Alkali silica reaction (ASR) has, until recently, been considered to present a low risk to concrete in the South Island of New Zealand. The discovery in 2006 of evidence of ASR and delayed ettringite formation (DEF) associated with extensive deterioration of precast piles on two South Island structures prompted further investigation to identify the extent and severity of ASR and DEF in other South Island precast concrete bridge piles. The aim was to ensure affected structures could be managed effectively and thereby remain safe and serviceable, and to help identify effective means of minimising the risk of ASR/DEF in future structures. The work was carried out in New Zealand between 2008 and 2011.
The research found that despite the availability and use of potentially alkali reactive concrete aggregates in the Southland and Nelson areas, ASR/DEF was relatively uncommon and associated damage was generally minor, although cleaning of piles prior to routine inspection may reveal more cases in future. The findings suggested that ASR/DEF may be associated with the use of curing temperatures higher than those now specified, and recommended that current industry guidelines be amended to acknowledge the existence of alkali reactive aggregate in the South Island and the risk associated with elevated curing temperatures.