Hydraulic cement and method of producing same

Abstract

Ground mixtures of conventional Portland cementmaking components are mixed with relatively small amounts of boron-containing components, and the mixtures are burned at kiln temperatures substantially below those normally utilized to form clinker. The .[.resultant clinker is more easily grindable than that produced in conventional processes of Portland cement production, and the.]. cement resulting from the grinding of the clinker yields cementitious products possessing substantially higher compressive strength than is exhibited by Portland cement made from the same components in the absence of the boron-containing component.

We claim: 
     
       1. A hydraulic cement composition containing alphaprime dicalcium silicate as a hydraulically settable calcium silicate in an amount by weight of about 65 percent to about 85 percent of said composition .Iadd.and borate.Iaddend.. 
     
     
       2. A hydraulic cement composition according to claim 1 substantially free from tricalcium silicate and from beta dicalcium silicate. 
     
     
       3. A hydraulic cement composition according to claim 1 wherein the amount of free lime is less than about 2 percent by weight of said composition. 
     
     
       4. A hydraulic cement composition according to claim 1 further containing borates .Iadd.present in a 5:1, lime to boric oxide ratio on a molar basis.Iaddend.. 
     
     
       5. A hydraulic cement composition according to claim 4 wherein said borate calculated as B 2  O 2  is about 1 percent to about 3 percent by weight of said composition. 
     
     
       6. A hydraulic cement composition according to claim 5 wherein said borate is in solid solution in said alpha-prime dicalcium silicate. 
     
     
       7. A hydraulic cement composition according to claim 5 wherein said borate is B 2  O 3  in solid solution in said alpha-prime dicalcium silicate. 
     
     
       8. A Portland-type cement composition containing alpha-prime dicalcium silicate as a hydraulically settable calcium silicate in an amount by weight greater than the amount by weight of any other constituent in said composition. 
     
     
       9. A Portland-type cement composition according to claim 8 wherein said alpha-prime dicalcium silicate is about 65 percent to about 85 percent by weight of said composition. 
     
     
       10. A Portland-type cement composition according to claim 8 substantially free from tricalcium silicate and from beta dicalcium silicate. 
     
     
       11. A Portland-type cement composition according to claim 8 wherein the amount of free lime is less than about 2 percent by weight of said composition. 
     
     
       12. A Portland-type cement composition according to claim 8 further containing borate.Iadd., present in a 5:1, lime to boric oxide ratio on a molar basis.Iaddend.. 
     
     
       13. A Portland-type cement composition according to claim 12 wherein said borate calculated as B 2  O 3  is about 1 percent to about 3 percent by weight of said composition. 
     
     
       14. A Portland-type cement composition according to claim 13 wherein said borate is in solid solution in said alpha-prime dicalcium silicate. 
     
     
       15. A Portland-type cement composition according to claim 13 wherein said borate is B 2  O 3  in solid solution in said alpha-prime dicalcium silicate. 
     
     
       16. A hydraulic cement composition containing tricalcium aluminate, tetracalcium aluminoferrite and alpha-prime dicalcium silicate as hydraulically settable components .Iadd.and borate .Iaddend.and being substantially free from tricalcium silicate, and wherein said alpha-prime dicalcium silicate is present in an amount by weight greater than the amount by weight of either said aluminate or aluminoferrite. 
     
     
       17. A hydraulic cement composition according to claim 16 wherein said alpha-prime dicalcium silicate is about 65 percent to about 85 percent by weight of said composition. 
     
     
       18. A hydraulic cement composition according to claim 16 substantially free from beta dicalcium silicate. 
     
     
       19. A hydraulic cement composition according to claim 16 wherein the amount of free lime is less than about 2 percent by weight of said composition. 
     
     
       20. A hydraulic cement composition according to claim 16 further containing borate .Iadd.present in a 5:1, lime to boric oxide ratio on a molar basis.Iaddend.. 
     
     
       21. A hydraulic cement composition according to claim 20 wherein said borate calculated as B 2  O 3  is about 1 percent to about 3 percent by weight of said composition. 
     
     
       22. A hydraulic cement composition according to claim 21 wherein said borate is in solid solution in said alpha-prime dicalcium silicate. 
     
     
       23. A hydraulic cement composition according to claim 21 wherein said borate is B 2  O 3  in solid solution in said alpha-prime dicalcium silicate. 
     
     
       24. A method of making a Portland-type hydraulic cement that contains alpha-prime dicalcium silicate as a hydraulically settable calcium silicate which comprises forming an admixture of pulverized lime-containing material, silicon oxide-containing material, aluminum oxidecontaining material, iron oxide-containing material and a boron-containing substance sufficient to provide at least about 1% by weight of B 2  O 3  in said admixture, proportioning the amounts of said materials in said admixture stoichiometrically on the basis of potential tricalcium aluminate, tetracalcium aluminoferrite and alpha-prime dicalcium silicate compounds and borate at a ratio of five mols of calcium oxide per mol of B 2  O 3 , heating said admixture to fuse the components thereof into clinker and to form said alpha-prime dicalcium silicate in an amount greater than the amount of any other constituent, and grinding said clinker. 
     
     
       25. A method according to claim 24 wherein said boroncontaining substance is an oxide of boron, a compound containing an oxide of boron or a compound that yields an oxide of boron at the temperatures prevailing in a cement kiln. 
     
     
       26. A method according to claim 24 wherein said boroncontaining substance is boric acid anhydride, an acid of boric acid anhydride, a salt of boric acid anhydride, a polyboric acid, a polyborate of ammonium, sodium, potassium, calcium, barium, strontium or magnesium, a boron-containing mineral or a boroncontaining ore. 
     
     
       27. A method according to claim 24 wherein said boron-containing substance is boron trioxide, raw colemanite or refined colemanite. 
     
     
       28. A method according to claim 24 wherein the amount of said boron-containing substance as B 2  O 3  is in the range of about 1 percent to about 3 percent. 
     
     
       29. A method according to claim 24 wherein said pulverized materials are limestone, silica, alumina and iron oxide. 
     
     
       30. A method according to claim 24 wherein said admixture is heated at above about 2350° F. 
     
     
       31. A method according to claim 24 wherein said admixture is heated at below about 2750° F. 
     
     
       32. A method according to claim 24 wherein said admixture is heated at between about 2350° F. and about 2550° F. .Iadd.33. A method according to claim 24 wherein the lime content of the admixture prior to heating is about 0.5 percent in excess of theoretical. .Iaddend.