Study On The Physical And Mechanical Properties Of Alkali Activated Slag-fly Ash Gel

The research object of this paper is alkali-excited cementitious material.The current mainstream formulation and preparation methods are alkali exciter and solid silicate powder(common and commonly used with fly ash and slag)for reaction.Its advantages of high strength,good durability and low energy consumption have been widely concerned by researchers,but its shortcomings of fast coagulation and large shrinkage limit its application range.up to now,alkali-excited materials are considered as a new building cementitious material to replace OPC because of their good environmental benefits and excellent engineering properties.The preparation method of ordinary Portland cement is mature,The industrial chain is complete,but greenhouse gas emissions have always been the point of controversy,especially the current environmental monitoring more stringent,so in order to slow this trend or even replace traditional cement,alkali-inspired cementitious materials become a new type of building cementitious materials.In the current research,it is considered that good environmental protection benefits can be achieved.This study uses FA and Slag as cementitious materials to explore the working properties,physical and mechanical properties,including fluidity,reaction rate and compressive strength of alkali-activated slag-fly ash cementitious materials after incorporation of sodium lignosulfonate(MZS)and barium chloride(BC).the degree of hydration and the activation mechanism of dissolution of vitreous in the material were characterized by microscopic methods.The experimental research results are as follows:1.Strength is an important index in macroscopic characteristics,which directly affects the practical application of materials in engineering practice.Taking into account the strength and working performance of materials,the content of slag should be controlled at 60~70% wt.2.With the increase of MZS content,the compressive strength of the paste did not change obviously;the compressive strength of the paste increased first and then decreased with the increase of BC content in 7 days,and the strength of 28 days did not change obviously with the increase of BC content.The setting time of alkali activated slag-fly ash gel material increases with the increase of MZS content,and the setting time of slurry increases with the increase of BC content.The fluidity of the slurry was not significantly improved like ordinary Portland cement after incorporation of MZS;the higher the BC content,the worse the fluidity of the slurry.3.SEM observed that the slag was basically hydrated,and some attachments were wrapped on the FA surface,and a few FA did not have hydration,C-S-H the gel structure was relatively dense,which had little effect on the strength of the sample for28 days.The hydration heat release curve found that the hydration heat release curve mixed with MZS was basically consistent with the change situation of the BC sample,and two exothermic peaks appeared until the hydration entered a gentle period,the hydration was basically completed,and the gel in the slurry tended to be stable;the reaction of the slurry mixed with BC was obviously slower than the hydration rate of MZS.XRD analysis found that the diffraction peaks were mainly mullite 、 calcite 、quartzite in the slurry,and the hydration products were mainly C-S-H,these gels were mostly in amorphous morphology.The result of thermogravimetric analysis showed that with the increase of the MZS content,the curve change of the slurry was basically thesame as that of the KB,indicating that the strength and KB of the 28 days sample mixed with MZS did not change much,and the mass loss of the BC sample was obviously lower than that of the mixed sample.