Carapateena Mine: Robust Protection in a Challenging Environment

What was the OBJECTIVE at Carapateena Mine?

Carapateena Mine is a significant copper project in South Australia.

Hypersaline water from the mine groundwater used in processing causes problems with concrete service life. This is due to the very high salt content, but along with a high salt content, the sulphate content also goes up, creating two mechanisms of concrete degradation.

1. Salt contributes to reinforcing steel corrosion, and the lower pH of the hypersaline water eats away at the surface.
2. Sulphates cause the alkalis to be leached from the concrete matrix, turning it into a soft paste, which creates gouges and pits in the concrete surface.

This means concrete less than five years old needs major repairs to maintain structural integrity and service life. The objective is, therefore, to reduce the frequency of replacement needed.

What was our SOLUTION?

Colloidal silica hydrogel treatment is now incorporated into new concrete pours as an admixture and onto existing areas by spray application to prevent further damage. Hydrogels first reduce permeability and stop moisture transmission, taking moisture out of the corrosion equation. Secondly, hydrogels work by reacting with calcium hydroxide in the concrete, making it unavailable to be leached out of the concrete, as it’s now bound in a calcium-silicate-hydrate gel.

Further, because this is a liquid admixture and colloidal silica gets more out of the cement, the mix is workable and doesn’t affect set times. This translates to a better-quality concrete finish, as it’s easy to place and achieve compaction.

What were the RESULTS?

Concrete quality is already proving to be preserved for much longer periods of time than prior to the use of the treatment. The project is ongoing.

This case study is also available for download as a PDF.

For industry-specific responses to the care of concrete in the mining industry, visit our dedicated page.

A past webinar on the challenge of hypersaline water is available on-demand on our Invisible Strength site.