Page 123 - Construction Waterproofing Handbook

3.12 CHAPTER THREE
should be highlighted. Chlorides attack the reinforcing steel and can cause structural dam-
age after extended weathering. Many sealers have very poor chloride resistance.
Since water penetration begins on the surface, depth of penetration is not a particularly
important consideration. While all penetrating sealers must penetrate sufficiently to react
chemically with the substrate, many penetration depth claims are made on the solvent car-
rier rather than the chemical solids that form the repellency. The effective repellency must
be at the surface of the substrate to repel water. Water should only penetrate the surface
if there is cracking in the substrate, and if this is the case, no repellent can bridge crack-
ing or penetrate sufficiently to repel water in the crack crevice (see Fig. 3.5).
Penetrating capability is a better guide for a sealer’s protection against UV degradation.
Having the active compounds deeper into the substrate surface protects the molecules from
the sun’s ultraviolet rays that can destroy a sealers repellency capability.
When comparing the capability of sealers to penetrate into a substrate be sure to review
what is referred to as the uniform gradient permeation (UPG), which measures the penetra-
tion of the active ingredient rather than the solvent carrier. Most alcohol carriers will pene-
trate with the active ingredient deeper than those using a petroleum-based carrier will.

FIGURE 3.5 Clear repellents cannot repel water entering through substrate cracks.