Early age cracking of massive concrete piers

Abstract

The structural effects of hydration heat and rheological properties of concrete on massive castings are studied in this work. The objects of the study were several circular piers of a viaduct built in Italy. In the first few days after removal of scaffolding, an evident crack pattern was noticed on the surface of a great number of piers. The crack opening was very variable, from very thin ‘geographic map' micro-cracks to larger ones, both vertical and horizontal. The cracks were sometimes noticed just after scaffolding removal and always before the dead load of the girder and the service loads were applied. The aim of this work is the numerical simulation of what happened to the structure after casting in order to establish the causes of the unforeseen cracking. A non-linear finite-element coupled thermal and mechanical analysis was performed, which took into account the hydration heat, dimensions of the casting, the evolution of concrete mechanical properties over time during the hardening reaction, creep and differential shrinkage. A diffused cracking phenomenon arising in the first days after casting with a pattern similar to that seen in situ was numerically reproduced and calculated.