Crystalline cellulose reinforced cement

1. A cement composition comprising cement and crystalline cellulose formed by a redox reaction and which are substantially pure cellulose nanocrystals (CNCs) which are substantially free of all mono-, di- and oligosaccharides.

2. The composition of claim 1 wherein the redox reaction comprises oxidation with an inorganic persulfate, a hypohalite or hydrogen peroxide.

3. The composition of claim 2 wherein the redox reaction comprises the steps of:

(a) reacting a cellulosic material in an aqueous slurry comprising a transition metal catalyst and a hypohalite solution having an initial pH greater than about 6.0 and a final pH less than about 9.0; and

(b) recovering a crystalline cellulose fraction.

4. The composition of claim 3 wherein the hypohalite comprises hypochlorite, hypoiodite, or hypobromite.

5. The composition of claim 3 wherein the reaction of step (a) is continued or repeated until the appearance of crystalline cellulose is observed.

6. The composition of claim 5 wherein the CNCs are collected and treated with an alkaline solution to remove mono-, di- and oligosaccharides.

7. The composition of claim 6 wherein the alkaline solution comprises a solution of NaOH having a pH of about 12.0.

8. The composition of claim 7 wherein the alkaline solution is heated to between about 30° C. and about 90° C. to treat the CNC.

9. The composition of claim 5 wherein the reaction is continued by adding at least one additional amount of hypohalite.

10. The composition of claim 1 comprising aggregate, an air entrainer and a superplasticizer.

11. A cement composition comprising cement and crystalline cellulose which has been treated with an alkaline solution to remove mono-, di- and oligosaccharides.

12. The composition of claim 11 wherein the alkaline solution comprises a solution of NaOH having a pH of about 12.0.

13. The composition of claim 11 wherein the alkaline solution is heated to between about 30° C. and 90° C. to treat the crystalline cellulose.

14. The composition of claim 11 , wherein the crystalline cellulose comprises nanocrystalline cellulose.

15. The composition of one of claim 11 , wherein the crystalline cellulose is produced by a redox reaction.

16. The composition of claim 15 wherein the redox reaction comprises an oxidation step using an inorganic persulfate, a hypohalite or hydrogen peroxide.

17. A method of forming a cement composition, comprising the steps of:

(a) producing crystalline cellulose nanocrystals (CNCs) by oxidizing a cellulosic material;

(b) washing the CNCs with an alkaline solution to form substantially pure CNCs substantially free of mono-, di- and oligosaccharides; and

(c) mixing the CNCs with cement.