A fibrous mat-faced cementitious article comprising (a) a cementitious
core, and (b) a first fibrous mat comprising polymer or mineral fibers
and a hydrophobic finish on at least one surface thereof, wherein the
hydrophobic finish is in contact with the cementitious core, and a method
of preparing a fibrous mat-faced cementitious article, as well as a
method of preparing a water-resistant cementitious article comprising (a)
preparing an aqueous siloxane dispersion, wherein the dispersion
comprises about 4 wt. % to about 8 wt. % siloxane, (b) combining the
siloxane dispersion with a cementitious mixture to provide a cementitious
slurry, (c) depositing the cementitious slurry onto a substrate, and (d)
allowing the cementitious slurry to harden, thereby providing a
cementitious article.