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There are two applications for sand in a paver project. Choosing the right sand for the application that you are using to install is important to the longevity of your paver project. Having improper sand that does not meet the gradation standards will cause future problems for your project and ultimately unsightly results. This is why it is important to know what product you are using and why.
Best Paver Sand
Sand plays an important role in two aspects of a paver project. One is to provide a bedding layer for your pavers to be seated into and the other is for the joints of your pavers. Each of these aspects contribute to the horizontal interlock of the pavers, adding to the strength of the system as a whole. The jointing material, along with the creeping of bedding material from the bottom up after compaction, allows for the pavers to bear the load from outside forces without failure. Choosing the best sand for paving will contribute to this strength while also reducing failure of the pavement surface.
- Bedding Layer Sand for Pavers
- Jointing Sand for Pavers
The purpose of this sand is to provide a layer on top of the base material for the pavers to be laid on top of. This layer is screeded out in a uniform one inch depth on top of the larger aggregate base material. This sand is typically referred to as concrete sand or ASTM C33 sand and is small, but coarse, granular material made from the disintegration or crushing of rock. It has a larger granule than most sands allowing for the proper drainage of water at a higher than a finer sand.
Upon final compaction of the pavers, and typically the consolidation of the jointing compound, the bedding sand will creep up into the joint of the pavers assisting in the horizontal interlock of the pavement surface along with the jointing compound that is consolidated to the bottom of the joint meeting the bedding material. This final compaction is incredibly important to the overall strength and quality of installation.
Though concrete sand or ASTM C33 sand is traditionally used in the installation of pavers as a bedding layer, nowadays we are seeing a movement towards a new angular granule that is clear of the fine material that sand has. This is called High Performance Bedding or HPB and is an angular crushed aggregate with a maximum nominal size of 1/4″. This is washed and clear of dust fractions allowing water to flow through it with minimal resistance and reaches compaction rates of 90% without mechanical compaction. Concrete sand on the other hand compacts down approximately 1/4″ with the 1″ bedding layer. Similar to the concrete sand bedding layer, HPB is screeded at a uniform depth of one inch for the pavers to be laid on top of and compacted. It is typically used in the installation of an open graded base where the base material is constructed of 3/4″ crushed clear stone allowing the water that enters to system to flow through the bedding material and base material to be collected into a drainage system and exited out with minimal resistance.
The second use of sand for pavers is to fill the joints of the pavers. This sand is installed by sweeping it over the surface of the pavers and mechanically compacting it to consolidate it to the bottom of the joint while also seating the pavers into the bedding layer. This action is what allows for the horizontal interlock of the pavers contributing to the strength of the system. The jointing sand will drop to the bottom of the joint and the installer will add more sand sweeping it over the surface and continuing these steps of consolidating the jointing sand until it reaches 1/8″ below the top of the paver or the bottom of the chamfer of the paver.
There are several options for jointing material on the market today. One option is for a jointing sand. This is not the same as concrete sand. Its granules are more angular in comparison which works to limit the washout of the material. However, washout will still occur with this loose sand and typically a joint stabilizing sealer will be applied to lock in that material into the joints. Alternatively, a polymeric sand can be installed. The installation follows the same steps, except with a final activation step where the surface is watered according to the manufacturer’s guidelines to activate the sand allowing it to harden. This sand has become a popular choice in the hardscape industry.
Along with polymeric sand, there are several alternatives entering the market including resin based jointing compounds that are applied wet and are semi-permeable allowing water to penetrate through the joints and into the base material. With these compounds, water acts as the consolidator of the jointing compound rather than mechanical compaction, though a compactor can be used to assist in this consolidation process. If the pavers have spacers, mechanical compaction is preferred before installing the jointing compound to seat the pavers into the bedding layer if water will be relied upon to consolidate the jointing material.
During this compaction phase of the project, the surface of the pavers need to be protected from the vibratory action of the plate compactor to prevent scuffing, chipping, and breaking of the pavers. A plate compactor pad is typically installed on the plate compactor or a protective layer is used between the paving stones and the compactor itself. Alternatively there are rolling compactors for pavers that can be used as a specialized solution for this process.
These two different applications for sand in a paver installation present two different types of sand that are used in the installation process. Concrete sand cannot be used as a jointing material for your pavers and jointing sand cannot be used as a bedding layer for your pavers. The gradation of these two sands are different and each has a specialized purpose in the strength of the pavement system. Knowing this information will help you in becoming an educated installer and to be able to build proper interlocking concrete pavement systems that will stand the test of time and the loads that they support.