Table 1.

Materials and mixing methods used as sub-base to support trees.

Stones (80–150 mm)Stones/crushed stones (32–80 mm) (32–45 mm)Leca-concrete blocks* (100 × 100 mm)Crushed lava (32–45 mm)Crushed bricks (25–50 mm)Sand mix (0.2–0.5 mm)
Installation methodswater mix dry mixpremix water mixpremixpremix water mix dry mixpremix water mixpremix
Growing mediumtopsoiltopsoiltopsoiltopsoiltopsoilhumus/compost
Density of material (g/cm3)
Porosity of material (vol. – %)00approx. 15approx. 55approx. 300
Voids in compacted material (vol. – %)4545/4056383545
  • * Leca is the Danish commercial name for Light Expanded Clay Aggretates.