Crystalline cellulose reinforced cement
A cementitious composition comprises cement and crystalline cellulose or nanocrystalline cellulose formed from a cellulosic material by a redox reaction.
1 . A cement composition comprising cement and substantially pure cellulose nanocrystals (CNCs) formed by a redox reaction and having a carboxyl content of about 152 mmol/kg or less.
2 . The composition of claim 1 , wherein the CNC is substantially free of all mono, di- and oligosaccharides.
3 . The composition of claim 1 , wherein the carboxyl content on the surface of the CNC is measurable by conductimetric titration.
4 . The composition of claim 1 , wherein the redox reaction comprises oxidation with an inorganic persulfate, a hypohalite or hydrogen peroxide.
5 . The composition of claim 4 , 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.
6 . The composition of claim 5 , wherein the reaction of step (a) is continued or repeated until the appearance of crystalline cellulose is observed.
7 . The composition of claim 6 , wherein the CNCs are collected and treated with an alkaline solution to neutralize surface acid groups and reduce carboxyl content.
8 . The composition of claim 7 , wherein the alkaline solution comprises a solution of NaOH having a pH of about 12.0.
9 . The composition of claim 7 , wherein the alkaline solution is heated to between about 30° C. and about 90° C. to treat the CNC.
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 reduce its carboxyl content to about 152 mmol/kg or less.
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 12 , 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), having a carboxyl content of about 152 mmol/kg or less, by oxidizing a cellulosic material; and
(b) mixing the CNCs with cement.