Patent Publication Number: US-9840845-B2

Title: Building product including a metal carbonate and a process of forming the same

Description:
This application claims priority to and benefit of U.S. Provisional Patent Application No. 61/701,074, filed Sep. 14, 2012, which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure relates to building products and methods of forming building products, and more particularly to, building products including metal carbonates and processes of forming the same. 
     RELATED ART 
     Synthetic roofing shingle or tile can include a core material formed of generally less expensive material, and a skin material disposed on a plurality of surfaces of the shingle or tile. The skin material is generally more expensive and has weather-withstanding qualities. Further improvements in such shingles, tiles, and other building products are desired. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments are illustrated by way of example and are not limited in the accompanying figures. 
         FIG. 1  includes an illustration of a cross-sectional view of a portion of a mould after forming an exterior layer of a partially-formed building product within a cavity of the mould. 
         FIG. 2  includes an illustration of a cross-sectional view of the mould and exterior layer after forming an interior layer within the cavity of the mould. 
         FIG. 3  includes an illustration of a cross-sectional view of the mould and exterior layer after reacting the interior layer to form a metal carbonate in accordance with an embodiment. 
         FIG. 4  includes an illustration of a cross-sectional view of a substantially completed building product after removing the building product from the mould. 
         FIG. 5  includes an illustration of a cross-sectional view of a substantially completed building product in accordance with another embodiment. 
         FIG. 6  includes an illustration of a cross-sectional view of a substantially completed building product in accordance with a further embodiment. 
         FIG. 7  includes an illustration of a cross-sectional view of a substantially completed building product in accordance with still a further embodiment. 
         FIG. 8  includes an illustration of a cross-sectional view of a building that includes one or more building products in accordance with any of the embodiments described herein. 
     
    
    
     Skilled artisans appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the invention. 
     DETAILED DESCRIPTION 
     The following description in combination with the figures is provided to assist in understanding the teachings disclosed herein. The following discussion will focus on specific implementations and embodiments of the teachings. This focus is provided to assist in describing the teachings and should not be interpreted as a limitation on the scope or applicability of the teachings. 
     Before addressing details of embodiments described below, some terms are defined or clarified. When referring to an average diameter distribution, “D” followed by a number refers to percentile of the distribution that is less than an average diameter. For example, D10 of 1 micron means that 10% of the particles have an average diameter of 1 micron or smaller. 
     Except for atmospheric pressure, all pressures described herein are gauge pressures unless explicitly stated otherwise. 
     The term “rare earth,” within respect to the elements of the Period Table of the Elements, is intended to mean Sc, Y, La, and the lanthanide series. 
     As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a method, article, or apparatus that comprises a list of features is not necessarily limited only to those features but may include other features not expressly listed or inherent to such method, article, or apparatus. Further, unless expressly stated to the contrary, “or” refers to an inclusive-or and not to an exclusive-or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present). 
     Also, the use of “a” or “an” is employed to describe elements and components described herein. This is done merely for convenience and to give a general sense of the scope of the invention. This description should be read to include one or at least one and the singular also includes the plural, or vice versa, unless it is clear that it is meant otherwise. For example, when a single item is described herein, more than one item may be used in place of a single item. Similarly, where more than one item is described herein, a single item may be substituted for that more than one item. 
     Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The materials, methods, and examples are illustrative only and not intended to be limiting. To the extent not described herein, many details regarding specific materials and processing acts are conventional and may be found in textbooks and other sources within the roofing product arts and corresponding manufacturing arts. 
     A building product can include a first layer having a first material and a second layer having a second material and a third material that includes a metal carbonate. The first material can be different from the second material, and the second and third materials can include the same metal element. The first layer can be an exterior layer that is normally visible to humans, and the second layer can be an interior layer that is not normally visible to humans once the building product is installed. When forming the building product, the first and second layer can be formed and a fluid can infiltrate into pores of the second layer and react with the second material to form the third material. 
     The building product can be used in a variety of applications within a building. The building product may be a roofing product, cladding, a framing member, or another suitable application in which the building product is exposed to the outdoors. In another embodiment, the building product may be used along a wall, floor, or ceiling, or another suitable interior application. 
     The building product may be formed by a green process, that is, one in which atmospheric CO 2  or another greenhouse gas can be captured to form carbonic acid or a carbonate form, and thus, the process can be used to reduce CO 2  in the atmosphere and form a stable metal carbonate that is not readily converted back to CO 2  in normal use of the building product. Additional benefits can include using a less expensive or less visibly appealing material for the second layer and convert it to a compound that is more weather resistant, durable, has another desirable property, or any combination thereof. Additionally, a low density filler material or void containing filler material can be included in one or more layers to moderate the density of the building product. 
     Exemplary processes and products are illustrated in the figures and described below. The particular embodiments are merely illustrative and are not intended to limit the scope of the claims. After reading the specification, skilled artisans will appreciate that other embodiments not described herein can be used without departing from the scope of the invention. 
     In a particular embodiment, a process can use a mould to assist in forming the building product.  FIG. 1  includes a cross-sectional view of a portion of a mould  100  that includes a cavity  102 . The shape of the cavity  102  can correspond to the shape of the building product that is being formed. The surface of the mould  100  along the cavity  102  can have a smooth surface, a matte surface, a feature, or any combination thereof. An exterior surface of the building product being formed will have a relief feature, a cosmetic feature, another suitable feature, or any combination thereof. An exterior layer  104  is formed along the exposed surfaces of the cavity  102 . In a particular embodiment, the exterior layer  104  will be visible to humans when the building product is installed. If a feature is present within the cavity, the exterior layer  104  may completely cover or only partly cover the feature within the cavity  102 . The significance of completely or only partly covering the feature is described in more detail after formation of the building product is completed. The exterior layer  104  only partly fills and does not completely fill the cavity  102 . 
     The exterior layer  104  may be applied as a coating, a paste, pressed into place, or using another technique. If needed or desired, volatile or organic components within the exterior layer  104  may be driven off or otherwise removed before forming another layer within the cavity  102 . 
       FIG. 2  includes an illustration after an interior layer  204  (also referred to as the unreacted interior layer  204 ) is formed within the cavity  102 . In the embodiment as illustrated, the interior layer  204  completely fills a remaining portion of the cavity  102 . In another embodiment, the interior layer  204  may only partly fill and not completely fill the remaining portion of the cavity  102 . The interior layer  204  can be applied using any of the techniques as described with respect to the exterior layer  104 . In an embodiment, the interior layer  204  can be formed by using a solid material and compressing the solid material into the cavity  102 . In a particular embodiment, vibratory compaction can be used. 
     A volume occupied by the interior layer  204  may be larger than a volume occupied by the exterior layer  104 . In an embodiment, a ratio of the volume of the interior layer  204  to the volume of the exterior layer  104  occupies a volume that is at least approximately 1.1:1, at least approximately 1.5:1, at least approximately 2:1, at least approximately 3:1, at least approximately 5:1, or at least approximately 9:1. 
     On a comparative basis, the exterior layer  104  and the interior layer  204  are different from one another. The layers  104  and  204  can have the substantially the same composition but different open porosities or different average diameters. In another embodiment, layers  104  and  204  have different compositions. A material within the interior layer  204  will react with a carbonate to form a metal carbonate. The carbonate may or may not react with a material within the exterior layer  104 . In a further embodiment, the layers  104  and  204  may have different compositions, different porosities, different average diameters, or any combination thereof. Exemplary materials within the interior layer  204  will be described before describing materials for the exterior layer  104 . 
     The interior layer  204  may include a matrix and corresponding pores. Exemplary materials can include a metal oxide, a metal hydroxide, a metal sulfate, a metal silicate, a metal halide, another suitable metal compound, or any combination thereof. Each of the metal compounds can be a single metal element compound or a mixed-metal compound. 
     An exemplary metal oxide can include beryllium (for example, BeO), magnesium (for example, MgO), calcium (for example, CaO or CaO 2 ), strontium (for example, SrO), barium (for example, BaO), scandium (for example, Sc 2 O 3 ), yttrium (for example, Y 2 O 3 ), lanthanum (for example, La 2 O 3 ), neodymium (for example, Nd 2 O 3 ), any of the other lanthanide series oxides, any of the other actinide series oxides, titanium (for example, TiO, TiO 2 , or Ti 2 O 3 ), zirconium (for example, ZrO 2 ), hafnium (for example, HfO 2 ), vanadium (for example, VO, V 2 O 3 , VO 2 , or V 2 O 5 ), niobium (for example, NbO 2  or Nb 2 O 5 ), tantalum (for example, TaO 2  or Ta 2 O 5 ), chromium (for example, CrO, Cr 2 O 3 , CrO 3 , or CrO 2 ), molybdenum (for example, MoO 2 , Mo 2 O 5 , Mo 2 O 3  or MoO 3 ), tungsten (for example, WO 2  or W 2 O 5 ), manganese (for example, MnO, Mn 2 O 3 , MnO 2 , or Mn 2 O 7 ), technetium (for example, Tc 2 O or Tc 2 O 3 ), rhenium (for example, ReO 2  or Re 2 O 3 ), iron (for example, FeO or Fe 2 O 3 ), cobalt (for example, CoO, Co 2 O 3 , or Co 3 O 4 ), nickel (for example, NiO or Ni 2 O 3 ), ruthenium (for example, RuO 2  or RuO 4 ), rhodium (for example, RhO 2  or Rh 2 O 3 ), palladium (for example, PdO or PdO 2 ), osmium (for example, OsO or OsO 2 ), iridium (for example, IrO 2  or IR 2 O 3 ), platinum (for example, PtO, PtO 2 , PtO 3 , Pt 2 O 3 , or Pt 3 O 4 ), copper (for example, CuO, Cu 2 O), silver (for example, Ag 2 O), gold (for example, Au 2 O 3  or Au 2 O), zinc (for example, ZnO), aluminum (for example, Al 2 O 3 ), gallium (for example, Ga 2 O 3  or Ga 2 O), indium (for example, In 2 O 3 ), germanium (for example, GeO, GeO 2 ), tin (for example, SnO, SnO 2 ), lead (for example, PbO, PbO 2 , Pb 3 O 4 , Pb 2 O 3 , or Pb 2 O), antimony (for example, Sb 2 O 3  or Sb. 2 O 5 ), bismuth (for example, Bi 2 O 3 , Bi 2 O 5 , Bi 2 O 4 , Bi 2 O 3 , or BiO), a magnesium titanate (for example, MgTiO 3 ), a calcium titanate (for example, CaTiO 3 ), a strontium titanate (for example, SrTiO 3 ), a barium titanate (for example, BaTiO 3 ), a doped or partially substituted oxide (for example, Ca x Sr (1-x) TiO 3  or BaTi y La (1-y) O 3 ), another suitable metal oxide capable of forming a metal carbonate or any combination thereof. 
     In another embodiment, the metal hydroxide can include a magnesium hydroxide (for example, Mg(OH) 2 ), a calcium hydroxide (for example, Ca(OH) 2 ), a strontium hydroxide (for example, Sr(OH) 2 ), a barium hydroxide (for example, Ba(OH) 2 ), a titanium hydroxide (for example, Ti(OH) 2 ), a zirconium hydroxide (for example, Zr(OH) 4 ), a chromium hydroxide (for example, Cr(OH) 2 ), a manganese hydroxide (for example, Mn(OH) 2 ), an iron hydroxide (for example, Fe(OH) 2 ), a copper hydroxide (for example, Cu(OH) 2 ), a zinc hydroxide (for example, Zn(OH) 2 ), an aluminum hydroxide (for example, Al(OH) 3 ), or any combination thereof. 
     The metal sulfate can include MgSO 4 , CaSO 4 , SrSO 4 , BaSO 4 , a titanium sulfate (for example, TiSO 4  or Ti 2 (SO 4 ) 3 ), ZrSO 4 ), a chromium sulfate (for example, Cr 2 (SO 4 ) 3 ), a manganese sulfate (for example, MnSO 4 ), an iron sulfate (for example, FeSO 4 ), a nickel sulfate (for example, NiSO 4 ), a copper sulfate (for example, CuSO 4 ), ZnSO 4 ), Al 2 (SO 4 ) 3 ), another suitable metal sulfate capable of forming a metal carbonate, or any combination thereof. 
     The metal silicate can include a lithium metasilicate, a lithium orthosilicate, a sodium metasilicate, a beryllium silicate, a calcium silicate, a strontium orthosilicate, a barium metasilicate, a zirconium silicate, a manganese metasilicate, an iron silicate, a cobalt orthosilicate, a zinc orthosilicate, a cadmium metasilicate, a mullite, a rare earth oxyorthosilicate, a rare earth pyrosilicate, andalusite, silimanite, hyanite, kaolinite, or any combination thereof. 
     The metal halide can be a metal fluoride including MgF 2 , CaF 2 , SrF 2 , BaF 2 , a titanium fluoride (for example, TiF 3 ), a zirconium fluoride (for example, ZrF 4 ), a chromium fluoride (for example, CrF 2 ), a manganese fluoride (for example, MnF 2 ), an iron fluoride (for example, FeF 2 ), a copper fluoride (for example, CuF 2 ), a nickel fluoride (for example, NiF 2 ), ZnF 2 , AlF 3 ), a mixed-metal halide (for example, La x Ce( 1-x )Br 3  or Lu y Ce( 1-y )Cl 3 ), another suitable metal halide capable of reacting to form a metal carbonate, or any combination thereof. Alternatively, the anion of the metal salts may come, for example, from the following groups: hydroxides, nitrates, chlorides, acetates, formates, propionates, phenylacetates, benzoates, hydroxybenzoates, aminobenzoates, methoxybenzoates, nitrobenzoates, sulfates, fluorides, bromides, iodides, carbonates, oxalate, phosphate, citrate, and silicates, or mixtures thereof. 
     The exterior layer  104  can include any of the materials as described with respect to the interior layer  204 . Further, the exterior layer  204  can include pigments, colorants, antimicrobials, photocatalysts or other components to modify the appearance and aesthetics of the exterior layer or its functionality. 
     The exterior layer  104 , the interior layer  204 , or both may include a low density filler material or void containing filler material to moderate the density of the building product. Examples of such materials can include hollow glass microspheres, hollow ceramic microspheres, polymer microspheres, expanded perlite, volcanic ash, pumice, another suitable material, or any combination thereof. Such materials may or may not participate in the carbonation reaction described herein. 
     A material within the exterior layer  104  can have an average diameter, and a material within the interior layer  204  can a different average diameter. The average diameter of the material within the exterior layer  104  is no greater than approximately 95%, no greater than approximately 90%, no greater than approximately 80%, no greater than approximately 70%, no greater than approximately 50%, or no greater than approximately 20% of the average diameter of the material within the interior layer  204 . 
     In an embodiment, the material of the interior layer  204  has a D10 average diameter of at least approximately 0.001 microns, at least approximately 0.015 microns, at least approximately 0.11 microns, or at least approximately 1 micron, and in another embodiment, the D10 average diameter is no greater than approximately 300 microns, no greater than approximately 9 microns, no greater than approximately 0.7 microns, or no greater than approximately 0.01 microns. In an embodiment, the material of the interior layer  204  has a D50 average diameter of at least approximately 0.1 microns, at least approximately 0.7 microns, at least approximately 3 microns, or at least approximately 10 microns, and in another embodiment, the D50 average diameter is no greater than approximately 500 microns, no greater than approximately 60 microns, no greater than approximately 11 microns, or no greater than approximately 5 microns. In a further embodiment, the material of the interior layer  204  has a D90 average diameter of at least approximately 1 micron, at least approximately 9 microns, at least approximately 21 microns, or at least approximately 50 microns, and in another embodiment, the D90 average diameter is no greater than approximately 700 microns, no greater than approximately 300 microns, no greater than approximately 125 microns, or no greater than approximately 50 microns. In another embodiment, 
     In an embodiment, the material of the exterior layer  104  has a D10 average diameter of at least approximately 0.001 microns, at least approximately 0.003 microns, at least approximately 0.007 microns, or at least approximately 0.01 microns, and in another embodiment, the D10 average diameter is no greater than approximately 30 microns, no greater than approximately 8 microns, no greater than approximately 0.2 microns, or no greater than approximately 0.01 microns. In an embodiment, the material of the exterior layer  104  has a D50 average diameter of at least approximately 0.1 microns, at least approximately 0.8 microns, at least approximately 1.3 microns, or at least approximately 2 microns, and in another embodiment, the D50 average diameter is no greater than approximately 200 microns, no greater than approximately 21 microns, no greater than approximately 7 microns, or no greater than approximately 0.7 microns. In a further embodiment, the material of the exterior layer  104  has a D90 average diameter of at least approximately 1 micron, at least approximately 8 microns, at least approximately 19 microns, or at least approximately 30 microns, and in another embodiment, the D90 average diameter is no greater than approximately 500 microns, no greater than approximately 220 microns, no greater than approximately 110 microns, or no greater than approximately 30 microns. 
     In an embodiment, the exterior layer  104  has a smaller amount of open porosity as compared to the interior layer  204 . In a particular embodiment, the exterior layer  104  has an open porosity that is no greater than approximately 95%, no greater than approximately 90%, no greater than approximately 80%, no greater than approximately 70%, no greater than approximately 50%, or no greater than approximately 20% of an open porosity of the interior layer  204 . 
     In an embodiment, the interior layer  204  has an open porosity that is at least approximately 11%, at least approximately 20%, at least approximately 30%, at least approximately 50%, or at least approximately 70% of an open porosity of the exterior layer  104 . In another embodiment, the interior layer  204  has an open porosity that is at least approximately 5%, at least approximately 12%, at least approximately 17%, or at least approximately 25%, and in another embodiment, the interior layer  204  has an open porosity no greater than approximately 30%, no greater than approximately 23%, no greater than approximately 19%, or no greater than approximately 15%. In a further embodiment, the exterior layer  104  has an open porosity that is at least approximately 3%, at least approximately 7%, at least approximately 10%, or at least approximately 12%, and in another embodiment, the exterior layer  104  has an open porosity no greater than approximately 15%, no greater than approximately 12%, no greater than approximately 10%, or no greater than approximately 8%. In another embodiment, the interior layer  204  has a pore size that is at least about 0.01 microns, at least about 0.1 microns, or at least about 0.5 microns, and in another embodiment, no greater than about 100 microns, no greater than about 20 microns, or no greater than about 1 micron. 
     The process can continue with infiltrating a fluid into the pores of the interior layer  204  while the exterior layer  104  is present and adjacent to the interior layer  204 . Pores within the interior layer  204  can allow the fluid to provide a reactant to a material within the interior layer  204 . The reactant can be a carbonate of Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Sc, Y, La, Nd, Yb, or another lanthanide series element, Th or another actinide series element, Ti, Zr, Hf, V, Nb, Ta, Mo, W, Mn, Tc, Re, Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Cu, Ag, Au, Zn, Al, Ga, Ge, Sn, Sb, or any mixture thereof. In a further embodiment, the carbonate can be supplied as a carbonic acid. 
     The fluid may be a liquid or a gas. Skilled artisans may find use of a liquid, at the subsequent reaction conditions, to be particularly advantageous. In an embodiment, the liquid can include water, ammonia, an organic compound, another suitable medium for providing a reactant to the material of the interior layer  204 , or any combination thereof. The organic compound can include an alcohol (for example, C x H (2x+1) OH, wherein x is 1, 2, or 3); a polyol (for example, C x H 2x (OH) 2 , wherein x is 1, 2, or 3); a heteroaromatic (for example, a furan, a thiophene, a pyrrole, or a pyridine); an amine (for example, CH 3 (CH 2 ) n NH 2 , wherein n is 0, 1, or 2)); an ether, an ester, or a ketone having no more than 6 carbon atoms (for example, diethyl ether or acetone); a sulfoxides (for example, dimethylsulfoxide); an acetonitrile; another suitable organic compound; or any combination thereof. When an organic compound is used, skilled artisans may find such compounds that are relatively soluble in water to be particularly advantageous. In the organic compounds listed above, one or more H atoms may be substituted with one or more halides. 
     The pH of the fluid may be adjusted using an acid or a base. The acid can include an inorganic acid (for example, H 2 SO 4 , HCl, or HNO 3 ) or an organic acid (for example, citric acid, acetic acid, or oxalic acid). The pH of the fluid can be greater than 7, 8, 9, 19, 11, or 12. The base can include an inorganic base (for example, NaOH, KOH, or NH 4 OH) or an organic base (for example, CH 3 (CH 2 ) n NH 2  or ((CH 3 (CH 2 ) n ) x NH (4-x) OH, wherein n is 0, 1, or 2, and x is 1, 2, 3, or 4). For the organic acids and bases, one or more H atoms may be substituted with a halide. In a further embodiment, a surfactant, a buffer, a corrosion inhibitor, or another suitable compound may be used to achieve a desired characteristic or reduce an adverse effect, or any combination thereof can be used. 
     The process can further include reacting the carbonate with a material within the interior layer  204  to form a carbonate compound within the reacted interior layer  304 , as illustrated in  FIG. 3 . In an embodiment, the material is a metal compound, and the reaction forms a metal carbonate. 
     The processing conditions for the reaction may take place at a variety of pressures, temperatures and time periods. In an embodiment, the reaction is performed at a pressure of at least approximately 5 kPa, at least approximately 11 kPa, at least approximately 50 kPa, at least approximately 110 kPa, at least approximately 500 kPa, at least approximately 1.1 MPa, at least approximately 5 MPa, at least approximately 11 MPa, or at least approximately 50 MPa. In another embodiment, the reaction is performed at a pressure no greater than approximately 900 MPa, no greater than approximately 500 MPa, no greater than least approximately 90 MPa, or no greater than approximately 50 MPa, no greater than approximately 900 kPa, no greater than approximately 500 kPa, no greater than approximately 90 kPa, or no greater than approximately 50 kPa. In one embodiment, the reaction is performed at substantially ambient pressure. 
     In an embodiment, the reaction is performed at a temperature of at least approximately 20° C., at least approximately 50° C., at least approximately 80° C., at least approximately 110° C., at least approximately 150° C., at least approximately 200° C., at least approximately 250° C., or at least approximately 300° C. In another embodiment, the reaction is performed at a temperature no greater than approximately 1000° C., no greater than approximately 500° C., no greater than approximately 300° C., no greater than approximately 250° C., no greater than approximately 190° C., no greater than approximately 150° C., no greater than approximately 130° C., no greater than approximately 100° C., or no greater than approximately 90° C. In one embodiment, the reaction is performed at substantially ambient temperature. 
     In an embodiment, the reaction is performed for a time period of at least approximately 11 seconds, at least approximately 1.1 minutes, at least approximately 5 minutes, at least approximately 11 minutes, at least approximately 20 minutes, at least approximately 1 hour, at least approximately 11 hours, at least approximately 20 hours, at least approximately 50 hours. In another embodiment, the reaction is performed for a time period no greater than approximately 200 hours, no greater than approximately 90 hours, no greater than approximately 24 hours, no greater than approximately 5 hours, no greater than approximately 3 hours, no greater than approximately 2 hours, no greater than approximately 0.9 hour, or no greater than approximately 0.5 hour. 
     The reaction may be performed in an autoclave, a pressure pot, or another suitable apparatus capable of achieving the needed or desired processing conditions. After the reaction is completed, the combination of the exterior layer  104  and reacted interior layer  304  are removed from the mould  100 , and is illustrated as a building product  400  in  FIG. 4 . In the embodiment as illustrated, substantially all of the interior layer  204  is reacted to form the reacted interior layer  304 . When the building product  400  has a relief feature (not illustrated) along the exposed surface of the exterior layer  102 , the relief feature may affect only the exterior layer, or may extend to the reacted interior layer  304 . 
     While many materials, infiltrating fluids, reactant compounds, and processing conditions have been described, after reading this specification, skilled artisans will be able to determine one or more particular materials, infiltrating fluids, reactant compounds, and processing conditions that are particularly well suited for an application. A metal oxide can react with an infiltrating fluid including carbonic acid to form a metal carbonate. In an illustrative example:
 
CaO+H 2 CO 3 →CaCO 3 +H 2 O
 
     Alternatively, the material within the interior layer  204  can include a Group 2 or transition metal oxide, and the infiltrating solution can include a Group 1 metal carbonate that is dissolved in water or another aqueous solution. The carbonate anion can react with the Group 2 or transition metal oxide to form a Group 2 or transition metal carbonate. The reaction may be performed in a base to help hydrolyze the Group 2 or transition metal oxide before reacting with the carbonate anions. In a particular illustrative example:
 
CaO+2KOH→Ca(OH) 2 +K 2 O
 
Ca(OH) 2 +K 2 CO 3 →CaCO 3 +2KOH
 
     Thus, the overall reaction is:
 
CaO+K 2 CO 3 →CaCO 3 +K 2 O
 
     In a further illustrative example:
 
CaSO 4 +Na 2 CO 3 →CaCO 3 +Na 2 SO 4  
 
     After reading this specification, skilled artisans will appreciate that many other reactions may be used. CaCO 3  is present in many building materials and is extensively characterized. Thus, the formation of CaCO 3  may be desired. In other applications, other materials may be desired, and therefore, the formation of CaCO 3  is not to be construed as limiting the scope of the present invention. 
     Analogous carbonates can also be employed using barium or magnesium salts or other divalent metal cation salts to yield, for example, barium or magnesium carbonates. Alternatively, mixtures of cation metals may be included to produce mixed metal carbonates comprising one or more of calcium, magnesium, or barium, copper, iron, manganese, nickel, silver, or zinc. In certain embodiments, the solubility of the metal carbonate in water at 20° C. is less than about 0.05, less than about 0.004, less than about 0.001, or less than about 0.0008 grams per 100 grams of water. 
     The reaction can change the characteristics of the reacted interior layer  304  as compared to the unreacted interior layer  204  or the exterior layer  104 . Such characteristics can include open porosity, average diameter, or change in volume occupied when forming the building product. 
     The open porosity of the reacted interior layer  304  may be less than the open porosity of the unreacted interior layer  204 . In an embodiment, the open porosity of the reacted interior layer  304  is no greater than approximately 99%, no greater than approximately 95%, no greater than approximately 90%, no greater than approximately 80%, or no greater than approximately 70% of the open porosity of the unreacted interior layer  204 . In another embodiment, the reacted interior layer  304  has an open porosity of at least approximately 4%, at least approximately 11%, at least approximately 15%, or at least approximately 18%, and in another embodiment, the reacted interior layer  304  has an open porosity no greater than approximately 29%, no greater than approximately 22%, no greater than approximately 18%, or no greater than approximately 15%. The open porosity of the exterior layer  104  may still be less than the open porosity of the reacted interior layer  304 . In a particular embodiment, the exterior layer  104  has the open porosity that is at least approximately 11%, at least approximately 20%, at least approximately 30%, at least approximately 50%, or at least approximately 70% of an open porosity of the reacted interior layer  304 . 
     The average diameter of a material within the reacted interior layer  304  may be changed as compared to the corresponding unreacted material from the interior layer  204 . In an embodiment, the material within the reacted interior layer  304  has a D10 average diameter that is at least approximately 0.002 microns, at least approximately 0.02 microns, at least approximately 0.2 microns, or at least approximately 1 micron, and in another embodiment, the D10 average diameter no greater than approximately 400 microns, no greater than approximately 15 microns, no greater than approximately 1.2 microns, or no greater than approximately 0.05 microns. In an embodiment, the material within the reacted interior layer  304  has a D50 average diameter that is at least approximately 0.15 microns, at least approximately 1.2 microns, at least approximately 5 microns, or at least approximately 12 microns, and in another embodiment, the D50 average diameter no greater than approximately 600 microns, no greater than approximately 80 microns, no greater than approximately 14 microns, or no greater than approximately 7 microns. In an embodiment, the material within the reacted interior layer  304  has a D90 average diameter that is at least approximately 3 microns, at least approximately 12 microns, at least approximately 26 microns, or at least approximately 60 microns, and in another embodiment, the D90 average diameter no greater than approximately 750 microns, no greater than approximately 350 microns, no greater than approximately 140 microns, or no greater than approximately 60 microns. 
     Ideally, a volume occupied by the building product before the reaction (that is, the volume occupied by a combination of the exterior layer  104  and the unreacted interior layer  204  for the embodiment illustrated in  FIG. 2 ), also referred to as the pre-reaction volume, is substantially the same as the volume occupied by the building product  400  after the reaction (that is, the volume occupied by a combination of the exterior layer  104  and the reacted interior layer  304  for the embodiment illustrated in  FIG. 4 ), also referred to as the post-reaction volume. In actual practice, the volume may change such that the post-reaction volume is greater than or less than the pre-reaction volume. In an embodiment, the post-reaction volume of the building product  400  is within approximately 30%, within approximately 20%, within approximately 15%, within approximately 9%, within approximately 5%, or within approximately 2% of the pre-reaction volume of the building product. 
     Similar to the building product, ideally, a volume occupied by the unreacted interior layer  204  is substantially the same as the volume occupied by the volume occupied by the reacted interior layer  304 . In actual practice, the volume may change such that the volume of the reacted interior layer  304  is greater than or less than the volume of the unreacted interior layer  204 . In an embodiment, the volume of the reacted interior layer  304  is within approximately 30%, within approximately 20%, within approximately 15%, within approximately 9%, within approximately 5%, or within approximately 2% of the volume of the unreacted interior layer  204 . 
     In another embodiment, not all of the material within the interior layer  204  may react. As illustrated in  FIG. 5 , a building product  500  includes the exterior layer  104 , an unreacted portion of the interior layer  204 , and the reacted interior layer  304 . At least 0.0001% of the interior layer  204  may be reacted. In this particular embodiment, the thickness of the reacted interior layer  304  may provide sufficient protection to the building product  500  for conditions under which the building product  500  will normally be exposed. The unreacted interior layer  204  can have a density less as compared to the reacted interior layer  304 , and therefore, the mass of the building product  500  can be reduced by not reacting all of the interior layer  204 . The building product  500  may be used in an application where it is not located along a surface that is supposed to support a load, such as wall or ceiling panels, wall cladding or a framing member adjacent to a window or door. In an embodiment, no more than approximately 50%, no more than approximately 40%, no more than approximately 30%, no more than approximately 20%, or no more than approximately 9% of the interior layer  204  is reacted. 
     In another application, the building product may need to support a load in its normal use. For example, floor tiles may need to support humans or furniture, and roofing tiles may need to occasionally support humans during installation or maintenance of a roof. Thus, more of the interior layer  204  may need to be reacted. In an embodiment, at least approximately 50%, at least approximately 70%, at least approximately 80%, at least approximately 90%, or at least approximately 95% of the interior layer  204  is reacted. In a particular embodiment, at least approximately 99% or substantially all of the interior layer  204  is reacted. 
     In a further embodiment, the infiltrant can reach the exterior layer  104  and react with a portion of the exterior layer  104  to form an intermediate layer  604  between the reacted interior layer  304  and the exterior layer  104 , as illustrated in  FIG. 6 . The intermediate layer  604  may extend partly, but not completely, through the exterior layer  104 . In an embodiment, the intermediate layer  604  can extend to an interface penetration distance from an interface with the reacted interior layer  304 . In an embodiment, the interface penetration distance extends at least approximately 10%, at least approximately 20%, at least approximately 30%, at least approximately 40%, at least approximately 50%, at least approximately 60%, at least approximately 70%, at least approximately 80%, or at least approximately 90% of the distance from the interface to an outer surface of the exterior layer  104 , when compared to the originally formed exterior layer  104  (before the reaction). In an embodiment, the interface penetration distance extends at least approximately 0.011 mm, at least approximately 0.05 mm, at least approximately 0.11 mm, at least approximately 0.5 mm, at least approximately 1.1 mm, or at least approximately 5 mm of the distance from the interface with the interior layer  304 , and in another embodiment, the interface penetration distance extends no greater than approximately 11 mm, no greater than approximately 7 mm, no greater than approximately 4 mm, no greater than approximately 2 mm, no greater than approximately 0.9 mm, or no greater than approximately 0.5 mm of the distance from the interface with the interior layer  304 . 
     An open porosity of the intermediate layer  604  may be no greater than approximately 99%, no greater than approximately 97%, no greater than approximately 95%, no greater than approximately 90%, or no greater than approximately 80% of an open porosity of the exterior layer  104 . In an embodiment, the intermediate layer  604  has an open porosity of at least approximately 4%, at least approximately 8%, at least approximately 11%, or at least approximately 15%, and in another embodiment, has an open porosity no greater than approximately 28%, no greater than approximately 21%, no greater than approximately 17%, or no greater than approximately 13%. In a further embodiment, the intermediate layer  604  has an open porosity of at least approximately 4%, at least approximately 7%, at least approximately 10%, or at least approximately 14%, and in another embodiment, has an open porosity no greater than approximately 28%, no greater than approximately 20%, no greater than approximately 16%, or no greater than approximately 12%. 
     A volume occupied by the exterior layer  104  before the reaction is substantially the same as the volume occupied by a combination of the unreacted portion of exterior layer  104  and the intermediate layer  604 . In actual practice, the volume may change such that the volume after the reaction is greater than or less than the volume before the reaction. In an embodiment, the volume of the combination of the unreacted portion of the exterior layer  104  and the intermediate layer  604  is within approximately 30%, within approximately 20%, within approximately 15%, within approximately 9%, within approximately 5%, or within approximately 2% of the volume of the exterior layer  104  before the reaction. 
     The intermediate layer  604  can include a particular metal carbonate, wherein the particular metal of the metal carbonate originates from the exterior layer  104 . In another embodiment, the intermediate layer  604  can include a compound with a metal element from the interior layer  204  and a different metal element from the exterior layer  104 . 
     The exterior layer  104  may include an antimicrobial agent as originally formed, or the reaction with the interior layer  204 , the exterior layer  104 , or both can produce an antimicrobial agent. In a particular embodiment, the antimicrobial agent comprises a photocatalytic antimicrobial agent adjacent to a surface of the exterior layer  104  that is opposite another surface of the exterior layer  104  that lies closer to the interior layer  204 . In a further embodiment, the reaction produces Cu 2 O, Ag 2 O, SnO 2 , ZnO, TiO 2 , or any combination thereof. 
     In a further embodiment, a layer  704  can be placed on the interior layer  304 , the exterior layer  104 , or a combination thereof to produce the building product  700 , as illustrated in  FIG. 7 . The layer  704  may be an adhesive layer that can be used in attaching the building product  700  to a building structure. In another embodiment, the layer  704  may be a protective layer to prevent scratches or damage during shipping or installation, or an adverse interaction between the building product  700  and the building structure. For example, the layer  704  can include a dielectric layer that may prevent a voltaic cell from being formed between the building structure and the interior layer  304 , the exterior layer  104 , or both the interior layer  304  and the exterior layer  104 . 
     The building products as described herein can be useful in a variety of different applications. The building product can include a roofing product, a countertop, a ceramic tile, cladding for a building structure, or the like. In a particular embodiment, the cladding can include wall cladding, floor cladding, or ceiling cladding. In a further embodiment, the cladding includes a bathroom panel or tile or a shower stall panel or tile. In still another embodiment, the cladding includes exterior siding configured to be attached to an exterior of a building structure and exposed to an outdoor environment. 
       FIG. 8  includes an illustration of a side view of a structure  80  that includes different building materials. In the illustrated embodiment, the structure  80  includes a house or another habitat. Another structure can include a building, such as an office building, an outdoor structure for a pet, an outdoor structure that is exposed to the outdoors. The structure  80  includes a foundation  802  and stairs  804 . The structure  80  has walls that include siding  82 . In another embodiment (not illustrated), masonry or another material may present along the along an exposed surface along the walls of the structure  80 . The structure  80  further includes a door having a main body  842 , a window  844 , and a door knob  848 . Door frame  846  lies adjacent to sides of the door. The structure  80  still further includes a window  862  that is surrounding by window frame  866 . The window  844  or  862  can include substantially transparent or translucent glass, such as glass blocks commonly used to allow visible light to pass yet provide privacy to the occupants of the structure  80 . The structure  80  includes a roof  88  that is covered by roofing articles, such as roofing tiles  882 . Any of the siding  82 , the door  842 , and door frame  846 , the window frame  866  or the roofing tiles  882  can include any of the building products as previously described. 
     The formation of building products as described herein can help reduce atmospheric CO 2  or another greenhouse gas by capturing such gas to form carbonic acid or a carbonate compound. The carbonic acid or carbonate compound can react with a metal to form a stable metal carbonate that is not readily converted back to CO 2  in normal use of the building product. Thus, the process can be used to reduce CO 2  in the atmosphere and still form a useful the building product. Additional benefits can include using a less expensive or less visibly appealing material for an interior layer and convert it to a compound that is more weather resistant, durable, have another desirable property, or any combination thereof. The installation of the building products may not change or may be only slightly modified. 
     Many different aspects and embodiments are possible. Some of those aspects and embodiments are described herein. After reading this specification, skilled artisans will appreciate that those aspects and embodiments are only illustrative and do not limit the scope of the present invention. Embodiments may be in accordance with any one or more of the items as listed below. 
     Item 1. A building product can include: 
     a first layer having a first material; and 
     a second layer having a second material and a third material that includes a metal carbonate, wherein: 
     the first material is different from the second material; and 
     the second and third materials include the same metal element. 
     Item 2. The building product of Item 1, wherein the first material has a smaller average diameter as compared to the second material. 
     Item 3. The building product of Item 1, wherein the first material has a first average diameter, the second material has a second average diameter, and the first average diameter is no greater than approximately 95%, no greater than approximately 90%, no greater than approximately 80%, no greater than approximately 70%, no greater than approximately 50%, or no greater than approximately 20% of the second average diameter. 
     Item 4. The building product of Item 1, wherein the second material has a D10 average diameter of at least approximately 0.001 microns, at least approximately 0.015 microns, at least approximately 0.11 microns, or at least approximately 1 micron. 
     Item 5. The building product of Item 1, wherein the second material has a D10 average diameter no greater than approximately 300 microns, no greater than approximately 9 microns, no greater than approximately 0.7 microns, or no greater than approximately 0.01 microns. 
     Item 6. The building product of Item 1, wherein the second material has a D50 average diameter of at least approximately 0.1 microns, at least approximately 0.7 microns, at least approximately 3 microns, or at least approximately 10 microns. 
     Item 7. The building product of Item 1, wherein the second material has a D50 average diameter no greater than approximately 500 microns, no greater than approximately 60 microns, no greater than approximately 11 microns, or no greater than approximately 5 microns. 
     Item 8. The building product of Item 1, wherein the second material has a D90 average diameter of at least approximately 1 micron, at least approximately 9 microns, at least approximately 21 microns, or at least approximately 50 microns. 
     Item 9. The building product of Item 1, wherein the second material has a D90 average diameter no greater than approximately 700 microns, no greater than approximately 300 microns, no greater than approximately 125 microns, or no greater than approximately 50 microns. 
     Item 10. The building product of Item 1, wherein the first material has a D10 average diameter of at least approximately 0.001 microns, at least approximately 0.003 microns, at least approximately 0.007 microns, or at least approximately 0.01 microns. 
     Item 11. The building product of Item 1, wherein the first material has a D10 average diameter no greater than approximately 30 microns, no greater than approximately 8 microns, no greater than approximately 0.2 microns, or no greater than approximately 0.01 microns. 
     Item 12. The building product of Item 1, wherein the first material has a D50 average diameter of at least approximately 0.1 microns, at least approximately 0.8 microns, at least approximately 1.3 microns, or at least approximately 2 microns. 
     Item 13. The building product of Item 1, wherein the first material has a D50 average diameter no greater than approximately 200 microns, no greater than approximately 21 microns, no greater than approximately 7 microns, or no greater than approximately 0.7 microns. 
     Item 14. The building product of Item 1, wherein the first material has a D90 average diameter of at least approximately 1 micron, at least approximately 8 microns, at least approximately 19 microns, or at least approximately 30 microns. 
     Item 15. The building product of Item 1, wherein the first material has a D90 average diameter no greater than approximately 500 microns, no greater than approximately 220 microns, no greater than approximately 110 microns, or no greater than approximately 30 microns. 
     Item 16. The building product of Item 1, wherein the first layer has a smaller amount of open porosity as compared to the second layer. 
     Item 17. The building product of Item 1, wherein the first layer has a first open porosity, the second layer has a second open porosity, and the first open porosity is no greater than approximately 95%, no greater than approximately 90%, no greater than approximately 80%, no greater than approximately 70%, no greater than approximately 50%, or no greater than approximately 20% of the second open porosity. 
     Item 18. The building product of Item 1, wherein the second layer has an open porosity of at least approximately 5%, at least approximately 12%, at least approximately 17%, or at least approximately 25%. 
     Item 19. The building product of Item 1, wherein the second layer has an open porosity no greater than approximately 30%, no greater than approximately 23%, no greater than approximately 19%, or no greater than approximately 15%. 
     Item 20. The building product of Item 1, wherein the first layer has an open porosity of at least approximately 3%, at least approximately 7%, at least approximately 10%, or at least approximately 12%. 
     Item 21. The building product of Item 1, wherein the first layer has an open porosity of no greater than approximately 15%, no greater than approximately 12%, no greater than approximately 10%, or no greater than approximately 8%. 
     Item 22. The building product of Item 1, wherein the second layer has a pore size that is at least about 0.01 microns, at least about 0.1 microns, or at least about 0.5 microns; or greater than about 100 microns, no greater than about 20 microns, or no greater than about 1 micron. 
     Item 23. The building product of Item 1, wherein the first layer occupies a first volume, the second layer occupies a second volume, and a ratio of the second volume to the first volume is at least approximately 1.1:1, at least approximately 1.5:1, at least approximately 2:1, at least approximately 3:1, at least approximately 5:1, or at least approximately 9:1. 
     Item 24. The building product of Item 1, wherein the first material has a different composition as compared to the second material. 
     Item 25. The building product of Item 1, wherein the first material is capable of reacting with the same metal element under conditions at which the second material can react with the same metal to form the third material. 
     Item 26. The building product of Item 1, wherein the second layer further includes an antimicrobial agent, wherein the second material and the antimicrobial agent include the same metal element. 
     Item 27. The building product of Item 1, wherein the antimicrobial agent includes a photocatalytic antimicrobial agent adjacent to a surface of the first layer that is opposite another surface of the first layer that lies closer to the second layer. 
     Item 28. The building product of Item 27, wherein the antimicrobial agent includes Cu 2 O, Ag 2 O, SnO 2 , ZnO, TiO 2 , or any combination thereof. 
     Item 29. The building product of Item 1, further including an interphase compound between the first layer and the second layer, wherein the interphase compound includes a first constituent from the first material and a second constituent from the second material. 
     Item 30. The building product of Item 1, wherein the first layer further includes a particular metal carbonate, wherein the first material and the particular metal carbonate include the same metal element. 
     Item 31. The building product of Item 30, wherein the particular metal carbonate extends to an interface penetration distance from an interface with the first layer. 
     Item 32. The building product of Item 31, wherein the interface penetration distance extends partly, but not completely through the first layer. 
     Item 33. The building product of Item 31, wherein the interface penetration distance extends at least approximately 10%, at least approximately 20%, at least approximately 30%, at least approximately 40%, at least approximately 50%, at least approximately 60%, at least approximately 70%, at least approximately 80%, or at least approximately 90% of the distance from the interface to an outer surface of the first layer. 
     Item 34. The building product of Item 31, wherein the interface penetration distance extends at least approximately 0.011 mm, at least approximately 0.05 mm, at least approximately 0.11 mm, at least approximately 0.5 mm, at least approximately 1.1 mm, or at least approximately 5 mm of the distance from the interface. 
     Item 35. The building product of Item 31, wherein the interface penetration distance extends no greater than approximately 11 mm, no greater than approximately 7 mm, no greater than approximately 4 mm, no greater than approximately 2 mm, no greater than approximately 0.9 mm, or no greater than approximately 0.5 mm of the distance from the interface. 
     Item 36. The building product of Item 1, wherein the second material includes a metal oxide, a metal silicate, or a metal hydroxide. 
     Item 37. The building product of Item 1, wherein the second material includes a mixed-metal compound. 
     Item 38. The building product of Item 1, wherein the first material includes a metal oxide, a metal silicate, or a metal hydroxide. 
     Item 39. The building product of Item 1, wherein the first material includes a mixed-metal compound. 
     Item 40. The building product of Item 1, wherein the first material, the second material, or the first and second materials include a low density filler material or a void containing filler material. 
     Item 41. The building product of Item 1, wherein a solubility of the metal carbonate in water at 20° C. is less than about 0.05, less than about 0.004, less than about 0.001, or less than about 0.0008 grams per 100 grams of water. 
     Item 42. The building product of Item 1, wherein the building product includes a roofing product. 
     Item 43. The building product of Item 1, wherein the building product includes a countertop. 
     Item 44. The building product of Item 1, wherein the building product includes a ceramic tile. 
     Item 45. The building product of Item 1, wherein the building product includes cladding for a building structure. 
     Item 46. The building product of Item 45, wherein the cladding includes wall cladding, floor cladding, or ceiling cladding. 
     Item 47. The building product of Item 45, wherein the cladding includes a bathroom panel or tile. 
     Item 48. The building product of Item 45, wherein the cladding includes a shower stall panel or tile. 
     Item 49. The building product of Item 45, wherein the cladding includes exterior siding configured to be attached to an exterior of a building structure and exposed to an outdoor environment. 
     Item 50. A process of forming a building product can include: 
     providing a first layer having a first material; 
     providing a second layer having a second material that different from the first material, wherein the second layer has pores; 
     infiltrating a fluid into the pores of the second layer while the first layer is present and adjacent to the second layer, wherein the fluid includes a carbonate; and 
     reacting the carbonate with a metal compound within the second layer to form a metal carbonate within the second layer. 
     Item 51. The process of Item 50, wherein the first material has a smaller average diameter as compared to the second material. 
     Item 52. The process of Item 50, wherein the first material has a first average diameter, the second material has a second average diameter, and the first average diameter is no greater than approximately 95%, no greater than approximately 90%, no greater than approximately 80%, no greater than approximately 70%, no greater than approximately 50%, or no greater than approximately 20% of the second average diameter. 
     Item 53. The process of Item 50, wherein the second material has a D10 average diameter of at least approximately 0.001 microns, at least approximately 0.015 microns, at least approximately 0.11 microns, or at least approximately 1 micron. 
     Item 54. The process of Item 50, wherein the second material has a D10 average diameter no greater than approximately 300 microns, no greater than approximately 9 microns, no greater than approximately 0.7 microns, or no greater than approximately 0.01 microns. 
     Item 55. The process of Item 50, wherein the second material has a D50 average diameter of at least approximately 0.1 microns, at least approximately 0.7 microns, at least approximately 3 microns, or at least approximately 10 microns. 
     Item 56. The process of Item 50, wherein the second material has a D50 average diameter no greater than approximately 500 microns, no greater than approximately 60 microns, no greater than approximately 11 microns, or no greater than approximately 5 microns. 
     Item 57. The process of Item 50, wherein the second material has a D90 average diameter of at least approximately 1 micron, at least approximately 9 microns, at least approximately 21 microns, or at least approximately 50 microns. 
     Item 58. The process of Item 50, wherein the second material has a D90 average diameter no greater than approximately 700 microns, no greater than approximately 300 microns, no greater than approximately 125 microns, or no greater than approximately 50 microns. 
     Item 59. The process of Item 50, wherein the first material has a D10 average diameter of at least approximately 0.001 microns, at least approximately 0.003 microns, at least approximately 0.007 microns, or at least approximately 0.01 microns. 
     Item 60. The process of Item 50, wherein the first material has a D10 average diameter no greater than approximately 30 microns, no greater than approximately 8 microns, no greater than approximately 0.2 microns, or no greater than approximately 0.01 microns. 
     Item 61. The process of Item 50, wherein the first material has a D50 average diameter of at least approximately 0.1 microns, at least approximately 0.8 microns, at least approximately 1.3 microns, or at least approximately 2 microns. 
     Item 62. The process of Item 50, wherein the first material has a D50 average diameter no greater than approximately 200 microns, no greater than approximately 21 microns, no greater than approximately 7 microns, or no greater than approximately 0.7 microns. 
     Item 63. The process of Item 50, wherein the first material has a D90 average diameter of at least approximately 1 micron, at least approximately 8 microns, at least approximately 19 microns, or at least approximately 30 microns. 
     Item 64. The process of Item 50, wherein the first material has a D90 average diameter no greater than approximately 500 microns, no greater than approximately 220 microns, no greater than approximately 110 microns, or no greater than approximately 30 microns. 
     Item 65. The process of Item 50, wherein the first layer has a smaller amount of open porosity as compared to the second layer. 
     Item 66. The process of Item 50, wherein before reacting, the first layer has a first open porosity, the second layer has a second open porosity, and the first open porosity is no greater than approximately 95%, no greater than approximately 90%, no greater than approximately 80%, no greater than approximately 70%, no greater than approximately 50%, or no greater than approximately 20% of the second open porosity. 
     Item 67. The process of Item 50, wherein after reacting, the first layer has a first open porosity, the second layer has a second open porosity, and the first open porosity is at least approximately 11%, at least approximately 20%, at least approximately 30%, at least approximately 50%, or at least approximately 70% of the second open porosity. 
     Item 68. The process of Item 50, wherein the second layer has a pre-reaction open porosity before reacting, the second layer has a post-reaction open porosity after reacting, and the post-reaction open porosity is no greater than approximately 99%, no greater than approximately 95%, no greater than approximately 90%, no greater than approximately 80%, or no greater than approximately 70% of the pre-reaction open porosity. 
     Item 69. The process of Item 50, wherein before reacting, the second layer has an open porosity of at least approximately 5%, at least approximately 12%, at least approximately 17%, or at least approximately 25%. 
     Item 70. The process of Item 50, wherein before reacting, the second layer has an open porosity no greater than approximately 30%, no greater than approximately 23%, no greater than approximately 19%, or no greater than approximately 15%. 
     Item 71. The process of Item 50, wherein after reacting, the second layer has an open porosity of at least approximately 4%, at least approximately 11%, at least approximately 15%, or at least approximately 18%. 
     Item 72. The process of Item 50, wherein after reacting, the second layer has an open porosity no greater than approximately 29%, no greater than approximately 22%, no greater than approximately 18%, or no greater than approximately 15%. 
     Item 73. The process of Item 50, wherein before reacting, the second material has a pore size that is at least about 0.01 microns, at least approximately 0.1 microns, or at least approximately 0.5 microns; or no greater than approximately 100 microns, no greater than approximately 20 microns, or no greater than approximately 1 micron. 
     Item 74. The process of Item 50, wherein a solubility of the metal carbonate in water at 20° C. is less than about 0.05, less than about 0.004, less than about 0.001, or less than about 0.0008 grams per 100 grams of water. 
     Item 75. The process of Item 50, wherein the first material has a different composition as compared to the second material. 
     Item 76. The process of Item 50, wherein providing the first layer and providing the second layer includes: 
     partly filling a first portion of a mould with the first material; and 
     filling a second portion of the mould with the second material after partly filling the first portion. 
     Item 77. The process of Item 76, wherein providing the second layer further includes compressing the second material within the mould. 
     Item 78. The process of Item 77, wherein compressing is performed using vibratory compaction. 
     Item 79. The process of Item 50, wherein providing the first layer includes extruding the first layer onto the second layer before infiltrating the second layer. 
     Item 80. The process of Item 50, wherein the first layer occupies a first volume, the second layer occupies a second volume, and a ratio of the second volume to the first volume is at least approximately 1.1:1, at least approximately 1.5:1, at least approximately 2:1, at least approximately 3:1, at least approximately 5:1, or at least approximately 9:1. 
     Item 81. The process of Item 50, wherein before reacting, the building product occupies a pre-reaction volume, after reacting, the building product occupies a post reaction volume, and the post-reaction volume is within approximately 30%, within approximately 20%, within approximately 15%, within approximately 9%, within approximately 5%, or within approximately 2% of the pre-reaction volume. 
     Item 82. The process of Item 50, wherein before reacting, the second layer occupies a pre-reaction volume, after reacting, the second layer occupies a post reaction volume, and the post-reaction volume is within approximately 30%, approximately 20%, within approximately 15%, within approximately 9%, within approximately 5%, or within approximately 2% of the pre-reaction volume. 
     Item 83. The process of Item 50, wherein the fluid includes a liquid. 
     Item 84. The process of Item 83, wherein liquid includes water. 
     Item 85. The process of Item 83, wherein liquid has substantially no water. 
     Item 86. The process of Item 83, wherein liquid includes ammonia or an organic compound. 
     Item 87. The process of Item 83, wherein the liquid has a pH greater than 7, 8, 9, 10, 11, or 12. 
     Item 88. The process of Item 83, wherein the liquid has a pH less than 7, 6, 5, or 4. 
     Item 89. The process of Item 83, wherein reacting is performed at a pressure higher than atmospheric pressure. 
     Item 90. The process of Item 83, wherein reacting is performed at a pressure of at least approximately 5 kPa, at least approximately 11 kPa, at least approximately 50 kPa, at least approximately 110 kPa, at least approximately 500 kPa, at least approximately 1.1 MPa, at least approximately 5 MPa, at least approximately 11 MPa, or at least approximately 50 MPa. 
     Item 91. The process of Item 83, wherein reacting is performed at a pressure no greater than approximately 900 MPa, no greater than approximately 500 MPa, no greater than least approximately 90 MPa, or no greater than approximately 50 MPa, no greater than approximately 900 kPa, no greater than approximately 500 kPa, no greater than approximately 90 kPa, or no greater than approximately 50 kPa. 
     Item 92. The process of Item 83, wherein reacting is performed at a temperature of at least approximately 20° C., at least approximately 50° C., at least approximately 80° C., at least approximately 110° C., at least approximately 150° C., at least approximately 200° C., at least approximately 250° C., or at least approximately 300° C. 
     Item 93. The process of Item 83, wherein reacting is performed at a temperature no greater than approximately 1000° C., no greater than approximately 500° C., no greater than approximately 300° C., no greater than approximately 250° C., no greater than approximately 190° C., no greater than approximately 150° C., no greater than approximately 130° C., no greater than approximately 100° C., or no greater than approximately 90° C. 
     Item 94. The process of Item 83, wherein reacting is performed for a time period of at least approximately 11 seconds, at least approximately 1.1 minutes, at least approximately 5 minutes, at least approximately 11 minutes, at least approximately 20 minutes, at least approximately 1 hour, at least approximately 11 hours, at least approximately 20 hours, at least approximately 50 hours. 
     Item 95. The process of Item 83, wherein reacting is performed for a time period no greater than approximately 200 hours, no greater than approximately 90 hours, no greater than approximately 24 hours, no greater than approximately 5 hours, no greater than approximately 3 hours, no greater than approximately 2 hours, no greater than approximately 0.9 hour, or no greater than approximately 0.5 hour. 
     Item 96. The process of Item 50, wherein reacting further produces an antimicrobial agent. 
     Item 97. The process of Item 50, wherein the antimicrobial agent includes a photocatalytic antimicrobial agent adjacent to a surface of the first layer that is opposite another surface of the first layer that lies closer to the second layer. 
     Item 98. The process of Item 50, wherein reacting further produces Cu 2 O, Ag 2 O, SnO 2 , ZnO, TiO 2 , or any combination thereof. 
     Item 99. The process of Item 50, wherein reacting is performed such that an interphase compound is formed that includes a first constituent from the first material and a second constituent from the second material. 
     Item 100. The process of Item 50, wherein: 
     infiltrating the fluid includes infiltrating the fluid such that the fluid reaches the first layer; and 
     reacting the carbonate includes reacting the carbonate with a particular metal compound within the first layer to form a particular metal carbonate. 
     Item 101. The process of Item 100, wherein the particular metal carbonate extends to an interface penetration distance from an interface with the first layer. 
     Item 102. The process of Item 101, wherein the interface penetration distance extends partly, but not completely through the first layer. 
     Item 103. The process of Item 101, wherein the interface penetration distance extends at least approximately 10%, at least approximately 20%, at least approximately 30%, at least approximately 40%, at least approximately 50%, at least approximately 60%, at least approximately 70%, at least approximately 80%, or at least approximately 90% of the distance from the interface to an outer surface of the first layer. 
     Item 104. The process of Item 101, wherein the interface penetration distance extends at least approximately 0.011 mm, at least approximately 0.05 mm, at least approximately 0.11 mm, at least approximately 0.5 mm, at least approximately 1.1 mm, or at least approximately 5 mm of the distance from the interface. 
     Item 105. The process of Item 101, wherein the interface penetration distance extends no greater than approximately 11 mm, no greater than approximately 7 mm, no greater than approximately 4 mm, no greater than approximately 2 mm, no greater than approximately 0.9 mm, or no greater than approximately 0.5 mm of the distance from the interface. 
     Item 106. The process of Item 100, wherein the first layer has a pre-reaction open porosity before reacting, the first layer has a post-reaction open porosity after reacting, and the post-reaction open porosity is no greater than approximately 99%, no greater than approximately 97%, no greater than approximately 95%, no greater than approximately 90%, or no greater than approximately 80% of the pre-reaction open porosity. 
     Item 107. The process of Item 100, wherein before reacting, the first layer has an open porosity of at least approximately 3%, at least approximately 7%, at least approximately 10%, or at least approximately 12%. 
     Item 108. The process of Item 100, wherein before reacting, the first layer has an open porosity no greater than approximately 15%, no greater than approximately 12%, no greater than approximately 10%, or no greater than approximately 8%. 
     Item 109. The process of Item 100, wherein after reacting, the first layer has an open porosity of at least approximately 4%, at least approximately 7%, at least approximately 10%, or at least approximately 14%. 
     Item 110. The process of Item 100, wherein after reacting, the first layer has an open porosity no greater than approximately 28%, no greater than approximately 20%, no greater than approximately 16%, or no greater than approximately 12%. 
     Item 111. The process of Item 50, wherein before reacting, the first layer occupies a pre-reaction volume, after reacting, the first layer occupies a post reaction volume, and the post-reaction volume is within approximately 30%, approximately 20%, no greater than approximately 15%, no greater than approximately 9%, no greater than approximately 5%, or no greater than approximately 2% of the pre-reaction volume. 
     Item 112. The process of Item 50, wherein the second material includes a metal oxide, a metal silicate, or a metal hydroxide. 
     Item 113. The process of Item 50, wherein the second material includes a mixed-metal compound. 
     Item 114. The process of Item 50, wherein the first material, the second material, or the first and second materials include a low density filler material or a void containing filler material. 
     Item 115. The process of Item 50, wherein the first material includes a metal oxide, a metal silicate, or a metal hydroxide. 
     Item 116. The process of Item 50, wherein the first material includes a mixed-metal compound. 
     Item 117. The process of Item 50, wherein the building product includes a roofing product. 
     Item 118. The process of Item 50, wherein the building product includes a countertop. 
     Item 119. The process of Item 50, wherein the building product includes a ceramic tile. 
     Item 120. The process of Item 50, wherein the building product includes cladding for a building structure. 
     Item 121. The process of Item 120, wherein the cladding includes wall cladding, floor cladding, or ceiling cladding. 
     Item 122. The process of Item 120, wherein the cladding includes a bathroom panel or tile. 
     Item 123. The process of Item 120, wherein the cladding includes a shower stall panel or tile. 
     Item 124. The process of Item 120, wherein the cladding includes exterior siding configured to be attached to an exterior of a building structure and exposed to an outdoor environment. 
     Note that not all of the activities described above in the general description or the examples are required, that a portion of a specific activity may not be required, and that one or more further activities may be performed in addition to those described. Still further, the order in which activities are listed is not necessarily the order in which they are performed. 
     Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any feature(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature of any or all the claims. 
     The specification and illustrations of the embodiments described herein are intended to provide a general understanding of the structure of the various embodiments. The specification and illustrations are not intended to serve as an exhaustive and comprehensive description of all of the elements and features of apparatus and systems that use the structures or methods described herein. Separate embodiments may also be provided in combination in a single embodiment, and conversely, various features that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any subcombination. Further, reference to values stated in ranges includes each and every value within that range. Many other embodiments may be apparent to skilled artisans only after reading this specification. Other embodiments may be used and derived from the disclosure, such that a structural substitution, logical substitution, or another change may be made without departing from the scope of the disclosure. Accordingly, the disclosure is to be regarded as illustrative rather than restrictive.