ABSTRACT
New Zealand lies along the circumpacific belt of volcanic rocks which cover an area of 20000 km2 in the North Island (see Figure 9.1.). As this 20000 km2 area includes half the population of New Zealand, the aggregates derived from these volcanic rocks are present in a substantial percentage of the concrete used in the country. Many of these volcanic aggregates are potentially reactive with cement alkalis, and damage to concrete structures can occur if they are used without adequate controls. This chapter gives a brief description of the approach taken in New Zealand to allow the safe use of these volcanic aggregates in concrete, the tests carried out and work planned for the future.
