Synthetic class C fly ash and use thereof as partial cement replacement in general purpose concrete

• US 4,992,102 A
• Filed: 08/08/1988
• Issued: 02/12/1991
• Est. Priority Date: 08/08/1988
• Status: Expired due to Term

• Current Assignee: Lafarge North America Incorporated (Holcim Limited)
• Original Assignee: Ronald L. Barbour
• Inventors: Barbour, Ronald L.
• Primary Examiner(s): Chaudhuri, Olik
• Assistant Examiner(s): Griffis, Andrew
• Application Number:
  US07/229,454
• Time in Patent Office: 918 Days
• Field of Search: 106/89, 106/DIG. 1, 106/645
• US Class Current: 106/645
• CPC Class Codes: C04B 18/08 Flue dust , i.e. fly ash
• CPC Class Codes: C04B 18/162 Cement kiln dust; Lime kiln dust
• CPC Class Codes: C04B 28/04 Portland cements
• CPC Class Codes: C04B 40/06 Inhibiting the setting, e.g. mortars of the deferred action type containing water in breakable containers ; Inhibiting the action of active ingredients
• CPC Class Codes: C04B 7/26 from raw materials containing flue dust , i.e. fly ash C04B7/243 takes precedence
• CPC Class Codes: Y02P 40/10 Production of cement, e.g. improving or optimising the production methods; Cement grinding
• CPC Class Codes: Y02W 30/91 Use of waste materials as fillers for mortars or concrete
• CPC Class Codes: Y10S 106/01 Fly ash

Abstract

A synthetic Class C fly ash results from a substantially homogeneous blend of about 40-60% by weight of a Class F fly ash and about 60-40% by weight of cement kiln dust (CKD). This new fly ash can replace about 25-50% by weight of portland cement in conventional formulations with coarse and fine aggregate for making general purpose concrete and particularly ready-mix concrete with comparable compressive strength and like properties.

Claims

1. In a settable composition for producing general purpose concrete which comprises per cubic yard of the concrete to be produced an admixture of about 400-750 lbs. Portland cement, about 1600-2000 lbs. coarse aggregate of a size of at least about 3/8 inch, and sufficient fine aggregate of a size less than 3/8 and minor amounts of optional additives to yield one cubic yard when the admixture is combined with water equal to about 40-70% by weight of said cement, the improvement wherein more than about 25% up to about 50% by weight but not more than about 200 lbs. of said Portland cement is replaced with a homogeneous blend of (a) a fly ash having a combined content of silica, alumina and ferric oxide exceeding 70% and a calcium oxide content of less than 10% and (b) cement kiln dust, said blend having a combined content of silica, alumina and ferric oxide higher than about 50% but less than about 70% and a calcium oxide content higher than 10%.

2. The composition of claim 1 wherein said coarse aggregate has a size up to about 1".

3. The composition of claim 1 wherein said blend replaces at least about 30% of said Portland cement.

6. The composition of claim 1, wherein said blend contains about 40-60% by weight of said fly ash and about 40-60% by weight of said cement kiln dust.

7. The composition of claim 1, wherein said fine aggregate is graduated in size from about #100 up to about #4 sieve size and said coarse aggregate is graduated in size from abut 3/8" up to at least about 3/4" size.

4. A synthetic class C fly ash consisting essentially of a substantially homogeneous blend of about 40-60% by weight of (a) class F fly ash containing at least about 70% by weight of silica, alumina, and ferric oxide together and less than about 10% calcium oxide and (b) 60-40% by weight of cement kiln dust, said blend containing less than 70% of silica, alumina and ferric oxide together and more than 10% of calcium oxide.

5. The synthetic fly ash of claim 4 wherein said class F fly ash contains more than 80% combined weight of silica, alumina, and ferric oxide.

8. In the method of making general purpose concrete which comprises the steps of mixing concrete-making ingredients comprising 400-750 lbs. Portland cement, about 1600-2000 lbs. coarse aggregate of a size of at least about 3/8 inch, and sufficient fine aggregate of a size less than 3/8 and minor amounts of optional additional additives to yield one cubic yard when the admixture is combined with water equal to about 40-70% by weight of said cement, the improvement of replacing at least about 25% up to about 50% by weight but not more than about 200 lbs. of said Portland cement with the synthetic class C fly ash of claim 4.

9. The method of claim 8, wherein said fine aggregate is graduated in size from about #100 up to about #4 sieve size and said coarse aggregate is graduated in size from abut 3/8" up to at least about 3/4 size.