Soil & Base Preparation
2. Evaluate the soil. Whether for a Pervious driveway or parking lot take test borings to establish whether soil will drain enough to support the right sub base and the pervious pavement. This boring machine will bring to the surface, soils that contain significant levels of silt or clay that are either highly compressible, lack cohesion or will expand or contract with the absorption of moisture. They may not be suitable for pervious concrete pavement unless remediation steps are taken to stabilize that soil. Boring samples are usually taken at 6" intervals from the surface down to undesturbed soil or bedrock.
Engineering is an important part of successful Pervious Pavement. If roots or other organic debris remain the soil will later settle, and the pavement will crack. Have soil condition certified before placing sub-base.
3. Base Prepeartion. Before concrete is placed the sub-base must be compacted using a vibratory roller or other suitable equipment to a minimum density of 94% to 98%. The compacted base must be moist prior to the placement of paving material, but no puddles of free standing water can be tolerated. A poorly draining base will impede the pervious function. And properly prepared bases will not become rutted by ready mix trucks. Membranes installed between the base and the Pervious Concrete even if porous will eventually clog and prevent proper passage of rainwater.
A properly compacted base supports the weight of a fully loaded, ready-mix truck without creating ruts. Improperly compacted base will not only settle under the weight of the ready mix truck, but will continue to settle every time it rains resulting in cracks and raveling.
Compaction is usually done with a vibratory roller compactor. If fill is installed under the base it is usually installed in 6" layers with each layer being compacted.