Fiberglass mesh scrim reinforced cementitious board system

Abstract

A cementitious board system which is reinforced on its opposed surfaces by an improved glass fiber mesh scrim with thicker yarn and larger mesh openings to provide a cementitious board with improved handling properties while retaining tensile strength and long term durability. The fabric is constructed as a mesh of high modulus strands of bundled glass fibers encapsulated by alkali and water resistant material, e.g. a thermoplastic material. The composite fabric also has suitable physical characteristics for embedment within the cement matrix of the panels or boards closely adjacent the opposed faces thereof. The fabric provides a board system with long-lasting, high strength tensile reinforcement and improved handling properties regardless of their spatial orientation during handling. Included as part of the invention are methods for making the reinforced board.

1 - 13 . (canceled) 
     
     
         14 . A method of reinforcing a cementitious board system to provide a cement board with improved strength, nail pull strength and handling properties, comprising providing a core layer of cementitious material, the core layer having opposed planar surfaces and opposed edges, and at least one outer layer of alkali resistant fiberglass mesh scrim reinforcement embedded within the opposed planar surfaces, comprising:
 applying a fiberglass mesh scrim to the upper and lower surfaces of a core cementitious slurry by pouring the cementitious slurry through the mesh scrim to coat and embed the entire mesh scrim in the cementitious slurry before the slurry is dried;   wherein the fiberglass mesh scrim has between about 4×4 to about 6×6 strand of fiberglass fiber per inch of the mesh construction in both the longitudinal and transverse directions, respectively, and the fiberglass mesh is made from a coated fiberglass yarn, the yarn in an uncoated state has a nominal density of about 3700 to 5000 linear yards per pound of the fiberglass yarn; and   the coated yarn comprises 40-65 wt. % coating on a dry basis;   wherein the cementitious material comprises:   25 to 60 wt. %, on a wet basis, cementitious reactive powder comprising Portland cement,   10 to 40 wt. % water,   1 to 70 wt. %, on a wet basis, of filler;   optional additive selected from at least one member of the group consisting of water reducing agents, chemical set-accelerators, chemical set-retarders, air-entraining agents, foaming agents, shrinkage control agents, coloring agents, viscosity modifying agents and thickeners, and internal curing agents; and   the coating comprising alkali resistant polymer, wherein the yarn comprises 35-60 wt. % of said coating on a dry basis;   wherein the system has improved handling properties compared to prior cement board systems in allowing for deeper penetration and improved bonding of the mesh scrim to the core layer to proved a stronger bond between the cementitious core and the mesh scrim to prevent delamination, and   wherein the cement board system only needs to be scored once on each planar surface to allow for easy snapping of the cement board along the score line during installation of the cement board.   
     
     
         15 . The method of  claim 14 , wherein the filler comprises 1 to 10 wt of an expanded and chemically coated water tight and water repellant perlite filler. 
     
     
         16 . The method of  claim 14 , wherein the cementitious material also comprises about 0 to about 50 vol. %, on a wet basis, entrained air. 
     
     
         17 . The method of  claim 14 , wherein the cementitious reactive powder comprises, on a dry basis, about 25 to 100 wt. % Portland cement and 0 to 75 wt. % fly ash based on the sum of the Portland cement and fly ash. 
     
     
         18 . The method of  claim 14 , wherein the cementitious reactive powder comprises, on a dry basis, about 40 to 80 wt. % Portland cement, 0 to 20 wt. % high alumina cement, 0 to 7 wt. % calcium sulfate, 0 to 55 wt. % fly ash, based on the sum of the Portland cement, high alumina cement, calcium sulfate and fly ash. 
     
     
         19 . The method of  claim 14 , wherein the cementitious reactive powder comprises:
 35-60 wt. %, on a wet basis, cementitious reactive powder comprising Portland cement and optionally a pozzolanic material,   2-10 wt. %, on a wet basis, expanded and chemically coated water tight and water repellant perlite filler,   20-40 wt. % water,   10-50 vol. %, on a wet basis, entrained air,   optional additive selected from at least one member of the group consisting of water reducing agents, chemical set-accelerators, chemical set-retarders, air-entraining agents, foaming agents, shrinkage control agents, coloring agents, viscosity modifying agents and thickeners, and internal curing agents; and   10-25 wt. % secondary fillers selected from at least one member of the group consisting of expanded clay, shale aggregate, pumice, blast furnace slag, volcanic tuff, sand, expanded shale, expanded perlite, hollow ceramic spheres, hollow plastic spheres, expanded plastic beads, and mixtures thereof;   wherein the total of expanded and chemically coated perlite filler and secondary fillers is at least 20 wt. %.   
     
     
         20 . The method of  claim 14 , wherein at least one outer layer of fiberglass mesh reinforcement is on one pair of the opposed edges of the core, and
 wherein the fiberglass mesh scrim has a 4.0×4.0 strands per inch construction in both the lateral and transverse directions, and   wherein the fiberglass mesh is made with a fiberglass yarn, the yarn in an uncoated state has a nominal density of about 3700 linear yards per pound of the fiberglass yarn.   
     
     
         21 . The method of  claim 14 , wherein the fiberglass mesh is made from fiberglass yarn coated with an alkali resistant coating selected from the group consisting of wax, polyvinyl chloride, polyvinyl alcohol, polyvinyl acetate, polyester, acrylics, acrylonitrile, silicones, styrene-butadiene, polypropylene, epoxy and polyethylene and mixtures thereof. 
     
     
         22 . A method of making a reinforced cementitious board system with improved strength, nail pull strength and handling properties comprising a core layer of cementitious material having opposed planar surfaces and opposed edges, and at least one outer layer of an alkali resistant fiberglass mesh scrim reinforcement embedded in the opposed planar surfaces of the core layer, and optionally said at least one outer layer of said fiberglass mesh reinforcement on one pair of the opposed edges of the core, comprising the steps of:
 providing a core layer of cementitious material, the core layer having opposed planar surfaces and opposed edges, and at least one outer layer of alkali resistant fiberglass mesh scrim reinforcement embedded within the opposed planar surfaces, comprising:   applying a fiberglass mesh scrim to the upper and lower surfaces of a core cementitious slurry by pouring the cementitious slurry through the mesh scrim to coat and embed the entire mesh scrim in the cementitious slurry before the slurry is dried;   wherein the fiberglass mesh scrim has between about 4×4 to about 6×6 strands of fiberglass fiber per inch of the mesh construction in both the longitudinal and transverse directions, respectively, the mesh is covered on its entire surface by pouring the cementitious slurry through the mesh scrim to coat and embed the mesh scrim in the slurry, and the fiberglass mesh is made from a coated fiberglass yarn, the yarn in an uncoated state has a nominal density of about 3700 to 5000 linear yards per pound of the fiberglass yarn; and   the coated yarn comprises 40-65 wt. % coating comprising alkali resistant polymer and 35-60 wt % fiberglass yarn on a dry basis;   wherein the cementitious material comprises:
 25 to 60 wt. %, on a wet basis, cementitious reactive powder comprising Portland cement, 
 10 to 40 wt. % water, 
 1 to 70 wt. %, on a wet basis, of filler, 
 optional additive selected from at least one member of the group consisting of water reducing agents, chemical set-accelerators, chemical set-retarders, air-entraining agents, foaming agents, shrinkage control agents, coloring agents, viscosity modifying agents and thickeners, and internal curing agents; and 
   the coating comprising alkali resistant polymer,   wherein the yarn comprises 35-60 wt. % of said coating on a dry basis,   wherein the system allows for bonding of the mesh scrim to the core layer with a bond strength of 30 to 52 lbs between the cementitious core and the mesh scrim to prevent delamination compared to an identical core layer with an 8×8 strand fiberglass scrim construction which has a bond strength of 20 to 25 lbs,   wherein the cement board system only needs to be scored once on each planar surface to allow for easy snapping of the cement board along the score line during installation of the cement board, compared to two scores required on each planar surface for easy snapping of the cement board along the score lines during installation of a cement board having a 8×8 strand per inch fiberglass scrim, and   wherein the mesh scrim is embedded between about 0.03 to about 0.06 inches into at least one said planar surface of the cement core layer.   
     
     
         23 . The method of  claim 22 , wherein 1 to 10 wt % of the filler is an expanded and chemically coated water tight and water repellant perlite filler. 
     
     
         24 . The method of  claim 22 , wherein about 0 to 50 vol. %, on a wet basis, of the cementitious material is entrained air. 
     
     
         25 . The method of  claim 22 , wherein the cementitious reactive powder comprises, on a dry basis, about 25 to 100 wt. % Portland cement and 0 to 75 wt. fly ash based on the sum of the Portland cement and fly ash. 
     
     
         26 . The method of  claim 22 , wherein at least one outer layer of fiberglass mesh reinforcement is on one pair of the opposed edges of the core,
 wherein the fiberglass mesh scrim has a 4.0×4.0 strands per inch construction in both the lateral and transverse directions, and   wherein the fiberglass mesh is made with a fiberglass yarn, the yarn in an uncoated state has a nominal density of about 3700 linear yards per pound of the fiberglass yarn.   
     
     
         27 . The method of  claim 22 , wherein the fiberglass mesh is made from fiberglass yarn coated with an alkali resistant coating selected from the group consisting of wax, polyvinyl chloride, polyvinyl alcohol, polyvinyl acetate, polyester, acrylics, acrylonitrile, silicones, styrene-butadiene, polypropylene, epoxy and polyethylene and mixtures thereof.