Early age cracking of massive concrete piers

The structural effect of hydration heat and rheological properties of concrete on massive casting are studied in this work. The object of the study were several circular piers of a viaduct built in Italy. In the first days after the removal of the scaffoldings, 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 bigger ones, both vertical and horizontal. The cracks were noticed sometimes just after the 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 from the casting in order to establish the causes of the unforeseen cracking. A non-linear finite-element coupled thermal and mechanical analysis has been performed taking 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 the casting with a pattern similar to that seen in situ was numerically reproduced and calculated.