Study On The Modification Of Alkali Activated Slag Cement Mortar

The slag of granulated blast furnace has the potential of water hardness and the ability of cementing under the excitation of alkali.Compared with the same water-cement ratio of Portland cement,alkali activate slag with high early strength,low hydration heat,and the advantages of good durability,is expected to become one of the alternatives of Portland cement.However,alkali activated slag has a fast coagulation time and a large shrinkage,which limits its application.Therefore,it is helpful to study the modification of alkaline activated slag to promote its application in engineering.This subject has been conducted primarily in the following study:1.To study the effects of alum,gypsum,polypropylene glycol,2-methyl 2,4-pentyl glycol on the fluidity,mechanical properties and shrinkage performance of alkaline activated slag cement mortar.Alum and polypropylene glycol can improve the fluidity of the mortar,gypsum will have little effect on the fluidity of the mortar,and the dosage of 2-methyl 2,4-pentanediol will exceed 0.5 percent,and the mortar will be isolated and bleeding phenomenon.Single addition of alum,gypsum,polypropylene glycol,2-methyl 2,4-pentaerylenediol can reduce shrinkage to different degrees,but they also have certain side effects on mechanical properties.Considering the fluidity,mechanical properties and shrinkage properties of alkaline activated slag cement slurry,4%gypsum or 3%polypropylene glycol are relatively superior as modified materials.2.On the basis of the addition of admixture to the alkali activated slag cement mortar,the mineral admixture shall be incorporated,and the effect of the combination of admixture with mineral admixture on the fluidity,mechanical property,shrinkage and water absorption of the alkali slag mortar.A certain dosage of lime stone powder,glass powder,and limestone powder and glass powder composite made mixed gypsum or poly propylene glycol alkali slag cement mortar fluidity,strength,bibulous rate is increased;Limestone powder increases the shrinkage rate of alkali slag mortar mixed with gypsum or polypropylene glycol,and glass powder reduces the shrinkage rate of alkali slag mortar mixed with gypsum or polypropylene glycol,and the shrinkage of lime stone powder and glass powder compound is not greatly affected by the shrinkage rate of alkali slag mortar of gypsum or polypropylene glycol.3.The results of IR analysis showed that the hydration products of alkali-activated slag cement mortar were mainly calcium silicate hydrate?c-s-h gel?and zeolite minerals.Compared with ordinary Portland cement,it did not contain Ca?OH?₂ crystals and AFt.After adding gypsum into alkali slag mortar,AFt was formed,which improved the shrinkage performance of mortar to a certain extent.The results of SEM analysis showed that the alkaline slag mortar with different components had a significant hydration reaction at 28 days.The hydration products were closely connected and combined into a dense whole.The alkali slag mortar mixed with gypsum has a more compact microstructure than the reference group.The results of NMR analysis show that the pore size of alkali slag mortar with different components is smaller than that of cement mortar,indicating that alkali slag mortar has better pore structure.