Abstract: Geopolymer gel is a new type of inorganic cementitious material that mainly composed by three-dimensional aluminosilicate spatial network structure with a variety of amorphous to semi-crystalline phases. In this work, the pure geopolymer gel with different Ca content were prepared by sol-gel method, and their structures were characterized by X-ray diffraction. Different structures of N-A-S-H and C-A-S-H geopolymer gel, based on Monte Carlo method, were build and optimized under the Universal force field of Materials Studio (MS) , and its radial distribution function and structure parameters were worked out. The elastic modulus and X-ray diffraction pattern of different type of geopolymer gel were si-mulated. The results show that geopolymer gel can be divided into 4 systems by the content of calcium, named no calcium system, low calcium system, middle calcium system and high calcium system. The main structure of the 4 systems were different: N-A-S-H gel to no calcium system, N-A-S-H and C-A-S-H gel to low calcium and middle calcium system, C-A-S-H gel and Ca(OH)2 to high calcium system. The CaO of the low calcium system was less than 16.7%, and that in the high calcium system was more than 30%. Under the Universal force field, the elastic modulus of geopolymer increased by the content of Ca, and that of pure N-A-S-H gel and C-A-S-H gel were 22.04 GPa and 62.37 GPa, respectively. Through the radial distribution function distribution, the molecular structure of geoplymer gel was typically amorphous, and its average chemical bond length matched well with experiment values. The peaks of the radial distribution function of Si-O, Al-O and O-O bonds were divided in some way, and the chemical type of Si-O, Al-O and O-O bonds became more complicated with the increase of Ca.
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2020, Vol. 34 
