The susceptibility of recycled concrete aggregate to alkali silica reaction

Research at TRL has demonstrated that recycled concrete aggregates (RCA) can be used in structural concrete. However, there are some concerns regarding the susceptibility of RCA to alkali silica reaction (ASR). Initially a cautious approach was taken by the industry by classifying all RCA as highly reactive even though it was suspected that most were not. Recently the position changed so that RCA can now be classified as normally reactive provided certain conditions are met. This report describes a study to establish the reactivity of a range of RCA and natural aggregates. Six RCA and two natural aggregates were obtained and their engineering properties were measured. The aggregates were examined using petrography to determine their main constituents and estimate likely ASR reactivity. Concrete prisms were then cast from each aggregate, stored in warm, moist conditions and the expansion was measured over a period of one year. After testing, a petrographic analysis was carried out on thin slices cut from the prisms to determine whether ASR gel was present. The results showed that all the RCA would be classed as probably non-expansive equivalent to a low reactivity material. The petrographic analysis showed that some of the RCA were potentially ASR reactive and ASR gel was found in some of the prisms; however this had not resulted in significant expansion. The results support the change in general classification of ASR reactivity of RCA from high to normal. (A)


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  • Accession Number: 01011683
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • ISBN: 1-84608-037-1
  • Files: ITRD
  • Created Date: Dec 19 2005 3:25PM