Message text written by "BP - \"Astral Rendered Bee Wax -TM\""
>sodium silicate was the early store bought water proofing
agent used by masons in Ireland Scotland and the U.K;
 it is the base ingredient for Kiem  mineral systems; but perhaps Mike E.
could enlighten us  how it actually works and what its limitations are.<

I am hardly an expert in silicate chemistry or silicate coatings
formulation, though we have dabbled a bit at one time or another. There are
a number of commercial products based on sodium silicate and potassium
silicate, including clear solutions like the Ashford formula and Sinak, and
cement-based silicate treatments for waterproofing like Xypex, Vandex, Feb
Hyseal and many others. The waterproofing treatments supposedly work by
reacting with the alkali in lime or Portland cement to form calcium
silicate, a relatively stable crystal that can fill the voids in concrete.

In our limited work and experience we have found that the reactions of the
silicates can be tricky and sensitive to conditions. While good lab results
were obtainable under ideal conditions (essentially high alkalinity and
prolonged wet cure) these were difficult to duplicate in the field, and we
are aware of at least one rigorous set of Highway department tests in which
the silicate products tested failed miserably while most others tested
(e.g., silane, siloxane, acrylic and some others) all performed fairly
reliably.  Those tests were on "clean" concrete, and I suspect they would
do worse on older, salt-contaminated concretes.

There are some companies who specialize in silicate coatings, including
Keim in Germany and Sinak in San Diego,and clearly they have learned to
walk the line between solubility, slow reaction rates and sensitivity to
conditions. Properly formulated and applied, they can form highly stable
films. They also have good resistance to high temperatures, and I have read
that the coating used to line the rocket nozzles for the space shuttle was
based on sodium silicate.

Mike E.