SiO2/Al2O3 atomic ratio in the hardened binder depends mainly on the reactivity of Al–Si because not all the silica and alumina are reactive so even despite the fact Al and Si have synchrodissolution behaviour in alkaline solution, meaning they dissolve from the mineral in some linked form [2] one can not expect the same Si/Al ratio in the final hydration product as the one present in the original precursor material. Indeed most of the Al–Si materials cannot even supply sufficient Si in alkaline solution to start geopolymerization, this explains why they need extra silica provided in solution by waterglass, which influences the Si/Al ratio of the hardened binder. Mine waste Blaine fineness is low but is in the range of the most used slag based alkaline binders. Despite the fact that increased fineness led to increase reactivity that can be overcome by using highly alkaline–silicate activators. Fernandez-Jimenez et al. analysed the joint effect of specific surface, curing temperature, nature and concentration of alkaline activator and found out that specific surface is the factor least statistically relevant, also reporting mechanical decrease with specific surface increase when using NaOH and waterglass activator [33].