Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
1999-09-29
2001-07-10
Green, Anthony (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S725000, C106S727000, C106S806000, C106S823000
Reexamination Certificate
active
06258161
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to masonry concrete having improved freeze-thaw durability and to admixtures for achieving such improved freeze-thaw durability, and in particular to masonry units containing betaine as an air entraining agent, which may be used in combination with efflorescence control admixtures.
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 relatively fine aggregate (e.g., particles of which less than 5% have a diameter of 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 phrase it more accurately, a practically immeasurable fluidity. The slump property is determined by compacting 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 essentially “zero slump.”
The present inventors have discovered that the use of efflorescence control admixtures (ECAs), which are sometimes referred to as integral water repellants, such as calcium stearate dispersion, fatty acids, their salts or esters, oils, etc., may 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 C 1262 (1995) test method in the lab, revealed severe adverse effects of ECAs on the F/T durability of masonry units.
The present inventors therefore considered conventional air entraining agents (AEAs) which are known to increase F/T durability in conventional concrete. Conventional AEAs, such as gum rosin, VINSOL (tm) resin, and Tall Oil Fatty Acids, were evaluated for their ability to provide empty space within masonry concrete for receiving water that is displaced by ice formation, thus avoiding dangerous pressure-build up under freeze-thaw conditions. However, the inventors surprisingly discovered that conventional AEAs did not work in zero slump masonry units.
It should be mentioned here that AEAs operate to “entrain” air rather than to “entrap” it. AEAs stabilize air present in the mix (e.g., dissolved in mix water, folded-in and mechanically enveloped during mixing, present in intergranular spaces of cement, etc.). This is manifested by essentially spherical bubbles, typically between 0.001-1.25 mm. diameter, seen distributed relatively uniformly within the cement paste portion of the mix.
It is surmised by the present inventors that the nature of masonry units impedes the use of conventional AEAs because masonry concrete has smaller cement paste volumes than conventional concrete and because the masonry concrete mix is less fluid than a conventional concrete mix. This is also perhaps due to the fact that masonry concrete employs only relatively fine aggregate and has a zero slump characteristic. Combined with the fact that masonry concrete tends to have larger compaction void volume (i.e., interconnected voids which are not the same as entrained air voids), the very nature of masonry units thus defeats the efficacy of AEAs in entraining tiny air bubbles in the paste portion of masonry concrete mixes, and thus the attainment of F/T durability in masonry concrete is curtailed.
Accordingly, an improved masonry concrete admixture and masonry concrete having improved F/T durability are needed.
SUMMARY OF THE INVENTION
In surmounting the disadvantages of the prior art, the present invention provides an improved masonry concrete composition in which a betaine, which is an amphoteric air entrainer, is successfully used for entraining air in “zero slump” masonry concrete, thereby rendering it possible to incorporate efflorescence control admixtures (ECAs), such as fatty acid ECAs, into the masonry unit while minimizing the adverse effect that such ECAs have on their freeze-thaw durability.
An exemplary masonry concrete composition of the present invention therefore comprises a hydratable cement binder comprising 5-25% based on total dry weight of the composition; a relatively fine aggregate portion comprising 75-95% based on total dry weight of solids in the composition; a betaine in the amount of 0.01-1.0%, and more preferably 0.05-0.5% (solids on solids (s/s) cement); the composition, when wet, having essentially zero slump when tested by the standard cone method for measuring slump. Indeed, it was found that tiny air bubbles could be entrained in the cement paste fraction of the masonry units. The presence of such air bubbles is the key to the significant improvement in the F/T durability of masonry units.
The use of betaine surfactants are not only believed to be effective in entraining air in masonry units in the presence of ECAs, particularly fatty acid ECAs, but are also believed to be highly effective in entraining air in—and thus improving the freeze-thaw durability of—all masonry units in general.
Further features and advantages of the invention are provided hereinafter.
REFERENCES:
patent: 3663251 (1972-05-01), Moren et al.
patent: 4116706 (1978-09-01), Previte
patent: 4209336 (1980-06-01), Previte
patent: 4209337 (1980-06-01), Wagner et al.
patent: 4223732 (1980-09-01), Carriay et al.
patent: 4547223 (1985-10-01), Goto et al.
patent: 4814014 (1989-03-01), Arfaei
patent: 4913741 (1990-04-01), Lane et al.
patent: 4960465 (1990-10-01), Arfaei
patent: 4992104 (1991-02-01), Boutevin
patent: 5099922 (1992-03-01), Ganguli
patent: 5133409 (1992-07-01), Bour et al.
patent: 5147565 (1992-09-01), Bour et al.
patent: 5174820 (1992-12-01), Sakuta et al.
patent: 5213161 (1993-05-01), King et al.
patent: 5220960 (1993-06-01), Totten et al.
patent: 5281270 (1994-01-01), Totten et al.
patent: 5298069 (1994-03-01), King et al.
patent: 5298070 (1994-03-01), Cowan
patent: 5330006 (1994-07-01), Nahm et al.
patent: 5679150 (1997-10-01), Kerkar et al.
patent: 5720807 (1998-02-01), Izumi et al.
patent: 5782972 (1998-07-01), Abelleira et al.
patent: 5897699 (1999-04-01), Chatterji et al.
patent: 5900053 (1999-05-01), Brothers et al.
patent: 2032491 (1980-05-01), None
patent: 2096591A (1982-03-01), None
patent: 2292141A (1995-08-01), None
patent: 78-117681 (1978-09-01), None
patent: 55-47259 (1980-04-01), None
patent: 58-60293 (1983-04-01), None
patent: 58-140364 (1993-08-01), None
patent: 94-73339 (1994-04-01), None
patent: 7-291762 (1995-11-01), None
patent: 11-71146 (1999-03-01), None
Chemical Admixtures for Concrete, M.R. 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).
UK Search Report, The Patent Office, Feb. 7, 2000, 1 page.
Hazrati Kati
Kerkar Awdhoot V.
Walloch Craig T.
Baker William L.
Green Anthony
Leon Craig K.
W. R. Grace & Co.,-Conn.
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