Anti-flush trial for Central Hawke's Bay

Central Hawke's Bay District Council and Downer Group NZ will be proactively participating in an anti-flushing trial starting during the first few months of 2024. A section of Pōrangahau Road, between Bush Road and Wallingford Road that has the tendency to flush in the warmer weather has been selected to trial a new anti-flush product (bitumen). Data will be collected over the coming months to measure the performance of the anti-flush bitumen and if the product has a high success rate it may be used nationwide to improve the durability of NZ roads.

Committed to building a strong and resilient roading network, our teams are constantly seeking innovative ways to deliver benefits to our roads.

What is anti-flushing? 

The flushing of our roads surface is an issue that continues to threaten the strength of our roads. When flushing is occurring, the surface will become shiny as the bitumen (used to stick the chip to the road) rises to the top and the chip sinks below. Hawke's Bay summers are well known to cause this flushing effect. 

This issue leads to an increase in potholes and a reduction in grip on our roads and pavements. Road Science (a technical laboratory division of Downer Group NZ) have developed a product that acts as a barrier to flushing of road surfaces. The product is called 'Anti-flush' and acts by blocking the bitumen from rising to the top. The high-polymer binding is designed to suppress flushing and extend the seals lifespan.

Road Science have donated the product for the trial that will see it tested and data recorded to assess its viability for future use across New Zealand.