Floors' torch

Concrete Construction, Dec, 2002

Thank you for picking up the torch lit by Mssrs. Suprenant and Malisch concerning floor-covering delamination. We have been in the business of materials testing for 40 years, but it has been only in the past few years that we have seen floor-covering delamination problems. I suspect that when the smoke clears, indictments will go to the glue (mastic) and/or the additives and admixtures in the cement and concrete. The problem (delamination) can be solved by inventing hydrophilic glues compatible with cementitious material of pH 10 to 12. The glue should be able to bond to both the floor slab and the covering with a force in excess of the hydrostatic forces caused by the passage of moisture through the slab and floor covering. Finally, I predict that there will not be a consensus opinion of who is at fault.

--J. Ray Preston
Preston Testing & Engineering Co.
Macon, Ga.

Mr. Palmer's editorial in CONCRETE CONSTRUCTION (September, p. 7) in mentioning what to expect from concrete floors, neglected to indicate that concrete floors do also have a tendency to crack, even when the subbase is properly prepared and concrete is reinforced with rebar. As we all know, many factors contribute to cracks; therefore all conditions relating to concrete floor slabs must be at their best.

--Kenneth J. Walker
Jacoubowsky, Hawkins, Walker Architects
Monterey, Calif.

From reading your editorial in the September issue, I'm glad to see our industry trying new approaches to this significant problem. The symptoms of this problem, as you stated, are delaminated flooring systems and spalling, crumbling concrete. I feel that the true problem is the chemical reaction related to the migration of water through a concrete structure. Water dissolves back into solution the very reaction that is concrete. Concrete is merely a very hard sponge that will draw water from far below the surface it is placed on and will even draw moisture from the air seeking to balance with its environment. Water expands about 9% when it freezes, while at the same time the concrete is trying to contract, creating a contradictory environment where the concrete is bound to lose. If we could block the water, then we could break this cycle.

Surface sealers are a valid attempt to protect concrete from the introduction of water but they do nothing to stop ground water migration and the additional chemistry carried into the concrete. You could have the perfect mix of concrete, but if it is on or below grade, it is subjected to a constant mineral bombardment from below. Coupled with water, eventually the flooring systems will fail. This is verified by the presence of alkali at the surface-to-surface bond of failed systems, which is responsible for the breakdown of the bonding of glues, mastics, epoxies, paints, and mortars. But now there is a way to stop all of this from within the concrete structure--permanently. It sounds impossible, I know. But after 20 years in the swimming pool industry, seeing firsthand the ravaging effects of water on mortar-based products, I changed hats and am now working to educate people about an internal sealant that offers a workable and permanent solution to the effects of water. Please do not discount what I have said. This type of product will be growing in the market and should aid in producing a superior concrete product.

--Danny Metzger
Complete Sealing Solutions
Nashville, Tenn.