Preparation Of Geopolymer By The Fly-ash From Fengzhen Power Plant: An Experimental Study

Geopolymer is a new kind of inorganic materials. This research is to utilize coalfly ash from Inner Mongolia to synthesize geopolymers and research their properties,structure and mechanism of geopolymerization.In this experiment, coal fly ash is the main raw materials, sodium silicate(soluble glass) as structural template agent , NaOH as alkali –activator. The process ofpreparing geopolymer by the use of the coal fly ash is as follows: mix solid materialsand liquid, put the mixture into the mould, take it off from the mould. Thecompressive strength of the product can be more than 60 MPa.There are many factors that influence the compressive strength of thegeopolymer. It is showed that, the kind and the quantity of the solid raw material, theratio of the solid and liquid, the solidified time and temperature, the granularity of thesolid material, the consistence of the liquid, the pressure of the moulding and thesolidifying condition are the key factors.In the process of making geopolymer, no new crystal phases are found aftergeopolymerization. XRD analyses show that the crystal phase is mullite.The formation process of the geopolymer can be divided into four steps, i.e.,dissolution of glass particles from fly ash and kaolin in the liquid, diffusion from theparticle surface into interstitial site, concentrating and polymerization of thecomponents by geochemical reactions to form interstitial aluminosilicate gel, andremoval of extra water and solidification of the gel phase. The formation of the matrixphase, which is formed after the last steps, is of importance in the geopolymerizationof the materials. The sufficient reaction and the more amorphous phase in the productcan improve the compressive strength of the geopolymer.