Deformation Behavior Of Cementitious Mortar Stimulated By Alkali Under Different Curing Conditions

Alkali-stimulated cementitious material system is a new type of building material,which has a completely different hydration reaction process from traditional Portland cement.Its excellent mechanical properties and special structural characteristics have played an unprecedented role in civil engineering and other fields.At the same time,in the production process of traditional cement,a large amount of carbon dioxide and other gases are produced,making the current environmental problems and the development of human society have a greater conflict,and alkali activated cementing material because it does not contain limestone,in its production and reaction process will basically not produce carbon dioxide and other greenhouse gases.Therefore,the research on alkali-excited cementitious materials is gradually becoming the forefront of the field of building materials.The raw materials of alkali-activated cementitious materials include metakaolin,slag and fly ash.In order to make the reaction of raw materials more sufficient,alkaline activator must be used.In traditional cement concrete,high alkali concentration is the main factor of alkali aggregate reaction.Among them,alkali-silicic acid reaction is the most common reaction type,so it is worth exploring whether alkali-silicic acid reaction will occur in alkali-excited cementitious materials.To illustrate the alkali excitation gelled material deformation behavior of mortar and alkali silica reaction mechanism,this paper USES the cement,metakaolin and mixing 40%of metakaolin slag three gelled material,quartz,zeolite,and two kinds of basalt as aggregate,first tested the aggregate alkali activity,then studied the mixing of different aggregate of cement and two farming polymer mortar bar at 20℃,95%RH>environment,The deformation behavior of mortar curing in 1mol/L NaOH solution at 38℃ and 2mol/L NaOH solution at 80℃ at a certain age was studied.The composition and microstructure changes of raw materials and products at different ages were analyzed by means of XRF,XRD,SEM,FTIR and HCI titration,and the deformation mechanism of mortar under different curing conditions was compared comprehensively.Through the above research,the results show that under the same conditions,the deformation behavior of geopolymer mortar and cement mortar is different,and the reaction degree of alkali-silicic acid in geopolymer is much smaller than that of cement,and it will be quickly inhibited.Sustainability;under different curing conditions,the reaction process of geopolymers is completely different.Under low-temperature and low-alkali conditions,geopolymers will not expand due to alkali-silicic acid reaction,while expansion will occur under high-temperature and high-alkali conditions-The deformation process of shrinkage-expansion finally forms a zeolite(zeolite-like)structure,which can adsorb alkali and allow water molecules to pass freely without expansion and contraction;the incorporation of slag can increase the reaction degree of metakaolin and accelerate its reaction speed.Adjusting the mixing amount of slag can realize the control of different alkali active aggregates in a reasonable range;the aggregates with strong alkali activity will not show the expansion hazard of traditional cement concrete in the geopolymer.