Undersealing of slabs is a process utilized in filling small voids and sealing of fractures on the underside of concrete slabs. This eliminates unwanted movement in slabs with live load and prevents transmission of moisture through the concrete where the material comes into contact with the slab. It is primarily used on roads and highways but can be used in structures.
Preconstruction foam barriers are an “underseal” method in which an HDEP foam lift between 2 and 4 inches thick is applied inside the slab forms after mechanicals are installed prior to the slab pour. While there is minimal bonding of concrete and foam, this process will alleviate issues with moisture seepage as long as the barrier is not punctured or torn prior to the pour.