Is a vapor barrier needed when concrete is vacuum dewatered?
If the vapor barrier would be needed for the job were vacuum dewatering not used, it would also be needed with concrete that is to be vacuum dewatered. Where there is a porous soil below the concrete slab, air might be drawn through the slab in some circumstances if there were no vapor barrier separating it from the soil. If there were water below the slab it might also happen that water would be drawn through the slab if there were no vapor barrier.