An experimental set-up for cyclic loading of concrete

Innovative cementitious composite materials are drawing considerable interest due to their substantially improved mechanical properties as compared to ordinary cement-based materials. Their enhanced ductility is promising and particularly suited to structural applications under severe dynamic loading conditions. Cyclic response is essential to understand the effects of loading and unloading on the material, as well as to understanding how it behaves in the transition from tension to compression. It is also fundamental to identify its properties in terms of energy dissipation and strain-rate sensitivity. This paper presents the first part of an ongoing research project which aims to develop the constitutive relationship in innovative cementitious composites and its numerical implementation. Results from this research will facilitate the investigation of the ductility and durability of existing buildings. In this paper, an experimental set-up for uniaxial cyclic loading is described. It was developed to study reversed cyclic compression/tension loadings of innovative cementitious composites. To set the cyclic loading process, cylindrical specimens of concrete were tested. All the tests were performed on a Zwick testing machine with 50 kN load cell. The machine was customised with accessories specifically designed to meet test requirements, avoiding instability and bending moments during the alternating phases of uniaxial compression and tension. Strain gauges were used to measure lateral deformations. The customized machine has shown good performance so far. In order to test specimens with a higher number of cycles and a higher loading rate, improvements to the machine are currently under development. These tests will allow greater insight into the ductility of innovative cementitious composite materials.