Video showing crack propagation in a Propagation Saw Test (PST3). The strain magnitude shows a propagating strain concentration around the weak layer at z = 0.9 m (upper panel) while the vertical displacement w of the slab consecutively increases (blue line, second panel) and the horizontal displacement u(z = 0.1 m) indicates slab bending (orange line, second panel). At the same time, the third and fourth panel show the (vertical, horizontal) velocity (w ̇,u ̇) and acceleration (w ̈,u ̈) computed as the first and second time derivative of the displacements, respectively. At a time t = 740 ms a secondary crack in a weak layer, embedded in the slab at z = 0.4 m was initiated and propagated reversely after it is stopped as a consequence of two slab fractures (xSF =1.9 m and xSF = 2.8 m).