Walker said crews would have to mill and remove 4 to 5 inches of asphalt above the original concrete road surface.
State officials initially estimated only 325-foot sections of the north and southbound lanes were damaged but they later revised that figure to 800 feet.
Some sections of the original concrete also may need to be replaced due to heat and blast damage, Walker said.
Shortly after the blast, engineers were hopeful they could complete milling on Tuesday evening and open at least one lane of traffic overnight.
But the expanded estimate of the damaged section means it will take longer to complete repairs.
"We're not going to be able to complete it this evening," said Brent Walker, spokesman for the state Department of Transportation.
"We're now looking at some time tomorrow to open it," Walker said.
West Virginia Paving crews began work shortly before 6 p.m. Tuesday.
"They're going to be working around the clock," Walker said.
Drivers face lengthy detours as the work continues.
State officials said northbound interstate traffic should take I-79 north to Clarksburg/Bridgeport and take U.S. 50 west to reach I-77 at Parkersburg.
Southbound traffic should exit I-77 at Ripley and take W.Va. 62 west to Point Pleasant. There, drivers can take U.S. 35 south to Interstate 64 near Winfield and travel east to reconnect with I-77 in Charleston.
Drivers can get updates by following the Department of Transportation's Twitter account.