concrete specimens, especially at low temperatures. The average values for Ea-cond were found to be 29.8 kJ/mol for sealed specimens and 15.8 kJ/mol for saturated specimens, and corresponding average values of α are 3.25 %/°C and 2.00 %/°C, respectively. The values for Ea-cond for saturated specimens are closer to what is expected of a pore solution on its own.

Ultra-high performance concrete (UHPC) is a class of concrete materials that has received significant attention from the infrastructure community due to its favorable mechanical and durability performance. As the use of UHPC in infrastructure projects is becoming more common, there is an increasing interest in identifying appropriate testing techniques to assess the durability properties of UHPC-class materials. The dense microstructure of UHPC-class materials and the presence of a high concentration of fiber reinforcement have made it difficult to rely on existing standard testing approaches for concrete durability assessment. This study explores the application of various conventional-concrete durability test methods to UHPC, including electrical resistivity (American Association of State Highway and Transportation Officials (AASHTO) TP 119-22), freeze–thaw (ASTM C666), water absorption (ASTM C1585), and rapid chloride migration test (NT BUILD 492). The selected tests are meant to qualify and quantify the microstructural penetrability of UHPC to ions and fluids, a surrogate property commonly used as an indicator of durability. The findings from this study indicate that electrical resistivity can be used as a durability indicator for UHPC-class materials. Moreover, strong correlation between electrical resistivity and the chloride migration coefficient is identified, a potential benefit given that chloride migration can be used to estimate service lives of UHPC-class materials. Other tests, including freeze–thaw and water absorption, although identifying the favorable performance of UHPC relative to conventional concrete, were unable to provide insightful information through which the performance of individual UHPCs could be differentiated.

Concrete pavement durability in the United States is an important characteristic that owners are considering in new construction and rehabilitation projects, and many are including durability tests in the next generation of their specifications. Specifically, focus has fallen on electrically based testing owing to its rapid testing time and economical testing equipment. Results from electrically based tests have also been shown to be good inputs to service life models and can correlate with a wide range of other material properties used to understand how ions and fluid are transported through concrete. This study aimed to correlate the two most common electrically based test results (resistivity and formation factor) with more established and involved tests of transport properties, such as rapid chloride migration and water absorption. The major difference between these two tests resides in the conditioning solution, which is typically limewater for resistivity and an alkali-concentrated solution for the formation factor. Based on the results, both electrical resistivity and formation factor were deemed acceptable tools for mixture approval and acceptance, though formation factor demonstrated higher correlations with the other transport properties and, therefore, was preferrable for performance modeling. Overall, concrete resistivity and formation factor measurements at ages beyond 28 days could be used to indicate the durability of a concrete material during its lifespan. During the investigation, the authors observed that compressive strength measurements were independent of the type and volume of the conditioning solution.