Aerated composite materials, methods of production and uses thereof

Abstract

The invention provides novel aerated composite materials that possess excellent physical and performance characteristics of aerated concretes, and methods of production and uses thereof. These composite materials can be readily produced from widely available, low cost raw materials by a process suitable for large-scale production with improved energy consumption, desirable carbon footprint and minimal environmental impact.

What is claimed is: 
     
         1 . An aerated composite material comprising:
 a plurality of bonding elements, wherein each bonding element comprises:
 a core comprising primarily calcium silicate, 
 a silica-rich first or inner layer, and 
 a calcium carbonate-rich second or outer layer; 
   a plurality of filler particles having sizes of about 0.1 μm to about 1 mm; and   a plurality of voids,   wherein
 the plurality of bonding elements and the plurality of filler particles together form one or more bonding matrices and the bonding elements and the filler particles are substantially evenly dispersed therein and bonded together; and 
 the plurality of voids are bubble-shaped and/or interconnected channels account for from about 50 vol. % to about 80 vol. % of the composite material, whereby 
 the aerated composite material exhibits a density from about 300 kg/m 3  to 1500 kg/m 3 , a compressive strength from about 2.0 MPa to about 8.5 MPa, and a flexural strength from about 0.4 MPa to about 1.7 MPa. 
   
     
     
         2 . The aerated composite material of  claim 1 , wherein the plurality of bonding elements have a median particle size in the range from about 5 μm to about 100 μm. 
     
     
         3 . The aerated composite material of  claim 1 , wherein the filler particles are calcium-oxide rich materials. 
     
     
         4 . The aerated composite material of  claim 3 , wherein the filler particles are selected from lime and quartz. 
     
     
         5 . The aerated composite material of  claim 1 , wherein the filler particles are industrial waste materials. 
     
     
         6 . The aerated composite material of  claim 5 , wherein the filler particles are fly ash, slag, and silica fume. 
     
     
         7 . The aerated composite material of  claim 1 , wherein the plurality of bonding elements are chemically transformed from ground wollastonite and the filler particles are lime particles. 
     
     
         8 . The aerated composite material of  claim 1 , wherein the plurality of bonding elements are chemically transformed from a precursor calcium silicate other than wollastonite. 
     
     
         9 . The aerated composite material of  claim 1 , wherein the plurality of bonding elements are chemically transformed from a precursor calcium silicate comprising one or more of aluminum, magnesium and iron. 
     
     
         10 . The aerated composite material of  claim 1 , wherein the plurality of voids account for from about 50 vol. % to about 80 vol. % of the aerated composite material. 
     
     
         11 . The aerated composite material of  claim 10 , wherein the plurality of voids account for from about 65 vol. % to about 80 vol. % of the aerated composite material. 
     
     
         12 . The aerated composite material of  claim 1 , wherein the plurality of bonding elements are prepared by chemical transformation from ground wollastonite by reacting it with CO 2  via a controlled hydrothermal liquid phase sintering process. 
     
     
         13 . The aerated composite material of  claim 1 , wherein the plurality of bonding elements are prepared by chemical transformation from the precursor calcium silicate other than wollastonite by reacting it with CO 2  via a controlled hydrothermal liquid phase sintering process. 
     
     
         14 . The aerated composite material of  claim 1 , exhibiting a density from about 400 kg/m 3  to 1200 kg/m 3 , a compressive strength from about 2.0 MPa to about 6.0 MPa, and a flexural strength from about 0.66 MPa to about 1.32 MPa. 
     
     
         15 . The aerated composite material of  claim 14 , exhibiting a density from about 500 kg/m 3  to 1000 kg/m 3 , a compressive strength from about 2.0 MPa to about 6.0 MPa, and a flexural strength from about 0.88 MPa to about 1.32 MPa. 
     
     
         16 . The aerated composite material of  claim 1 , wherein the plurality of voids are caused by gaseous hydrogen produced by reacting an aerating agent with an acid. 
     
     
         17 . The aerated composite material of  claim 16 , wherein the aerating agent is a metal capable of reacting with acid to generate hydrogen. 
     
     
         18 . The aerated composite material of  claim 17 , wherein the aerating agent is a powder comprising at least one of aluminum, iron, zinc, calcium carbide, and a mixture thereof. 
     
     
         19 . The aerated composite material of  claim 1 , further comprising an additive is selected from rheology modifying admixtures, pigments, retarders, and accelerators. 
     
     
         20 . The aerated composite material of  claim 1 , wherein the pigment comprises one or more of black iron oxide, cobalt oxide and chromium oxide. 
     
     
         21 . A process for producing an aerated composite material, comprising:
 forming a wet mixture, wherein the wet mixture comprises:
 water, 
 a particulate comprising calcium oxide or silica having a median particle size in the range from about 10 μm to about 1 mm; 
 a ground calcium silicate having a median particle size in the range from about 1 μm to about 100 μm, and 
 an aerating agent, 
   casting the wet mixture in a mold;   allowing the aerating agent to generate a gaseous product thereby causing volume expansion of the wet mixture; and   curing the expanded mixture at a temperature in the range from about 20° C. to about 100° C. for about 6 hour to about 60 hours under an atmosphere of water and CO 2 .   
     
     
         22 . The process of  claim 21 , wherein curing the expanded mixture is performed under a pressure ranging from ambient atmospheric pressure to about 30 psi above ambient and under a CO 2  concentration ranging from about 50% to about 99% to produce an aerated composite material. 
     
     
         23 . The process of  claim 21 , wherein forming a wet mixture comprises mixing the following ingredients in the specified order of addition:
 adding water;   adding and mixing ground calcium silicate;   adding and mixing the particulate comprising calcium oxide or silica to form a uniform slurry; and   adding and mixing the aerating agent.   
     
     
         24 . The process of  claim 21 , wherein the wet mixture further comprises an additive selected from rheology modifying admixtures, pigments, retarders, and accelerators. 
     
     
         25 . The process of  claim 21 , wherein curing the expanded mixture is performed at a temperature in the range from about 20° C. to about 80° C. for about 5 hours to about 40 hours under a vapor comprising water and CO 2  and having a pressure in the range from about ambient atmospheric pressure to about 30 psi above ambient atmospheric pressure. 
     
     
         26 . The process of  claim 25 , wherein curing the casted mixture is performed at a temperature in the range from about 30° C. to about 70° C. for about 10 hours to about 30 hours under a vapor comprising water and CO 2  and having a pressure in the range from about ambient atmospheric pressure to about 60 psi above ambient atmospheric pressure. 
     
     
         27 . The process of  claim 21 , wherein the ground calcium silicate is selected from wollastonite, pseudo-wollastonite, rankanite, belite, and alite. 
     
     
         28 . The process of  claim 21 , wherein the particulate calcium oxide is selected from lime and wollastonite. 
     
     
         29 . The process of  claim 21 , wherein the aerating agent is selected from aluminum, iron, zinc, calcium carbide in powder form. 
     
     
         30 . The process of  claim 21 , wherein the aerating agent is hydrogen peroxide in liquid form. 
     
     
         31 . The process of  claim 21 , wherein
 the ground calcium silicate comprises ground wollastonite,   the particulate calcium oxide comprises ground lime, and   the aerating agent comprises aluminum powder.   
     
     
         32 . The process of  claim 31 , wherein the particulate composition comprises about 83.5 wt. % to about 94.8 wt. % of ground wollastonite, about 5 wt. % to about 15 wt. % w/w of ground lime, and about 0.2 wt. % to about 1.5 wt. % of aluminum powder. 
     
     
         33 . An aerated composite material prepared by a process according to  claim 21 . 
     
     
         34 . The aerated composite material of  claim 33 , exhibiting a density from about 300 kg/m 3  to 1500 kg/m 3 , a compressive strength from about 2.0 MPa to about 8.5 MPa, and a flexural strength from about 0.4 MPa to about 1.7 MPa. 
     
     
         35 . An article of manufacture made from the aerated composite material of  claim 33 . 
     
     
         36 . An article of manufacture made from the aerated composite material of  claim 1 . 
     
     
         37 . The article of manufacture of  claim 36 , selected from the group consisting of standard blocks, cored blocks, cladding blocks, shaftwall and fire blocks, lintel blocks, tongue and groove blocks, wall panels, floor panels, roof panels, plates, sidings, frames, fences, decorative and landscaping products, and parking stops.