Summary of research on the effect of LiNO3 on alkali–silica reaction in new concrete

This paper summarizes findings from a research study conducted at the University of New Brunswick in collaboration with the University of Texas at Austin, and CANMET-MTL, on the effect of LiNO3 on ASR in new concrete. The studies included expansion testing, silica dissolution measurements and microstructural examinations of cement systems containing glass and two different reactive aggregates (NB and NS). Only a small proportion of the data are presented here for the purpose of highlighting the principal findings of this investigation. Based on these findings, it is proposed that the inhibiting effect of LiNO3 against ASR in new concrete is attributed to the formation of two reaction products in the presence of lithium, these being a crystalline lithium silicate compound (Li2SiO3) crystal and a Li-bearing, low Ca silica gel. These two phases could serve as a diffusion barrier and protective layer to prevent the reactive silica from further attack by alkalis. It was found that the reason the two reactive aggregates selected responded differently to LiNO3 was due to the difference in their textural features. The NB aggregate contained reactive volcanic glass particles, the surface of which was immediately and equally available to sodium, potassium and lithium, and thus a Li–Si barrier was able to form quickly. The reactive phase in the NS aggregate was microcrystalline and strained quartz, which was embedded in a dense matrix of a non-reactive predominantly alumino-silicate phase and was not easily accessible to lithium.