The smaller the width of a crack, the greater the capillary force and suction height, but the slower the penetration time. The greater the width of a crack, the smaller the capillary force and suction height, but the faster the penetration time. The greater the cement factor which is completely hydrated, the less porous the concrete and the more dense and water-tight. Water vapor transmission is the migration of hydrogen molecules from a higher pressure to a lower pressure. This vapor transmission or vapor drive will continue until these pressures are equalized.
Vapor drives travel from an area of high relative humidity to low relative humidity.
Outdoors this will vary depending on the proximity to large bodies of water. The lower the perm rating, the better a vapor barrier is. The mixing water is utilized more effectively in the hydration process. Bleed-water, shrinkage, and finishing times are reduced. Tests performed conclusively show that in concrete with a dosage rate of 1 gallon per cubic yard, vapor transmission is reduced over one half.