The 2015 Winter left behind plenty of "headaches" to our transportation system in TN. As TTAP traveled around the State we were able to experience firsthand what was left of our roads after all the sleet, ice and snow. It was amazing to see all the tree damage in the Cumberland Plateau as well as navigating through the series of potholes in West TN. In the last Roadtalk we had an article on debris management and for the current newsletter my focus will be on pointing you to resources on pothole patching.
Appropriately, NCHRP (National Cooperative Highway Research Program) has just released Synthesis 463 on Pavement Patching Practices. Despite advances in material selection and pavement design, pavement distresses and failures still occur (Figure 1). When they do so, on a small scale, or in fairly isolated locations patching is the most common maintenance technique used to restore pavement functionality. While actual figures are difficult to obtain, it is safe to assume that well over $1 billion is spent each year to maintain roadways in the United States. In 1999, it was estimated that more than $1 billion was spent annually in the United States on pothole and costs have increased since then. With such a large expenditure of tax dollars, it is important to ensure that the funds are spent in a cost effective manner and that the investments in patching result in improved pavement performance and longer service lives.
NCHRP 463 presents the current state of the practice regarding pavement patching practices and updates the information available on patching practices to enable agencies to make informed decisions about their own patching policies and procedures. It is intended to document the state of the practice for patching relatively small-scale defects or distresses in both asphalt and concrete pavements. Large-scale patches, wedge and level (or level-up patching), and pre-overlay patching are not the focus. In particular, the document examines the following:
The main focus of this document is on reactive, manually installed patches over relatively small areas; however, some information was also gathered on planned and machine fabricated patches. The focus is also on patching that is intended to serve traffic for some time, whether temporarily or permanently, and does not include patches placed immediately before placement of an overlay.
For the most part, the definitions of the distress terms used herein correspond to those in the Distress Identification Manual for the Long-Term Performance Program - DIM - (http://www.fhwa.dot.gov/publications/research/infrastructure/pavements/ltpp/reports/03031/03031.pdf). Many states use this manual and therefore are familiar with the terminology.
In asphalt pavements, the most common distresses that can be repaired by patching include potholes, deterioration around cracks, delaminations, rutting, or raveling. The DIM does not include deterioration around a crack as a distress, but does include high severity cracking, which could describe this type of deterioration. In this document, the term "delamination" refers to the separation of one layer of an asphalt pavement from the underlying layer; some refer to this as "peeling." In the DIM, this would be categorized as a pothole. One distinguishing feature of a delamination versus a pothole is that a delamination has a flat bottom at the top of the underlying layer, whereas a pothole is bowl-shaped. Figures 2 and 3 illustrate potholes and delaminations,respectively.
To learn about the latest information on patch preparation, patch material, placement methods and much more please go to http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_syn_463.pdf and download NCHRP 463 - Pavement Patching Practices.