Structurization processes of cement composites modified with electrolytic additives

Building Materials

There has been research on the impact of AlCl3 and FeCl3 solutions on kinetics of cement hardening. The research was carried out in two comparative versions, one of which had the saline solutions introduced into cement as gauge liquid (“water–1% electrolytic solution”), the other had them as additives, synthesized in suspensions “cement – (water–1% electrolytic solution)”. It has been stated that the use of AlCl3 and FeCl3 solutions as gauge liquids leads to reduction of compression resistance values of modified cement rocks. The value of 28-day hardness, compared to plain cement, is reduced by 18 % in case of cement gauging with AlCl3 solution, and by 27% in case of binder gauging with FeCl3 solution. On the contrary, the composites, produced by means of introducing the additives, synthesized within suspensions, into cement paste, have shown a significant boost in 28-day hardness compared to plain sample – by 30 and 23 % accordingly. The analysis of the result studies of the additives by means of XPA and IR-spectral analysis has shown that within the structurization of additives the interrelated changes take place, due to the rapid decrease of portlandite amount and carbonization. The authors suppose the acceleration of setting and the higher strength of cement composite with the introduced additive, synthesized by means of cement exposure to 1 % AlCl3 solution, to take place due to synergic influence of a number of factors: intensive growth of ettringite crystal seeds and badly crystallized phases of hydrated calcium silicates of tobermorite-like structure; reduction of Ca(OH)2 in the hard phase of a cement rock; and carbonization effect, which includes the formation of crystal phase for Ca8Al12Fe2C12(CO3)∙(OH)2∙22H2O. The improvement of density properties of a cement composite after introducing the additive, synthesized by means of cement exposure to 1 % FeCl3 solution, is probably facilitated by gauging of Ca(OH)2, or may be explained by “working” CaCO3 and ettringite microcrystals, catalyzing the intergrowth of composite skeletal frame, or by “working” gelatinous hydrated calcium ferrites and silicates, characterized by a high surface area, which facilitate and boost interphase contacts, increasing the density of cement systems.