Pozzolan blends

• US 5,223,035 A
• Filed: 12/09/1991
• Issued: 06/29/1993
• Est. Priority Date: 08/29/1990
• Status: Expired due to Term

• Current Assignee: Lafarge Canada Incorporated (Holcim Limited)
• Original Assignee: Lafarge Canada Incorporated (Holcim Limited)
• Inventors: Hopkins, Donald S., Lehoux, Paul H., Anderson, Rayburn R., Oates, David B.
• Primary Examiner(s): BRUNSMAN, DAVID M
• Application Number:
  US07/804,359
• Time in Patent Office: 568 Days
• Field of Search: 106/705, 106/707, 106/709, 106/710, 106/716, 106/735, 106/736, 106/DIG. 1, 106/697
• US Class Current: 106/707
• CPC Class Codes: C04B 18/062 Purification products of smoke, fume or exhaust-gases
• CPC Class Codes: C04B 18/08 Flue dust , i.e. fly ash
• CPC Class Codes: C04B 28/18 containing mixtures of the silica-lime type
• CPC Class Codes: C04B 7/02 Portland cement
• CPC Class Codes: Y02W 30/91 Use of waste materials as fillers for mortars or concrete

Abstract

An unground, fine pozzolan having a sulphur content determined as wt. % SO₃ of 5 to 25 wt. % is employed in admixture with Portland cement to provide a blended hydraulic cement which has increased compressive strength characteristics as well as extended retardation time without the need for separate addition of gypsum; the pozzolan may also be admixed with fly ash to provide a pozzolan blend for use with Portland cement with reduced Portland cement content and use of Class C fly ash; the pozzolan is derived by reaction of coal flue gases with an atomized vapor of slaked lime.

Claims

1. A concrete article comprising a particulate pozzolanic blend of a mixture of fly ash particles of a Class C flyash having a sulphur content determined as wt. % SO₃ of less than 5 wt. % and a blaine fineness of not more than about 5,000 cm² /g, and an unground, fine pozzolan being the product of reaction between flue gases, generated by the burning of sub-bituminous coal, with an atomized slurry of slaked lime, said fine pozzolan having a sulphur content determined as wt. % SO₃ of 5 to 25 wt. %, and a blaine fineness of 7,000 to 10,000 cm² /g, said fine pozzolan containing about 65 to 75%, by weight of an amorphous component and 25 to 35%, by weight, of a crystalline component;

said blend comprising in weight %, 70 to 90% of said fly ash and 10 to 30% of said fine pozzolan;

Portland cement particles; and

aggregate;

said Portland cement particles comprising 50 to 80%, by weight, based on the weight of said Portland cement and said pozzolanic blend, and said pozzolanic blend comprising 20 to 50%, by weight, based on the weight of said Portland cement and said pozzolanic blend;

said article having a compressive strength of at least 1000 psi.

2. A concrete article according to claim 1, wherein said pozzolan contains about 70% by weight of said amorphous component and about 30% by weight of said crystalline component.

3. A concrete article according to claim 2, wherein said amorphous component is a fly ash component and said crystalline component contains about one-third gypsum;

about one-sixth total of bassanite and calcium sulphate anhydrite;

about one-sixth portlandite and about one-third total calcium sulphite, quartz and calcite.

4. A concrete article according to claim 1, wherein said mixture comprises about 40% of a first Class C fly ash, about 40% of a second Class C fly ash and about 20% pozzolan, and has a specific gravity of 2.49 to 2.55 g/cm³ and a fineness such that 13.5 to 20% is retained on a #325 sieve, said mixture having a sulphur content, determined as wt. % SO₃ to 4 to 5%, said first Class C fly ash being characterized as follows:

space="preserve" listing-type="tabular">______________________________________ Chemical Composition Silicon dioxide (SiO.sub.2), % 36.2 Aluminum Oxide (AL.sub.2 O.sub.3), % 17.2 Iron Oxide (Fe.sub.2 O.sub.3), % 5.8 TOTAL 59.2 Calcium Oxide (CaO), % 25.4 Sulfur Trioxide (SO.sub.3), % 2.1 Alkalies as Na.sub.2 O, % 1.8 Moisture Content, % 0.06 Loss of Ignition, % 0.4 Physical Properties Fineness, +325 sieve, % 8.9 Pozzolanic Activity Index Portland Cement @ 28 days, % 99 Lime @ 7 days, psi -- Water Requirement, % 87 Soundness, % 0.09 Specific Gravity 2.63 ______________________________________

and said second Class C fly ash being characterized as follows;

space="preserve" listing-type="tabular">______________________________________ Chemical Composition Silicon dioxide (SiO.sub.2), % 33.9 Aluminum Oxide (AL.sub.2 O.sub.3), % 18.4 Iron Oxide (Fe.sub.2 O.sub.3), % 6.2 TOTAL 58.5 Calcium Oxide (CaO), % 26.7 Sulfur Trioxide (SO.sub.3), % 3.6 Alkalies as Na.sub.2 O, % -- Moisture Content, % 0.06 Loss of Ignition, % 0.2 Physical Properties Fineness, +325 sieve, % 12.7 Pozzolanic Activity Index Portland Cement @ 28 days, % 97 Lime @ 7 days, psi 1360 Water Requirement % 88 Soundness, % 0.11 Specific Gravity 2.67. ______________________________________

5. A concrete article according to claim 1, wherein said sulphur content of said fine pozzolan is 7 to 24 wt. % and said blaine fineness of said fine pozzolan is 7,250 to 9,750 cm² g.

6. A concrete article according to claim 1, wherein said sulphur content of said fine pozzolan is 12 to 20 wt. % and said blaine fineness of said fine pozzolan is 7,250 to 9,750 cm² /g.

9. A concrete article according to claim 1, wherein said blend comprises in weight %, 80% of said Class C fly ash and 20% of said fine pozzolan.

10. A concrete article according to claim 1, wherein said mixture has a sulphur content, determined as wt. %, SO₃ of 4 to 5%.

11. A concrete article according to claim 10, wherein said fly ash comprises a mixture of a first Class C flyash and a second Class C fly ash said first Class C fly ash being characterized as follows:

space="preserve" listing-type="tabular">______________________________________ Chemical Composition Silicon dioxide (SiO.sub.2), % 36.2 Aluminum Oxide (AL.sub.2 O.sub.3), % 17.2 Iron Oxide (Fe.sub.2 O.sub.3), % 5.8 TOTAL 59.2 Calcium Oxide (CaO), % 25.4 Sulfur Trioxide (SO.sub.3), % 2.1 Alkalies as Na.sub.2 O, % 1.8 Moisture Content, % 0.06 Loss of Ignition, % 0.4 Physical Properties Fineness, +325 sieve, % 8.9 Pozzolanic Activity Index Portland Cement @ 28 days, % 99 Lime @ 7 days, psi -- Water Requirement, % 87 Soundness, % 0.09 Specific Gravity 2.63 ______________________________________

and said second Class C fly ash being characterized as follows;

space="preserve" listing-type="tabular">______________________________________ Chemical Composition Silicon dioxide (SiO.sub.2), % 33.9 Aluminum Oxide (AL.sub.2 O.sub.3), % 18.4 Iron Oxide (Fe.sub.2 O.sub.3), % 6.2 TOTAL 58.5 Calcium Oxide (CaO), % 26.7 Sulfur Trioxide (SO.sub.3), % 3.6 Alkalies as Na.sub.2 O, % -- Moisture Content, % 0.06 Loss of Ignition, % 0.2 Physical Properties Fineness, +325 sieve, % 12.7 Pozzolanic Activity Index Portland Cement @ 28 days, % 97 Lime @ 7 days, psi 1360 Water Requirement % 88 Soundness, % 0.11 Specific Gravity 2.67. ______________________________________

12. A concrete article according to claim 1, having a compressive strength of at least 1350 psi.

13. A concrete article according to claim 1, having a compressive strength of at least 1700 psi.

14. A concrete article according to claim 1, comprising an autoclave cured article.

7. A concrete article according to claim 7, wherein said sulphur content of said fine pozzolan is 15 to 18 wt. % and said blaine fineness of said fine pozzolan is 7,250 to 9,750 cm² /g.

8. A concrete article according to claim 7, wherein said fine pozzolan has a specific gravity of from 2.43 to 2.53 g/cm³.

15. A concrete article comprising a mixture of 50 to 80%, by weight, Portland cement particles and 20 to 50%, by weight, of a particulate blend of fly ash particles of a Class C fly ash and an unground, fine pozzolan, being the product of reaction between flue gases, generated by the burning of sub-bituminous coal, with an atomized slurry of slaked lime, said blend comprising in weight %, 70 to 90% of said fly ash and 10 to 30% of said fine pozzolan, said pozzolan having a sulphur content determined as wt. % SO₃ of 15 to 18 wt. %, a blaine fineness of 7,250 to 9,750 cm² /g, a specific gravity of 2.43 to 2.53 g/cm³ ;

and containing about 65 to 75%, by weight of an amorphous component and 25 to 35%, by weight of crystalline component, said amorphous component being a fly ash component and said crystalline component containing about one-third gypsum; and

aggregate, said article being an autoclave cured article having a compressive strength in excess of 1700 psi;

said article having a compressive strength up to 20% higher than a corresponding article employing a Class C fly ash instead of said blend.