Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
1999-10-13
2001-10-16
Green, Anthony (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S724000, C106S726000, C106S727000, C106S728000, C106S806000, C106S808000, C106S810000, C106S823000, C524S006000
Reexamination Certificate
active
06302955
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to compositions and methods for improving freeze-thaw durability in masonry units, and more particularly to the use of certain nonionic alkylaryl polyether alcohols, which may be successfully used in combination with efflorescence control admixtures, in masonry concrete and concrete masonry units.
BACKGROUND OF THE INVENTION
Masonry units, sometimes referred to as concrete masonry units (CMUs), include segmental retaining wall (SRW) units, pavers, and architectural blocks, all of which are made from a “masonry concrete” which is comprised of hydratable cement binder and fine aggregate (e.g., particles of which less than 5% have a diameter greater than 0.375 inch). Masonry concrete lacks the coarse aggregate (typically greater than 0.5 inch diameter) that is further used in conventional concrete, such as, for example, ready-mix concrete.
More significantly, masonry concrete differs from conventional concrete because it is said to have zero “slump,” or, to employ a more accurate definition, it is said to have a practically immeasurable fluidity. The slump property is determined by placing wet masonry concrete into an inverted cone and then removing the cone, and measuring the distance (if any) by which the cone-molded sample drops in height. See ASTM C143 (1988) (“Standard Test Method for Slump of Portland Cement Concrete”). Typically, the slump of masonry concrete is 0-0.75 inches, and thus masonry concrete is said to have an essentially “zero slump.”
The present inventors believe that the use of fatty acid-based efflorescence control admixtures (ECAs), which are sometimes referred to as integral water repellants, such as calcium stearate dispersion, fatty acids and their salts and esters, etc., can cause an appreciable loss of freeze-thaw durability in masonry units (e.g., made of zero slump masonry concrete). Efflorescence is the appearance of white, patchy stains on the face of masonry units during their manufacture or after their installation in the field. Once installed in the field, the masonry blocks are subjected to routine weathering conditions, one of them being alternate freezing and thawing (F/T) cycles. Recent testing of F/T durability of masonry units (SRW), using the ASTM C1262 (1995) test method in the lab, revealed severe adverse effects of ECAs on the F/T durability of masonry units.
Accordingly, an improved masonry concrete admixture, masonry concrete having improved freeze/thaw durability, and methods for making these, are urgently needed.
SUMMARY OF THE INVENTION
The present invention concerns the inventors' surprising discovery that certain surfactants improve freeze/thaw (“F/T”) durability of masonry units containing efflorescence control agents, and especially when F/T durability is tested pursuant to ASTM C1262 (1995).
An illustrative composition of the invention for improving F/T durability comprises (i) a nonionic alkylaryl polyether alcohol having the general formula R-Ø-(OCH
2
CH
2
)
x
OH, wherein R is a C
4
-C
8
alkyl group (most preferably, a branched octyl group), Ø represents a phenol group, and “X” represents an integer in the range of 3-70; and (ii) an efflorescence control admixture selected from calcium stearate, fatty acids and their salts and esters (e.g., C
4
-C
22
fatty acid or its salt or derivative), polyvinyl alcohol, silanes, and siloxanes and latexes (e.g., acrylic, butadiene, etc.). An exemplary fatty acid (salt) may comprise calcium stearate in dispersion form.
Another illustrative embodiment of the present invention is a masonry composition which comprises (i) a hydratable cement binder (5-25% based on total dry weight of the composition); (ii) a fine aggregate portion (80 to 95% based on total dry weight of the composition of particles of which less than 5% have a diameter of greater than 0.375 inch); and (iii) an alkylaryl polyether alcohol having the formula R-Ø-(OCH
2
CH
2
)
x
OH, wherein R is a C
4
-C
8
alkyl group, Ø represents a phenol group, and “X” represents an integer in the range of 3-70 (said alkylaryl polyether alcohol being present in the composition in the amount of 0.001-5.0% (s/s cement); the composition, when wet, having essentially zero slump when tested by ASTM C143 (1988) (standard cone test for measuring slump). The exemplary masonry composition may further comprise an efflorescence control admixture (e.g., a fatty acid or its salt or derivative (e.g., C
4
-C
22
); e.g, calcium stearate), and/or optionally a betaine as a further F/T durability improving component.
Exemplary methods for improving the freeze/thaw durability of masonry units comprises incorporating the above-described alkylaryl polyether alcohol, either separately or together with (a) an efflorescence control admixture (such as a fatty acid or its salt or derivative) and/or (b) a betaine.
An exemplary method of the invention for making a freeze/thaw durability admixture for masonry concrete comprises (i) providing an efflorescence control admixture (e.g., fatty acid or its salt or derivative); (ii) optionally heating the efflorescence control admixture (it if it is not in liquid form) so as to render it into liquid form; (iii) combining said efflorescence control admixture while in liquid form with a hydroxide solution (e.g., calcium hydroxide, potassium hydroxide, sodium hydroxide, lithium hydroxide, etc.). If the efflorescence control admixture is a fatty acid, this method will obtain the salt of the fatty acid, and the hydroxide solution may further comprise an alkylaryl polyether alcohol having a C
4
-C
8
alkyl group (preferably, branched octyl group). Optionally, but preferably, this dispersion is milled or ground to reduce the size of dispersed particles (e.g., fatty acid salt particles within the aqueous dispersion).
Further features and advantages of the invention are provided hereinafter.
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UK Search Report, The Patent Office, Feb. 7, 2000, 1 page.
Chemical Admixtures for Concrete, M.R. Rixam and Rixom and N.P. Mailvaganam, E. & F.N. Spon, London, New York, pp. 97-100. (1986) (No Month).
Triton X-Series Surfactants, Nonionic Octylphenol Polyether Alcohols, Union Carbide Corporation, 1997, pp. 1-20. (No Month).
Hazrati Kati
Kerkar Awdhoot V.
Baker William L.
Green Anthony
Leon Craig K.
W. R. Grace & Co.,-Conn.
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