Alkali–silica reaction (ASR) expansion: Pessimum effect versus scale effect

Abstract

The effect of aggregate size on ASR expansions has been largely studied and conflicting results exist concerning the aggregate size that leads to the highest ASR expansion. Most of the research works clearly show a pessimum effect of aggregate size on ASR expansion. However, all the results available in the literature were obtained using different experimental conditions and the combined effects of other important parameters, such as specimen size used in the expansion tests, have often been neglected. This paper aims to investigate the combined effect of specimen size and aggregate size on ASR expansion. Experimental results highlight a scale effect, a combination of the effects of aggregate size and specimen size on ASR expansion. This scale effect appears to be influenced by the reactive silica content of the aggregate. Modelling at microscopic level is used to propose a quantification of this effect.

Multi-scale analysis of alkali–silica reaction (ASR): Impact of alkali leaching on scale effects affecting expansion tests

“…In the case of expansion in NaOH solution, alkali concentration stays high and 187 calcium concentration too low to stop the production of expansive gels. In such 188 conditions, there is no apparent threshold as shown in [9]. This is well reproduced by 189 the proposed relations since [30].…”

“…However this remains theoretical since no leaching data was available and a 469 pessimum effect can exist even when leaching is impossible (storage in alkali 470 solutions [9]). Experiments with different sizes of reactive aggregate and control of 471 alkali leaching would be necessary to estimate the proportions of expansion decrease 472 that are due to alkali leaching and to gel permeation (which is the explanation 473 The volume of gels thus calculated can be used in mechanical modelling.…”

“…Moreover, the decrease of expansion with the specimen 430 size could then be explained by the alkali leaching alone. In this case, it was not 431 useful to assess the volume of gels lost by permeation through cracks as for 432 20 experiments on specimens kept in alkali solution [9]. This effect of gel permeation 433 appeared to be negligible compared with the alkali leaching effect for the sizes of 434 specimens and the conditions of this experiment.…”

“…and ASR-gel permeation through cracks [7]- [9] lead to larger expansions in larger 32 specimens according to the storage conditions [5], [8]- [10]. These phenomena greatly 33 impact the ASR-expansion measured on specimens, which raises the question of 34 whether such measurements should be used to represent expansion in conditions 35 existing in real structures.…”

Special Issue: Aging Management of Nuclear Power Plant

“…ASR in concrete were studied extensively using accelerated aging methods (Diamond and Ong 1994;Smaoui et al 2005;Poole 2007;Temuujin et al 2009;Garci Juenger and Jennings 2011;Nuruddin et al 2011;Bahadure and Naik 2013;Gao et al 2013;KupwadePatil and Allouche 2013;Memon et al 2013). However, these studies were conducted at the material level (or in other words on small-scale specimens).…”