Roth Concrete Lifting’s process of raising and stabilizing concrete slabs with dual component polyurethane foams.

 

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 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.

 

 

What can be done with settled concrete?

Nothing: Settled concrete is an issue that needs to be addressed, not only from an aesthetic standpoint, but most importantly from a liability standpoint. The Americans with Disabilities Act (ADA) of 1990 defines a ‘trip hazard’ as any vertical change of over 1/4 inch or more at any joint or crack. Since the ADA demands strict compliance, trip hazards represent a legal liability to clients. Cities, school districts, hospitals, private communities, shopping malls, universities, apartment complexes, and other property owners are all extremely concerned with this liability.

 

Grinding: This is an inexpensive option that is unattractive. Grinding exposes aggregate in the concrete which makes this unappealing. The integrity and strength of the slab is also compromised when using this method. Slabs that continue to settle after grinding cannot be raise back to original levels.

 

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: May be done with traditional mudjacking or cementitous grouting. This process utilizes a hydraulically powered pump to install a slurry mix under the slab with enough pressure to compact weak soil underneath and raise the slab. Water, fly ash, top soil, sand, clay, agricultural lime, and cement are materials used to create these slurries. This method, when used on subgrade that has already settled, adds excessive weight and may lead to resettling.

 

Roth Concrete Lifting Process: With polyurethane, 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 and raising concrete.

 

Raising concrete with polyurethane foam is done with incremental injections. Lifting foam will fully expand within 10-15 seconds. This allows the applicator to monitor the raise and prevents over raising the slab.

 

Void Filling: Concrete settling is not the only issue that foam can solve. Voids under slabs are often present in areas where wash out or excessive settling can occur.

 

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.

 

Foam specifically designed for joint/slab stabilization has a very long reaction time and minimal expansion strength. It will take longer to expand allowing for better coverage under the slab or down a joint.

 

Roth Concrete Lifting’s process and material will provide long lasting repair to sunken or moving concrete slabs in need of lifting and/or stabilization. The repair method has proven to be more cost effective for the customer and save them time in completing their repairs. Time is of the essence when considering commercial projects where productivity could be lost when replacing slabs as opposed to the process of raising them with polyurethane foam.

 

Roth Concrete Lifting encompasses residential, commercial, industrial, and government projects involving small walk way slabs, factory floors, airport runways and highways.