Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
2002-03-01
2004-08-17
Green, Anthony J. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S711000, C106S712000, C106S819000, C428S402000, C501S035000
Reexamination Certificate
active
06776838
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to pozzolanic cements, and more specifically relates to a white pozzolan derived from glass manufacturing by-products, and to the method for producing the white pozzolan. The invention relates as well to cement compositions based on the white pozzolan, such as white and pigmented blended pozzolanic cements of high durability for use in applications such as white or colored architectural concrete, building materials, and manufactured cementitious products. Although the white color of the pozzolan and its consequent use with white cement can generate great added value, the white pozzolan also functions as a high performance pozzolan with grey cement.
DEFINITIONS
As used herein the following definitions shall apply, which are adopted from ASTM C-618: Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in Concrete:
“Pozzolan—A siliceous or siliceous and aluminous material which in itself possesses little or no cementitious value but will, in finely divided form and in the presence of moisture, chemically react with calcium hydroxide at ordinary temperatures to form compounds possessing cementitious properties.
Class N Pozzolan—Raw or calcined natural pozzolans that comply with the applicable requirements for the class as given herein, such as some diatomaceous earths; opaline cherts and shales; tuffs and volcanic ashes or pumicites, calcined or uncalcined; and various materials requiring calcination to induce satisfactory properties, such as some clays and shales.
Class F Fly Ash—Fly ash normally produced from burning anthracite or bituminous coal that meets the applicable requirements for this class as given herein. This class fly ash has pozzolanic properties.
Class C Fly Ash—Fly ash normally produced from lignite or subbituminous coal that meets the applicable requirements for this class as given herein. This class fly ash, in addition to having pozzolanic properties, also has some cementitious properties.”
BACKGROUND OF THE INVENTION
In a representative glass fiber manufacturing facility, typically 10-20 wt % of the processed glass material is not converted to final product and is rejected as industrial by-product or waste and sent for disposal to a landfill. This rejected material represents a substantial cost to the industry and also generates a consequent detrimental impact on the environment. While the rejected by-product referred to may have widely varying physical form, ranging from thick fiber bundles to partially fused fiber agglomerates and shot, it is evident from chemical analyses of various samples recovered at different times, that the material still has a substantially constant chemical and mineralogical make-up. Thus, unlike wastes from many other industrial processes which typically have widely varying chemical and mineralogical properties, the waste from the glass fiber manufacturing process is very consistent in composition and still benefits from the stringent engineering quality control applied to the glass-making process itself. This consistency is a major advantage to any potential utilization of the glass fiber manufacturing waste.
More specifically, the glass formulations of great relevance to this invention are those of low alkali calcia-alumina-silica compositions (CaO—Al
2
O
3
—SiO
2
or “CAS”) typically used for commercial glass fiber manufactured to comply with ASTM D-578. These formulations are given in Table 1. The compositions are vitreous and by virtue of their components have very low levels of discolorants. These compositions are expressed conventionally in terms of the element oxide and are not meant to imply that the oxides, crystalline or otherwise, are present as distinct compounds in the amorphous glasses.
TABLE 1
Composition Range
Component (Element Oxide)
(% by Weight)
Silicon dioxide, SiO
2
52-62
Aluminum oxide, Al
2
O
3
12-16
Iron oxide, Fe
2
O
3
0.05-0.8
Calcium oxide, CaO
16-25
Magnesium oxide, MgO
0-5
Sodium oxide + potassium oxide (Na
2
O + K
2
O)
0-2
Boron oxide, B
2
O
3
0-10
Titanium dioxide, TiO
2
0-1.5
Fluorine, F
2
0-1
Mineralogical Composition (XRD)
Amorphous (glassy)
Several features are immediately evident from inspection of the data in Table 1. First, the general chemical and mineralogical composition of the glass fiber material is very similar to amorphous (glassy) calcium alumino-silicate materials, such as blast-furnace slag and Class C fly ash, that are commonly used as cementitious or pozzolanic admixtures in portland cement concrete; second, the alkali (Na
2
O+K
2
O) content of the glass is very low (0 to 2%); and third, with their inherently low iron contents (0.05 to 0.8%), the glasses have little or no color. Low alkali content and chemical consistency differentiates the glass fiber manufacturing waste from post consumer waste glass, for example container bottles and flat glass, that have widely varying chemical composition, generally high alkali content, and in the case of container/bottle glass are highly colored.
Conventionally, white portland cement is used in a variety of applications, including but not limited to: white or light colored architectural concrete; precast concrete panels; cast stone monuments and statuary; ornamental landscaping; decorative flooring tiles and terrazzo; wall cladding, stuccos and plasters; tile grout; caulk and white cement paint.
White portland cement by itself does not have good durability, particularly under service conditions where it is exposed to attack by sulfate solutions and other aggressive chemicals. This is because the chemical composition of white cement is different from gray Portland cement in order to obtain the desirable white color. The main difference is that white cement has a very low iron content which during the manufacturing process leads to the formation of much higher tricalcium aluminate C
3
A content in the finish clinker. Typically during cement manufacturing, C
3
A reacts with iron oxide to form tetracalcium aluminoferite (C
4
AF). The lack of iron oxide in white cement results in high levels of tricalcium aluminate that are the reason for the well known susceptibility of white cement to chemical deterioration when exposed to an environment that is rich in sulfate. Such an environment can be found in many soils and in seawater. A high C
3
A content can also contribute to the increase in volume changes that can result in the formation of cracks in hardened concrete.
Cementitious and pozzolanic admixtures used with portland cement, such as blast-furnace slag, fly ash, silica fume and metakaolin, are characteristically fine particulate powder materials that are comparable in fineness to portland cement. In addition to improving the economics of production through cement replacement, these “supplementary cementing materials” are also well known to improve the long term durability of cement and concrete products, for example by reducing deterioration due to attack by aggressive chemical media, such as sulfate, and expansion due to reactions between the aggregates and the cement alkalis (so-called “alkali-aggregate reaction” or AAR).
These pozzolans, however, have chemical components that inevitably impart an undesirable dark color to white cement that negates the reason for using the material. For this reason, use of the architecturally desirable white cement has been somewhat limited to applications where there is no likelihood of exposure to sulfate and other aggressive chemicals. This is unfortunate because major markets for white and light colored concrete and concrete products exist in the coastal regions where exposure to high sulfate containing soils and seawater spray are likely.
Another additive that has been used in white cement is metakaolin. See for example U.S. Pat. Nos. 6,007,620, and 6,033,468, disclosing an interground white blended cement based on metakaolin. Metakaolin however, aside from its relatively high costs, differs from the pozzolan of this invention, in typically impar
Cornelius Bruce J.
Graves Philip L.
Hemmings Raymond T.
Nelson Robert D.
Albacem LLC
Green Anthony J.
Klauber & Jackson
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