After CHEMSHINE is poured into holes drilled in rocks or concrete, the expansive stress gradually increases with time, and reaches to more than 6000 t/m2 at room temperature after 24 hours. As the CHEMSHINE generates its expansive stress, the material to be cracked undergoes a process of (1) crack initiation, (2) crack propagation, (3) the increase of crack width. Therefore, this fracture mechanism is distinguished from a breakage by blasting.
The mechanism by the expansive stress of CHEMSHINE is shown in Fig. 1. Cracks initiate from an inner surface of the hole, being caused by tensile stress at a right angle with the compressive stress which occurs by the expansive stress of CHEMSHINE. The expansive stress of CHEMSHINE continues even after the appearance of cracks, the cracks propagate and also new cracks initiate during the process. Usually, for a single hole, 2-4 cracks initiate and propagate. When a free surface exists, the crack, as shown in Fig. 2, is pushed apart mainly by the shear stress, and a secondary crack also arises from the bottom of the hole running toward the free surface.
