Cementitious materials

1. A granulated hydrophobing additive for rendering cementitious material hydrophobic, comprising an organosilicon component and a binder polymer deposited on a particulate carrier so as to form a film, characterised in that an emulsifier for the organosilicon component is deposited on the particulate carrier together with the organosilicon component and the binder polymer, wherein the organosilicon component comprises a dialkoxysilane and/or a trialkoxysilane, and the particulate carrier comprises zeolite, wherein the film comprises the binder polymer.

2. A granulated hydrophobing additive according to claim 1 , characterised in that the emulsifier is a water-soluble polymer.

3. A granulated hydrophobing additive according to claim 1 , characterised in that the binder polymer is a water-insoluble polymer.

4. A granulated hydrophobing additive according to claim 3 , characterised in that the emulsifier comprises polyvinyl alcohol and the binder polymer comprises polyvinyl alcohol and polyvinyl acetate.

5. A granulated hydrophobing additive according to claim 1 , characterised in that the organosilicon component further comprises an organopolysiloxane.

6. A granulated hydrophobing additive according to claim 5 , characterised in that the organopolysiloxane comprises polydimethylsiloxane.

7. A granulated hydrophobing additive according to claim 5 , characterised in that the organopolysiloxane comprises methylalkylsiloxane units in which the alkyl group contains 2-20 carbon atoms.

8. A granulated hydrophobing additive according to claim 7 , characterised in that the organopolysiloxane comprises alkyl groups bearing a trialkoxysilyl moiety.

9. A granulated hydrophobing additive according to claim 5 , characterised in that the organopolysiloxane comprises a condensation product of a trialkoxysilane.

10. A granulated hydrophobing additive according to claim 1 , characterised in that the organosilicon component comprises a trialkoxysilane of the formula ZSi(OZ′) 3 in which Z represents an alkyl, substituted alkyl, aryl or substituted aryl group having 1 to 20 carbon atoms and each Z′ represents an alkyl group having 1 to 6 carbon atoms.

11. A granulated hydrophobing additive according to claim 10 , characterised in that Z represents an alkyl group having 6 to 18 carbon atoms and each Z′ represents an alkyl group having 1 or 2 carbon atoms.

12. A granulated hydrophobing additive according to claim 1 , characterised in that the carrier has a mean particle size of 0.2 to 50μm.

13. A granulated hydrophobing additive for cementitious material prepared by the process of applying an organosilicon component and a binder polymer to a particulate carrier from aqueous emulsion so as to form a film, wherein the organosilicon component comprises a dialkoxysilane and/or a trialkoxysilane, and wherein the particulate carrier comprises zeolite, and wherein the film comprises the binder polymer.

14. A cementitious material in powder form, comprising dry cement and a granulated hydrophobing additive as defined in claim 1 in an amount sufficient to give from 0.01 to 2% by weight of the organosilicon component based on the weight of the dry cement.

15. A process for imparting to cementitious material a hydrophobic character, comprising mixing into the cementitious material a granulated hydrophobing additive as defined in claim 1 .

16. A granulated hydrophobing additive for rendering cementitious material hydrophobic as defined in claim 1 , wherein the binder polymer comprises polyvinyl alcohol and the emulsifier comprises polyvinyl alcohol.

17. A granulated hydrophobing additive for rendering cementitious material hydrophobic, comprising an alkoxysilane, an organopolysiloxane, a binder comprising polyvinyl alcohol, and a particulate carrier comprising zeolite, characterised in that an emulsifier for the organosilicon component is deposited on the particulate carrier together with the alkoxysilane, the organopolysiloxane and the binder, wherein the binder forms a film.

18. A granulated hydrophobing additive according to claim 1 , wherein:

the organosilicon component is present in an amount ranging from 5 to 35 wt. %;

the binder polymer is present in an amount ranging from 1 to 10 wt. %; and

the particulate carrier is present in an amount ranging from 50 to 85 wt. %, all based on the total weight of the granulated hydrophobing additive.