Fly ash processing and manufacture of articles incorporating fly ash compositions

A method of forming a shaped article having a matrix containing sintered fly ash, the method comprising the steps of:

• providing in a mould a mixture containing a fly ash composition comprising fly ash and a plasticising agent, the fly ash composition being in a powder form having an average particle size of less than 50 μm (micron), and wherein the fly ash composition includes greater than 70% fly ash by dry weight of the fly ash composition, and wherein the plasticising agent being capable of binding the fly ash particles in the fly ash composition together on pressing of the fly ash composition;
• pressing the particulate fly ash mixture by uniaxial pressing at a pressure of greater than 200 kg/cm2 in the mould to temporarily bind the mixture to form a green article shaped by the mould, wherein the water content in the green article is less than 6 wt % of the total weight of the green article, and wherein the modulus of rupture of the green article is greater than 1.5 kg/cm2 so as to enable handling of the green article by handling equipment;
• and
• firing the green article to sinter the fly ash;
• wherein the mixture has substantially no green strength prior to pressing the mixture.