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A study of the ASR of an aggregate with high chert content by means of ultra-accelerated mortar bar test and pore fluid analysis

Author: Larbi, J.A. · Visser, J.H.M.
Type:article
Date:2002
Institution: TNO Bouw
Source:Heron, 2, 47, 141-159
Identifier: 330349
Keywords: Materials

Abstract

Various studies have indicated that the use of some ultra-accelerated mortar bar expansion test methods for assessing the alkali-silica reactivity of concrete aggregates (particularly those using 1 M NaOH solution at 80 oC) can give rise to misleading results causing certain types of aggregates to be inappropriately accepted. This is the case if the aggregates contain more than 2 % by mass of reactive constituents, in the form of porous chert or flint and chalcedony. To date, no explanations have been given for this anomaly. This paper deals with a study aimed at investigating this anomaly. A sample of crushed sea gravel, dredged from the southeast coastal waters of England, containing 12.5 % of reactive constituents, was used for the study. Fractions of the crushed sea gravel amounting to 0, 25, 50, 75 and 100 % of the total aggregate fraction and corresponding to 0, 3.1, 6.3, 9.4 and 12.5 % reactive constituents, were incorporated in mortar bars, which were subsequently subjected to RILEM ultra-accelerated mortar bar expansion test. At the end of the test, the bars were examined by means of concrete petrography to establish whether or not attack due to ASR had taken place. The study was designed in this way in order to examine whether or not North Sea gravel from the southeast coastal waters of England exhibits a pessimum effect