Experimental investigation of the mechanisms by which LiNO3 is effective against ASR

Alkali–silica reaction: Current understanding of the reaction mechanisms and the knowledge gaps

“…Later work by Tremblay and co-workers [155] did not support many previously held theories about the mechanisms by which LiNO 3 may reduce ASR. Mechanistic work relying on pore and immersion solution analysis, XRD, SIMS and petrographic examination provided results suggesting the following classes of mechanisms may be unlikely as the cause of ASR reduction by Li: pH reduction, increased solubility limit of silica to prevent gelation, formation of a protective coating, nonexpansive crystalline product, and non-to less-expansive amorphous gel.…”

“…Mechanistic work relying on pore and immersion solution analysis, XRD, SIMS and petrographic examination provided results suggesting the following classes of mechanisms may be unlikely as the cause of ASR reduction by Li: pH reduction, increased solubility limit of silica to prevent gelation, formation of a protective coating, nonexpansive crystalline product, and non-to less-expansive amorphous gel. From their study, the mechanism most supported was that the presence of lithium provided increased chemical stability and reduced dissolution of reactive silica due to reasons other than pH reduction or formation of a protective coating [155]. Clearly, this debate has not been settled and more research into the impact of lithium salts on different aggregate mineralogies is needed to definitively make conclusions on the mechanisms by which lithium controls alkali-silica reaction in concrete.…”

A thermodynamic and kinetic model for paste–aggregate interactions and the alkali–silica reaction

“…Interestingly, Li + exhibits unique behavior with respect to both sol stabilization and silica dissolution ( [14] p. 359); for example, addition of lithium hydroxide can be used to stabilize sols (and therefore prevent gel precipitation) whereas sodium hydroxide induces coagulation. This unique behavior of lithium with respect to silica sols offers a possible explanation for a role of lithium in ASR treatment or prevention unrelated to any pH effect [42,43]. Although not directly related to pH and sol precipitation, experiments by Marshall and Warakomski [44] on solubility of silica gels in salt solutions demonstrated that silica solubility decreases significantly in the presence of high salt concentrations, with the effect greater for alkaline earth cations than for alkali cations (i.e., Mg 2+ = Ca 2+ N Li + N Na + N K + ).…”

Alkali–silica reaction: Kinetics of chemistry of pore solution and calcium hydroxide content in cementitious system

“…However, various published research results on the composition of the pore solution in the cementitious systems [42][43][44] ) in pore solution are very low and quite stable after the early hydration period. As a result, the effects of these additional ions on the kinetics of changes in alkali concentrations can be assumed to be constant.…”

“…In addition, the contents of Ca(OH) 2 and the expansions of mortar bars were also quantified to investigate the relationship between Cement and Concrete Research 71 (2015) [36][37][38][39][40][41][42][43][44][45] these parameters and the change in the chemistry of pore solution obtained from samples undergoing ASR. Specifically, the effects of following parameters on the chemistry of pore solution and the content of calcium hydroxide (Ca(OH) 2 ) are described: (a) length of curing time (up to 130 days), (b) temperature (23°C, 38°C, and 55°C), and (c) presence of reactive or non-reactive aggregates.…”