Background and problem addressed
As societies become increasingly urbanised, there is a vulnerability to flooding because impermeable infrastructure are wholly incapable of absorbing rainfall. Climate change is predicted to increase the likelihood of major storm events by 59%. In 2019 the annual global costs of flooding was £60bn and it is forecasted to increase to £500bn by 2030.
Permeable pavements are Sustainable Urban Drainage Systems (SUDS). These are porous materials that rapidly drain surface water, enabling stormwater to pass through otherwise impermeable infrastructure. However, conventional permeable pavements have the following drawbacks and limitations:
- They are prone to premature clogging degrading their performance and service life, needing frequent maintenance (increasing costs).
- They have poor freeze-thaw resistance, leading to deterioration of the surface.
- They have low strength and are limited to low bearing applications such as pedestrian footpaths and car parks.
A novel high-strength clogging resistant permeable pavement (CRP) has been developed at Imperial College London. The key innovations of this pavement are:
- a new engineered pore structure with low tortuosity, which increases the permeability, reducing the probability of sediment clogging, improves freeze-thaw resistance and increases the strength.
- it utilises a higher strength self-compacting cementitious mix, which also improves the freeze-thaw durability.
Rigorous lab testing confirmed the superior performance of this new material when compared with conventional permeable pavements. It has high strength (> 50 MPa) and high permeability (> 2 cm/s) yet does not clog despite extensive cyclic exposure to sand and clay. It is at least twice as strong and ten times more permeable than conventional systems of equal porosity, which completely clogged after just a few cycles of sediment exposure. Therefore, this new pavement can be used in a wider range of settings. It is more durable, requires less maintenance and its superior performance will deliver material and cost savings, making it commercially viable.
A new interlocking tile system has also been developed to deploy at scale as cast in situ slab or pre-cast pavers. The tiles are lightweight for ease of transportation and installation. These are placed on an aggregate sub-base and self-compacting cementitious material applied to the required thickness. The process is quick, simple and versatile, resulting in a controllable surface finish. This system has been used to successfully delivered at scale in the trial site at Imperial’s White City Campus (pictures below).
- Flood mitigation – protects properties
- Sustainable urban drainage system – contributes to groundwater recharge
- Prevents aquaplaning and stormwater runoff
- Superior performance will deliver material and cost savings
- Commercially viable
Compared to conventional permeable concrete:
- CRP is twice as strong and ten times more permeable.
- It is clogging resistant and requires less maintenance.
- More durable.
- Specialist contractors are not needed, and it can be installed easily.
- It can be deployed at scale as cast in situ slab or pre-cast pavers.
Intellectual property information
The International patent application is now published under the number WO2020/099868. The patent application is pending in Europe, the US, India, Singapore, Malaysia and Thailand.
Link to published paper(s)
A. Kia, H.S. Wong, C.R. Cheeseman, ‘High-Strength clogging resistant permeable pavement’, International Journal of Pavement Engineering, ISSN:1029-8436.
A. Kia, H.S. Wong, C.R. Cheeseman, ‘Defining clogging potential for permeable concrete’ Journal of Environmental Management, 2018, 220, 44-53.
A. Kia, H.S. Wong, C.R. Cheeseman, ‘Clogging in permeable in permeable concrete: A review’ Journal of Environmental Management, 2017, 193, 221-233.