Two-part polyurethane expanding foams are used in many applications from slab lifting to sealing of leaking underground utility infrastructure. A wide range of formulations are available, however the overall process is a controlled, high-pressure injection of two chemical components that come into contact in a pre-determined ratio at the outlet of the injection gun. Once the materials contact, a rapid, exothermic reaction takes place to create expanding polyurethane foam. Typical free-rise expansion rates for two-part systems range between 15 to over 40 times the original combined liquid volume. It is important to note that the same amount of free-rise expansion will not take place in a confined space, however the material expansion will impart force on the surrounding media. This force is responsible for uplift, penetration into leaks and voids and some compaction of underlying soils.
The most common application of the two-part polyurethane systems is floor slab and foundation lifting. Based on the original design specifications, the expanding properties of the two-part systems are ideally suited for filling shallow subsurface voids and lifting and re-leveling slabs and light structures by displacing loose soils below grade until the polyurethane material becomes confined. Once the material has filled any voids and has achieved confinement, the expansion process continues to impart an uplift force to the light structure above. NEC Keystone has the capabilities and experience to remediate settling slabs and light structures and guarantees 80% leveling on all of our slab and light structure lifts. During the injection process, NEC Keystone constantly monitors all involved structural and floor slab elements for lift by means of a ZipLevel Pro 2000 manometer at interior slab locations and laser levels and/or surveyor’s transits at exterior wall locations to ensure that lift is achieved in a controlled manner. While achieving a level floor surface or foundation element is the main goal, some of the ancillary benefits of the process include closure of interior and exterior wall and joint cracks, closure of slab cracks with reduction or elimination of vertical crack offset and reduction or elimination of moisture intrusion at the interior of the building envelope.
NEC Keystone prides itself on treating each remediation site as if it were our own home. We take unique steps to ensure the limitation/exclusion of collateral damage to the structure and to ensure constant cleanliness of the job site. Most importantly, NEC Keystone approaches each project as a unique challenge and customizes injection schemes and protocols to ensure the desired result is obtained while limiting the clients’ exposure to the normal hassles of polyurethane grouting.
Suitable applications of Two-part polyurethane systems:
* Slab and Light Structure lifting and re-leveling
* Repair of leaking utility infrastructure
* Filling of shallow subsurface voids
* Specific cases of annular space grouting