Biaxial compression tests and failure criteria for high strength steel fiber and carbon nanotube reinforced concrete

High strength steel fiber and carbon nanotube reinforced concrete (HSSFCNRC) is a new type of high-strength composite concrete with good fluidity, high strength, toughness, durability and other significant advantages. In order to investigate the strength and deformation characteristics of HSSFCNRC under multi-axial stress states, a serial of biaxial compression tests with different stress ratios were conducted on high-strength plain concrete (HSPC) and HSSFCNRC, respectively. The failure modes of specimens were observed, the condition parameters, such as the ultimate stresses and the peak strains were obtained. By comparative analysis, Kupfer-Gerstle failure criterion, Song Yu-pu model and Yang Jian-hui model can all be used in HSPC and HSSFCNRC, but the envelope curves are superior to the envelope lines, and the envelope of HSSFCNRC can cover that of HSPC. The meridian of Song Yu-pu model is elliptic curve, and the precision is better. Although the simple meridian proposed in this paper is straight line, a conclusion is drawn that it can satisfy the requirements of engineering applications by the comparative analysis of octahedral stress and strain space failure criteria.