Polyurethane Vs. Slurry

Which is a better material to use for lifting concrete?

Concrete lifting is a growing industry that, much like other industries, has developed new ways to accomplish the same result.

For years, concrete lifters all over Utah have pumped slurry below sunken driveways; sidewalks, RV pads, steps and patios to lift them back into their original position. A small hole is drilled into the slab needing to be lifted and a cement-based material is pumped below the slab. Once the void is filled, the pressurized grout will lift the slab into place.

Polyurethane foams are making their way into many different industries. They are being modified and changed to do all kinds of things. One of these is to lift concrete. Much like the slurry method, small holes are drilled in the slab and material is pumped below until and the slab begins to lift. The two-part foam enters below the sunken slab in liquid form. When the two parts mix, a chemical reaction forms causing the foam to expand and lift upward.

Polyurethane Drawbacks

Polyurethane concrete lifting, while neat and new, has some serious drawbacks that you may want to consider before getting out your checkbook. The biggest drawback to lifting sunken concrete with polyurethane is the cost. You may have already received estimates form both slurry and poly-lifting contractors. For the most part, the bids seem pretty comparable. Well here’s the problem. Of course the poly-lifting contractor knows he needs to provide a similar priced estimate to lift your concrete, but what are the hidden costs? Polyurethane is so expensive that the contractor has to sell it to you in pounds and you will probably pay between $7 - $10 per pound.

Because poly is so “light and fluffy” it must compress before it will lift your concrete. This compression can get very expensive because the slab won’t lift until the void below is full of highly compressed foam.

Think of blowing up a balloon. Easy right? Now put a book on the balloon…. a lot harder now because you need more air to lift and raise the weight of the book. The same is true when lifting concrete with polyurethane.

Now the Math

Foam manufacturers say it takes 3 lbs of foam per 1 cuft of slurry to lift the weight of a concrete slab. Basically 3 lbs of foam equals 1 cuft of slurry. That means for every 1 cuft of slurry pumped under your slab, it would take 3 lbs of foam to do the same job. If you are being charged even just $7 per lb, that is $21 per cuft and $567 per cuyd. In contrast, slurry will cost you a fraction. You will pay about $5 per cuft or $150 per cuyd.

The reason this is so important is because the contractor doesn’t know what size void you have under your concrete. The concrete won’t lift until it is full and he can only make his best GUESS before he begins the job. If the material amount included with your estimate isn’t enough to fill the void below your sunken slab, you will be left to pay for any additional material needed to lift the concrete.

So while the poly estimate may seem close in price to the slurry estimate…. The cost of using polyurethane to lift sunken concrete can get out of control in a big hurry.