Les alcalins appartiennent-ils à la structure des gels, produits des alcalis-réactions dans les bétons ?

Using two distinct series of experiments, the behaviour of the alkalis (Na, Li) in solutions equilibrated with a synthetic get (CaO/SiO 2 = 0.5), analogous to the gels produced by the alkali-reactions in concretes, was studied. In the first series of experiments, a fixed volume (10 ml) of a 0.01 M LiCI solution is introduced, after precipitation of the get, into n identical get (Ca-Si)/solution (Na) systems in equilibrium, then n. 20 ml of distilled water (n = 0, 1, 2, 3). Once a new equilibrium has been established, the amounts of Na and Li in solution are determined in each one of the n systems. In the second series of experiments, Li is introduced in the same amounts, before precipitation of the get, into the n systems, the remainder of the experimental process being unchanged. The results obtained corroborate that Na and Li, comply with the process of simple dilution, as a function of n. It comes out from this study that Na and Li, take no part in the get structure and are present in a free state in the ambient solutions. We can assume that this is probably the case for the alkali-reaction gels in concretes.