All the concrete needed for the pedestrian tunnel at the Lake Lanier Olympic Venue off Ga. 284/Clarks Bridge Road should be poured by Friday. From there, “it takes at least 30 days for the concrete to cure to strength needed to support the roadway and traffic,” said Teri Pope, district spokeswoman for the Georgia Department of Transportation. “About half the time of the detour (in place for the work) is for concrete to cure,” she said.