Pavers – Possible Problems
By Caleb Contois, January 21, 2022
Cross-section of pavement installation
Compaction of Subsoil and Base
There are many phases in the installation of an interlocking concrete pavement. One of the most crucial steps of the process is compaction. Insufficient compaction of the subsoil or base will result in settlement or, in the case of driveways, rutting of the pavers.
Proper compaction ensures that the soil and base will withstand the downward forces that are applied by pedestrian or vehicular traffic.
Another key component to creating a secure pavement structure is utilizing a proper edge restraint. An edge restraint reinforces the perimeter of the pavement system so that the pavers remain interlocked when horizontal forces are applied to the surface.
A poorly executed edge restraint will result in the pavers shifting away from each other over time.
The 1 inch of bedding sand between the base and the pavers is another vital element that ensures the pavers remain interlocked. It is also essential to allow for proper water drainage.
Here at Peakview Outdoor Living, we use polymeric sand to fill the joints between pavers. Polymeric sand is a unique mixture of sand and additives that harden when exposed to water. The typical procedure is as follows:
- Compact pavers
- Sweep polymeric sand into the paver joints
- Compact pavers again to allow for the sand to fill any gaps underneath the pavers
- Repeat step 2
- Water the pavement to activate the polymeric sand
Some of the benefits of using polymeric sand include strong interlock for the pavers, elimination of weed growth between pavers, and effective water drainage by preventing the water from falling in between the paver joints and into the base.
settlement from improper compaction
Settlement occurs when the subgrade or base beneath the pavers has not been adequately compacted. Over time, the soil or base begins to descend, resulting in the affected area sinking lower than the surrounding pavers.
It is important to note that minor settlement can always occur after a pavement installation. The settlement that can occur even after proper compaction is minimal and not a cause for concern.
Settlement from improper compaction threatens the integrity of the pavement structure, ruins its aesthetic appeal, and weakens its functionality. This kind of settlement is most common near house foundations and where the pavement meets a concrete edge such as a sidewalk connecting to a driveway or a curb.
The soil near house foundations, particularly in new development, tends to be loose. It is important that contractors spend the necessary time compacting and testing this area for proper density in order to avoid major settlement.
settlement from loose bedding sand
Contractors have different options when deciding what to use for the layer of bedding sand. Problems arising from improper bedding sand installation are minimized through the use of polymeric sand, however, it could occur in some situations.
For example, let us say that you are having a paver driveway installed and that this driveway connects to a sidewalk, as it does in the majority of residential neighborhoods. Imagine that along the edge of the sidewalk that meets the driveway there are cracks right around where the 1 inch of bedding sand is being placed. If the bedding sand is not properly secured so that it remains in place, it can be swept into the cracks over time which will cause settlement.
In the scenario above, it is assumed that concrete sand was used and that the sand has been displaced by water passing through the bedding layer. As for polymeric sand, we can imagine that the sand closest to the surface has hardened due to the additives, and that there is no risk of the sand being washed away by water. However, some of the poly sand beneath the pavers remained dry during installation, and the vibration of the vehicle rolling over the pavers causes the sand to move into the cracks, thus creating settlement.
An effective way to prevent sand from moving into cracks along an abutting concrete structure is to use geo-textile fabric between the concrete and the pavement system. Geo-textile will block the cracks and retain the bedding sand.
rutting from vehicular forces
Rutting is the deformation of the pavement structure that stems from improper compaction. The turning of a vehicle’s tires pushes the pavers against the weak foundation, creating a warped appearance in the pavement driveway.
paver displacement from weak edge restraint
There are two main options available to contractors when choosing an edge restraint; edging manufactured from plastic or other materials, and traditional poured-in concrete edging.
Both are viable, but we at Peakview Outdoor Living use a product called Xtreme Edge made by the company Alliance Gator, which is an alternative to traditional poured-in concrete. Similar to polymeric sand, Xtreme edge contains polymer additives that activate when exposed to water. This decreases the amount of water needed to mix with the product and also makes it less rigid than traditional concrete. Another benefit to using Xtreme Edge is the tiny 3D-micro-mesh fibers that stretch out when mixing with water. These fibers provide additional support and prevent the Xtreme Edge from breaking apart as seen in traditional concrete.
Interlocking concrete pavements are durable, long-lasting structures when installed properly. The potential problem areas covered in this blog are the most common in the industry, and they are also easily avoidable. Hire a contractor you trust to get the job done right the first time, and enjoy your pavement system as a beautiful addition to your outdoor living space.
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