Work is scheduled to start in January 2015 with completion by 2017.
The Balfour Beatty Skanska joint venture is a construction partner to Connect Plus – the company responsible for managing and upgrading the M25 network.
Work on junction 30 in Essex will provide enhancements to the motorway where it meets the A13 at Thurrock.
At the height of construction the scheme will employee more than 70 people, with many local specialist subcontractors and supply chain partners contributing to the work.
Balfour Beatty Joint Venture Board member Phil Clifton said: “Our Balfour Beatty Skanska construction joint venture is a highly successful collaboration that has delivered many schemes around the M25.
“The junction 30 scheme will benefit from a project team which already has extensive knowledge of the M25 and this busy intersection and which has a proven ability at offering sustainable and innovative solutions for the Highways Agency.”