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During concrete pavement construction, comprehensive information on concrete strength development is necessary for knowledgeable scheduling decisions. To improve in situ strength estimation, nondestructive tests can be combined to maximize available information and increase collection efficiency. Ultrasonic testing has a higher accuracy in strength estimation for early age concrete and the external device allows for more data to be easily collected, while maturity testing can use temperature models to predict strength development. A procedure was created that combines these methods and their strength models in the laboratory for improved and increased field strength data. Using the procedure allows more data to be collected with greater accuracy and provides an adjustable, predicted strength development. This improves the efficiency of fast-track construction projects without resorting to costly alternatives by providing more information on strength development of in situ concrete than traditional strength testing or nondestructive methods individually. [ABSTRACT FROM AUTHOR]

Highlights • Attenuation of horizontal shear waves in the frequency range of 20–150 kHz was studied. • Size and material properties of aggregates had a significant role in the attenuation of shear waves. • Shape of aggregates slightly affects the attenuation of shear waves in concrete. • Air voids slightly attenuated the shear waves for frequency higher than 80 kHz. • Scattering attenuation was not significant for the frequencies lower than 50 kHz. Abstract Although ultrasonic transducers that emit horizontal shear waves are widely used in practice, no investigation has been conducted to study the attenuation of shear waves in concrete due to scattering by aggregates and air voids. Horizontal shear waves preserve more energy in comparison with longitudinal waves when propagating in concrete in low frequencies. However, the lower wavelength of shear waves increases the potential of their scattering attenuation in concrete. In this paper, we developed a 3D numerical tool and used it to study the scattering attenuation of horizontal shear waves in concrete in the 20–150 kHz frequency range. We showed that the scattering attenuation in this frequency range strongly depends on the size and material properties of aggregates. The shape of the aggregates and the presence of air voids slightly affected the scattering attenuation. [ABSTRACT FROM AUTHOR]

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Quantitative nondestructive characterization of defects and inclusions in portland cement concrete structures are realized in this paper via extended reconstructions for linear array ultrasound systems. This is accomplished through generalization of traditional Kirchhoff-based synthetic aperture focusing technique migration to mitigate the effects of limited aperture and handle multiple scans as a single virtual array with increased effective aperture. Pearson’s correlation is utilized to account for uncertainty in relative position of individual measurement and mitigate the need for robotic precision when placing adjacent scans. The robustness of the method is demonstrated on artificially generated data as well as in-situ measurements for assessment of internal portland cement concrete characteristics such as inclusions and cracks. [ABSTRACT FROM AUTHOR]

Dowels are inserted at the mid-depth of joints in jointed concrete pavements that are exposed to heavy loading to provide load transfer and reduce pumping and faulting. Dowel alignment tolerances in North America have traditionally been strict, although not based on substantial performance data. In this paper, new laboratory testing methods are proposed for evaluation of the effects of dowel misalignment on concrete joint behavior. In these tests, dowels with various levels of rotations and translations were subjected to pullout and shear loading. It was found that dowel misalignment does not have a significant effect on pullout and shear forces for certain ranges of misalignments, which far exceed the tolerances recommended by the Federal Highway Administration. At the same time, it was found that extreme cases and combinations of misalignment resulted in a significant decrease in initial stiffness and shear capacity. Therefore, there is a need for the establishment of rational alignment tolerances. The results of this study provide important information for the development of such tolerances. [ABSTRACT FROM AUTHOR]

Ultrasonic tomography is a non-destructive testing method that allows for the internal visualization of concrete structures without causing any damage. This technique is widely employed to detect reinforcement and various types of damage, including voids, cracks, rebar corrosion, and debonding, among others. To enhance the accuracy and clarity of concrete tomograms, numerous image generation techniques have been explored. With the ever-increasing volume of information, it can become challenging to grasp the overall landscape and identify areas for improvement. The present work offers a comprehensive systematic review of the diverse image reconstruction techniques employed and the innovative developments within this research field. The prevalent techniques for both transmission and reflection tomography have been analyzed, delineating their respective characteristics. Furthermore, enhancement techniques have been recorded, and their discussion is provided. This comprehensive overview provides the basis for outlining future developments in ultrasonic tomography for concrete elements. [Display omitted] • Review of image reconstruction (IR) methods for ultrasonic tomography of concrete. • Contextualization of concrete tomography scenario among other research fields. • Discussion of IR techniques for concrete transmission and reflection tomography. • New enhancement methods for improving image accuracy are presented and discussed. • Overview of future possibilities in concrete imaging with ultrasonic tomography. [ABSTRACT FROM AUTHOR]

• We modified the imaging condition of reverse time migration to reduce the artifacts. • We introduced a new normalization factor to consider more precisely the spreading attenuation in imaging condition. • We introduced a modification factor to the imaging condition to consider scattering attenuation in concrete members. • We showed that using the proposed approaches one can image the entire boundary of a cavity located in a concrete medium. Cross-correlation imaging condition of reverse time migration generates high-amplitude artifacts in the reconstructed images. In addition, due to geometrical spreading and scattering attenuations, this imaging condition assigns amplitudes to the points of the reconstructed image that are not a true representative of the reflection coefficient of the scanned medium at those points. These all can lead to a reduction in quality and misinterpretation of the reconstructed images. In this paper, we proposed new imaging conditions to mitigate high-amplitude artifacts and to assign more accurate amplitudes to an RTM image by considering geometrical spreading and scattering attenuation in concrete members when horizontal shear waves are used for imaging. We used data obtained by transmitting horizontal shear waves to 3D synthetic homogeneous and concrete specimens and demonstrated the effectiveness of the new imaging conditions. [ABSTRACT FROM AUTHOR]

Improving early-age concrete strength measurement is an important step toward opening new pavements to traffic quickly without risking long-term performance due to early age damage. The maturity method is well established as an appropriate estimation of strength; however, it contains certain unavoidable limitations. Non-destructive ultrasonic testing using shear wave velocity can be used as a complementary testing. An in-situ comparison of these strength estimation methods was performed on a 200-mm thick concrete pavement for two weeks after placement. Both methods predicted reasonable concrete strength gain trends for in-situ pavement. The linear array ultrasonic method was found to have major advantages regarding portability, strength-gain variation and testing speed. [ABSTRACT FROM AUTHOR]