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This paper evaluates fracture toughness of sodium aluminosilicate hydrate (N-A-S-H) gel formed through alkaline activation of fly ash via molecular dynamics simulations. The short- and medium-range order of constructed N-A-S-H structures shows good correlation with the experimental observations signifying the viability of the N-A-S-H structures. The simulated fracture toughness values of N-A-S-H (0.4 – 0.45 π‘€π‘ƒπ‘Ž π‘š0.5) appears to be of the same order as the available experimental values for fly ash-based geopolymer mortars and concretes. These results suggest the efficacy of the molecular dynamics simulation towards obtaining realistic fracture toughness of N-A-S-H which is otherwise very challenging to obtain experimentally and no direct experimental fracture toughness values are yet available. To further assess the fracture behavior of N-A-S-H, number of chemical bonds formed/broken during elongation and their relative sensitivity to crack growth are evaluated. Overall, the fracture toughness of N-A-S-H presented in this paper paves the way for multiscale simulation-based design of tougher geopolymers.


fly ash, geopolymer, sodium aluminosilicate hydrate gel, fracture toughness, molecular dynamics simulations




Journal of Applied Physics 127, 165107 (2020);