@DiamondHell The fill material should be a course graded angular aggregate preferably from an Igneous rock such as Basalt or Granite 4/40mm BS EN 13242 and 7533-13:2009.
@DiamondHell Unfortunately crushed chalk is not a suitable fill material for a Terram Geocell used for tree root protection. Chalk is a relatively soft Calcium Carbonate based rock will dissolve in rain water resulting in elevated pH levels and reduced permeability.
The #Terram team is proud to have teamed up with @BBC's The Million Pound Build for Children in Need, in Swansea!
The BBC team spent 11 days building a center and supported housing for young people in care and leaving care using Terram's #Geotextiles and #Geocells products.