Page 122 - Construction Waterproofing Handbook

ABOVE-GRADE WATERPROOFING 3.11
TABLE 3.4 Penetrating Sealer Properties

Advantages Disadvantages
Resistant to ultraviolet weathering Can damage adjacent substrates,
especially glass and aluminum
Effective for abrasive wear areas Causes damage to plants and shrubs
Excellent permeability ratings Not effective on wood or hard
finish materials such as glazed tile

CHOOSING THE APPROPRIATE REPELLENT

Without any doubt, choosing the correct water repellent for a specific installation can be a
difficult task. Sealer manufacturers offer you little assistance as you try to find your way
through the maze of products available, reported to be as many as 500 individual systems.
Even though there is a finite number of families of sealers, as outlined in the following
sections, within each family manufacturers will try to differentiate themselves from all oth-
ers, even though most are very similar systems.
There are numerous chemical formulations created using the basic silicon molecule that
forms the basis for most of the penetrating sealers. These formulations result in the basic
family groups of: Silicones, Silicates, Silanes, and Siloxanes. There is often confusion as
to the basic families of sealers; for example, some will classify Siliconates as a family even
though it begins as a derivative of a Silane. From these basic groups, manufacturers for-
mulate numerous minor changes that offer little if any improvements and only tend to con-
fuse the purchaser into thinking they are buying something totally unique.
Derivatives include Alkylalkoxysiloxane (siloxane), Isobutyltrialkoxysilane (silane),
Alkylalkoxysilane (silane), methylsiloxanes, and many blends of the family groups such
as a silane/siloxane combination. These formulations or chemical combinations should not
confuse a prospective purchaser. With a few basic guidelines, the best selection for each
individual installation can be made easily.
First, any water repellent used should have the basic characteristics necessary for all
types of installations: sufficient water repellency, and long life-cycling under alkaline
conditions. The latter, performance in alkaline conditions, usually controls how well the
product will perform as a repellent over extended life cycling. For the penetrating sealers
listed above, no matter how well the product repels water during laboratory testing, the
product will virtually become useless after installation if it cannot withstand the normal
alkaline conditions of concrete or masonry substrates. Concrete in particular has very
high alkaline conditions that can alter the chemical stability of penetrating sealers, result-
ing in a complete loss of repellency capability.
Therefore when reviewing manufacturer’s guide specifications, the high initial repellency
rates should not be depended upon solely; rather emphasize the test results of accelerated
weathering, especially when application is used on concrete or precast concrete substrates.
Verify that the accelerated weathering is tested on a similar substrate, as masonry or most
natural stones will not have alkaline conditions as high as concrete.
In addition, when the proposed application is over concrete substrates with substantial
reinforcing steel embedded, the resistance of the repellent to chloride ion infiltration