Development of High Friction Surface Treatment Prescreening Protocols and an Alternative Friction Application

Abstract

The use of high friction surface treatments (HFST) has become increasingly popular to help improve roadway friction properties and reduce the number of lane-departure and breaking-related accidents. Conventional HFST installation consists of applying an epoxy-resin material to an existing roadway surface and “gluing” a hard, highly angular fine aggregate to the roadway surface. When constructed correctly, skid resistance values (SN40) are often measured in the upper 60s and 70s. However, this functional overlay does not come without potential issues. Performance and service life is strongly dependent on the quality of the construction process, as well the quality of the substrate, which is often difficult to assess in situ. The paper summarizes the forensic testing of three HFST installations in New Jersey—one performing well and two showing premature failure. Testing procedures and preliminary criteria for existing asphalt pavement surfaces were developed to address whether or not epoxy-resin HFST is a viable option. Additionally, the paper summarizes the development and forensic testing of a potential alternative to the epoxy-resin based HFST application. This alternative surface, called a high friction chip seal (HFCS), incorporates the same hard, highly angular fine aggregate but using asphalt binder as the “gluing” medium within the chip seal application process. Three different aggregate sources were evaluated using the HFCS application on Rt 68 in New Jersey. Laboratory testing of the aggregates, as well as field measurements of the test sections, were conducted. It was found that HFCS could be a potential alternative for areas where premature HFST failure is a concern.

Analysis of High-Friction Surface Texture with Respect to Friction and Wear

“…To adapt Halling's geometry of contact, one can assume the following: Surface 1 is that of the underlying pavement; Surface 3 is that of the tire and can be considered, as a first approximation, as smooth; and Surface 2 is that of the HFS with h is the thickness of the epoxy binder and σ is the standard deviation of the height distribution of the calcined bauxite aggregates (Figure 19b). Considering an embedment of the aggregates of 50% (which is a good application of the HFS [7]), a first approximation of σ could be σ = 2Sq (Figure 19b). With increasing wear, e.g., increasing loss of aggregates and then decreasing Sq (based on Figure 15a), the ratio h/σ should increase from 0.5 (initial application) to 1 when the tire touches the binder.…”

“…Based on the above explanation, tests have been developed in the laboratory to characterize HFS in view of predicting performance before its application. Bennert in [7] mentioned two types of tests employed in the United States to assess the bonding capacity of HFS and the durability of the binder. The pull-out test helps to see if the failure occurs in the substrate or the coating, or at the interface of the coating/substrate.…”

“…Bennert et al [7] defined six failure mechanisms, which include those cited in [2] with some variants related to the crack patterns. All authors agree on the causes of the failures: delamination is generally linked to the installation and the curing of the binder, and aggregate loss (resp.…”

“…In the present paper, the failure mechanism of interest is the aggregate loss because it represents the predominant failure mode at the test site (see the experiment set-up and data collection). Discussions in the rest of the text will be focused on this mechanism (readers can refer, for example, to works in [1] and [7] for more details on the other mechanisms).…”