LAUSR

Based on uniaxial and triaxial compression tests, the present study investigates the mechanical properties of high-strength concrete (HSC), ultrahigh-strength concrete (UHSC) and the corresponding mortars with the same mix proportions of the matrixes of two types of concretes. The tests recorded the mechanical responses including peak stress, axial strain at peak point and failure modes of HSC, UHSC and mortars specimens. The test results show that the compressive strength and deformation capacity of concretes and mortars gradually grow higher with the increasing of confining pressure, and the enhancement of confining pressure on the compressive strength of mortar is significantly lower than that of concrete. For HSC and UHSC, the enhancement on compressive strength has a negative relationship with the uniaxial compressive strength and similar relationship is also found between the two types of mortars. Compared with the mortar, the increase in confining pressure can, to some extent, better enhance the deformation capacity of concrete. There are three failure modes of concretes and mortars under the confining pressure: vertical splitting failure, oblique shear failure and extrusion flow failure. Confining pressure has very little effects on the initial tangent modulus, the initial tangent modulus of the two types of concretes is larger than that of corresponding mortars, and the addition of coarse aggregate can improve the tangent modulus of HSC more significantly than UHSC. Failure surfaces for concretes and mortars under triaxial stress were identified by using the four-parameter failure criterion.