In a traditional installation of interlocking pavement surfaces, a Granular A material is used for the construction of the base. This has many different names in different regions including 3/4 minus. It is among the recommended aggregates for base construction by the Interlocking Concrete Pavement Institute for a traditional installation. Though we do rely on it in some aspects of our paver installs in our business, with the emergence of open graded bases we have become increasingly less reliant on this material.
What is Granular A
Granular A, A Gravel, or 3/4 inch minus is a mixture of sand and crushed gravel or rock. With mechanical compaction and reaching 98% standard Proctor Density, this material provides adequate stability and load support for paver bases. Through this compaction and with the loads that the base will bear, the coarse aggregate should not degrade. The larger granules should pass a hardness test in order to ensure this. In the field, the easiest way to see this would be to use a swiss army knife and put one of granules under pressure to see if it breaks apart.
This material should be installed in lifts based on the force of the compactor that you will be using. The lifts should be installed with no elevations exceeding +/- 3/8 inch. This allows for the proper compaction of these lifts without the compactor moving up or down elevations where the plate of the compactor should be parallel with the base material to ensure proper compaction. As a rule of thumb, 1,000 pounds of capacity force that the compactor is capable of for every one inch of lift.
What is Granular A Used For
- Paver Base Material
- Retaining Wall Base Material
This material is used in a traditional paver base install. We use it in some installation, most specifically in a driveway installation or in front entrances that are tied into an asphalt pavement driveway. However, for the most part we opt for a synthetic base installation for projects that can be installed on the existing grade or for an open graded base. Both of these installation options do not require a Granular A material.
For most of our retaining wall installations we opt for an A Gravel base, though an open graded material can be used as an alternative. The difference in both of these installations would be the positioning of the drainage pipe in behind the wall. If using this material for the base of the wall and a 3/4 inch crushed stone as a drainage in behind the wall, a non-woven geotextile should be used to separate the two in order to avoid migration between the two materials.
Granular A Calculator
Knowing how much gravel you need requires three measurements from your project. You need to measure the length in feet, the width in feet, and the depth in inches that you will need for your gravel to fill. Using these measurements, you can fill in the formula below to calculate the amount of cubic yards of the material that you will need to order for your project.
[Length (in feet) x Width (in feet) x Depth (in inches)] x 0.003 = Total Cubic Yards