Study On The Preparation And Properties Of Metakaolin-based Geopolymers Under Different Curing Method

Geopolymer is a new type of cementitious material,which has the characteristics of good chemical stability,high early strength,green energy saving and environmental protection.However,its large-scale application is still limited by curing conditions.The geopolymer reaction is the same as conventional thermal curing materials.The curing temperature has a certain influence on the geopolymerization reaction.Increasing the temperature at the beginning of the reaction can accelerate the rapid dissolution of silicon-aluminum materials-aggregate,thereby affecting its performance.In this paper,the research on metakaolin base geopolymer under different curing methods,mainly including temperature-rising curing and electric curing,the main work and research results are as follows:(1)The preparation and performance of early high-strength geopolymers under different curing temperatures(20℃,60℃ and 90℃)were studied.The mechanical change is explained by microscopic morphology changes,mercury intrusion test analysis(MIP)and chemical composition changes,and the reasons for the changes in the mechanical strength of geopolymers at different curing temperatures is reasonably explained.The results show that the compressive strength and flexural strength reach the best under the curing temperature of 60℃.(2)The metakaolin base geopolymer slurry was electro-cured,and the reasons for the temperature change of the geopolymer under different voltages were explained by the changes of microscopic morphology and chemical composition.The study found that as the voltage increases,the current increases,and the sample temperature gradually increases,especially when the AC voltage is 9V,the internal temperature of the geopolymer sample can increase to 115°C when the curing time is 15 minutes.However,the analysis of mercury intrusion test showed that the average pore size gradually increased with the increase of voltage,mainly because the temperature was too high,and the dissolved silica-alumina monomer quickly geopolymerized into a gel,wrapped on the unreacted metakaolin,which would hinder the metakaolin.As a result,the dissolution of the pores will cause the late reaction to fail and the pore size becomes larger.(3)The metakaolin-based geopolymer after curing and curing with alternating current.The study found that as the alternating voltage increases,the internal temperature peak of the geopolymer sample increases,the peak reaching time decreases,and the compressive strength increases.The AC voltage is The compressive strength at 5V increased by 36% compared with ambient temperature curing,and 32% compared with oven curing at the same time.In the microstructure,with the increase of AC voltage,the gel structure is dense,with fewer pores,and the adhesion between the carbon fiber and the gel interface is very good;FTIR analysis shows that as the AC voltage increases,the Si-O-Si bond and the Si-O-Al bond stretches and vibrates asymmetrically,and the wavelength shifts to a lower direction,resulting in an increase in compressive strength.