Impact of aluminum on the structure of geopolymers from the early stages to consolidated material

The aim of this study is to assess the effects of the addition of aluminum (NaAlO) into the activating solution on the geopolymerization reactions and the characteristics of the porous network. It was established by liquid state NMR that the speciation of the aluminosilicate oligomers and then the mean degree of polymerization were modified by the addition of sodium aluminate in the activating solution. Time-resolved SAXS and rheology results on geopolymer pastes showed that the molar ratios Si/Al and (Si + Al)/NaO in the activating solution play a major role in the geopolymer properties at liquid and solid state. Indeed, the geopolymer percolating network appeared sooner and the properties of the porous network were dramatically changed with the addition of the NaAlO. On the other hand, two geopolymers having identical final chemical composition but a different activating solution composition, showed to the same setting time and the same porous network characteristics