Shells provide a good cement diet supplement

Shells provide a good cement diet supplement
Published: 10 January 2008

In a probable world first, Holcim New Zealand can now use mussel shells to supplement limestone in its cement. The company has received resource consent to discharge contaminants from stored mussel shells at its Cape Foulwind quarry, near Westport. “It’s the first time that mussel shells have been used in the cement-making process, so as far as we know,’’ Holcim’s Westport works manager Chris Dempsey said.

About 400 tonnes of shells would be trucked to the quarry weekly, mostly from the Sealord factory in Nelson which had large stockpiles. Up to 20,000 tonnes of shells would be stored in limestone-capped stockpiles at the Cape Foulwind quarry for between four and six months. Mr Dempsey said mussel shell was almost pure calcium carbonate, a fundamental raw material for cement. It was now sourced from limestone in the quarry but mussel shells provided a “particularly pure’’ supplement. “The benefit comes from having a higher quality raw material. The cement quality will be the same. Essentially it is a cheaper way of supplementing the limestone that we need,’’ he said. “We’ve still got about 50 years worth of limestone in the quarry, so it’s not trying to extend the life of the quarry. It’s to utilise good quality material for our processing but also to solve an ecological problem for the companies producing the
mussels.’’