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Recently, self-healing technologies have emerged as a promising approach to extend the service life of social infrastructure in the field of concrete construction. However, current evaluations of the self-healing technologies developed for cementitious materials are mostly limited to lab-scale experiments to inspect changes in surface crack width (by optical microscopy) and permeability. Furthermore, there is a universal lack of unified test methods to assess the effectiveness of self-healing technologies. Particularly, with respect to the self-healing of concrete applied in actual construction, nondestructive test methods are required to avoid interrupting the use of the structures under evaluation. This paper presents a review of all existing research on the principles of ultrasonic test methods and case studies pertaining to self-healing concrete. The main objective of the study is to examine the applicability and limitation of various ultrasonic test methods in assessing the self-healing performance. Finally, future directions on the development of reliable assessment methods for self-healing cementitious materials are suggested.

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Significant increases in rail loads, as well as growing interest in providing higher-speed passenger rail services, is placing new and increasing existing demands on fastening systems and concrete sleepers. Consequently, there is a strong need to better understand the response of fastening systems and concrete sleepers to these significantly increased demands. This paper presents an experimentally validated three-dimensional (3D) finite element (FE) model of a fastening system and concrete sleeper that can be used to study and improve the design and performance of these systems. In this 3D FE model, the following mechanisms that are critical to the performance of fastening systems and concrete sleepers are included: frictional interaction between components of the fastening system; interaction between shoulders and concrete; and the plastic behavior of each component in the system. The FE model is validated using laboratory experimental tests, in which a lateral load is applied to a single concrete sleeper with two sets of fastening systems. The validated FE model is used to analyze the sleeper/fastening system under different loading scenarios involving various vertical and lateral load combinations. Both component stress and system deflection of the model are analyzed to investigate the system performance at the component and system levels. The results of the study show that FE modeling can be used to investigate the complex behavior of fastening systems and concrete sleepers.