A new approach to assessing the performance of ASR inhibitors in concrete

A methodological approach, based on some innovative reactivity parameters such as the threshold alkali level (TAL) of aggregates and the tolerable driving force (Delta(tol)) of the deleterious expansive process associated with alkali-silica reaction (ASR), is proposed in order to assess the alkali-reactivity of aggregates and compare the effectiveness of different types of ASR inhibitors (low-alkali Portland cements, lithium compounds, and blended cements manufactured with active mineral additions). The effectiveness of the ASR inhibitors, expressed in terms of Delta(tol), is related to the naturally available alkali content of concrete and the TAL of the aggregate used in the concrete mix. The potential minimum contribution of alkalis (L (im)) by a given ASR inhibitor to the concrete mix is proposed as a specific efficacy parameter. The relationships between the effective dose levels of mineral additions or lithium compounds and the efficacy parameters Delta(tol) and L (im) have also been identified. The test procedures for the experimental determination of such parameters are described and some methodology applications to published ASR expansion data are reported.