Composite materials made from plant fibers bonded with portland cement and method of producing same

• US 4,406,703 A
• Filed: 12/04/1980
• Issued: 09/27/1983
• Est. Priority Date: 02/04/1980
• Status: Expired due to Term

• Current Assignee: Weyerhaeuser Company (Weyerhauser)
• Original Assignee: Permawood International Corporation
• Inventors: Guthrie, Bernard M., Torley, Robert B.
• Primary Examiner(s): Poer, James
• Application Number:
  US06/213,040
• Time in Patent Office: 1,027 Days
• Field of Search: 106/76, 106/81, 106/93, 106/99, 8/115.5, 8/116
• US Class Current: 106/731
• CPC Class Codes: B28B 1/525 containing organic fibres, e.g. wood fibres B28B1/526, B28B1/527 take precedence
• CPC Class Codes: C04B 18/26 Wood, e.g. sawdust, wood shavings
• CPC Class Codes: C04B 18/28 Mineralising; Compositions therefor
• CPC Class Codes: C04B 22/08 Acids or salts thereof C04B22/0013 takes precedence
• CPC Class Codes: C04B 24/12 Nitrogen containing compounds organic derivatives of hydrazine hydrazine C04B22/00
• CPC Class Codes: C04B 28/04 Portland cements
• CPC Class Codes: C04B 28/26 Silicates of the alkali metals
• CPC Class Codes: C04B 40/00 Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability active ingredients C04B22/00 - C04B24/00; hardening of a well-defined composition C04B26/00 - C04B28/00; making porous, cellular or lightening C04B38/00; mechanical aspects B28, e.g. conditioning the materials prior to shaping B28B17/02
• 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

The specification discloses a method of producing composite building materials from a mixture of plant fibers bonded with portland cement. Plant fibers, cement and soluble silicates in certain proportions are mixed and heated under pressure for a short period to get physically stable product that can be cured under atmospheric conditions to full strength. The plant fibers may initially be pretreated with an aqueous solution containing dichromate or permanganate ion prior to adding the cement to negate the adverse effects of set inhibiting water-soluble compounds in the fiber. Other chemicals may be added to modify the reaction and improve the product.

Claims

1. In a method of producing composite materials from plant fibers containing water-soluble compounds and portland cement the step comprising contacting the plant fibers with a material selected from the class consisting of dichromate ion and permanganate ion to substantially negate the adverse effects of the water-soluble compounds in the plant fibers on the setting of the cement.

2. A method of producing composite materials from portland cement and plant fibers containing cement set inhibiting compounds comprising:

contacting plant fibers with dichromate ion;

mixing the treated plant fibers with portland cement and water;

molding the mixture into a predetermined configuration; and

curing the molded mixture.

3. The method of claim 2 wherein the plant fibers are wood fibers.

4. The method of claim 3 wherein the plant fibers are contacted with an aqueous solution containing dichromate ion in an amount ranging from approximately 0.5% to 8% of the oven dry weight of the plant fibers.

5. The method of claim 3 wherein the ratio of portland cement to plant particles is approximately 0.5:

1 to approximately 4;

1 according to weight.

6. The method of claim 2 wherein the water to cement ratio is approximately 0.5 to approximately 2 according to weight.

7. The method of claim 2 wherein the plant fibers are contacted in an acidified aqueous solution containing dichromate ion for a period of time sufficient to permit the dichromate ion to react effectively with the cement set inhibiting compounds at or near the surface of the plant fibers.

8. The method of claim 2 wherein the fibers are contacted with a sulfite solution prior to treating them with dichromate ion.

9. The method of claim 2 wherein the plant fibers are contacted in an aqueous solution containing the dichromate ion and also containing aluminum sulfate in an amount ranging from approximately 0.5% to approximately 6% of the oven dry weight of the plant fibers.

10. The method of claim 2 and further comprising the step of adding calcium chloride to the mixture prior to molding in an amount ranging from approximately 0.5% to approximately 5% of the weight of the cement.

11. The method of claim 2 wherein triethanolamine is added to the mixture prior to molding the same.

12. The method of claim 2 wherein the mixture is molded under compression at approximately 150 psi to approximately 600 psi.

13. The method of claim 12 wherein the compression is carried out at a temperature of between about 100°

F. and 220°

F.

14. The method of claim 13 wherein the compression is carried out in a substantially saturated atmosphere.

15. The method of claim 2 wherein the fibers are western red cedar.

16. The method of claim 2 wherein the fibers are douglas fir.

17. The composite material produced by the method of claims 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or 16.

37. The method of claim 2 wherein subsequent to the step of contacting the plant fibers with dichromate ion the plant fibers are subjected to the further step of mixing the fibers with a soluble silicate present as 41°

Be aqueous solution in an amount in excess of four but less than twenty-four percent by weight of the weight of the portland cement.

18. A method of producing composite material comprising the steps of:

contacting plant fibers containing cement set inhibiting compounds with an aqueous solution containing dichromate ion in an amount ranging from approximately 0.5% to approximately 8% of the oven dry weight of the plant fibers and aluminum sulfate in an amount ranging from approximately 0.5% to approximately 6% of the oven dry weight of the plant fibers;

holding the aqueous plant fibers/dichromate/aluminum sulfate mixture for a period of time sufficient to permit the dichromate ion to react effectively with the cement set inhibiting compounds in the plant fibers;

mixing an alkaline substance into the last mentioned mixture in an amount sufficient to substantially neutralize the mixture;

mixing portland cement into the last mentioned mixture in an amount sufficient so that the ratio of portland cement to plant fibers is approximately 1;

1 to approximately 4;

1 according to weight;

molding the last mentioned mixture into a predetermined configuration; and

curing the molded mixture.

19. The method of claim 18 wherein the alkaline substance is sodium silicate.

20. The method of claim 18 wherein the ratio of water to cement in the mixture is from approximately 0.3 to approximately 2 according to weight.

21. The method of claim 18 and further comprising mixing calcium chloride into the mixture prior to molding in an amount ranging from approximately 0.5% to approximately 5% of the weight of the cement.

22. The method of claim 18 wherein triethanolamine is added to the mixture prior to molding in an amount of between 0.05 and 0.15% of the portland cement.

23. The method of claim 18 wherein the mixture is molded under compression at approximately 150 psi to approximately 600 psi.

24. The method of claim 18 wherein the plant fibers are western red cedar.

25. The method of claim 18 wherein the plant fibers are douglas fir.

27. The composite material produced by the method of claims 18, 19, 20, 21, 22, 23, 24, 25 or 26.

26. A method of producing composite material comprising the steps:

contacting plant fibers containing cement set inhibiting compounds with an aqueous solution containing dichromate ion in an amount ranging from approximately 0.5% to approximately 8% of the oven dry weight of the plant fibers and aluminum sulfate in an amount ranging from approximately 0.5% to approximately 6% of the oven dry weight of the plant fibers;

allowing the aqueous plant fibers/dichromate/aluminum sulfate mixture to stand for a period of time sufficient to permit the dichromate ion to react effectively with the cement set inhibiting compounds in the plant fibers;

mixing an alkaline substance into the last mentioned mixture in an amount sufficient to substantially neutralize the mixture;

mixing portland cement into the last mentioned mixture in an amount sufficient so that the ratio of portland cement to plant fibers is approximately 1;

0.5 to approximately 4;

1 according to weight and so that the water to cement ratio is approximately 0.5 to approximately 1.2 according to weight, and also mixing calcium chloride into the last mentioned mixture in an amount of approximately 2% of the weight of the cement;

forming the last mentioned mixture into a mat;

cutting the mat into discrete portions;

placing the mat portions between pre-heated upper and lower caul plates;

conveying the caul plates with the mat portions therebetween into a stack press;

compressing the mat portions in the stack press at a psi of from approximately 150 to approximately 600 in an atmosphere of live steam for a period of time sufficient to cause the cement to set sufficiently to prevent the plant fibers returning to their uncompressed position;

removing the upper and lower caul plates and the compressed mat portions from the stack press; and

removing the compressed mat portions from between the upper and lower caul plates.

28. In a method of producing composite materials from plant fibers and portland cement the steps of mixing together plant fiber, portland cement and a soluble silicate as 41°

Be aqueous solution in amount greater than four but less than twenty-four percent by weight, based on the weight of the cement, molding the mixture into a predetermined configuration and while maintaining said molded configuration, rapidly heating the molded mixture to a temperature in excess of 140°

F. for a period of time sufficient to effect setting of the mixture to a degree of set whereby said fibers are restrained from movement within said configuration.

29. The method of claim 28 wherein said molded configuration is heated to a temperature of between 175°

-180°

F.

30. The method of claim 28 wherein said silicate is waterglass and comprises between about eight to twenty-four percent by weight of portland cement.

31. The method of claim 30 wherein said waterglass comprises between about eight to sixteen percent by weight of the weight of the portland cement.

32. The method of claim 30 wherein said waterglass is selected from the class consisting of aqueous solutions of sodium silicate and potassium silicate.

33. The method of claim 28 wherein said fibers are contacted with acidifying agent prior to mixing with the cement and silicate.

34. The method of claim 28 wherein said fibers are contacted with dichromate ion-containing solution prior to mixing with the cement and silicate.

35. The method of claim 28 wherein said plant fibers comprise wood.

36. The method of forming a composite of plant fiber and portland cement which comprises the steps of:

contacting plant fibers with an acidifying solution,

mixing the fibers with a soluble silicate and portland cement, the silicate being present as 41°

Be aqueous solution in amount in excess of four but less than twenty-four percent by weight of the weight of portland cement,

placing the resulting mixture under pressure and submitting the same to an atmosphere of steam for a period sufficient to raise the temperature of the mixture to between 140°

F. and 200°

F.,

thereafter removing the mixture from said atmosphere and releasing the pressure,

thereby to form a substantially dimensionally stable composite of said portland cement and fibers which can cure to full strength without deformation of the composite.