Why is structural soil effective?
Structural soil is specific soil mixed with a specific type of gap-upgraded rock (typically 75mm clear) and a binder. The reason structural soil works well is that the gaps created by the rock are filled with the soil, allowing tree roots to grow in that soil. This penetration allows the tree access to a larger space underground, and has the double function of preventing the tree roots from lifting up the hard surface, i.e.
the sidewalk that is on top. The rock provides the necessary stability for the pavement. The combination results in a drastic decrease in cracking ashpalt.
Best Places for Structural Soil
Structural soil has become the best solution for tree-growing in urban settings. This type of soil has been proven to improve tree growth in paved areas, therefore it is the best way to promote street tree planting. Structural soil is used to provide a solid base, which is meant to support masses and at the same time allow for the growth of roots. The result is a perfect crack-free pavement, with a healthy tree growing as expected.
How does the structural soil get tested?
The testing of structural soil is essentially a three-part process. The soil must be tested separately. The rock must be tested and sourced with a specific sieve size attached to it to determine that it is in fact a clear rock and not a minus rock. With a minus rock all of which would be filled and therefore the soil would be effective.
There is also a stabilizing compound that is used with structural support to help the soil adhere to the rock. The specifications for this material would come directly from the stabilizer supplier; there are more than one of these.
Who can make structural soil?
Like any engineered soil, structured soil is a technical process which is best done by people who understand all the specific components and have all the components readily available with testing and prior knowledge. Making good structural soil to specification is an extremely important endeavour. Structural soil that is not up to specification is a very difficult situation to remediate once it's already in the ground. Not all structural soils are the same. They come in different specifications, which are suited for various weather conditions. All the elements that make up structural soil are mixed together.
