Hydrated calcium aluminate based expansive admixture
First Claim
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1. An expansive additive for controlling shrinkage in a cementitious mixture, comprising:
- calcium aluminate particles where at least 75% by mass of said particles are hydrates of C3AH6, CAH10 or a mixture thereof, where C represents CaO, A represents Al2O3, and H represents H2O, said mass of said particles being fully hydrated;
an expansion effecting sulfate containing compound for effecting expansion in said mixture; and
calcium hydroxide.
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Abstract
An additive, a mixture incorporating the additive and a method of formulating a mortar incorporating the additive. The additive is based on calcium sulfoaluminate composed of C3AH6 and CAH10 where C=calcium oxide, A=aluminum oxide and H=water. The admixture includes gypsum and calcium hydroxide. The calcium aluminum hydrates are obtained by hydration of high alumina cement particles to eliminate any lack of hydration in the core of the particle. The method involves the preparation of such particles and the mix incorporates the particles to produce a homogeneously hydrated cement additive.
9 Citations
40 Claims
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1. An expansive additive for controlling shrinkage in a cementitious mixture, comprising:
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calcium aluminate particles where at least 75% by mass of said particles are hydrates of C3AH6, CAH10 or a mixture thereof, where C represents CaO, A represents Al2O3, and H represents H2O, said mass of said particles being fully hydrated;
an expansion effecting sulfate containing compound for effecting expansion in said mixture; and
calcium hydroxide. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 12)
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11. A cementitious mixture having reduced shrinkage upon curing, comprising:
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cementitious material;
calcium aluminate particles where at least 75% by mass of said particles are hydrates of C3AH6, CAH10 or a mixture thereof, where C represents CaO, A represents Al2O3, and H represents H2O, said mass of said particles being fully hydrated;
an expansion effecting sulfate containing compound for effecting expansion in said mixture; and
calcium hydroxide. - View Dependent Claims (13)
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14. A method for synthesizing hexagonal phase calcium aluminate hydrate particles, comprising the steps of:
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i) providing a source of calcium aluminate particles;
ii) hydrating said calcium aluminate sufficiently to form a slurry;
iii) agitating said slurry sufficiently for hydration to occur and form hexagonal phase calcium aluminate hydrate particles;
iv) maintaining the temperature of said slurry to prevent thermal conversion of said hexagonal phase calcium aluminate hydrate particles to cubic phase calcium aluminate particles; and
v) drying said slurry at a temperature to prevent thermal conversion of said hexagonal phase calcium aluminate hydrate particles to cubic phase calcium aluminate particles. - View Dependent Claims (15, 16, 17, 18, 29, 30, 31)
i) cementitious material;
ii) an expansion effecting sulfate compound for effecting expansion in said mixture;
iii) calcium hydroxide; and
iv) presynthesized calcium aluminate hydrate particles formed by the method of claim 14.
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30. The method as set forth in claim 29, wherein said expansion effecting sulfate compound is a calcium sulfate compound.
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31. The method as set forth in claim 30, wherein said calcium sulfate compound is selected from the group consisting of calcium sulfate dihydrate, calcium hemihydrate and calcium anhydrite.
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19. A method for synthesizing cubic phase calcium aluminate hydrate particles, comprising the steps of:
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i) providing a source of calcium aluminate particles;
ii) hydrating said calcium aluminate sufficiently to effect hydration of at least 75% by mass of said particles in a slurry;
iii) agitating said slurry sufficiently for hydration to occur;
iv) maintaining the temperature of said slurry in a range sufficient to convert any hexagonal phase calcium aluminate particles formed to cubic phase calcium aluminate hydrate particles; and
v) drying said slurry. - View Dependent Claims (20, 21, 22, 32, 33, 34)
i) cementitious material;
ii) an expansion effecting sulfate compound for effecting expansion in said mixture;
iii) calcium hydroxide; and
iv) presynthesized calcium aluminate hydrate particles formed by the method of claim 19.
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33. The method as set forth in claim 32, wherein said expansion effecting sulfate compound is a calcium sulfate compound.
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34. The method as set forth in claim 32, wherein said calcium sulfate compound is selected from the group comprising calcium sulfate dihydrate, calcium hemihydrate and calcium anhydrite.
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23. A method for synthesizing cubic phase calcium aluminate hydrate particles, comprising the steps of:
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i) providing a source of calcium aluminate particles;
ii) hydrating said calcium aluminate particles;
iii) curing said mixture in a humid atmosphere for a period sufficient to prevent self desiccation at a temperature sufficient to effect conversion of hexagonal phase particles to said cubic phase calcium aluminate hydrate particles; and
iv) drying said mixture. - View Dependent Claims (24, 25, 26, 38, 39, 40)
i) cementitious material;
ii) an expansion effecting sulfate compound for effecting expansion in said mixture;
iii) calcium hydroxide; and
iv) presynthesized calcium aluminate hydrate particles formed by the method of claim 23.
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39. The method as set forth in claim 38, wherein said expansion effecting sulfate compound is a calcium sulfate compound.
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40. The method as set forth in claim 38, wherein said calcium sulfate compound is selected from the group consisting of calcium sulfate dihydrate, calcium hemihydrate and calcium anhydrite.
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27. A method for synthesizing hexagonal phase calcium aluminate particles, comprising the steps of:
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i) providing a source of calcium aluminate particles;
ii) hydrating said calcium aluminate particles;
iii) curing said mixture in a humid atmosphere for a period sufficient to prevent self desiccation at a temperature sufficiently low for preventing conversion of hexagonal particles to cubic particles; and
iv) drying said mixture. - View Dependent Claims (28, 35, 36, 37)
i) cementitious material;
ii) an expansion effecting sulfate compound for effecting expansion in said mixture;
iii) calcium hydroxide; and
iv) presynthesized calcium aluminate hydrate particles formed by the method of claim 27.
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36. The method as set forth in claim 35, wherein said expansion effecting sulfate compound is a calcium sulfate compound.
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37. The method as set forth in claim 35, wherein said calcium sulfate compound is selected from the group consisting of calcium sulfate dihydrate, calcium hemihydrate and calcium anhydrite.
Specification