Concrete structures, while they may seem invincible, are actually subject to a wide variety of environmental stresses – many of which can cause damage such as cracks, heaving, or even sinking. Once settlement begins, the damage almost always gets worse as time goes on, and the soil beneath the structure continues to erode.
Once you’ve decided that you want to repair, rather than go for a full-on replacement, you need to consider which method is best. Mud-jacking (also commonly known as slab jacking and pressure grouting) is a well-known tried and tested solution for lifting sunken and uneven concrete slabs. However, thanks to recent technology, polyurethane injections are also becoming a common alternative solution. So which method is the best? Here are some advantages and disadvantages of both to help you make up your mind.
Mud-jacking is a commonly used method to raise sunken concrete, raising slabs by pumping grout through it. Water is combined with a dense limestone aggregate and injected into drilled holes to fill any spaces that have been created as a result of soil compaction or water erosion. Once the areas are successfully filled, the concrete slab is pushed back up from below.
- A common method that many contractors are familiar with
- Inexpensive compared to other procedures
- Environmentally friendly – the injection contents are constructed from naturally occurring materials
- Equipment is cheaper than its polyurethane counterpart
- Not always very reliable and usually needs to be replaced after a certain amount of time
- The injected slurry is very heavy compared to the material used in polyurethane injections and can cause soil compression underneath the concrete block
- The injectable material is rough in texture which means that it won’t completely fill all of the underlying gaps below the slab
- The slurry is prone to washing out if exposed to any underground water thanks to heavy rainfall, water pipes or poor drainage
The injection uses a closed-cell polymer foam that seals gas pockets to prevent any water from being soaked up. The material is injected via a hole, with the foam passing into, through and below the concrete block. Once the foam reaches beneath the slab, the reaction between the expansion of bubbles in the foam lifts the block back up.
- Polyurethane injections are long-lasting
- Makes the final result more aesthetically pleasing thanks to a smaller injection hole compared to the larger holes used in mud-jacking
- The closed-cell foam flows easily making the method less messy and is lightweight meaning that there will be no additional soil compression
- The soil below the concrete slabs mix well the with the material
- Has a density that is sufficient enough to fully fill all of the cavities that are below the sinking foundation.
- The procedure is newer and therefore fewer contractors have knowledge or access to the method
- Not widely available to homeowners or smaller contractors who specialise in residential work
- The process is more expensive than mud jacking thanks to the required equipment and materials