Issue 78

M. S ł owik et alii, Fracture and Structural Integrity, 78 (2026) 393-408; DOI: 10.3221/IGF-ESIS.78.23

fresh evidence on how aggregate–matrix interactions control tensile failure, offering both practical implications for design and new insights for the understanding of concrete fracture mechanisms.

M ATERIALS , METHODS AND RESULTS

Tensile strength of concrete – test methods he uniaxial tensile test constitutes the primary approach for evaluating the direct tensile strength of concrete. The test is usually performed by a uniaxial tensile test on prismatic specimens. Examples of loading arrangements used during the uniaxial tests are illustrated in Fig. 1.

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Figure 1: Examples of setups in direct tensile strength tests of specimens: with ball joints fixed on broadened ends of the specimen (a), with stiff steel plates glued to the end surfaces (b), with friction grips (c). Various factors affect the accurate determination of the uniaxial tensile strength of concrete [15]. Achieving a uniform stress distribution during a direct tensile test is challenging because local stress concentrations may occur. In addition, the obtained results are frequently influenced by load eccentricities, which mainly result from the irregular distribution of the aggregate particles. Owing to all the challenges which the uniaxial tensile test presents, indirect methods for testing the tensile strength of concrete are recommended in engineering practice. Among them are a flexural test and a splitting test which are already well known [16-18], but also some new methods have been recently proposed in the literature, for example by Al-Abdaly et al. [19] or Wang et al. [20]. When performing a flexural test [21], a prismatic specimen is subjected to a bending moment. The length of the tested specimen should not be less than 3.5 times the nominal cross-sectional dimension d, while the span between the support rollers is typically set to 3d. Two methods of loading, a one-point and a two-point loading method, are described in the code [21] (Fig. 2). Since the three-point bend test generally produces results that are approximately 13% higher, the four-point bend scheme is recommended as the reference method.

Figure 2: Types of loading arrangements in the flexural test: four-point bend test (a), three-point bend test (b).

The Brazilian splitting tensile test is an indirect method for determining the tensile strength of concrete, which is the most frequently used in laboratories and is commonly established as a standard method. The method was suggested by Carneiro [22] and has been tested by several researchers, such as Wright [23] and followed by Hannant [24, 25], Malhotra [26], Kadlecek and Spetla [27]. At present, the procedure of the splitting test is standardised, and it is presented in the code [2],

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