were 100 x 100 x 600mm in size. A 60mm high stress riser at the center of span and two 45mm high risers at the two ends were provided on the bottom surface of the mold to produce concentrated stress and reduce thickness at the center of the slab. The risers at the ends restrict the longitudinal movement and cracks were induced at the thin section above the middle riser. Figure 1 shows the geometry of the restrained mold.