The preventive methods used to control the alkali-silica reaction in portland-cement concrete include using low-alkali cements, mineral admixtures, and chemical admixtures. The use of chemical admixtures is based on the concept that one can interfere with the reactions, thereby limiting the formation of the gel or changing its expansive nature or both. To change the expansive nature of the gel, admixtures that would either preferentially replace the alkalies or immobilize them are used.
The influence of several chemical admixtures on the alkali-silica reaction and the resulting expansion in mortar bars are investigated in our research. Hydroxides and chloride salts were added to the mixing water at initial molar concentrations of 1 or 2. The following salts were evaluated: NaOH, KOH, LiOH, NaCl, KCl, LiCl, CaCl2, MgCl2, and AlCl3. Because alkali-silica reactions often occur slowly, accelerated methods of testing were necessary. The ASTM C 1260 test method [1] was selected and performed on mortar bars. The characteristics and composition of the alkali-silica reaction products formed in the mortar samples were analyzed using a SEM (Scanning Electron Microscope) with EDX (Energy Dispersive X-Rays) capabilities.

The expansion test results showed that the chloride salts with monovalent cations are the most damaging, followed by those with divalent and trivalent cations. These results support a theoretical model that explains the volume change behavior of the alkali-silica reaction product gels formed in mortar bars. This model attributes the swelling of the reaction product gels to double-layer repulsion forces. For a given bulk ionic concentration, the double-layer model indicates that larger expansive pressures are expected to develop when the negative charges of the silicate particles are offset by a diffuse layer of monovalent ions; comparatively smaller pressures develop when the diffuse layer is composed of ions of higher valence.

from M. Prezzi, P.J.M. Monteiro, and G. Sposito, Alkali-Silica Reaction - Part 2: The Effect of Chemical Additives , ACI Journal JAN-FEB, V95 N1:3-10, (1998).