Pavement Slab Pumping: How to Detect and Correct it?

  • Pavement Slab Pumping: How to Detect and Correct it?

    Did you know that pavement slab pumping is one of the main factors contributing to the concrete slab letdown? Once the damage has occurred the value of correcting it by the mud jack treatment can’t be minimized.


    What is Slab Pumping?

    Slab pumping occurs at the edges, joints and sometimes at the cracks of the pavement. The moisture that has penetrated the subgrade via the cracks or joints is forced out, in the process the moisture or water carries along with the soil particles. If the process continues there is a void that is created. The void then accumulates more water. If not stopped, the process goes on and on until the pavement becomes sunken and unsupported.


    Mud-Jack Treatment for Slav Pumping

    The damage is correct through a procedure called mud jacking. During this procedure, an operator uses the compressor and drills holes. The mud jacking team pumps the slurring underneath the pavements until it starts rising or going up. Once the slurring mixture is sufficiently pumped, the operator at the nozzle end signals the other operator at the mud jack to stop concrete pumping. 

    The operator then inserts a pointed wooden plug. This plug is used to help retain pressure and prevent the flow back of mixtures. This is done until the hole is ready to be permanently plugged.

    If the mud jack treatment is done before the pavement breaks, then the process is categorized as a preventive treatment. But if the treatment is done after the pavement has failed, then it is termed as a corrective procedure. 

    But in both of the procedures, the pavement ends up being supported. The treatment reduces the processing cracks and breakage greatly.


    Causes of Slab Pumping

    Slab pumping is always a result of four main factors. Namely:

    • Free water
    • Cracks and joints
    • Incompatible subgrade soil
    • Massive axle loads

    These four factors are the ones that decrease the lifespan of the pavement. It is always good to keep an eye on such aspects to eliminate them immediately for the pavement to last for long.

    However, joints and cracks on the pavement can’t be eliminated. Getting rid of the incompatible subgrade soil on the other hand is possible but very expensive. About the free water, the problem can be controlled. More effort should be put to retard the letdown of the Portland cement especially on highways and airport runways.


    Recognizing the Early Stages of Slab pumping

    Slab pumping occurs in the following stages;

    • Undue centre line spalling
    • Ejection of water or moisture from the cracks or joints
    • Change in the colour of the pavement by the soil next to the joints or cracks
    • Holes at the edges of the pavement
    • Faulty joints and cracks
    • Finally, the breakage of the pavement: occurs at the corner or centre line


    If there is continued slab pumping the upgrades will be washed out. This will leave the slab without stability. In other words, the slab will be left unsupported. If the pavement continues receiving huge axle loads it will eventually break.

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