Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-09-28
2003-11-25
Szekely, Peter (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C427S393600, C427S403000
Reexamination Certificate
active
06653373
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to cementitious compositions and related methods. More specifically, it relates to cementitious compositions and admixtures which are resistant to aggressive environments such as aqueous chemical environments, as might be found in a swimming pool or spa.
2. Description of the Related Art
Cementitious compositions or materials as the terms are used herein are used in their commonly used but broad sense to include compositions, materials, products, etc. which include as a component cement. The term includes such things as concrete, shotcrete, plaster, stucco, and the like. Cementitious materials are used in a tremendous variety of applications. In recent years there has been increased commercial interest in cementitious products which have surface coloration. Examples would include cementitious sculptures, building exteriors such as walkways and concrete railings, swimming pools, and spas. It has generally been preferred in many applications that the colored particles or pigments be imbedded or blended into the cementitious material, rather than merely painted or otherwise placed on the surface of a cementitious product. In such applications, the quality of the colored particles placement, such as the uniformity of color, has been important. The use of pigments in such applications has been disadvantageous in that it is difficult to properly disperse the pigments, they make it more difficult to control the resulting texture, and they are subject to ultraviolet light degradation, fading, etc. The nature of the cementitious materials and known methods for pigmentation also have placed limits on the range of colors that may be created with cementitious products.
Cementitious materials commonly are exposed to aggressive fluids, such as water, aqueous solutions, fluids which include minerals, acids, alkaline fluids, etc. These fluids usually react with the components of the cementitious material to degrade its integrity. An example of such degradation would include circumstances where the aggressive fluid reacts with and/or dissolves soluble portions of the cementitious material and thereby removes the soluble or partially-soluble component or components from the cementitious matrix. This often results in weakening the cementitious material, marring or pitting of its surface, and detracting from its effectiveness in the given application.
The deterioration of cementitious products by aggressive fluids has been the subject of study and investigation for years. See, e.g., F. M. Lea,
The Chemistry of Cement and Concrete,
3d Ed., Chemical Publishing Co., Inc., 1971. A number of different types of attacks by aggressive fluids on cementitious products have been identified in the literature. For example, N. P. Mailvaganam,
Repair and Protection of Concrete Structures,
CRC Press, 1992, identifies five classes of attacks, including Type I (simple leaching of calcium hydroxide), Type II (reactions between attacking solutions and cement compounds resulting in the formation of secondary compounds, which are either leached out or remain in an unbound form, resulting in gradual strength loss), Type III (reaction similar to Type II, but resulting in the crystallization of the reaction products giving rise to expansive forces which disrupt the concrete), Type IV (crystallization of salts directly from the attacking solution causing disruption of the concrete), and Type V (corrosion of the embedded steel reinforcement resulting from breakdown of the passivation zone by aggressive solutions).
Beginning in the mid-1960's, a phenomenon known as “spot etching” began to be discussed in various trade publications within the swimming pool industry. Spot etching has come to be known as the selective dissolution of calcium hydroxide from the cementitious components of plaster, also known as marcite, that is used to finish the pool. Swimming pool plaster typically is a relatively thin (⅜ inch to ¾ inch) layer of a cementitious matrix comprising a mixture of white cement and calcium carbonate aggregate such as limestone or marble. This type of plaster has been one of the most commonly applied concrete pool finishes used in the United States over the past 40 years. Spot etching of these plaster surfaces appears as small areas, usually rounded in nature, having a typical size about ⅛ inch to ¾ inches, with increased porosity and permeability as compared to non-etched areas. This spot etching phenomenon has grown into one of the most significant concerns in the swimming pool industry as it relates to pool interior finishes.
The increased incidence of spot etching and other aggressive fluid deterioration phenomena are believed to be attributable to a number of factors. Prior to the 1960's, the primary sanitizers used by swimming pool and spa owners to kill microorganisms such as bacteria and algae were alkali chlorine compounds such as calcium hypochlorite (pH 11.7) and sodium hypochlorite (liquid chlorine, pH 13). These chlorine products are characterized by high pH's, and they usually contribute to increases in pH, calcium hardness, and/or total dissolved solids (TDS) levels of water in swimming pools. They often cause migration of the mineral or metallic ions out of solution, resulting in scaling or precipitation or both. These products typically were not used in conjunction with stabilizer or cyanuric acid, and they had to be added frequently to maintain a consistent chlorine residual as sunlight dissipated the chlorine in the water.
By the mid-1970's, acidic sanitizers such as trichloro-s-triazinenrine, and bromochlorodimethylhydantoin, were gaining popularity due to their long lasting nature and ease of use. These sanitizers, however, resulted in the decrease of total alkalinity and, if uncorrected, of water pH levels.
As the popularity of acidic sanitizers increased, a trend developed in the U.S. municipal water treatment industry toward softer water. This softer water, in which mineral and divalent metallic constituents were removed, improved the palatability of the potable water supply. But it had detrimental effects on cementitious products such as swimming pool plaster. By decreasing the concentration of these mineral components, particularly calcium carbonate and other calcium salts, the carbon dioxide-carbonate equilibrium was shifted such that greater dissolution of soluble calcium components of the cementitious products such as calcium hydroxide was promoted. See, e.g., F. M. Lea,
The Chemistry of Cement and Concrete,
3d Ed., Chemical Publishing Co., 1971, Chapter 12. Spot etching and similar deterioration phenomena resulted. These effects also occurred or were enhanced by the increased presence of acid rain and other forms of air pollution, which have contributed to the aggressiveness of water and other aggressive fluids by increasing the acidity of the fluids.
Two primary approaches have been suggested for addressing etching of cementitious products by aggressive fluids—control of the chemistry of the fluid, such as swimming pool water balance, and (2) providing a chemically inert barrier between the cementitious product and the aggressive fluid. See, e.g., E. Dow Whitney,
A Study of Marcite
(
Plaster
)
Deterioration in Swimming Pools,
(1991), at page 50.
Control of fluid chemistry is not feasible in many cementitious product applications. Even in those applications for which such control is feasible, it requires greater attention and maintenance. For example, in the swimming pool context, swimming pool owners have had to more diligently monitor and adjust their pool water using chemical additives in an effort to maintain a proper chemical balance and avoid deleterious etching effects. Pool owners often lacked the knowledge of when and how to do the testing and make the adjustments to water chemistry, and they often lacked the ability or discipline to do so each time they were required.
The approach of providing a chemically inert barrier has been problemati
Garrett Gregory
Mariano Vito
Applied Materials Technologies, Inc.
Sullivan Law Group
Szekely Peter
LandOfFree
Method for treating a swimming pool surface does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for treating a swimming pool surface, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for treating a swimming pool surface will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3176996