A bituminous surface treatment A bituminous surface treatment (BST), also known as a seal coat or chip seal, is a thin protective wearing surface that is applied to a pavement or base course. BSTs can provide all of the following: A waterproof layer to protect the underlying pavement. Increased skid resistance. A filler for existing cracks or raveled surfaces. An anti-glare surface during wet weather and an increased reflective surface for night driving. Historically, BSTs have been in use since
