GreenTips

The environmental impact of concrete is often a point for debate. On one hand, the manufacture of cement involves high amounts of energy, which means it has a high embodied energy. On the other hand, because of concrete’s high thermal mass, it can allow the building fabric to absorb heat from the sun or other sources and retain it, releasing it later in the day and therefore reducing energy demands. Good thermal mass is an essential feature of good quality passive solar design. Further information can be found via the ConcreteThinker website or the Sustainable Concrete website

The use of cements with a recycled content can significantly reduce the embodied energy, with various products containing a recycled content of anywhere between 10 and 70%. The recycled content used in cement is typically pulverised fly ash or other industrial waste material.

Consideration should also be given to the use of crushed recycled aggregate. A number of companies supply recycled aggregate, but care needs to be taken to ensure that chemicals in the materials do not affect the performance of the concrete.

In all cases aggregates and sand should be sourced from the closest location available to reduce energy required for transportation.

A good source of background information on the use of concrete can be found at the Cement and Concrete Association website.

Greenbuild Technical Information Search

Searches major New Zealand building industry information sites.