Here at New Dawn, we install permeable paving to suit any application! But the difference between us and the next is that we are permeable specialists that keep everything in-house with no subcontractors involved. That’s why, when quality is required, civil engineers and landscape archit ects specify for us by name like in the detail below.
But what’s the secret to quality heavy duty permeable paving?
With any type of surface paving (think paving tiles or natural stone pavers), the actual “heavy lifting” is performed not by the surface, but by the substrate (ie. concrete slab) beneath.
Our resin-bound permeable paving is no different. By tailoring the permeable concrete base that we install the resin-bound surface over, we can ensure the pavement is suitable for various vehicle loadings.
When do you need a heavy duty permeable pavement?
There are various reasons that architects and engineers specify heavy duty pavements over traditional “domestic” concrete paving. It’s generally required in situations where trucks are going to be trafficking the surface. Some scenarios we’ve encountered include:
- Driveways or roadways on multi unit development sites where garbage trucks will be collecting bins on the property
- Parking areas for commercial properties where trucks may be making deliveries
There’s also a planning requirement in the Bushfire Management Overlay for driveways in bushfire prone areas to be suitable access for fire fighting vehicles, which includes a minimum weight loading of 15 tonne and minimum width of 3.5m, as well as rules on gradients and turning radii.
How to specify heavy duty permeable concrete?
Our resin bound paving is a highly durable surface suitable for sustained vehicle traffic. But the secret to our heavy duty pavements is our fully reinforced permeable concrete substrate beneath the resin bound permeable paving.
For a typical pavement with expected occasionally heavy vehicle (up to 30 tonne) loadings, a minimum permeable concrete thickness of 200 mm is required, as well as hot-dip galvanised SL92 reinforcement central in slab with minimum 50 mm top cover.
The sub-base beneath the permeable concrete should also be considered, with reactive clay soils sometimes needing bedding/isolation layers of 14 mm screenings (no-fines screened crushed rock). This is highly site specific and the requirements should be determined by New Dawn following initial excavation works.
It is highly recommended that non-woven geotextile fabric (grade A24 or higher) be installed over the natural ground to prevent the upwards migration of fines through the pavement. Any bedding rock should be placed on top of the geotextile fabric to separate it from soft areas in the natural subgrade.
(Disclaimer: the maximum loading of ANY slab-on-ground concrete pavement will vary depending on the soil bearing capacity of the subgrade immediately beneath the pavement. That’s why “structural” concrete constructions (eg. building slabs) have engineer designed footings! Our permeable concrete specifications are tried and tested, and are over and above the typical concrete specifications for “normal” concrete heavy duty pavements. But if a site-specific critical maximum loading is required, soil testing and engineer calculations are required.)
Case Study: Access Roads with Permeable Paving
This development site featured 73 individual townhouses plus a large apartment complex in the centre. The main access road through the site featured heavy duty concrete with heavy duty permeable paving sections to allow garbage truck access.
The civil contractor (our client) installed first the heavy duty concrete pavement sections, leaving us the permeable paving sections to install as infills.
A24 bidim geotextile fabric was first installed over the engineered sub base, then galvanised SL92 reinforcing placed ready for the permeable concrete pour.
To create expansion joints between paving sections, full depth expansion foam was applied to the adjacent concrete before galvanised N16 450 mm dowels were inserted into 20 mm dia. holes in the adjacent slabs. By installing “loose” dowels in oversized holes, it allows for a small amount of differential lateral and vertical movement between the permeable and normal concrete sections, as well as normal expansion.
The permeable concrete was then placed and screeded to 20 mm below finished level. You’ll notice in the photo that bar chairs are not placed under the reinforcing. Permeable concrete will not flow under or around “normal” combination bar chairs, so if they are used then it would leave voids under the chairs, potentially weakening the pavement. Instead, the mesh is manually lifted during the pour, with Danley SOG chairs (with no void beneath) used sparingly as required in deeper sections.
Once cured, the permeable concrete sections were then surfaced with 20 mm of our resin bound permeable paving.
The access road was then utilised by countless concrete trucks and other delivery trucks whilst the other civil works around the site were completed.
Case Study: Firetruck Rated Access Way for Townhouse Site
This 23 townhouse site with basement carpark had two main entries leading to the central driveway. CFA and council required the two driveways to be suitable for fire fighting vehicles, with a minimum 15 ton vehicle loading. The developer selected our heavy duty permeable paving system to meet these requirements.
Because the permeable paving areas abutted the basement, we installed substantial subsurface drainage to minimise the amount of water from under the permeable paving getting into the basement drainage system. Additional drainage pits were also required for the agi pipes to connect into, so we were engaged to also construct concrete drainage pits as part of our works.
Once the drainage trenches were excavated into the clay subgrade, the whole paving area was fully lined with bidim A24 nonwoven geotextile fabric before the agi pipes were laid, and a layer of 14 mm screenings installed as both bedding for the paving and a drainage layer. By ensuring that the agi trenches are lined with geofabric BEFORE the pipes are laid, it separates the fines of the clay from the drainage system preventing silt buildup and blockages.
With subsurface drainage and screening sub base complete, galvanised SL92 reinforcing was laid and a loosely dowelled expansion joint installed against the suspended driveway slab. Then the permeable concrete was installed at a depth of 200 mm to allow for heavy vehicle loadings.
Town planning requirements also specified an upstand kerb to the sides of all driveways. To prepare for this, the permeable concrete base was poured 150 mm wider on the sides, and upstand galvanised N12 dowels were cast into the permeable concrete once it had been screeded. The kerb was then poured on top of the permeable concrete by the civil contractor (prior to our resin bound paving installation).
We then left the site for a couple of months whilst all the external works, including landscaping were carried out. The permeable concrete base allowed all the final works to be completed mud-free. Some paint and render was spilt on the permeable concrete, but since the resin bound paving was yet to be installed, it didn’t matter as it would be covered over by the final surface.
The permeable concrete base was pressure cleaned by the builder, and then we returned to install the final resin bound permeable paving surface in the final two weeks of the project, ensuring that the final driveways were sparkling for the handover!
What’s the secret to successful heavy duty permeable paving?
Experience! There are a lot of differences between permeable paving and “normal” concrete, from subbase preparation to screeding and finishing, and everything in between. Your best chance of success is to pick up the phone and chat to a permeable specialist like us today! 🙂