Preparation And Characterization Of Porous Insulation Materials Derived From Fly Ash

In our country,Tongliao of Inner Mongolia has abundant coal resources,but mainly in lignite and bituminous coal with low calorific value of 3100 cal/kg.These coals can only be used for power plant fuel.Due to producing a large number of inferior fly ash,it has caused serious pollution of the local environment.So making full use of these fly ash is of great significances to local economic development and environmental improvement.In order to explore a feasible way to utilize fly ash from Inner Mongolia,the topic focused on using the fly ash to prepare autoclaved porous materials.Based on a series of experiments and characterization,the physical and chemical properties of fly ash,the activity of fly ash and activating,the mass ratio of raw material and its relationship of product performances,and the key factors influencing the strength of product were studied,respective.It was shown that the fly ash was of coarser,which particles of less than 45?m only accounted for 22.6%,and of more than 80?m was up to 33.3%.The content of silicon oxide and alumina oxide reached to 84.8%,but mainly in quartz and mullite.The content of SiO2 and Al2O3 of hydration was few.The glass phase content was only 41.2%.Based on the above,the fly ash belonged to the poor quality and low activity fly-ash.With using Na2CO3 as excitation agent,SiO2 and Al2O3 were effectively released.As a result,the activity of strength of fly ash was effectively improved.Through a single variable and the orthogonal experiment method,the combination ratio of raw material of B05 level sample was determined with fly ash:lime:cement:gypsum:aluminum paste:Na2CO3=70:19:9:2:0.13:0.5,water-solid ratio of 0.52.C/S exercised the formation and crystalline state of tobermorite,and then affected the strength of the products.When C/S was 0.48,hydration products were mainly gel,the number of tobermorite was only 5.3%,the sample was of a low compressive strength.With increasing C/S,the generation of tobermorite gradually increased,and the crystallinity was also getting better,so the compressive strength increased.When C/S was 0.53,the content of tobermorite reached to 15.0%,and hydration products crossed closely.But increasing C/S to 0.55,crystal arranged directionally,and the content of tobermorite reduced to 14.7%,the strength of sample began to decrease.Steam pressure affected the generation of tobermorite by changing SiO2 dissolution rate.With the pressure enhancing,the dissolution rate of SiO2 of raw material constantly increased,and the generated content of tobermorite also increased.When pressure was up to 1.1 MPa,the content of tobermorite did not change with enhancing the pressure.Holding time affected the state of hydration products.When holding time was 5 h,the size of crystal was smaller,more hole clearance existed among the hydration products.With the time extending,the tobermorite of willow leaf shape grew up gradually,and the crystallinity was getting better,structure was more compact.When holding time was up to 8 h,the state of tobermorite had translated to wide leaf,and the compressive strength began to reduce.Samples in investigation were prepared by compounding materials in accordance with the combination ratio of fly ash:lime:cement:gypsum:aluminum paste:Na2CO3=70:19:9:2:0.13:0.5,0.52 water-solid,and by autoclaving at 188 C under hydrothermal conditions with steam pressure 1.IMPa for 6 h.The dry density,compressive strength,and thermal conductivity of the resultant were 493 kg/m3,3.85 MPa,and 0.109W/(m·K)respectively.The technical indicators were superior to the requirement of national standard level of B05 classy.