Every aspect of an interlock concrete pavement system plays a role in the strength of the pavement. The sand in the joints of the paving stones is incredibly important to the interlock of the pavers and the ability to bear loads that the pavement surface will experience throughout its lifetime. It is no doubt that the step of sanding paver joints (not actually using sand paper, but installing sand into the joints of the pavers) plays a major role in the interlock concrete pavement system. In this article, we are going to walk through the options to use to sand paver joints and the step-by-step process to accomplish this.
Role of Sand for in Between Pavers
Interlock concrete pavement is a strong system that is rigid, but flexible. It bears the load that travels on top of it and moves with the earth, making it the optimal pavement option. The sand between the pavers or in the paver joints plays a big role in the strength of the system. This sand is swept into the joints and provides one of three interlocking of the pavement. This is called horizontal interlock. This resists the movement of pavers with the load that travels on the surface of the pavement.
Prior to sweeping in the jointing material, you will notice that if you step on the pavers they may not feel as rigid as expected. Without a jointing compound installed into the joints, the system is not rigid and those pavers are able to move horizontally as a load is moving over the surface. After a joint sand is swept and compacted into the joints, the system now promotes horizontal interlock and you will feel the rigidity of the surface as you walk across the surface.
Paving Joint Filler Options
There are several options to choose from for your jointing compound. Each of them has their benefits and drawbacks that are covered below.
- Jointing Sand
- Polymeric Sand
- Jointing Compounds
- Jointing Chips
This is a sand that is made of fine materials and elongated granules that help to resist washout. It has no additives to it that you will see with other options below and comes with the easiest installation method. However, it is prone to washout, weed growth, and insects. To prevent these drawbacks, a joint stabilizing sealer is typically installed on top of it after installation once the pavers have fully cured according to the manufacturer’s guidelines. Without the use of a sealer, this is the least expensive jointing compound to purchase and to install. This material cannot be installed in wet conditions or when the sand itself is wet. Water is still able to work its way through the jointing material especially if not sealed.
This sand has additives to it that are water activated causing the sand to harden. This process comes with an extra step in comparison to jointing sand as after installation of the sand, the sand must be activated. This extra step also presents some complications, as not following the specific manufacturer’s guidelines can cause failure to the polymeric sand. In addition, it costs more for the material itself. It prevents washout, weed growth, and insects. However, it does not completely eliminate them entirely especially when improperly installed. This material cannot be installed in wet conditions either or when the sand itself is wet. Once installed, water penetrates through the joint at a very low rate, as low as 3%.
This is a wide range of sands that are resin-based. They are sometimes two part mixtures or installed with water as the consolidation of the jointing material to the bottom of the joint. They are typically more expensive than polymeric sand and take more time to install. They are also typically semi-permeable allowing for the penetration of water with minimal resistance. They are also newer to the market in comparison to the options already presented.
This option is for permeable installations where you want the water to flow through with the least amount of resistance. These are angular chips engineered to lock together to prevent washout. You can also opt to install a joint stabilizing sealer on top of them to further prevent washout. Insects and weed growth is less likely to use this joint material in comparison to jointing sand because of its size. The base material needs to be able to drain the water that enters the system through these joints.
Installing Sand for Interlock Joints
There is a typical installation process for joint sand, whether it is jointing sand or polymeric sand. For jointing compounds, the installation will vary depending on whether it is a two part mixture or if it installed with water. If sand is being used for the installation (jointing or polymeric) this is how you are going to install it.
Note: If you are installing polymeric sand, it is important to consult the manufacturer’s guidelines for the activation stage of the process as well as the timeframe to which you can install it prior to a rain event.
- Ensure that the surface of your pavement is clean, free of debris, and dry. This may mean that you will want to pressure wash the surface if it and allow it to dry during a day of sun. Just because the surface is dry does not mean that the joints are dry. Allow time for this cleaning of the surface of the stones and the drying of the same. Sweeping the debris and dirt that gets tracked onto the surface of the pavement during the construction will promote weed growth, prevent proper drainage of water that enters the joints, or cause the failure of the jointing compound.
- Calculate the quantity of sand needed. Every paver has a varying amount of jointing material required based on the number of joints caused by the size of the paver, the joint thickness, and the depth of the pavers. Consult with the manufacturer to be able to calculate the number of bags or weight of sand needed to complete your installation.
- Sweep the sand into the joints. If you are using polymeric sand, you will not want to drop a full bag of sand into one pile and sweep it around. You do not want to sweep the sand more than 10 feet in any direction. Doing this will separate the mixture of the sand and lead to the failure of the joint. Instead of dumping the sand into one pile, dump the sand out over a 50 square foot area and sweep it into the joints from there. We find that using a stiff bristle push broom and soft bristle push broom mixture provides the best results. When the joints are filled, sweep off any excess sand from the surface. This will prepare you for the next step.
- Compact the sand into the joints of the pavers. This is completed by using an appropriate vibratory plate compactor with a protective layer between the compactor and the pavers. Failure to use a protective layer will lead to the scuffing, chipping, or breaking of the pavers. You can use a protective pad that will clamp onto your compactor for this, use plywood or other pad that can be spread out over the area, or a specialized piece of equipment for this stage called a paver roller compactor. You will also want to make sure that the compactor itself and the protective layer that you are using is free of debris. The vibratory action will cause any debris to fall onto the surface of the pavers and if run over with the compactor will scuff the pavers. Compact around the perimeter of the paving surface and work your way inwards and then complete a second pass horizontally or vertically through the entire surface. This will consolidate the jointing material down to the bottom of the joint while also seating the pavers into the bedding layer. At this point you will feel the firmness of the pavers as horizontal interlock is achieved. The joint sand will settle a significant amount at this time.
- Continue the last two steps as many times as necessary to fill the joints to 1/8″ below the top of the paver or the bottom of the paver chamfer, whichever is lower. This will take more time depending on the thickness of the paver joints. The thinner the joint, the more times you will have to repeat this process.
- Sweep off the surface to clear it off. If you are using polymeric sand, blow off the surface using a leaf blower to remove any dust or excess sand. You can then follow the manufacturer’s guidelines to activate the sand using water. It is important that you use only one brand of sand for this and that you carefully follow the activation guidelines. A final blowing off of water or debris on the surface after the activation may be required.
If you follow these steps for sanding your paver joints, you will ensure a proper installation that will help the horizontal interlock of the interlock concrete pavement system that you install. In addition to these steps, make sure that you consult with the manufacturer’s instructions especially when installing polymeric sand or other jointing compounds as they may vary in the activation phase of the installation.