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Why Does Concrete Sink?

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Concrete sidewalk

Concrete sinks because it’s heavy! When the soils underneath a concrete slab are unable to support its weight, the slab will sink. This is called slab settlement, and this uneven concrete condition frequently happens on Atlanta driveways, sidewalks, walkways, garage floors, and foundations in the area and all over the country.  


If soils support part of the concrete slab, and other sections do not, then the unsupported pieces may crack away from the other section and result in unlevel concrete.


Concrete’s Worst Enemy

Moisture is concrete’s worst enemy. It seeps into the pores of untreated concrete, and when temperatures drop, the trapped moisture expands as it turns into ice.

Concrete may be durable, but it’s not indestructible. The expansion from excess moisture destroys the pores and weakens the concrete, resulting in concrete slabs that pit and flake.

Primary Causes of Sinking Outdoor Concrete:

Soil Shrinkage, Compaction & Settling


Different types of soil have different load-bearing capacities. When a soil’s load-bearing capacity is exceeded, the soil will compact and settle.
It’s also possible for the soil beneath a slab to settle and compact of its own accord. Soil that contains large amounts of clay and/or silt, as much of Georgia’s soil does, will shrink substantially when it dries out.

As the soil compacts underneath a concrete slab, the unsupported slab will sink as well, usually cracking in one or more areas as a result.

Washout Of Soils

The soil underneath your driveway, that patio, or concrete steps is also highly susceptible to Georgia’s ever-changing weather and climate changes. Just as compaction or shrinkage can occur during periods of drought, during heavy rains, or when the ground thaws out after freezing during winter, that same soil can wash out and erode. Once this occurs, your soil can provide little to no support for the heavy concrete that rests on top of it.

As water moves underneath your concrete slabs, it can wash away the soil that’s supporting the weight of the overlying concrete. As this happens, a void is created underneath. Over time, with nothing to support it, your concrete slab will begin to crack, sink, or cave in. Suddenly, you’ve got a significant concrete settlement problem, safety hazard, and potential loss of resale value.


The Permanent Solution to Fix Sunken Concrete

In previous years, mudjacking has been the traditional method for Atlanta sinking concrete repair – but is it your best option? Mudjacking involves injecting a slurry of cement and soil beneath the concrete slab. However, if the soil or fill upon which the slab was installed is weak or poorly compacted, the mudjacked slab will more than likely go right back to sinking, making it a temporary solution to lifting your concrete.


At AquaGuard, we have a better solution: PolyRenewal™® injection. This Atlanta sinking concrete repair process takes the original concept of mudjacking and combines it with modern knowledge and technology. It’s lightweight, provides a greater lifting power than mudjacking, and requires little to no waiting for it to cure. 

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