Potholes – a proactive approach

Simon Everett, the director of Solution-SE, has 40 years’ experience with technical and management roles associated with pavement maintenance, bitumen and asphalt.

Potholes are the bane of road users and maintenance teams worldwide, often blamed on poor compaction and rolling techniques during road construction. While these factors can contribute to early degradation, the root cause of potholes is far more complex. 

The fundamental issue is not simply mechanical failure but instead the infiltration of water into the pavement structure. Without addressing this critical issue, reactive maintenance measures, such as backfilling potholes with cold mix asphalt, merely serve as holding measures or temporary fixes for a much larger intervention.

To create durable road networks, proactive waterproofing strategies and preservation treatments are essential.

Water ingress

Potholes form when water infiltrates the road surface, weakening the underlying layers by washing fine material from the pavement matrix and ultimately causing the asphalt to break apart. This process occurs in a series of steps that start with surface cracking, where small cracks develop in the asphalt due to climatic conditions, aging asphalt and traffic loads. These cracks allow water to penetrate the surface.

Once inside the pavement, water softens and weakens the base and subgrade materials, reducing their ability to support traffic loads. In cooler climates, trapped water will freeze and expand, then, when temperatures rise, the ice melts, leaving voids that cause further pavement collapse under traffic loads.

 As vehicles pass over weakened pavement, stress accelerates material breakdown, eventually leading to pothole formation.

Without preventing water ingress, no amount of reactive maintenance will offer a sustainable solution.

Coldmix repairs

Coldmix asphalt is often used to quickly fill potholes, providing an important and immediate, albeit temporary, solution. 

While useful for emergency fixes, Coldmix does not solve the underlying problem as effectively as waterproofing solutions like crack sealing, and prefabricated chipseal patches.

While the Coldmix method can restore surface integrity in the short term, it fails to address the underlying issue – moisture intrusion. The absence of waterproofing in these patches means that potholes frequently reappear within weeks or months.

Instead of continually spending resources on ineffective patching, there is opportunity for road-controlling authorities to focus on long-term solutions that prevent cracks and water ingress before potholes develop.

Proactive waterproofing

To prevent pothole formation and extend the lifespan of asphalt pavements, the shift to better waterproofing and preservation strategies makes financial sense.

Isolated cracked areas can be remedied with a polymer-modified bituminous repair product that forms a waterproof seal over cracks and minor surface defects and prevents water infiltration before it compromises the pavement structure. 

Applying a polymer modified sealcoat, micro-surface treatment, or chipseal, protects the asphalt surface from oxidation and moisture infiltration, slowing down the formation of cracks and subsequent potholes.

Improving the surrounding drainage by ensuring adequate surface and subsurface drainage will prevent the water accumulation that leads to weakening of pavements. Cleared culvert entrances and exits enable water to flow. Effective drainage structures will lower the water table playing a crucial role in keeping roads dry.

These methods offer one of the best returns on maintenance investment, and the US-based Pavement Preservation and Recycling Alliance (PPRA) has shared the success of these key principles with their application in Bend City, the most populous city in the state of Oregon, which has similar temperatures to NZ (aside from higher snow levels than parts of NZ). 

Bend City, says the PPRA, transformed “a declining pavement network into a model of efficiency and effectiveness. “Over the course of eight years, pavement managers at Bend took their network from a PCI of 68 to a PCI of 82 on arterials and collectors, broadened their treatment toolbox, and grew the budget substantially by demonstrating the importance of proactive management to decision makers.”

A notable advancement in proactive pavement preservation is BRP Road Patch. This polymer-modified prefabricated chipseal patch has been proven over its 30 years, demonstrating significant success with pavement maintenance. 

Its formulation enhances resistance to water ingress and cracking, making it particularly effective for long-term waterproofing. The application is also straightforward, making for quick and efficient repairs, targeting crack areas and waterproofing potholes. It integrates with the existing asphalt or chipseal so provides a durable, long-term repair.