Rheological measurements of suspensions are often performed using a rotational rheometer.In this type of rheometer, the tested fluid is sheared between two surfaces, one of which is rotating to generate a laminar flow of the fluid between the surfaces (i.e., a Couette flow). Manufacturers of commercially available rheometers generally recommend the use of a standard oil of known viscosity to verify that the rheometer is operating correctly. However, in the case of concrete rheometers, this approach would require large volumes of oil and was deemed not economically During the certification of SRM 2493, it was found that differences in rheometer geometry affect the accuracy of the rheological measurements. In order to gain fundamental insight about the impact that different rheometer geometries have on measurements of suspensions, a comprehensive analysis was conducted on three different rheometer families. The analysis included both experimental testing and computer simulation. The comparison between the model and rheological results showed that the increased viscosity due to the addition of the 1 mm beads to SRM 2492 was significantly higher in the Couette model than in the experimental data. It was also determined that some geometries, such as a double spiral, resulted in a higher viscosity than a simple serrated cylinder or vane. This finding led to the inference that slippage should also be considered. Ultimately, this report highlights that industrial rheometers experience slippage issues caused by their choice of geometry and their internal boundary conditions (free surfaces), and discusses the most accurate alternative available for calibrating rheometers.i ______________________________________________________________________________________________________ This publication is available free of charge from: https://doi

The accurate measurement of the density of hydraulic cement has an essential role in the determination of concrete mixture proportions. As more supplementary cementitious materials (SCM), such as fly ash, and slag, or cement replacements materials such as limestone and calcium carbonate are used in blended cements, knowledge of the density of each powder or of the blended cement would allow a more accurate calculation of the proportions of a concrete mixture by volume instead of by mass. The current ASTM standard for measuring cement density is the “Test Method for Density of Hydraulic Cements” (ASTM C188-14), which utilizes a liquid displacement method to measure the volume of the cement. This paper will examine advantageous modifications of the current ASTM test, by alcohol substitutions for kerosene. In addition, a gas (helium) pycnometry method is evaluated as a possible alternative to the current standard. The described techniques will be compared to determine the most precise and reproducible method for measuring the density of hydraulic cements and other powders.

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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.

The use of cementitious grouts in prefabricated bridge element (PBE) connections is a common practice in the USA. Given the important role that these connections play within the infrastructure, the grout materials used must provide good flowability, mechanical and durability properties, low shrinkage, and good bond to the precast concrete element. However, this type of grout material has shown serviceability issues in the form of volume instabilities (primarily shrinkage). The inclusion of internal curing (IC) in cementitious grouts with the goal of reducing shrinkage has been successfully demonstrated in a previous study. The research presented in this paper extends upon that prior study and assesses the IC effect on properties relevant to PBE grout connections. The paper uses novel experimental techniques such as the dual ring test, formation factor concepts, and microstructural analysis to evaluate improvements in cracking, bond, and durability performance. The results show that, while the IC grouts did not alter the bond performance, they improved their cracking and durability properties. The inclusion of IC in cementitious grouts is presented here as a strategy to increase the durability and thus sustainability of bridge structures.