As Fig. 7 shows, an increase of porosity (that is, an increase of w/c ratio) supposes a delay in the generation of the crack. This can be interpreted as due to the highervvoid space available to accomodate the oxides withoutvpressing the surrounding concrete. Figs. 8 and 9 presentv the differences found between top and bottom cast bar positions of the bars in series-2 specimens without stirrups. Similar results were found in specimens with stirrups. It can be observed that the top cast position delays the cracking propagation.