This paper presents preliminary results of estimating the ratio of past expansion of ASR-affected concrete structures by two methods, and correlations with five petrographic stages of ASR:i)rim formation, ii)exudation of sol/gel around the aggregate, iii)cracking of aggregate,iv) extension of gel-filled cracks into cement paste, v) precipitation of ASR gel along cracks into air voids distant from the aggregate, and vi) development of network of gel-filled map-cracks. Past expansion was estimated by fitting the monitoring data with Larive's equation defining the sigmoidal expansion curves (τ_1,τ_c, ε~∞). Another method of estimating the past expansion was to measure the crack index, i.e. total crack width per unit length of concrete surface. By defining the past expansion and maximum crack width in terms of exponential functions, and by subdividing the advanced stages v) and vi) into several classes according to crack width, all the stages of ASR were arrayed on alog-linear scale of past expansion, irrespective of the rock type of the aggregate. Some Japanese volcanic gravel and sand produced past expansion >1% and ultimate expansion (ε~∞) >3%, which the distribution and scatter of the crack width within and between structures.
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