Axial tensile behavior of hybrid steel-polypropylene fiber reinforced high-strength lightweight concrete

In practical engineering, concrete materials are mainly damaged by tension, especially for high-strength lightweight concrete (HSLC) whose tensile performance is not as satisfactory as ordinary concrete under the same compressive strength. Adding fibers is one of the most effective methods to improve the tensile properties of concrete. In this study, the tensile behavior of hybrid fiber reinforced HSLC was investigated through direct tensile test. The tensile stress-strain curve was obtained and the tensile toughness was calculated. Furthermore, the cracking process was measured and captured synchronously by digital image correlation (DIC) measurement. The results indicated that hybrid fibers enhanced the tensile properties of HSLC at both micro and macro levels. Polypropylene fibers increased the tensile toughness of HSLC by inhibiting the propagation of micro-cracks. Steel fibers improved the peak stress, peak strain, and tensile toughness of HSLC by extending the propagation path of macro-cracks and restraining the increase of the width of macro-cracks. According to the test results, an equation for the axial tensile stress-strain curve of the hybrid fiber reinforced HSLC related to fiber characteristic parameters was formulated, which can be used as a reference for engineering design.