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Step 3 Concrete Lifting and Leveling with Polyurethane Injection

Polyurethane Injection for Concrete Raising

You’ve probably stumbled across uneven concrete slabs before. This is a common problem, especially if the concrete slabs have been placed over soft ground. Fixing this issue isn’t as complex as it may seem to be at first glance because replacement isn’t the only option. Concrete raising can be more affordable. One of the ways concrete is raised is by using polyurethane foam, a foam that expands instantly. Read on to learn more about how foam polyurethane can be used in concrete raising jobs. 

How It Works     

Though the administration may seem complex, it’s really quite simple. The three basic steps of concrete raising are: 


How Polyurethane Concrete Raising Works

Soil Load-Bearing Capacity 

Another aspect of concrete raising that is crucial to understand is soil load-bearing capacity. If the soils are weak then the weight-bearing ability of foam polyurethane won’t be distributed equally. This is because the undensified soil will inevitably slip under the weight of the concrete. This, in turn, will cause the concrete to become uneven once again. If soil densification is determined to be a necessary process, it will look something like this: 

-An inspection will be completed to determine where the injections must be done in order to properly densify the soil. A large three-to-five square foot grid pattern will be laid out where the injections will be done at different depths. 

-The first injections are completed just below the surface level in order to condense and strengthen the soil.  

-The following injections are shot from the top-down, with each following layer having the capability to densify against the top layers. This will strengthen the overall weight-bearing ability, and ensure that the slab will not slip back down by the lower soils consolidating over time.  

Choosing The Right Type 

There are two main types of foams that can be used for raising concrete. The reactivity and density of the foam needs to be determined before moving on with the process. Two factors must be considered: 


A slow reacting foam is typically used when a larger void needs to be filled. The foam will spread more evenly and thicker, thus allowing for greater coverage. A quick reacting foam won’t spread evenly and won’t have the same amount of spread that is offered with a slower reaction. Having control will allow the workers to ensure that the slab isn’t raised too greatly and lines up precisely with the other slab. 


A denser foam will be used if a larger weight needs to be held. If the slab doesn’t weigh very much (relatively speaking) and the void is large, a lower density foam will be used to fill in the void easier. Density is an important factor to consider as this will determine the success of the operation and whether the polyurethane will be able to hold the weight of your slab. 

For Your Understanding 

To summarize, though concrete raising is based around the environment, there is a basic process to it. Because polyurethane can be used to lift slabs in almost any structure, it’s important to gauge the environment and determine why the concrete slabs are uneven to begin with. This information will ultimately determine what kind of polyurethane needs to be used and what style of injection will be done. Slow reaction polyurethane is best used for large voids to increase the spread and ensure an even rise. Density is also a factor that will be determined based on how much weight the polyurethane needs to bear. It’s clear that Polyurethane jacking is the most effective form of concrete raising, far superior to replacing concrete entirely.