Shear Strength of Captive and Short Columns Made of Ultrahigh Strength Concrete with Nanobasalt Particles

Short columns attract extreme shear force during earthquakes, which may lead to severe column damage and even catastrophic structure collapse. In this research, nanobasalt is produced to construct ultrahigh performance concrete (UHPC) to improve the shear behavior of the short columns. First, the mechanical properties are investigated, and results revealed that the nanobasalt percentages (3%, 6%, and 9%) improve the compressive strength by 35.6%, 64.8%, and 19.5%, the tensile strength by 44.5%, 53.6%, and 16.3%, and the flexural strength 16.2%, 25.3%, and 6.1%, respectively. However, the inclusion of the nanobasalt reduces the concrete flowability. The optimum percentage, for best properties development, is 6%, which yields UHPC of 135 MPa. Then, short column specimens were cast, using the developed UHPC, and tested to investigate their shear performance development. The results disclosed that the 6% nanobasalt concrete improved the shear capacity by 29% compared with the control specimen.