Preparation conditions and hydration process of metakaolin geopolymer

The optimum preparation conditions and hydration process of Qingdao metakaolin geopolymer are studied,focusing on the influence of water cement ratio,mixing amount of alkali activator and water glass modulus,to the compressive strength of geopolymer. Compressive strength increased when the water cement ratio was 0. 35,the content of alkali activator to metakaolin was 21% and the modulus of the activator molar ratio of SiO2/ Na2 O was 1. 4. The compressive strength of this sample was 71 MPa when cured at 50 ℃ for 9 d followed by 25 ℃ for 19 d. The hydration process is studied by XRD and SEM. The changing of the microstructure of geopolymer in different time is shown in the test. In the hydration process of geopolymer,they were dehydrated and condensed to form small geopolymer precursors,then changed into big ones. The geopolymer precursors were finally connected into a network structure,forming a dense structure. The main hydration product is network silica alumina gel which is amorphous and its XRD diffraction ranges from 20° to 30°.