Effect of Sol-type Nano-SiO2 and Plasticizer on the Properties of Fly Ash-Slag Geopolymer
Geopolymer is a new type of green cementitious material which is expected to replace ordinary Portland cement to reduce carbon emissions in civil engineering industry.However,the poor fluidity and large drying shrink-age of fly ash-slag geopolymer restrict its further application in the engineering field.Therefore,the effects of com-pound plasticizer and sol-type nano-SiO2 on the working performance,drying shrinkage and compressive strength of fly ash-slag geopolymer were studied through experiments,and the related mechanisms were analyzed.The experi-mental results show that as for the system with the mass ratio of fly ash-slag of 7∶3,compared with the fly ash-slag geopolymer without sol-type nano-SiO2 and plasticizer,the fluidity increases from 176 mm to 198 mm,the drying shrinkage at 27 d decreases by 31.2％,and the compressive strength at 3,7,28 d increases by 52.2％,24.5％and 32.3％,respectively when the content of sol-type nano-SiO2 and plasticizer is 0.2％and 1.0％,respectively;The addition of sol-type nano-SiO2 and plasticizer increased the active silicon source involved in the reaction and formed more N-A-S-H and C-(A)-S-H gel products,which made the structure of the hardened material more compact.This study can provide reference for the further research and application of fly ash-slag geopolymer.
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