Properties And Microstructure Of Geopolymer Containing Superabsorbent Polymer

The drying shrinkage of geopolymer has been the main reason limiting its application.In this paper,the influence of super absorbent polymer(SAP)on three kinds of geopolymer,i.e.fly ash based(F-based),fly ash-slag based(FS based)and fly ashslag-silica based(FSS based),are studied,with the emphasis on the fluidity,setting time,mechanical properties and drying shrinkage of geopolymers after adding sap.Based on FTIR,MIP,SEM and superfield microscopy,the mechanism of SAP action on geopolymers is explored,which provides theoretical basis for the large-scale use of geopolymers in the future.The results show that the addition of SAP can reduce the fluidity of geopolymer,and the addition of extra amount water can make up for the loss of fluidity.When the extra amount water is 20 g / g,the fluidity of SAP modified geopolymer is the same as that of the control group.The water absorption properties of sap in the three geopolymers are almost the same.In the fly ash based and fly ash-slag based polymers,the addition of SAP will reduce the setting time.With the increase of the additional water ratio,the setting time of geopolymer will increase,which is greater than that of the control group without sap.The setting time of fly ash-slag-silica based geopolymer will increase with the addition of sap,and will continue to increase with the increase of the ratio of extra water.Adding SAP will reduce the mechanical properties of geopolymers.When the amount of sap is too large,adding 10 g / g of extra water can make the mechanical properties of geopolymers reach a peak by improving the fluidity,and then continue to add extra water will reduce the mechanical properties.The addition of sap and appropriate amount of extra water inhibited the drying shrinkage of geopolymer.When the content of sap was 0.3%,the drying shrinkage of F based geopolymer decreased by 27.5%,when the content of sap was 0.2%,the drying shrinkage of FS based geopolymer decreased by 13%,and the drying shrinkage of FSS based geopolymer decreased by 34.9%.The results of pore structure analysis show that the addition of SAP will reduce the content of small pores in geopolymer and the most probable pore size of large pores.However,adding too much extra water will increase the content of pores and drying shrinkage of geopolymers.The analysis results of macropore under the superfield microscope show that the content of macropore will increase when sap is added,and the effect of extra water on the content of macropore is small.SEM results show that there are many micro cracks in geopolymer,which are reflected in SEM as large pores,and the decrease of the content of large pores indicates that the micro cracks of geopolymer are reduced.FTIR results show that the internal curing effect of SAP promotes the reaction degree of geopolymer.