Time-dependent brittle creep-relaxation failure in concrete

In real-world engineering applications, concrete is usually subjected to both creep and stress relaxation. Observations are necessary to understand this coupling process. This paper presents the results of brittle creep-relaxation experiments performed on concrete. Instead of tending to an asymptotic value, the stress in all the test specimens dropped sharply with a rapid increase in the strain before failure, when the boundary displacement was kept constant. The acceleration in the tertiary stage exhibited power-law behaviour, with the exponent − α being − 0·58 ± 0·13 for the stress rate and − 0·56 ± 0·12 for the strain rate. For each specimen, the time-to-failure exhibited power-law dependence on the secondary creep (relaxation) rate, with the exponent being 0·97 ± 0·09 for strain and 0·98 ± 0·09 for stress. These results suggest that it should be possible to predict the time-to-failure of concrete by monitoring its behaviour during the steady and critical stages.