Preparation Of Fly Ash-based Phosphate Geopolymer Materials And Performance Studies

Nowadays,the world is in the post-epidemic era,the rapid development of industrialization and modernization in various countries,the aggravation of the global "greenhouse effect" accompanied by the accumulation of a large number of solid wastes as industrial by-products,relying only on traditional landfill and other treatment methods is far from meeting the needs of China’s ecological civilization construction,and also goes against the original intention of high-quality economic development,so it is urgent to solve this problem.Geopolymerization technology has been recognized as a new alternative to ordinary Portland cement,providing a new option for the disposal of industrial wastes such as fly ash and tailings.Compared with the preparation process of ordinary Portland cement,CO2 emissions can be reduced by about 80%,and the utilization rate of waste resources can be greatly improved when it is green and environmentally friendly.Fly ash was used as the main raw material,phosphate solution was used as the initiator in this paper,,and the Box-Behnken experimental design method in the response surface method was used to select the moisture content,liquid-cement ratio and curing temperature of the provocant as the response factors,and the mechanical properties(compressive strength,bonding strength)as the response values,and the optimal mixing ratio of fly ash-based phosphate geological polymers was obtained.On the basis of this ratio,the retarding effect of five retarders and their influence on the mechanical properties of specimens were studied.According to the results obtained by the optimization of the response surface design,the optimal mixing ratio of fly ash-based phosphate geopolymer is: 67.04%,the liquid-cement ratio is 0.65,and the curing temperature is 65.56 ℃,the compressive strength of the specimen reaches 47.6 MPa and the bonding strength reaches 6.4 MPa,and the relative error with this result is only 2.7% and 5.88%.The microscopic detection results of fly ash-based phosphate ground polymer showed that in a relatively high curing temperature environment,a series of geological polymerization reactions such as polypolymerization and polycondensation of the internal active substances of fly ash under the action of phosphate initiator underwent a series of geological polymerization reactions.With the increase of the curing period,the degree of geological polymerization reaction also increases,forming an obvious three-dimensional network structure,and the specimen structure is dense.However,there are slight cracks on the surface,which is one of the reasons that affect the strength of fly ash-based phosphate geopolymer specimens.The citric acid in the retarder used has an obvious blocking effect on the solidification process of fly ash-based phosphate geopolymer slurry,and has a relatively good retarding effect.The incorporation of citric acid will have a certain degree of influence on the compressive strength of fly ash-based phosphate geopolymer specimens,and decrease with the increasing amount of citric acid adrangement.