The ready mixed concrete industry is reducing its environmental loading through a series of initiatives and process efficiencies. Many ready mixed concrete producers use recycled water, extracted from their production operations. Additionally, the extensive use of water-reducing admixtures typically enables water reductions of around 10% and a corresponding reduction in the use of cementitious material.
With enhanced understanding of the impact of water and waste disposal, there has been considerable progress in reducing wastewater discharge across the industry’s production facilities. It is now common practice to use chemical wash waste systems and aggregate reclaimers to minimise wash waste and water from the cleaning of truck-mixer bowls and plant.
The New Zealand ready mixed concrete industry has developed a publication to assist with the on-site management of concrete wash water. This publication is availalbe from the New Zealand Ready Mixed Concrete Association's website.
In some New Zealand urban markets, most notably Auckland, the supply of virgin aggregate is becoming limited.* As a result it is now viable to establish recycled concrete aggregate facilities in these regions. These plants are able to accept, process and on-sell recycled concrete aggregate. Recycled concrete aggregate is separated from its recyclable reinforcing steel, and can be processed into specific aggregate sizes.
The New Zealand Green Building Council has recently launched Green Star NZ, an environmental rating system for buildings. Green Star NZ awards points within its environmental impact categories for the incorporation of recycled materials in construction projects. As such, when a concrete structure is eventually demolished (most probably as it has no further use rather than failure due to age), the demand for recycled concrete as an aggregate source for structural concrete will increase from those seeking maximum Green Star NZ certification.
*Park, Stuart. (1999). Recycled concrete construction rubble as aggregate for new concrete. BRANZ SR 86. Porirua.