In geopolymerization process water plays a major role

In geopolymerization process, water plays a major role in removal of solid particles as well as in hydrolysis of the dissolved Al3+ and Si4+ ions at the high HOAt of the activating solution [12]. The pH and Si/Al ratio greatly influences the formation of Ca compounds in geopolymers in solid material containing SiO2, Al2O3, and CaO [55]. It has been established by previous studies that alkalinity is a necessary precondition for destruction of raw material. Pure water cannot activate the solid material in the system of alkaline activation (i.e., rich in SiO2 and CaO which is a cementitious material). It requires large amounts of OH- anion in the pure water to facilitate such a process [12]. Addition of water helps not only the transfer of ions and polycondensation of Al and Si monomeric/oligomeric species but also provides the medium for the dissolution of aluminosilicate precursors and speciation [12]. The alkali-activated mechanism causes polycondensation reaction of geopolymeric precursors such as forming alumino-silicate oxide with alkali polysialates resulting in polymeric Si–O–Al bond [55]. It has the formula Mn[–(SiO2)z–AlO2]n·wH2O, where M is the alkali element, n is the degree of polymerization generating different types of poly(sialates), z is 1, 2, 3 or higher up to 32, and w ? 3.