Experimental Study On The Mechanical Properties,Crack Resistance And Impermeability Of Alkali-activated Fly Ash Material Improved By Fiber

By designing the mix proportion of alkali activated materials and selecting the content of sodium hydroxide as the factor variable,the mechanical properties and setting law of alkali activated mortar specimens are experimentally studied and compared with cement mortar specimens.On this basis,the effects of carbon fiber,basalt fiber and polypropylene fiber on the mechanical properties,fluidity,crack resistance and impermeability of alkali activated materials are studied by changing the type and amount of fiber.The main conclusions are as follows:(1)The compressive and flexural tests show that with the increase of sodium hydroxide content,the mechanical properties of the specimens first increased significantly and then decreased continuously.The sodium hydroxide content of 24g(5.3% of the gel mass percentage)was the best,and the compressive strength of alkali activated specimens was obviously better than that of cement samples.The condensation experiment shows that with the increase of sodium hydroxide content,the initial setting and final setting time continue to shorten,and finally remain stable.The alkali activated material has significant rapid setting characteristics.(2)The experiments of fiber reinforced compressive strength and flexural strength show that the addition of fiber leads to a slight decrease in compressive strength,but a significant increase in flexural strength.The reinforcing effect of carbon fiber is better than that of basalt fiber,and the reinforcing range of polypropylene fiber is the smallest.The fluidity experiment shows that the addition of fiber leads to the decrease of fluidity,the influence of polypropylene fiber is lower than that of carbon fiber,and basalt fiber has the greatest influence on fluidity.When the content of carbon fiber is 0.5%,the compressive strength of the specimen is reduced by 10%,the flexural strength is increased by 25%,and the fluidity is reduced by 6.7%.(3)The crack resistance experiment shows that the characteristics of rapid setting and early strength are the reasons why the crack resistance of alkali activated material is better than that of cement under the experimental conditions.0.1% carbon fiber content can significantly improve the crack resistance of alkali activated specimens,while the same strengthening effect of carbon fiber(0.1%)can be achieved only when the content of basalt fiber and polypropylene fiber reaches 0.7% and 0.5% respectively.When the content of carbon fiber reaches 0.5%,the cracking of the specimen can be completely restrained,while the content of basalt fiber and polypropylene fiber needs to reach 1.0% and 0.9%.The super-high tensile strength of carbon fiber,high adhesion with alkali activated materials and good dispersion are the reasons why its reinforcement is obviously better than other fibers.(4)impermeability test shows that alkali activated concrete has better impermeability than cement concrete,and alkali activated material polymerization produces lump and flake hydrated calcium aluminosilicate gel,which makes the microstructure more compact and better overall.The addition of carbon fiber and polypropylene fiber can further improve the impermeability of alkali activated concrete.With the increase of fiber content,the impermeability of alkali activated concrete increases first and then decreases.The addition of basalt fiber leads to the continuous decrease of impermeability.The agglomeration of fibers leads to the increase of micro pores and cracks,which is the main reason for the decrease of impermeability.Figure 43 Table 32 Reference 113...