Bridges

Durability design of piles is usually carried out based on AS 2159 and AS 3600. It is widely known that the durability of concrete in acid sulphate environments is significantly influenced by the type of binder; however this is not recognised in AS 2159 or AS 3600. Also little supporting information is available in AS 2159 and AS 3600 to give confidence that a pile complying with these standards would provide a design life of 100 years. Some information is availableabout the comparative performance of concrete prepared from various binders in acid sulphate environments. However the quantification of the service life in such environments is not available. Also very little data on the field performance in acid sulphate conditions is available due to the difficulty in obtaining such data.

A bridge at Banora Point was recently de-commissioned and provided a unique opportunity to access a pile and procure concrete samples. The concrete was examined to assess the extent of deterioration due to acid sulphate soil as those piles were known to be located in acid sulphate ground conditions. The microstructure of the concrete was studied to examine any changes due to deterioration caused by the acid sulphate environment. Thereby the extent of degradation to the concrete could be assessed and provide an estimate of its expected service life. Such information would be valuable in future durability design of concrete for piles in acid sulphate environments and will also increase the confidence of achieving a design life of 100 years. The adequacy of AS 2159 and AS 3600 will also be assessed.