An experimental study of the specimen geometry effect on the axial performance of cement-based grouts

Abstract Cement grouts are widely used as construction materials in civil engineering and bonding agents in mining engineering. To reveal the influence of the specimen geometry on the axial performance of grouts, a number of Uniaxial Compressive Strength (UCS) tests on four kinds of grouts were executed. The highlight of this paper is that the grout performance was reflected on different aspects, including the UCS, the axial strain where UCS occurred, the elastic modulus, the post-failure behaviour and failure modes. The results show that the specimen geometry had a direct impact on the grout performance. Cube specimens consistently had higher strength than cylinder specimens. And the difference between them ranged from 8.4% to 23.4%. For the axial strain where UCS occurred, cube specimens also had much higher values, with the difference ranging from 21.4% to 56.2%. Inversely, cube specimens had smaller elastic modulus than cylinder specimens. And the difference between them ranged from 23.9% to 45.8%. To confirm the above findings, T tests were conducted. The results proved that the specimen geometry made a significant difference on the grout performance. Additionally, after the UCS, axial stress of cube specimens declined gently with the axial strain. By contrast, after the UCS, axial stress of cylinder specimens dropped violently. Last, for cube specimens, vertical or horizontal tensile failure may occur. However, for cylinder specimens, vertical tensile failure or inclined shear failure may occur. This study demonstrates that when analysing the axial performance of grouts, the specimen geometry should be critically considered.