Research On The Composition, Structure And Performance Of Aluminosilicate Inorganic Polymer Materials

Aluminosilicate inorganic polymer(Geopolymer,GP)is a kind of new-type cementitious materials with three-dimensional network based on the polycondensation of[SiO4]and[AlO4]-monomer/ionic group/oligomersor.It has been received much more attention in area of building materials because of the valuable properties among cement,glass,ceramic,metal and polymers.Most of natural resources,tailings and industrial wastes containing Si and Al could be used as the raw materials in GP.The process of polycondensation and formation of network occurred at relatively low temperature(<100 ?)without calcination process,which would effectively reduce energy consumption and CO2 emissions.Similarity of GP with aluminosilicate Zeolite,rocks,ceramics and glasses in composition and structures make it the proper precursors for artificial aluminosilicate.It can be seen that GP materials have remarkable ecological,green and circular characteristics.However,there are many contradictions and disputes for the forming process,structure evolution and the relationship between properties and composition design.Therefore,this paper focuses on researching formation process,structure and performance of GP.Firstly,fromation process and structures of GP have been simulated.It is shown that the Si-Al polycondensation prefered to Si-Si polycondensation reaction and the GP gel was more likely to develop into a three-dimensional network structure which was similar to the structure of the scaffold-structured silicates.Then,Si/Al and M/Al(M=Li,Na,K,Rb,Cs...,alkali metal ions)were used as the two key factors to research the Na-GP and K-GP system.Polycondensation reaction with relatively low rate and long duration times lagged behind the dissolution and depolymerization process during GP formation.There is no obviously effect of the type of alkali metal ion on GP formation mechamism.However,M/Al,Si/Al and reaction temperature would affect the reaction rate and progress.Relatively high reacation temperature is not suitable for the mechanical properties of GP because of the higher early reaction rate and the zeolitization of gels.Mesoporous microstructures of Na-GP and K-GP gels further proved the zeolite-like structure of GP.Na-GP gels with low Si/Al have obvious zeolitization trendency under hydrothermal conditions,which might result in the mechanical performance degradation.However,it was suitable to synthesize self-supported zeolite or zeolite profile.Excellent hydrothermal stability of K-GP system was observed,which made the K-GP a more suitable cementitious material.The usege of GP in cementitous materials was evaluated based on composition design and forming process,structure,structure evolution from the perspective of workablity and long-time mechanical properties of GP mortar.Results showed that GP had high early strength and later strength characteristics.The workability and mechanical properties could be effectively controlled by adjusting M/Al,Si/Al,curing methods,water/binder ratio and alkali metal ion.However,rather low growth rate or degradation of mechanical properties of GP with low Si/Al might cause potential safety hazard of building structures.So,special attention in design should be paid according to the requirement of engineering.Design and preparation methods of GP were introduced to research the Cs-GP system considering the potential application of rocks,ceramics,Zeolites containing Cs in waste solidification,senior functional ceramics and high temperature catalytic.Cs-GP and the pollucite have excellent selectivity and lattice solidification of radionuclide Cs.However,soluble Cs salts might precipitate out in Cs-GP containing complex ions,and it still needed to be hydrothermal or high-temperature treating to form pollucite.In additon,sub-micron pollucite powders with sphere-like or hollow sphere-like structures were also researched,which would be applied in high temperature catalytic,adsorption filtration or micro reactor.