Research On The Properties Of Geopolymer By Autoclaved Process

Geopolymer, a new inorganic nonmetallic cementing material, which is manufactured mainly from various active aluminosilicate minerals and alkali-activator, is prepared by proper forming process and certain curing condition. For now, some scholars always pay more attention on the standard curing condition or the curing condition with the temperature less than 100 degrees on the preparation of geopolymer. There is less study on the autoclave curing process.Through the orthogonal test and single factor experiment, first, this paper reports a study on the factors affecting the performance of geopolymer pas te, especially the quartz powder admixture, the modulus of waterglass, and the content of alkali activator. Then there is a discussion on the impact of some factors to the compressive strength of geopolymers, including the quartz powder admixture, the modu lus of waterglass, the content of alkali activator, water-cement ratio, the autoclave curing time. The microstructure of products was studied by SEM with focusing on the role that the quartz powder plays in the autoclaved stage in alkali surroundings. Besi des, the effects of mineral admixture such as slag and fly ash on the performance of geopolymer were discussed. At last, a preliminary research was made on the anti-acid erosion performance of geopolymer material.The results showed that:(1)The modulus of waterglass, and the content of alkali activator had a great effect on the setting time and fluidity of geopolymer paste. The addition of the quartz powder might not change the setting time of geopolymer paste, but it decreased the fluidity of geopolymer paste.(2)The addition of the quartz powder improved the compressive strength of geopolymers, and the quartz powder was tightly bound to hydration products. The microstructure studies showed that the quartz powder became activated in the autoclaved stage in alkali surroundings with its surface was eroded.(3)With the conditions of quartz powder content of 50%, the modulus of waterglass of 1.6, the content of alkali activator of 16%, water-cement ratio of 0.46, and autoclave curing time of 3 hours, the stren gth of geopolymers could reach 76.6 MPa. Proper reaction time was benefit to make the reaction carried out adequately with the development of the compressive strength. But too long a time for the autoclaved stage reduced the compression strength of geopoly mers.(4)Fluidity improvement would be increasing as the admixture increased. The admixture had a great effect on the setting time of geopolymer paste. The addition of the slag improved the compressive strength of geopolymers. By adding 5%(mass fraction) slag, the compressive strength of geopolymers got a 66 percent improvement. The addition of the fly ash reduced the compressive strength of geopolymers.(5)The autoclave curing time and the content of alkali activator had a great effect on the anti-acid erosion performance of geopolymer material. The geopolymer material prepared by lower content of alkali activator and longer autoclave curing time had the high strength remanent ratio and weight remanent ratio soaked in the acid solution for 28 days.