Developing a climate based binder selection guideline.

Standard practice in New Zealand for binder selection for State Highways in recent years is to use harder penetration grade binders with less added volatile diluents (flux oil and cutter). This practice was initiated by research that showed that using harder binders slows the onset of flushing during summer. However, subsequent research has shown that there is little evidence to support the concept of harder binders slowing the development of flushing but the precedents have been set and harder binders have become the standard. The current justification supplied by specifiers for the continued use of harder binders is that they lower the risk of chipseal bleeding (binder pickup by tyres) during summer. This paper outlines the background to, methodology of, and preliminary results of trials of a binder selection guideline based on binder performance at the high and low temperatures likely to be encountered at the location of the chipseal construction site. (a) For the covering entry of this conference, please see ITRD abstract no. 0612AR242E.