High-dynamic strengthening of cementitious materials subjected to uniaxial compression

Abstract

Infrastructures made of reinforced concrete such as e.g. tunnels and bridges, must withstand exceptional loads, caused by earthquakes, car impacts, accidential blast loads, etc. The latter two belong to the high-dynamic loading regime where strain rates are typically larger than 1/s. In this regime, the strength of concrete specimens increases significantly with increasing loading rate. The reason for this strengthing effect is still debated. This provides the motivation for the present contribution which is devoted to the analysis of high-dynamic compression tests on cement pastes, mortars, and concretes. An elasto-brittle model for high-dynamic strengthening is employed, which was proposed by Fischer et al. (2014) and extended towards consideration of the scatter of the quasi-static strength values by Binder et al. (2017). The aim of the present contribution is twofold. At first, the quantitative assessment of the predictive capabilities of the described model is extended towards consideration of experimental data from Hao & Hao (2013). Secondly, the question is tackled how to represent high-dynamic strength values of different materials (cement pastes, mortars, and concretes) in one diagram, such that a meaningful direct comparison becomes possible. The latter goal is achieved by comparing two independent measures of the increase of the compressive strain during the failure process of a specimen: the first one refers to the measured Dynamic strength Increase Factor (DIF), the quasi-static strength, and Young’s modulus and the second one to the the strain rate, the characteristic crack propagation length, and the crack propagation speed.