Synthetic pozzolans

Abstract

Synthetic pozzolans are produced using local materials to provide a cementitious material that is uniform in chemistry and properties independent of the location where the materials are obtained. Two methods of production are described. One is a high temperature process in which materials are processed in a semi-molten or molten state. The second process is a low temperature aqueous process.

What is claimed is: 
     
         1 . A synthetic pozzolan comprising:
 at least 10% by mass of an activatable amorphous phase comprised of one or more of siliceous, aluminosiliceous and aluminous material, said activatable amorphous phase configured to be activated by conducting a chemical reaction to form a cementitious compound.   
     
     
         2 . The synthetic pozzolan of  claim 1 , further comprising a crystalline phase. 
     
     
         3 . The synthetic pozzolan of  claim 2 , wherein said crystalline phase comprises in its majority crystalline melilite. 
     
     
         4 . The synthetic pozzolan of  claim 2 , wherein said crystalline phase comprises in its majority crystalline plagioclase feldspar. 
     
     
         5 . The synthetic pozzolan of  claim 2 , wherein said crystalline phase comprises in its majority crystalline alkali feldspar. 
     
     
         6 . A method of making a synthetic pozzolan, said synthetic pozzolan comprising at least 10% by mass of an activatable amorphous phase, the method comprising the step of performing a solid state reaction in a high temperature process to produce a clinker. 
     
     
         7 . The method of making a synthetic pozzolan of  claim 6 , wherein said step of performing a solid state reaction in a high temperature process comprises the steps of:
 selecting one or more precursor raw materials;   analyzing the chemical compositions of said one or more precursor raw materials;   blending said one or more precursor raw materials to obtain a blended precursor composition with a bulk molar ratio of Ca to the sum of Al, Fe, Mg, Si of 0.5-1.0 and a sum of metal oxides of Al, Fe and Mg of at least 14% by weight; and   heating said blended precursor composition to a temperature between 800° C. and 1400° C. for a time sufficient to react said blended precursor composition to produce a melilite based clinker.   
     
     
         8 . The method of making a synthetic pozzolan of  claim 6 , wherein said step of performing a solid state reaction in a high temperature process comprises the steps of:
 selecting one or more precursor raw materials;   analyzing the chemical compositions of said one or more precursor raw materials;   blending said one or more precursor raw materials to obtain a blended precursor composition with a bulk chemistry of AlSi 2 O 8  with the addition of a one or more of CaAl (anorthite end member), NaSi (albite end member), or KAl (orthoclase end member) with a molar ratio of the CaAl+NaSi+KAl components to AlSi 2 O 8  of 0.8-1.2 to 1; and   heating the blended precursor composition to a temperature between 800° C. and 1400° C. for a time sufficient to react said blended precursor composition to produce a plagioclase feldspar based clinker.   
     
     
         9 . The method of making a synthetic pozzolan of  claim 6 , further comprising the step of using of a pretreatment chemical to improve a reaction rate or a maximum extent of reaction of said solid state reaction over said reaction rate or said maximum extent of reaction that is observed in the absence of said pretreatment chemical. 
     
     
         10 . The method of making a synthetic pozzolan of  claim 9 , wherein said pretreatment chemical is an organic acid solution containing at least one of acetic acid, citric acid, tartaric acid, gluconic acid, and oxalic acid. 
     
     
         11 . The method of making a synthetic pozzolan of  claim 6 , comprising the step of introducing said pretreatment chemical during grinding of the clinkers. 
     
     
         12 . The method of making a synthetic pozzolan of  claim 6 , comprising the step of introducing said pretreatment chemical to a ground clinker. 
     
     
         13 . A method of making a synthetic pozzolan, said synthetic pozzolan comprising at least 10% by mass of an activatable amorphous phase, the method comprising the step of performing an aqueous reaction in a low temperature process. 
     
     
         14 . The method of making a synthetic pozzolan of  claim 13 , wherein said step of performing an aqueous reaction in a low temperature process comprises using a precursor comprising a silicate mineral configured to decompose or incongruently dissolve to form an activatable amorphous phase and a precursor chemical configured to aid in the decomposition or dissolution of the precursor mineral. 
     
     
         15 . The method of making a synthetic pozzolan of  claim 13 , further comprising the step of percolating a CO 2  containing waste gas through a reactor. 
     
     
         16 . The method of making a synthetic pozzolan of  claim 13 , wherein said precursor chemical is an acid. 
     
     
         17 . The method of making a synthetic pozzolan of  claim 13 , wherein said precursor chemical is derived from CO 2  gas. 
     
     
         18 . The method of making a synthetic pozzolan of  claim 13 , wherein said precursor chemical is synthesized from CO 2  gas. 
     
     
         19 . The method of making a synthetic pozzolan of  claim 13 , wherein said precursor mineral is selected from a naturally obtained mineral, a siliceous limestone, a clay, wollastonite, olivine, and feldspar. 
     
     
         20 . The method of making a synthetic pozzolan of  claim 13 , wherein said precursor mineral is a manmade material selected from ordinary Portland cement, a calcium sulfoaluminate cement, a calcium aluminate cement, a carbonateable calcium silicate cement, and synthetic foundry sand. 
     
     
         21 . The method of making a synthetic pozzolan of  claim 13 , wherein said precursor mineral is a synthetically produced pozzolan. 
     
     
         22 . The method of making a synthetic pozzolan of  claim 13 , wherein said precursor mineral is selected from a waste material, slag and fly ash. 
     
     
         23 . The method of making a synthetic pozzolan of  claim 13 , wherein said activatable amorphous phase comprises SiO 2  and Al 2 O 3 . 
     
     
         24 . A composite material produced by the blending of a synthetic pozzolan of  claim 1  with an activator and water. 
     
     
         25 . The composite material of  claim 24  wherein the activator is selected from hydraulic cement (1-70 wt %), free lime (1-20 wt %), calcium hydroxide (1-20 wt %), and alkali hydroxides (NaOH, KOH 1 to 10 wt %), individually or in combination.