Reconsideration of ASTM C1260 test results in the light of a recent kinetic model

A recent kinetic model based on nucleation and growth kinetics was used to elucidate the influence of the type (fineness, total alkali content) of Portland cement on the diagnosis of the ASTM C1260 test method with regard to the alkali–silica reactivity (ASR) of five natural siliceous sands of known petrographic characteristics and field performance. Some attempts were also made to apply the kinetic model for interpreting the ASTM C1260 test results obtained when an appositely modified version of this test method was used to assess the capability of lithium nitrate additions in suppressing or mitigating deleterious ASR with a given aggregate. It was found that the kinetic model is capable of discriminating the alkali-reactivity of the sands investigated, through the use of a plot of the two kinetic parameters, M and ln k, derived from the model and assuming ln k as a reactivity criterion. Differently from what was observed using a percentage expansion criterion for defining potentially reactive aggregates, the use of ln k as a reactivity criterion yields an ASR diagnosis for every sand that is independent of the type of Portland cement used in the ASTM C1260 test. A modified version of the ASTM C1260 test procedure can be successfully used to assess the capability of lithium nitrate additions in suppressing deleterious ASR. Application of the kinetic model provides a suitable means of determining effective lithium dosages for deleterious ASR suppression in ASTM C1260 tests.