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Alkali Silica Reaction

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 Investigations and research in alkali aggregate reaction conducted by Industrial Research Limited (formerly DSIR chemistry) and Opus International Consultants Limited (formerly Works Consultancy Services Limited) have been funded through contracts with the Foundation for Research Science and Technology and Transit New Zealand, and the organisations that preceded them. 

The Cement and Concrete Association of New Zealand funded this revision of TR3 in partnership with the New Zealand Ready Mixed Concrete Association and Winstone Aggregates.

New Zealand has been fortunate that despite the use of reactive aggregates in concrete, there have been few cases where damage due to alkali aggregate reaction (AAR) has necessitated extensive remedial repairs.This has largely been due tothe early recognitionofthe potential for reaction and careful use oflow alkali cements in areas where there was the greatest risk. The first edition ofthispublicationdrew on findings of extensive studies by DSIR Chemistry Division and the Ministry of Works and Development during the 1950’s and 1960’s. These were reviewed by a working party, chaired by David Barnard ofCCANZ, toprepare guidelines that could be used to minimise the damage caused by AAR in future construction. 

While all members of the Working Party contributed to information gathering and decisions required to produce this document, D.A. St John, DSIR Chemistry Division, undertook the principal editing and writing role.Thisreflected hisconsiderable experienceof New Zealandalkali aggregate reactionsand knowledge of international research. Since then, ongoing work by D.A. St John and R.L. Goguel of Industrial Research Limited (formerly DSIR Chemistry Division) and S.A. Freitag ofOpus International Consultants Limited (formerly Works Consultancy) has clarified the extent and severityof the reaction in New Zealand, and explained someunusual cases of AAR observed in concrete structures.

 Information gained fromthese studies includes the contribution ofalkalis fromaggregates (often in amounts outweighing the contribution from other sources), the applicability of tests for assessing aggregate reactivity, greater understanding about the behaviour of greywacke aggregates, and the fact that many precautions onlyalleviate the reaction,rather than prevent it. 

There have alsobeen significant developments in the management of AAR internationallysince the 1991 edition was published. 

There still remain unanswered questions, but it is believed that this edition will provide sufficient information for users and manufacturers of concrete to use materials available in New Zealand with minimal risk to damagefromAAR. It is hopedthat the electronic format will permit appropriate revisions tobe made with minimal effort infuture toaccommodatelocal andinternational developments.