Study On The Compressive Strength And Reaction Level Of Alkali-Activated Fly Ash-GGBFS Blend

Geopolymer is an inorganic polymer with three-dimensional network structure which is formed by geological polymerization of natural mineral materials or industrial wastes rich in silicon and aluminum with alkali activator.Taking fly ash,blast furnace slag and other industrial solid wastes as the main raw materials for the preparation of geopolymer is of great significance to the concept of promoting the application of geopolymer to reduce the amount of cement and the sustainable development of civil engineering.At present,the research on composite cementitious materials is very limited.Few scholars have conducted quantitative analysis on the number of gels produced by geopolymerization in the complex alkali excitation system,nor have they proposed reliable analysis methods,nor established the relationship between the compressive strength and the number of gels.Based on the above research background,this paper studied the factors and mechanisms affecting the compressive strength and reaction level of the alkali-activated fly ash-slag composite cementitious material(AAFS)in a binary cementitious system composed of fly ash and slag.The research contents and main conclusions are as follows:(1)According to the test results of the compressive strength of AAFS net slurry at different ratios,the compressive strength of AAFS decreases with the increase of liquid-solid ratio and modulus under different slag content,and increases first and then decreases with the increase of concentration.When the liquid-solid ratio,modulus and concentration are at the same level,the compressive strength of AAFS shows a trend of first increasing,then decreasing and then increasing with the increase of slag content.(2)Through orthogonal test,it is found that the slag content has the greatest influence on the AAFS compressive strength,followed by the concentration of the activator,the liquid-solid ratio and the activator modulus.(3)According to the results of phase analysis of XRF,XRD.FT-IR and acid dissolution test,the reaction level of fly ash in AAFS can be determined by measuring the dissolution rate of AAFS in solution with pH=0.(4)The acid dissolution test of the composite cementitious material shows that the addition of slag improves the geological polymerization reaction level of fly ash in most cases.When the slag content is constant,the reaction level of fly ash increases with the decrease of the activator modulus and the increase of the liquid-solid ratio.With the increase of the concentration,the reaction level of fly ash increases first and then decreases,and the promotion effect of low slag content on the reaction level of fly ash is more significant.When the concentration of activator is low,the reaction level of fly ash increases with the increase of slag content.When the activator concentration is high,the slag content first increases and then decreases with the increase of the slag content,and the slag content corresponding to the highest reaction level of fly ash gradually decreases.