Route 8 North in Ansonia has reopened near exit 19 after two separate crashes on Thursday that closed the road for hours and had traffic backed up to Trumbull.
The road reopen at 4:30 a.m. on Friday, according to Ansonia police.
The first crash involved a pickup hauling a box trailer carrying 55-gallon drums of silicone-based foam insulation, according to officials from the State Department of Energy and Environmental Protection.
State police said Chris Roche, 38, of Fairfield, was driving, somehow lost control of the truck and hit a guardrail.
At least one of the drums was leaking after the crash. As temperatures dropped, the material hardened on the road.
The driver had permits for the materials, but the chemical poses a significant health risk by both inhalation or by skin contact, according to DEEP.
No injuries were reported. Crews were brought in to clean up the chemicals and mill the road, which took several hours.
The second crash involved a tractor-trailer that jackknifed near the first crash scene.