Transit New Zealand's Napier region is located on the East Coast of the north island. A significant portion of the state highway network traverses mountainous terrain with a narrow curvilinear alignment. In the early 1990s flushing and bleeding caused by chipseal layer instability was becoming a significant problem throughout the Napier region. A combination of aging pavements with increasing chipseal layer depth, wide temperature extremes and inappropriate maintenance treatments of bleeding chipseals was creating problematic lengths of flushed and bleeding chipseals throughout the state highway network. This paper looks at chipseal layer instability, the factors that cause these chipseals to become problematic and reviews cost effective solutions that are available to reduce or eliminate the negative impact that these chipseals cause. It also reviews the changes required to the Transit New Zealand Performance Based specification, introduced in 1995, to include the construction and assessment of chipseals used to treat layer instability. (a) For the covering entry of this conference, please see ITRD abstract no. E217100.
Abstract