The joints of your interlocking concrete pavement projects installed properly with the proper jointing compound are one aspect that provides a strong pavement solution that will withstand the test of time. These joints provide horizontal interlock to the system, allowing it to bear loads that the pavement will experience. One such jointing compound that is extremely popular is polymeric sand. This sand is swept and compacted into the joints of the pavers and activated with water. It then solidifies and provides a rigid, but flexible joint for the pavement. Though it is an excellent product that the industry has embraced and it continues to improve with new generations of sands being released by manufacturers, it is not without problems that may occur because of environmental conditions or improper installation. These problems that you may or may have already experienced are covered in this article.
Common Polymeric Sand Problems
It is important to note that some of these problems are specific to polymeric sand mostly due to improper installation of base material, bedding material, or the polymeric sand itself. However, some of these problems are common to other jointing compounds and sometimes even more so common with other jointing compounds. Polymeric sand is a great product that when installed properly will hold up for several years for your project especially if maintained properly.
That being said, here are some problems that you may experience with polymeric sand and why they may occur:
- Insects or Weeds in Paver Joints
- Moss or Mold in Paver Joints
- Polymeric Sand Did Not Harden
Polymeric sand inhibits weed growth and insects. It does not completely stop it. Weeds will grow anywhere including in solid rock. It does not take much for a seed to get stuck and begin to grow. Especially if you have a project that is underneath trees or other vegetation, it is important to every once in while blow off your project to prevent any seeds from sprouting in the joints of your project. If installed improperly, the polymeric sand may crack or begin to peel which leaves exposed sand for weeds to begin to grow or insects to begin making a home. To prevent this from happening, ensure that your polymeric sand is installed properly and that your space is maintained.
If installed in a shaded area, moss or mold may begin to grow especially in the joints of your pavers. This is because the joints are the low spot of the pavement for water to sit which invites moss or mold to grow. This is difficult to prevent especially in areas that do not get a lot of sun, but consistent maintenance of the area will be beneficial to prevent this growth. Additionally, ensuring your project has proper slope for the water to promptly drain off of the surface of the pavement and preventing water from sitting in the joints and inviting this growth.
This is a common problem with improper installation of the polymeric sand itself, not necessarily a problem with the polymeric sand. Installation of polymeric sand requires quite a few steps to be followed properly and the right environmental factors. Failure to follow the steps as outlined by the manufacturer will lead to the failure of the polymeric sand. It is important to note that every manufacturer has a different activation process for their polymeric sand. Water is the common activator of the sand, but the duration and wetting process of the surface of the pavement varies and could lead to failure if not completed properly. Here are some reasons why your polymeric sand did not harden:
- The polymeric sand was not compacted into the joints, allowing it to reach the bottom of the joint. If this step is skipped, polymeric sand will choke itself on the way to the bottom and prevent further granules from reaching the bottom. Though the joint looks like it is full, there are air pockets in the joint that will hold water and cause the polymeric sand to fail. To prevent this, simply run a plate compactor with a protective pad over the surface of the pavement after sweeping the polymeric sand into the joints and sweeping any excess off. This will vibrate the sand to the bottom of the joint. Repeat these steps until the joints are full to 1/8″ below the top of the paver or bottom of the chamfer of the paver after compacting.
- As previously stated, improper activation of the polymeric sand will also lead to failure. Every manufacturer has different activation processes that need to be followed and sometimes different activation processes for their different sands. Consult the manufacturer or read the list of instructions on the product prior to installation.
- In addition to the activation process, manufacturers differ on the time that is required for the sand to set prior to a rainfall. If rain is in the forecast, you will likely need to wait for another time to be able to install the polymeric sand. Rushing this step will lead to inevitable failure of your polymeric sand and it is not worth the risk.
- In addition to rainfall, the temperature needs to be above a certain amount as specified by the manufacturer. This, along with rainfall, can make installing in the Fall and Spring in some regions a bit difficult. But waiting for the right day or two to be able to fit in an install is crucial to the installation of polymeric sand.
- Sometimes people try to cut corners. You just cannot get away with it and build a quality installation. One common way to cut a corner with polymeric sand is to fill the joint up partially with another inexpensive sand before installing polymeric sand on top. This does not work. Each manufacturer requires a full joint depth of polymeric sand or have a minimum depth that is required for thinner material.
- Improper application is one that is overlooked. There are polymeric sands for concrete overlays, small joints, large joints, and others that now do not require compaction. One thing is for certain, if you try to use a polymeric sand that is not rated for the application of your project, it will fail. If you are installing flagstone with larger joints, make sure you opt for the more expensive polymeric sand that is rated for those joint widths and do not exceed those.
- Using the wrong base or bedding layer will lead to poor drainage conditions. For example, stone dust is sometimes used as bedding or even base material for a project which is not a material that should ever be used for interlocking concrete pavement. This material prevents drainage of water and inevitably causes the failure of the polymeric sand in the joints of the pavers.
- Erosion of the polymeric sand can go beyond a poor installation. If a downspout is placed right on top of a paver project, it is likely over time going to erode that sand out of the joint. Sprinkler systems near projects may also accomplish the same result or at least keep the joints damp enough to invite moss and mold growth over time especially if there is not sufficient slope in the project.
What this looks like is only the top portion of the polymeric sand hardens and eventually peels off the surface exposing polymeric sand underneath that is loose. This could be to any of the reasons listed in the previous point where the polymeric sand did not harden. It could also mean that the joints of the polymeric sand were filled too high and the polymeric sand is beginning to fall apart or erode away from the traffic above it. It is important when installing polymeric sand that the joints are filled to 1/8″ below the top of the paver or the bottom of the chamfer on the paver, whichever is lower.
If polymeric sand is not properly cleared off of the surface of the pavers or it is installed when the pavers are still wet, it will harden to the surface upon activation. Prior to activating the polymeric sand, make sure that you clean off the surface of any dust or granules. Use a soft bristle push broom to sweep off the area and then use a leaf blower to blow off the surface of any remaining dust and particles regardless of whether or not the manufacturer says this step is not required. Make sure to check the corners of projects where polymeric sand mounds are created with the blowing process.
How to Remove Polymeric Sand From Pavers
If your polymeric sand hardens on the surface of pavers, which sometimes happens in corners of a project as it is difficult to blow this polymeric sand out, you can simply heat up some water in a pot and pour it on the surface of the stone why scrubbing with a nylon brush. The hot water will reactivate the polymers in the sand, loosening the sand from the surface. If you have a project where the sand has solidified on the surface of a large area of pavers, then you are likely going to need a hot water pressure washer to clean it all off.
Some polymeric sand brands are worse than others with this. A lot of manufacturers claim that their sand is haze free, but when it comes down to it they may leave some residue or dust particles on the surface and when activated will leave a cloudy effect over the surface of the pavers. As stated above, it is important to use a soft bristle push broom to complete a final sweeping of the surface followed by blowing the surface with a leaf blower to remove any fine dust particles before activating the polymeric sand. Taking your time with this step in the process ensures that you are left with a quality project.
How to Remove Polymeric Sand Haze from Pavers
Most polymeric sand manufacturers have a polymeric sand haze remove. It is a chemical that is mixed with water and sprayed onto the surface followed by a scrubbing and rinsing. Work to first prevent polymeric sand haze from happening before opting for this solution.
Though there is a lot that can go wrong with polymeric sand, it definitely has numerous benefits over other alternatives and is still one of the most installed jointing compounds for paver projects. Following the steps to proper polymeric sand installation and planning your project carefully will ensure that success of your paver joints and the polymeric sand installed in them. Failure to do so will lead to having to fix the problem and having to re-sand the pavers.