Study On Mechanical Properties Of Alkali-Activated Fly Ash-Cement

Fly ash,cement,lime and alkali activators are used as raw materials in the process of alkali-activated fly ash-cement cementitious materials,and the fly ash can be used in the preparation process.The preparation process is simple,the energy consumption is low and the environmental pollution is little.Features.At present,the domestic and foreign research mainly focus on the type of alkali stimulant,and the way of alkali excitation on the mechanism and performance improvement of fly ash alkali,and made a lot of research results,but alkali-activated fly ash-cementitious material still exists some problems.In this paper,the mechanical properties,XRD and SEM were used to study the mechanism of alkali-activated system,such as fly ash-cementitious material components,alkali excitation conditions,and so on.And the effects of the composition of the fly ash and cement emulsion on the compressive strength,flexural strength,hydration product and microstructure of the fly ash-cement binder system with high content of fly ash were studied.Based on the gray relational theory,the effects of alkali-activated fly ash-material component of the cement binder system,the curing period,the mathematical model of the relationship between mechanical properties.The main conclusions are as follows:The effects of alkali activator,styrene-acrylate emulsion and lime components on the mechanical properties of high volume fly ash-cement binder system at room temperature were studied.The results show that when the lime content is 10%,the compressive and flexural strength of fly ash cement paste can reach 16.8MPa and 7.3MPa respectively.But with the increase of lime content,the compressive strength and flexural strength of fly ash-cement binder decrease.With the increase of fly ash content,the effect of equal mass of alkaline activator on the activity of fly ash is reduced.When the alkali activator is 10%,the compressive strength and compressive strength can reach 15.6MPa and 7.2MPa.However,when the alkali activator is more than 10%,its strength will be detrimental.When 1%styrene-acrylic emulsion is used,The mechanical strength of the cementitious material is increased,but the excess styrene-acrylic emulsion will reduce the mechanical properties of the cementitious material.The effects of alkali activator,styrene-acrylate emulsion and lime components on the hydration products and microstructure of high volume fly ash-cement binder system were studied.The results show that the amount of C-S-H and AFt in the hydration product of cementitious material 7d can be increased by increasing the content of lime and alkali activator and water-cement ratio in the composite cement paste.SEM showed that the fibers were generated in the hydrated products of the cement-modified fly ash-cement binder.The glassy state of fly ash in the 7d cement paste mixed with 10%lime was destroyed,and more hydrated products appeared around the fly ash particles.The surface of fly ash particles was obviously hydrated in fly ash-cement cementitious material with 10%alkali activator for 7 days,but the alkali excitations were not obvious at 3d.Based on the gray relational theory,the effects of various components and mechanical properties of fly ash-cement binder system were studied.The results show that the effect of lime,alkali activator and water-binder ratio on the early compressive and flexural strength of alkali-activated fly ash-cementitious cementitious material system is alkaline activator>lime>water/binder ratio.The gray correlative degree between fly ash and cement is 0.7460,0.6757,and it is 0.7460,0.6757 and 0.6757 at 3d,7d and 28d,respectively.The mathematic model can be used to characterize the relationship between alkali activator,styrene-acrylic latex and lime components and the curing age and mechanical properties of alkali-activated fly ash-cement binder.