Disclosed herein are low density fiber cement articles, such as fiber cement building panels and sheets, comprised of multiple overlaying fiber cement substrate layers having small and uniform entrained air pockets distributed throughout. Also disclosed herein are air entrainment systems and methods for manufacturing aerated low density fiber cement panels or sheets with consistent air void content and uniform air void distribution. Also disclosed herein are air entrainment technologies adapted to work in conjunction with the Hatschek process to produce aerated fiber cement articles having controlled air void content and distribution.

A fiber cement material formulation comprising a cementitious binder, a siliceous material, fiber, alumina trihydrate and a bifunctional low density additive wherein the bifunctional low density additive comprises any one or more of diatomaceous earth, recycled autoclave fiber cement dust or cellulose dust. The fiber cement material formulation optionally further comprises a secondary low density additive which may be perlite. In some embodiments, a fiber cement article manufactured from the fiber cement material formulation comprises a density of approximately 1.1 g/cm.sup.3 or below.

A fiber cement material formulation comprising a cementitious binder, a siliceous material, fiber, alumina trihydrate and a bifunctional low density additive wherein the bifunctional low density additive comprises any one or more of diatomaceous earth, recycled autoclave fiber cement dust or cellulose dust. The fiber cement material formulation optionally further comprises a secondary low density additive which may be perlite. In some embodiments, a fiber cement article manufactured from the fiber cement material formulation comprises a density of approximately 1.1 g/cm.sup.3 or below.

The present invention provides fiber cement articles, such as roof tiles having improved impact and hail resistance and methods for making them. The fiber cement articles comprise cement, an optional filler, reinforcing fibers, such as poly(vinyl alcohol) fibers or a mixture of cellulosic and synthetic fibers, one or more core-shell aqueous emulsion polymers having a crosslinked rubbery core with a calculated glass transition temperature (calculated Tg) of from −20 to −140° C., and an at least partially grafted acrylic or vinyl shell polymer having a calculated Tg of from 20 to 170° C., and having a Z-average primary particle size of from 55 to 800 nm, or, preferably, from 140 to 650 nm. The solids weight ratio of the crosslinked rubbery core to the shell of the core-shell aqueous emulsion polymer may range from 85:20 to 97:3.

The present invention provides fiber cement articles, such as roof tiles having improved impact and hail resistance and methods for making them. The fiber cement articles comprise cement, an optional filler, reinforcing fibers, such as poly(vinyl alcohol) fibers or a mixture of cellulosic and synthetic fibers, one or more core-shell aqueous emulsion polymers having a crosslinked rubbery core with a calculated glass transition temperature (calculated Tg) of from −20 to −140° C., and an at least partially grafted acrylic or vinyl shell polymer having a calculated Tg of from 20 to 170° C., and having a Z-average primary particle size of from 55 to 800 nm, or, preferably, from 140 to 650 nm. The solids weight ratio of the crosslinked rubbery core to the shell of the core-shell aqueous emulsion polymer may range from 85:20 to 97:3.

The present invention relates to a process for providing a fiber cement product, the process comprising the steps of (a) providing an uncured fiber cement product, (b) curing the uncured fiber cement product, (c) optionally abrasive blasting of at least part of the surface of the cured fiber cement product, (d) treating the cured fiber cement product with CO2 (so-called carbonation) at a concentration of 0.01 to 100%, at a temperature of 5 to 90° C., relative humidity of to 99% for a period of 1 minute to 48 hours. The obtained fiber cement products show less efflorescence.

The present invention relates to a process for providing a fiber cement product, the process comprising the steps of (a) providing an uncured fiber cement product, (b) curing the uncured fiber cement product, (c) optionally abrasive blasting of at least part of the surface of the cured fiber cement product, (d) treating the cured fiber cement product with CO2 (so-called carbonation) at a concentration of 0.01 to 100%, at a temperature of 5 to 90° C., relative humidity of to 99% for a period of 1 minute to 48 hours. The obtained fiber cement products show less efflorescence.

The present invention relates to methods for the production of air-cured fiber cement products. More particularly, the present invention provides methods for the production of air-cured fiber cement products, at least comprising the steps of: (a) Providing cured fiber cement powder by comminuting cured fiber cement material; (b) Providing an aqueous fiber cement slurry comprising water, cementitious binder, natural or synthetic fibers and between about 5M % and about 40M % of said cured fiber cement powder; (c) Providing a green fiber cement sheet; and (d) Air-curing said green fiber cement sheet thereby providing an air-cured fiber cement product.

The present invention relates to methods for the production of air-cured fiber cement products. More particularly, the present invention provides methods for the production of air-cured fiber cement products, at least comprising the steps of: (a) Providing cured fiber cement powder by comminuting cured fiber cement material; (b) Providing an aqueous fiber cement slurry comprising water, cementitious binder, natural or synthetic fibers and between about 5M % and about 40M % of said cured fiber cement powder; (c) Providing a green fiber cement sheet; and (d) Air-curing said green fiber cement sheet thereby providing an air-cured fiber cement product.

The present invention relates to colored fiber cement products at least comprising: —a cementitious matrix comprising a black pigment and/or a colored pigment, and —synthetic fibers, characterized in that said synthetic fibers are pigmented with at least one white pigment. The present invention further relates to methods for the production of these colored fiber cement products as well as to uses thereof in the building industry.