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Concrete collapses when the underlying sub-base aggregates scour due to insufficient compaction or natural erosion. Sunken concrete can result to various structural defects such as bowed basement walls, cracked foundations, uneven concrete pads, recessed sidewalks, unlevel concrete junctions, foundation settling and failed retaining walls. If these minor defects are not remediated, it can escalate to major structural problems and water runoff. Aside from being an aesthetic issue, uneven surfaces pose major trip hazards to pedestrians, thereby decreases the functionality of the sidewalks and driveways.

The common solution for uneven foundations or sinking driveways and sidewalks is to demolish the old concrete slab and pour a new one. However, this process is costly and takes considerable amount of time and inconvenience. Nowadays, we now use an alternative solution that is less intensive called mudjacking, also known as slabjacking, pressure grouting, or concrete levelling. Mudjacking is the process of injecting concrete slurry beneath the sunken concrete slab in order to raise it back into its original elevation.

The installer drill small holes into the concrete, then slurry, composed of different materials, such as cement, sand, soil, limestone, bentonite clay, water or expanding polymers, is pumped into it. The appropriate slurry depends on the type of application and the installer’s preference. The injected slurry fills any voids which forces the concrete to rise back into place. The drilled holes are then patched up with hydraulic cement. After a curing period of 1-2 days, the slurry strengthens and amalgamates the underlying soil, which prevents the slab from sinking further. Although mudjacking is not a complicated process, it must be done only by trained tradesman because amateur or sloppy workmanship can lead to more damages. The locations of the underground utility lines such as electrical lines, drain pipes, and sewers must be identified first to evaluate is such lines can withstand the mudjacking process.

Advantages of mudjacking over the traditional way of demolishing and re-pouring concrete include:

• Environmentally friendly. Mudjacking rehabilitates the existing concrete that could have ended up in the landfill;

• Fast installation. Mudjacking may only take hours, whereas concrete pouring could take days depending on the curing time;

• Inexpensive. Because there is no demolition involved, the price of mudjacking is approximately half as much as concrete replacement; and

• Efficiency. Mudjacking requires less labour, equipment, and disturbances to the surrounding.

However, mudjacking have some limitations in situations such as:

• Presence of sinkhole or swampy soil underneath.

• When the concrete surface is spalling or remaining concrete has completely collapsed. The mudjacking process could further damage the concrete surface even after it is elevated back into place.

• The concrete has swollen up due to expansive soil, in which the only solution for this to demolish and re-pour the cement.

Republished from: “Mudjacking”, Green Building, Pilipino Express.

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