CPB will deliver three separate packages of work at Robe Valley in the Pilbara, including various earthworks and civil works associated with the development of Robe Valley.

"CIMIC Group companies have a strong track record of delivering significant projects to the iron ore industry," CIMIC CEO Michael Wright said.

"With our decades of experience in the Pilbara we offer major mining clients certainty and confidence in construction, mining and industrial services."

The projects will be completed by the end of 2021.

Rio and its Japanese partners last year approved US$1.55 billion of sustaining capital for Robe River, the bulk of which was to be used to develop new deposits at Robe Valley.

First production is forecast for 2021.

CIMIC shares last traded at A$33.54, valuing the company at $10.86 billion. Rio shares opened at $102.26.