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Hastings District Council - Polymer Modified Binder Solution for Asphalt Surfacing Performance

Hastings District Council had a number of roundabout and intersections sites ready for structural rehabilitation due to excessive rutting, shoving and cracking. 

Heavy duty structural asphalt was recommend by the consultant as a long lasting solution to provide resistance for turning traffic. However, the Council considered this option too expensive and an alternative was needed. The alternative still needed to meet the demands of a highly stressed environment.

Solution

To solve Hastings District Council’s issue, Downer engaged Road Science. Road Science developed a modified binder for thin asphalts. Extensive rutting and fatigue testing was carried out on the asphalt incorporating this binder. These tests proved the binder demonstrated endurance and could fix the issues being faced by the Council for a reduced cost.

For the 2011/2012 rehabilitation and reseals programme, an asphalt incorporating this modified binder was selected. The thickness of the asphalt was chosen so longevity could be achieved.

Road Science ensured the flexural tensile strain was calculated and considered for each pavement design. As the Road Science modified binder is considerably more flexible than conventional bitumen, incorporating it into an asphalt allows it to cope with higher deflections. Materials Road Science prepared the asphalt mix, AC14 with Road Sciences’ proprietary highly polymer modified bitumen, RS3 High Strength. RS3 High Strength has been specially formulated to allow for superior performance in fatigue, rutting and high shear environments.

The asphalt had the following performance properties: 

  • Wheel Track Depth of 1.3 mm for 10,000 passes @ 60°C 
  • Fatigue – 28.6% reduction in flexural stiffness over 1 million cycles

Summary

The proven performance of the Road Science polymer modified asphalt used on Rangitane Road (where the pavement is flexible, with high shearing forces due to heavy vehicles negotiating the tight radius bend), clearly demonstrates that this Road Science designed treatment is a successful cost effective replacement for structural asphalt. Please see photo below showing Rangitane Road.

 

Overview Hastings District Council had a number of roundabout and intersections sites ready for structural rehabilitation due to excessive rutting, shoving and cracking. Road Science developed a modified binder for thin asphalts. Extensive rutting and fatigue testing was carried out on the asphalt incorporating this binder. These tests proved the binder demonstrated endurance and could fix the issues being faced by the Council for a reduced cost.