DOT digs into decay under I-40

"It is crumbling, and as road pressure goes on the top portion, it is crumbling in," said DOT spokesman Steve Abbott. 

Before the upgrade began, workers drilled into the roadbed, extracting cores that show the extent of the problem. "It is not solid in some places. It is crumbling in some places," Abbott said.

The core samples showed a dark top layer – the road surface – and, underneath, the result of a chemical reaction where water had seeped into the mixture of cement and other materials.

Years after the road was built, DOT officials learned that chemicals in some of those ingredients reacted poorly with one another. 

"They now know: Don't pair this with this because it is going to go bad," Abbott said.

It's not a phenomenon unique to Raleigh. "Airports and roads all over the place, it was the same thing," he said.

The Fortify project will require that all the crumbling old mixture be dug up, stripped away and replaced. Workers continued taking core samples through the week of Oct. 28 to determine how deep the road is and predict how hard their project will ultimately be.

In addition to replacing the highway, crews will extend two miles of auxiliary lanes to help manage additional traffic and fix 14 bridges in the construction zone.

The contractor, Granite Construction Company, will begin daytime work in early December along the 2.5-mile section of Interstate 440 between I-40 and the U.S. Highway 64/264 interchange.