Use of Lithium to Control Expansion Due to Alkali-Silica Reaction in Concrete Containing U.K. Aggregates

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Title: Use of Lithium to Control Expansion Due to Alkali-Silica Reaction in Concrete Containing U.K. Aggregates

Author(s): B. Q. Blackwell M. D. A. Thomas and A. Sutherland

Publication: Special Publication

Volume: 170

Issue:

Appears on pages(s): 649-664

Keywords: Aggregates; alkali-silica; reactions; concretes; expansion; flint; fly ash; lithium.

Date: 7/1/1997

Abstract:
The paper presents a brief review of the literature pertaining to the effect of lithium salts on alkali-silica reaction (ASR) and some recent data from a laboratory study of the efficacy of lithium hydroxide monohydrate (LiOH.H2O) in suppressing ASR expansion in concrete containing reactive U.K. aggregates. A synthesis of the published data indicates that the effect of lithium on ASR is not strongly influenced by the form of lithium used and that mortar-bar expansion may be effectively eliminated if sufficient lithium is added such that [Li/(Na+K)] > 0.70 to 0.80. -Expansion tests were carried out on concrete prisms cast with two different reactive U.K. aggregates and a range of cement and alkali levels. Some mixtures mcorporated lithium hydroxide monohydrate (LiOH.H2O) such that the lithium-cement alkalies molar ratio was 0.74 (,i.e. [Li/(Na+K)] = 0.74). Lithium was effective in reducing the expansion and preventing cracking in all the concretes; the maximum expansion observed in lithium-bearing concretes was 0.023% after 1 year. Higher expansions were observed in lithium-bearing concrete containing a highly-reactive siltstone compared with similar concrete containing flint sand, although expansions were still low. Although little significance can be attached to these differences, the possibility of a relationship between the safe level of lithium and the level of reactivity of the aggregate is discussed (i.e. more reactive aggregates require higher dosages of Iithium). Lithium additions resulted in shrinkage of fly ash concrete containing reactive aggregate. It is probable that lower levels of lithium are required when used in combination with pozzolans, if the level of such material is not sufficient to completely eliminate expansion by itself.