Effect of Strain Rate on Compression Mechanical Parameters of Ultrahigh-Toughness Cementitious Composites

The present paper investigates the influence of strain rate (ranging from 1.95×10−5 s−1 to 0.83×10−2 s−1) and fibers volume fraction on the fundamental mechanical properties of ultrahigh-toughness cementitious composites (UHTCC) by using a combined compression extensometer. The experimental results showed that a significant strain rate effect can be observed, in terms of compressive strength, elastic modulus and Poisson’s ratio of UHTCC. When the strain rate increased from 1.95×10−5 to 0.83×10−2 s−1, the compressive strength increased 16.1%, the elastic modulus increased 20.6%, and the Poisson’s ratio increased 6.0%. The brittleness of UHTCC enhanced as the strain rate increased. The volume fraction of fibers also affects the strain rate effect of mechanical properties. With the increase of fiber content, the strain rate effects of compressive strength and elasticity modulus increase, while the strain rate effect of Poisson’s ratio decreases. The mechanism of the strain rate effect was investigated by a scanning electron microscope. A formula for calculating elastic modulus of UHTCC at low strain rate was proposed. The results can provide a theoretical basis for the design of structure, stress and deformation calculation and nonlinear finite element analysis of UHTCC under seismic loads.