The following article has been taken from: National Plasterers Council, Technical Manual, Sixth Edition: Port Charlotte, FL: Technical Advisory Committee, 2009. Page 7.
The swimming pool cementitious coating consists of a mixture of hydraulic cement (typically white), white sands (typically limestone, quartz/silica or dolomite), and/or other aggregate, special additives (which aid in the placement and finishing of the cementitious surface), and water. The water reacts with the cement chemically, to form a hard rock-like material that, together with the sand, and/or aggregate, created a very strong coating. Supplemental (retemper) water is often added, giving the plasterer, the ability to pump, place, spread, and properly finish the cementitious coating. Cementitious surface coatings serve the useful purpose of lining the interior of the substrate structure or “shell” of a swimming pool. Plasterers work with trowels to create a finish that is smooth and almost watertight. Cementitious surface coatings are actually semi-permeable membranes, and as such, small amounts of moisture slowly permeate through these coating. However, many people consider these cementitious surface coatings to be, for the most part, “watertight” surface finish.
As with many hand-troweled finish products, certain characteristic fluctuations are to be expected as being inherent to the finish. Some fluctuation in the coloration, levelness, or texture of the surface coating’s finish is to be expected as a normal occurrence in all hand-troweled cementitious coatings. The benefits of the hand-trowel finish include increased density and smoothness of the surface, which in turn increases durability. The benefits of the colored aggregate finish, the exposed aggregate finish, or the polished finish, include aesthetic appeal and concealing of minor surface fluctuations.
Most cementitious surface coating complaints involve the following factors:
- Improper maintenance of the swimming pool surface coating or of the swimming pool water.
- Plastering application defects of failures.
- Material defects of failures.
- Normal of inherent fluctuations in raw materials, the plaster application, or the hydration and curing processes that are mistakenly considered to be flaws or failures.
- Some combination of the above.