Anisotropic behavior and thermal effects on concrete through evaluation of fracture parameters using three-point bending tests

Understanding the behavior of concrete under varying conditions is critical for structural applications. The anisotropic behavior of concrete is critically evaluated by examining larger concrete blocks cut in five different orientations (0, 22.5, 45, 67.5 and 90°) and subjected to varying thermal regimes (25 and 680 °C). Key fracture mechanics characteristics, such as fracture toughness and fracture energy, are computed using Three-Point Bending Tests (TPBTs) to describe the behavior of crack initiation and propagation. The degree of anisotropy, defined as the ratio of the highest to the lowest peak load, ranges between 1.15 and 1.24, indicating reductions of 13.5–19.7%. Elevated temperatures of 680 °C significantly reduce fracture toughness by approximately 89% in specimens with a height of 5 cm and 91% in 8 cm specimens. Similarly, fracture energy decreases substantially at 680 °C, by approximately 30% in 5 cm specimens and 47–50% in 8 cm specimens, compared to 25 °C. These results highlight the critical influence of orientation and temperature on the mechanical performance of concrete. This novel approach to understanding concrete’s anisotropic properties aids in developing more robust structures capable of withstanding diverse mechanical and environmental stresses, ultimately contributing to safer and more reliable construction practices.