We pump a mixture of clay, fine aggregate and portland cement into strategically placed small diameter holes drilled through the sunken slabs.

Raising the sunken slabs while compressing the subbase requires very little pressure.  The uplift motion is slow, usually about 1/4 inch per minute. Visualize one squre foot of concrete sidewalk. In one square foot of sidewalk there are 144 square inches ( 12"  x 12" = 144 sq.in.)  If we pump with only 10psi of pressure, theoretically we are applying  1,440 lbs. Of lifting force on the one squre foot of sidewalk   (144 x 10 = 1,440). A 4" thick piece of sidewalk weighs only about 50lbs per square foot; 1440 lbs of lifting force is more than enought to restore the concrete. 

Thanks to the physics of hydraulics, we have plenty of raising power with just a small amount of pumping pressure.  The process is safe, simple, and cost effective.

After the slab is raised to the proper level, the holes are filled with concrete and finished to match the surface of the surrounding concrete

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