It is important to stress that, concrete with has different consistency. The method of vibrating the form or concrete mix within the form is different. concrete must not be over vibrated. Under an automated system vibration should be held down to a ¼ of the time normally used to vibrate standard concrete. The cement paste is much heavier than the bead, therefore over vibration will cause the concrete to settle to the bottom of the form or cause a sponge effect, when molding or extruding. will not float within the mix design.