| In this paper,fly ash and slag were used as raw materials,and water glass and NaOH were applied as activator to prepare alkali activated fly ash/slag blended material.The effect of water glass modulus and slag addition on setting time,fluidity and compressive strength of alkali-activated fly ash/slag blended system were studied.The early exothermic reaction,microstructure,reaction products and pore struture were investigated to explore the reaction mechanism of alkali-activated fly ash/slag blended system.The main results are as follows:The setting time of alkali activated fly ash / slag blended system is relatively short,and the initial coagulation occurs in the range of 30~45min.When the modulus of activator is 0,1or 1.5,the setting time of the sample decreases with the increase of the slag content.When the modulus of the activator is 2,the setting time of the sample increases with the increase of the slag content.Modulus of activator is 0,liquid alkali activating system is the worst;when the activator modulus is 1.0-1.5,liquid alkali activating system is relatively good;when the activator module 2,incorporation of slag flow can improve the system performance.With the increase of slag content,the compressive strength of alkali activated materials can be significantly improved.The flow properties of alkali activated fly ash / slag blended system can be improved effectively by adding water reducing agent.When the activator modulus is 0,the compressive strength of the poor performance of alkali activated system;when the activator modulus is 1.0-1.5,can be prepared with good mechanical properties of alkali activated materials;when the activator modulus is 2,the compressive strength of alkaliactivated system has great development after 7d.At the same time,when the slag content is30%,the strength of the blended system is the most obvious.The results of alkali activated fly ash/slag blended hydration heat test show that,slag increases,or stimulating agent modulus smaller then,the exothermic peak acceleration of alkali activated fly ash appears early,the time span is small,and the cumulative heat release of the system.The initial setting time of alkali activated system appears near the peak of additional initial peak or accelerating peak.Exothermic reaction system can reflect the degree of the reaction system to a certain extent,for the excitation system of water glass,7 days cumulative heat release system is high,the 7 day strength is higher;but not the cumulative heat release to describe the effects of different activators on the strength of the system.SEM of the sample were observed,the study found that the activator modulus of 1 or 1.5samples of the 7 days of the most dense microstructure;when the activator in the module is 0,the prepared samples of the loose structure in 7 days;incorporation of slag micro structure can improve the alkali activated materials get more dense samples.The results of energy spectrum analysis(EDS)showed that the higher the modulus of the activator,the higher the content of Si in the reaction products.The higher the slag content,the higher the content of Ca in the reaction products.The MIP results show that the modulus of 0 activator,alkali activating system maximum porosity;when the activator modulus is 1 or 1.5,pore structure of the system is more compact;when the modulus is increased to 2,the porosity of the system increased significantly.The greater the amount of slag,the more dense pore structure. |
