Why does concrete settle?

The stability of a concrete slab is directly proportional to the quality of the base it is poured on. Poor base conditions can be attributed to:

Poor or improper compaction of the base:
Failure to properly compact base materials before pouring can lead to hastened settling. The weight of the slab will further compact the base after curing and settlement can happen quickly.

Climate:
The freeze and thaw cycle experienced in many regions causes the ground underneath the slab to expand when frost is present. This in turn will cause slabs to heave or raise. When the frost melts the slabs will settle and most often not to their original elevation. Slabs may become uneven resulting in trip spots. Drought often causes soil such as expansive clays to shrink (desiccation) causing settling issues for concrete slabs. When expansive clay soils encounter wet conditions they may swell leading to shifting concrete that needs leveling.

Erosion:
Many different factors can lead to eroded base materials under concrete. Damaged water lines or sewer lines can lead to washout of base materials causing slabs to settle. Improperly placed downspouts can cause pooling of water which can lead to erosion.

Machine/Traffic Vibrations:
Concrete slabs may move or settle in industrial/highway settings where movement and heavy loads are present. The vibrations from the machinery and passing traffic can lead to the base compacting and the slabs settling or slab movement.

Slab Curl/Rocking Slabs:
Slab curl occurs when a relatively large section of concrete is poured. During the curing process, the top of the slab may cure slightly faster. This leads to slabs that curl and may rock and be unstable. Vibration may also causes slabs to eventually settle.

 

faq01

faq02

What can be done with settled concrete?

Grinding:
This is an inexpensive option that is unattractive. Grinding exposes aggregate in the concrete which makes this esthetically unappealing. The integrity and strength of the slab is also compromised when using this method. What is often overlooked regards grinding is that slabs that continue to settle after grinding cannot be raised back to the original elevation and replacement then becomes the only viable option.

Replacement:
This option is the most expensive option. It is also very time consuming. This method may lead to downtime for businesses, losses of productivity, and lost revenues. The colors will not match existing adjacent concrete

Raising & Stabilizing:
With Polytek360 Inc. the method for concrete raising utilizes the slab itself as a means of delivering raising, void filling, and stabilizing foam. A 5/8” hole is drilled through the slab into the subgrade. A tapered delivery port is then installed in the 5/8”hole. The injection gun, which delivers the dual component polyurethane material, is then connected to the port. Material is then injected through the port and slab. Expansion of the material occurs within seconds, compressing loose soils, driving out water and raising the concrete.

Raising concrete with polyurethane foam is done with precision incremental injections. Our lifting foams can fully expand within 3-5 seconds. This allows our technicians to accurately monitor the raise and prevent any over lifting of the slab.

Void Filling:
Concrete settling is not the only issue that Polytek360 Foam can solve. Voids under slabs are often present in areas where wash out or excessive settling can occur. This material will weigh on average 15-25 times less than a traditional mudjacking or cementitious group mix. This lightweight material will put less stress on an already failed subgrade. The process of drilling, port installation, and injecting the material is the same as the raising process. All dual component polyurethane foams create heat when installed. Depending on size of void, and type of foam being used, void fills may need to be done in a layering method to allow heat to dissipate safely.

Joint/Slab Stabilization:
Slab stabilization is often required when slabs lack support, but may or may not be settled. Slabs can crack when loads exceeding its capacity are applied . Slab/joint stabilization applications require the voids to be filled to eliminate movement and offer support. Polytek360 foam specifically designed for joint/slab stabilization has a very long reaction time and minimal expansion strength. This product will take longer to expand allowing for better coverage under the slab or down a joint.

 

Core-Sample

Slab_feature

void_feature

inside2