Page 124 - Construction Waterproofing Handbook

ABOVE-GRADE WATERPROOFING 3.13
Some manufacturers will make claims as to the size of their active molecules being so
small that they penetrate better than other compounds using larger molecules. While this
may be the case, compounds with larger molecules usually repel water better than those
using smaller molecules.
The amount of solids or active ingredient is always a much-trumpeted point of compar-
ison. Certainly, there is a minimum amount of solids or active agent to produce the required
repellency, but once this amount is exceeded there is no logic as to what a greater concen-
tration will do. For the majority of penetrating sealers, 10 percent active compounds seems
to be the minimum to provide sufficient water repellency, with 20 percent moving towards
the maximum return for the amount of active agent necessary. While manufacturers will
often exceed this to increase a product’s sales potential, the value of its in-place service
capability is often no more than those with a smaller percentage of active compounds.
When considering film-forming repellents, a greater percentage of solids is important since
these solids are deposited directly on the surface of the substrate and left to repel water
directly and without the assistance of the substrate environment. With film-forming repellents,
the closer to 100 percent solids, the more likely the repellent will be capable of repelling water.
When trying to compare products through the maze of contradictory and confusing infor-
mation available, it is best to review the results of completed standard and uniform tests that
are most appropriate for the substrate and service requirements required. The next section
expands on the most frequently used testing to compare products, a much better guide than
reading sales literature about percent solids, size of molecule, and chemical formulations. In
most cases it is not appropriate to make comparison without the use of standard testing, and
no product should be considered without this critical information being provided. Recognize
however, that these tests are conducted in the pristine conditions of a laboratory that are never
duplicated under actual field conditions. This requires that a sufficient margin of error or
safety factor be used for actual expectations of performance results in actual installations.

Sealer testing
Several specific tests should be considered in choosing clear sealers. Testing most often
referred to is the National Cooperative Highway Research Program (NCHRP). This is the
most appropriate test for concrete substrates including bridges and other civil construction
projects. Although often used for testing horizontal applications, it remains an effective
test for vertical sealers as well. NCHRP test 244, Series II, measures the weight gain of a
substrate by measuring water absorption into a test cube submerged after treatment with
a selected water repellent. To be useful, a sealer should limit weight gain to less than
15 percent of original weight and preferably less than 10 percent. Test results are also
referred to as “a reduction in water absorption from the control [untreated] cube.” These
limits should be an 85–100 percent reduction, preferably above 90 percent.
Testing by ASTM includes ASTM D-514, Water Permeability of Masonry, ASTM C-67,
Water Repellents Test, and ASTM C-642, Water Absorption Test. Also, federal testing by
test SS-W-110C includes water absorption testing.
Any material chosen for use as a clear sealer should be tested by one of these methods to
determine water absorption or repellency. Effective water repellency should be above 85 percent,
and water absorption should be less than 20 percent, preferably 15–10 percent.
Weathering characteristics are important measures of any repellent, due to the alkaline
conditions of most masonry and concrete substrates that will deter or destroy the water