Analysis Of Influencing Factors On Geo-polymerization Process Of Alkali-activated Fly Ash

As a new green material,alkali-activated materials have excellent engineering and technical performance,prominent attribution of sustainable development and huge market potential.Compared with traditional cement and concrete materials,alkali-activated m aterials have significant performance advantages and economic benefit and have become the research focus at home and abroad,on concrete pavement reparation,preparation and reinfor cement of soft soil foundation in road engineering.But in current researches,the raw materials of alkali-activated material concentrate mainly on metakaolin and slag,whereas the theory focus on the fly ash produced alkali-activated material is less likely to be found.Also,the lack of systematical and further studies on alkali-activated reaction mechanism and preparation of fly ash limits its development and potentially utilize in this field.In this paper,fly ash as the main raw materials were used to prepare alkali-activated fly ash material,based on the orthogonal and parallel test,optimizes the mixture ratio.And this preparation method is simple and cost-effective.By study the fluidity,setting time and strength of alkali-activated fly ash material,a systematic analysis was made on the influence of the factors including fly ash,cement ratio,environment temperature,etc.Select the representative mixture ratio and observe its microstructure using scanning electron microscopy(SEM).The conclusions are as follows:Alkali-activated material with good performance were prepared by the class F fly ashes of level I,II and class C fly ash,but the class C fly ashes have more advantages in enhancing early setting and hardening.Compared with the NaOH,KOH solutions,the sodium silicate solution activated better results,and the best modulus range are 1.2~1.3.The alkali-activator has suitable dosage range,and the optimum is 1molNa2 O,1.3molSiO2(Per kilogram of raw materials),and the alkali-activator should be aged 24 h.The addition of slag can significantly improve mechanical property,shorten the setting time of cement paste,and on the basis of adding 20% slag,the compound additions of 4-12% silica fume is helpful to improve the material mechanics performance.With nature atmosphere condition,high temperature is more advantageous to the reaction of polymerization.And the best temperature in steam curing condition is 75℃,and curing time is 24 h.It can be observed by SEM whichcomposition of Slag can add gel phase to the internal systems and obtain dense structure.The lower modules of sodium silicate is helpful for the surface corrosion of fly ash particles,and around the particles,the deposition of reaction product increases.The macroscopical technical performance of alkali-activated fly ash material are decided by its polymerization process,and this article studies its main influencing factors.