Study On The Toughening And Hydration Mechanism Of Fly Ash-slag Based Geopolymer

Geopolymer is a new type of building cementitious material with low energy consumption and environmental protection.Its raw materials come from a wide range of sources,usually formed by the reaction of industrial solid waste and alkaline initiators,and has the advantages of high strength and good durability,which is conducive to realizing the resource utilization of solid waste and meeting the needs of energy conservation,emission reduction and low-carbon development.In this thesis,fly ash-slag base polymer was prepared by using fly ash and slag from bulk industrial solid waste as raw materials,and water glass solution and sodium hydroxide as alkaline initiators.Through the three-factor four-level orthogonal test,the optimal mixing ratio of fly ash-slag base polymer was obtained,and the toughening study was carried out according to the characteristics of high brittleness and poor toughness of geological polymer.The main research contents and conclusions of this thesis are as follows:(1)Through the adaptation test,the three-factor four-level orthogonal test based on the mass ratio of fly ash and slag,the amount of excitiator and the modulus of water glass were determined,and the primary and secondary laws of the influence of each factor on the fluidity,setting time,flexural strength and compressive strength of the fly ash-slag base polymer were obtained,and the mixing ratio of the geological polymer with better performance was finally determined.(2)On the basis of the optimal mixing ratio of fly ash-slag base polymer,the freeze-thaw cycle test,high temperature resistance test,sulfate erosion test and drying shrinkage test were studied,and the results showed that the mechanical properties of the geological polymer decreased sharply after 40 freeze-thaw cycles;After the sample was calcined at 200℃ for 3 hours,the strength was increased by 12.3% compared with the standard cured sample,and when the calcination temperature was 400℃,the compressive strength of the sample could still be maintained at 82.7MPa;and in different concentrations of sulfate solution,the geological polymer showed good erosion resistance;the fly ash-slag base polymer contracted faster in the early stage,and more than 80% of the ultimate shrinkage could be completed in the first 28 days.(3)Based on the above research,polyvinyl alcohol,polypropylene fiber and basalt fiber were used to toughen the fly ash-slag base polymer,and the impact resistance test was carried out on the geological polymer samples mixed with basalt fiber,and the results showed that the basalt fiber had the best toughening effect on fly ash-slag base polymer,and when the length of basalt fiber was 12 mm and the dosage was 1.0vol.%,the 28 D flexural strength and compressive strength were increased by 41.5% and 5.4% respectively.After the addition of basalt fiber,the number of initial cracks,final cracks,ductility ratio and post-crack energy dissipation of geopolymer samples increased to varying degrees.At the same time,the impact resistance times of basalt fiber geological polymer composites are better subject to the two parameters Weibull distribution.(4)The hydration products and microstructure of fly ash-slag base polymer materials were analyzed,and the results showed that the hydrated calcium silicate(C-S-H)gel,hydrated aluminum silicate gel(N-A-S-H)and some zeolite-like products bonded inert particles that were not completely reacted to form a geopolymer material with dense structure.