Hydrophobic finish compositions with extended flow time retention and building products made thereof

A mat-faced cementitious board comprising:

• a cementitious core;
• a fibrous mat having a first inner surface facing at least one face of the cementitious core, and a second opposite outer surface, wherein the fibrous mat comprises a glass mat substrate having non-woven glass fibers, a uniformly distributed binder comprising a first polymer binder but no inorganic filler, and a binder coating comprising a second polymer binder and inorganic filler, wherein the inorganic filler is selected from at least one member of the group consisting of inorganic pigment and inorganic binder,
• the binder coating is present in an amount of about 40 lbs./MSF to about 165 lbs./MSF to overlay the fibrous mat comprising the uniformly distributed binder,
• the fibrous mat having opposed first and second sides,
• wherein the binder coating uniformly penetrates the glass mat substrate from the first side of the coated glass mat substrate to a depth which is a fraction of the thickness of the coated glass mat substrate;
• and
• a layer of hydrophobic finish composition to overlay the first side of the fibrous mat comprising the uniformly distributed binder and the binder coating comprising;
• (i) hydraulic component comprising fly ash, the fly ash comprising Class C fly ash in an amount from about 50% to about 85% by weight of the hydrophobic finish composition on a water inclusive basis;
• (ii) film-forming polymer in an amount of about 5% to about 25% by weight of the hydrophobic finish composition on a water inclusive basis;
• and
• (iii) an extended flow time retention agent comprising at least one member of the group consisting of carboxylic acids, salts of carboxylic acids, and mixtures thereof,
• wherein said carboxylic acids have the chemical formula (II):
• wherein R is an organofunctional group;
• wherein the salts of carboxylic acid have the chemical formula (III)
• wherein R is as defined in formula (II) and X+ is a cation,
• wherein the extended flow time retention agent is in an amount of 0.05% to 1.00% by weight of the hydrophobic finish composition on a dry basis;
• wherein the layer of the hydrophobic finish composition adheres to the first side of the fibrous mat having the uniformly distributed binder and coated with the binder coating and the cementitious core adheres to the opposed second side of the fibrous mat, wherein at least a portion of the binder coating is between the glass mat substrate having the uniformly distributed binder and the layer of hydrophobic finish composition, and
• wherein penetration of the binder coating into the glass mat substrate thickness is 10 percent to 75 percent.