It can be seen that energy absorption increases gradually with the age, from 3 to 28 days, at par to the compressive strength. Figure 9 shows panels after they were tested. It is important to observe the crack patterns; round panels test (ASTM C-1550) forces the development of three cracks in a “Y” pattern, and square panels test (EN-14488-5) allows the development of several principal cracks and some secondaries. This is: strains can be redistributed in square panels, but not in round ones due to the support conditions of each test