A picture speaks a thousand words. Take a look at this cast-in-place wall. It was poured with a hard-rock mix, no plasticizer, low slump, on a hot day, with congested reinforcement and block-outs. Rock pockets and voids can occur when these conditions are present – even with thorough vibration. However, inadequate or incomplete vibration exacerbates the situation, as seen here. In an extreme case such as this, the engineer will have to decide between exposing and patching the voids, or demolishing the wall and starting over.