Issue 22 – November 2010
Standards New Zealand has published Amendment 1 to the Specification for Portland and blended cements (General and special purpose) NZS 3122:2009. NZS 3122 specifies requirements and methods for testing hydraulic cements consisting of Portland cement or of mixtures of Portland cement and mineral additions. Amendment 1 to NZS 3122 includes the following key changes:
- increase of the permitted mineral additions from 5% to 10% for type GP and type GB cement
- clearer definitions of cement types.
Amendment 1 aligns New Zealand cement manufacturing practice with a worldwide initiative aimed at reducing the carbon footprint of concrete. Increasing the permitted amount of mineral additions allows the clinker factor in cement to be reduced, thereby reducing carbon dioxide emissions and energy consumption associated with Portland cement production.
As part of the amendment project, the New Zealand Portland Cement Association compared prototype formulations of Type GP cements containing 10% mineral additions with current Type GP cements produced in New Zealand. The test results showed that the prototype cements met NZS 3122 performance requirements and that differences in the mechanical and durability performance of concrete attributed to the use of the prototype cements were generally smaller than the typical variability associated with other factors.
Before finalising the amendment, the committee considered the results from the test programme and how the proposed change in cement composition might affect concrete materials, manufacturing processes, and products.