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How does polyurethane lifting work?

By Dalinghaus Construction

Lifting concrete with polyurethane is a process that takes a lot of simple physics into play.  The amount of recovery that you are able to get out of a slab of concrete is dependent on a lot of underlying factors.  Not only does the amount of area that is needing to be recovered play a role, but also the construction of the slab plays a massive role in what can actually be recovered.  Let's dive into how the process actually can lift a sunken slab of concrete.

When you are looking at a sunken piece of concrete you first have to envision of how this slab of concrete will react once you start the lifting process.  Once you do so, you can then figure out where you are going to perform you first injection.  After you have drilled a 5/8" hole through the slab you can then install an injection port for the polyurethane to flow threw the slab and into the underside of the slab.  We then hook up the injection gun to the injection port and begin the polyurethane injection process.  We will inject polyurethane threw the hole until we start to see movement out of the slab.  We continue to do this until the slab has been set back into place as it was when it was initially poured.

The way that the polyurethane is able to do this is, when it is first injected through the slab it will typically fill any voids or cavities that are under the slab.  Once these have been filled the polyurethane will continue to be injected as it will actually start to compact the soils that the slab was resting on.  It will continue to compact the soils until it gets to a point where it is easier to lift the slab rather than densify the now compacted soils.  It will continue to bounce back and forth between compacting the soils and lifting the slab until the slab have been lifted to the desired elevation.  

It is a simply process if you think about it.  It is easier for the polyurethane to lift the concrete and it's weight rather than try to push and compact the soils into the earth.  Although some soils require more polyurethane to be injected to densify the soils it will eventually get to a point that it is easier to lift the slab of concrete than to continue to push the soils downward.

Here are the steps simplified:

  1. Analyze the area to be lifted
  2. Drill 5/8" hole threw the slab
  3. Install polyurethane gun
  4. Begin injecting polyurethane material
  5. Monitor slab movement 
  6. Stop injection once recovery has been attained
  7. Remove gun and port
  8. Grout hole

 

 

 

Tags: Foundation Education

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