The contractor is now set to start the project in the next few weeks.
Work involvesdualling the 7.8km stretch between Brynmawr to Tredegar to reduce congestion, improve visibility and add overtaking opportunities.
Wales’ transport minister Carl Sargeant said: "The A465 is a crucial artery of our transport network and the principal road link between West Wales and the Midlands.”
He said that the scheme would also help the local economy. “An improved Heads of the Valleys route will play a role in tackling poverty for the region by improving links to key sites within education, health centres and jobs,” he said.
Carilion was appointed contractor in March 2010 and is supported by consultants Arup and TACP.