Mud Jacking – CJGeo

Mud jacking is a process for raising and supporting settled, uneven concrete using a cement-based grout which primarily consists of lime or sand.  The process, material and good applications are detailed below.  Our residential sister company, Concrete Jack, started out as a mudjacking contractor, and we have completed thousands of mud jacking projects throughout the Mid-Atlantic.  Our mud jacking crews are friendly, experienced, and work with the most efficient and safe equipment.

What Mud Jacking is Good For

About the only thing mud jacking is good for in industrial and infrastructure applications is lifting small sections of sidewalk.  Therefore, we recommend polyurethane grouting for lifting most slab floors, heavily-loaded slabs, and slab foundations. However, we have lifted everything from sidewalks to interstate highway bridge approaches using mud jacking.  Our estimators are familiar with the advantages of both processes, so are capable of recommending which is most appropriate for your situation.  The project profiles below have more information about some of our specific mud jacking projects we’ve completed.

How Mud Jacking Works

CJGeo’s skilled technicians are experts at mud jacking, a process that has been around since the 1930’s, and which works by injecting grout material under sunken or unsupported concrete to raise it back to its original levels.  After being injected under the concrete, the grout dries out and stiffens to permanently support the affected areas.  Mud jacking works on almost any type of flat concrete, whether it be inside of a house, around a pool, on the top of your front porch or slabs of your sidewalk or driveway. It doesn’t take much pressure to raise concrete, our employees are careful and our concrete leveling equipment is compact, so we can work in almost any environment, safely and effectively.  There are three easy steps to mud jacking:

Drill holes through affected concrete
Inject grout to raise & support concrete
Clean & patch holes

Mud Jacking Material

Depending on the application, CJGeo uses a lime or sand-based grout for mud jacking.  We add Portland cement to the sand-based grout to dry it out a bit.  Sometimes, we put enough Portland in the grout that it will harden, however for almost all applications, just letting the grout slowly dry out to the moisture content of the surrounding soil is sufficient for the loads which a slab will see.  Because mud jacking is used to repair slabs that are in good condition, the mud jacking grout isn’t used for load distribution.  Therefore, in most cases, the grout only needs to be slightly stronger than the underlying soil, which rarely requires significant quantities of cement. Concrete sidewalks around most facilities are only 3.5 to 6 inches thick, so they only weigh a few pounds per square inch.  

Even with no cement in CJGeo’s mud jacking grout, the grout has sufficient strength to hold up the concrete, even if the grout is moist enough that you can push your finger into it.  Keeping the grout from curing (getting really hard) makes it easy for you to do things like run utilities, electrical lines or drainage pipes under repaired areas in the future. A common misconception about mudjacking is that concrete (a mix of Portland cement, sand, stone and water) is pumped under the areas being repaired.  Concrete is a very poor choice for a mud jacking material; it is relatively expensive, doesn’t move well through the voids below slabs, and if you ever want to tear out the original concrete, it makes that process much more difficult. Other materials are used for processes similar to slab jacking.  Polyurethane grouting involves pumping high density polyurethane foam under the concrete, and sometimes cellular concrete is used to fill large voids below concrete.

History of Mud Jacking

Mud jacking, which is also called slab jacking, was started in the 1930s in Iowa to correct settlement and frost heave of roadway slabs and curb & gutter.  The earliest pumps, like the one in this photo, were somewhat primitive.  Today’s mud jacking pumps are mobile, powerful and hydraulically powered.  Concrete Jack’s pumps are capable of pumping pressures up to 500 psi, and depending on the grout mix can pump up to 100 feet. The trucks used for mud jacking have also evolved a lot.  Our sister company Concrete Jack’s original trucks required shoveling dry grout mix into a mixer and adding water and Portland cement manually.  Now, we run automatic trucks which batch the mud jacking material, Portland cement and water in a horizontal hydraulic mixer, no shoveling required.  This makes operations safe and reliable, and enables us to mix and place up to 10 cubic yards an hour of material with each truck.