ER38 Ensuring affordable concrete supply post 2020 for New Zealand (May 2020)

Construction growth in the Auckland-Waikato region has increased the demand for Waikato river sand, which is known to be a reactive aggregate in terms of alkali silica reaction. Concrete producers could better utilise this resource if research could show it was safe to increase the concrete alkali limit above the current 2.5 kg/m³ for normal concrete.

Research was therefore started in 2017 and the test programme set out to answer several questions that included the following:

• Can the default concrete alkali limit be lifted from 2.5–2.7 kg/m³?
• How do accelerated mortar bar and concrete prism testing compare with quick chemical tests?
• Can these modern expansion tests be used to detect pessimum proportion effects and the influence of elevated curing temperature?

This research report summarises the findings to date and makes recommendations for further action, most notably on revision of CCANZ TR3.