Search Results (4)

High Friction Surface Treatments (HFSTs) are frequently used to increase skid resistance and reduce collisions, particularly in crash-prone zones, including horizontal curves and intersections. Epoxy-based binders traditionally have been the sole option for HFSTs, but their drawbacks, such as high costs and compatibility challenges, have led to the search for substitute binders, including asphalt-based options. This study investigates the comparative performance of highly modified asphalt-based binders, including polymer-modified, mastic, and highly modified emulsions, in HFST applications using two aggregate types, Calcined Bauxite (CB) and Rhyolite with different gradations, with an emphasis on their frictional properties, durability, and resistance to polishing. Laboratory evaluations, including the Pendulum Tester (BPT), Dynamic Friction Testing Equipment (DFT), Surface Texture Measurement Apparatus (CTM), and Binder Bond Strength Test (BBS), were carried out to examine the Coefficient of Friction (COF), Mean Profile Depth (MPD), and aggregate bonding and retention. In terms of durability and friction, this study indicated that highly modified asphalt-based binders performed better than PG binders and conventional emulsions. The highest BPT values, both prior to and following polishing, were consistently observed for CB, with the emulsion containing the highest reactive polymer modifier showing the smallest decrease in BPT value (12.86% for CB and 10.34% for Rhyolite). Epoxy showed a greater COF retention over lengthy polishing cycles; however, highly polymer-modified (PM) binders like PG82-22 (PM) performed better than Epoxy under specific conditions. The macrotexture analysis revealed that Epoxy-based samples retained surface texture for further polishing cycles, while Mastic2 and PG82-22 (PM) also showed strong MPD retention. These findings highlight the importance of optimizing aggregate–binder combinations to ensure durable and effective HFST applications. Full article

High Friction Surface Treatments (HFSTs) are recognized for enhancing friction between tires and road surfaces, with reduced road accidents being a key benefit. Epoxy-based HFSTs, though widely used, come with challenges like compatibility issues with existing pavements, higher installation and removal costs, and reduced durability tied to substrate quality. Recently, state agencies have increasingly focused on developing asphalt-based alternative binders for HFST applications as highlighted in the National Cooperative Highway Research Program (NCHRP) RFP #NCHRP 10-145. This study introduces asphalt-based HFSTs as an alternative to traditional epoxy-based treatments. Various aggregate types were examined for friction performance and the effect of polishing cycles on asphalt-based HFST. Tests such as the British Pendulum Test (BPT), Dynamic Friction Tester (DFT), and Circular Track Meter (CTM) were conducted to assess the Coefficient of Friction (COF) and Mean Profile Depth (MPD) before and after polishing cycles. Additionally, a Life Cycle Cost Analysis (LCCA) was performed to determine the economic advantages of asphalt-based HFSTs over epoxy treatments. The goal was to develop a method to convert diverse project and material data into comparable outputs like net present value (NPV), enabling comparisons between alternatives. Results from the LCCA demonstrated that the use of specific asphalt-based binders combined with optimized aggregate gradation not only achieves performance levels comparable to traditional HFST options but also improves cost efficiency. Full article

High Friction Surface Treatments (HFST) are recognized for their effectiveness in enhancing skid resistance and reducing road accidents. While Epoxy-based HFSTs are widely applied, they present limitations such as compatibility issues with existing pavements, high installation and removal costs, and durability concerns tied to substrate quality. As an alternative to traditional Epoxy-based HFSTs, this study investigated the effects of aggregate gradation as designated by agencies on the performance of asphalt-based HFST. Various aggregate types were assessed to evaluate friction performance and the impact of polishing cycles on non-Epoxy HFST. It was found that adjustments in aggregate size and gradation may be necessary when transitioning to asphalt-based HFSTs, given the different nature of asphalt as more temperature susceptible compared to Epoxy. Various asphalt binder grades were considered in this study. A series of tests, including the British Pendulum Test (BPT), Dynamic Friction Tester (DFT), Circular Track Meter (CTM), Micro-Deval (MD), and Aggregate Imaging Measurement System (AIMS), were conducted to measure Coefficient of Friction (COF), Mean Profile Depth (MPD), texture, and angularity before and after polishing cycles. The results showed that the COF in asphalt-based slabs decreased more significantly than in Epoxy-based slabs as polishing cycles increased for HFST and medium gradations. However, in coarse gradation, the COF of slabs using asphalt-based binder matched or even surpassed that of Epoxy after polishing. Notably, the PG88-16 binder for Calcined Bauxite (CB) had the smallest reduction in COF after 140K polishing cycles, with only a 19% decrease compared to a 23% reduction for Epoxy. Full article

Based on the fact that bauxite clinker has minor thermal conductivity and better skid resistance and wear-resisting property, it can be used in HFST (high friction surface treatment) or the abrasion layer of asphalt mixture to replace or partly replace the existing aggregate. Bauxite clinker is classified into mainly six types according to different chemical composition contents. The selection of bauxite clinker as aggregate is not only for the economic value, but also for improving the adhesion between aggregate and asphalt, which has a certain blindness This study evaluated the characteristics of different types of bauxite clinker. The adhesion of different types of bauxite clinker with asphalt was evaluated by means of agitating hydrostatic adsorption method and surface free energy theory. The effect of characteristic parameters of bauxite clinker on adhesion was evaluated by grey correlation entropy analysis. The results show that Type B and D bauxite clinker aggregates have the best adhesion to asphalt. The outcome of grey entropy correlation analysis shows that the parameters which characterize the structural indexes of bauxite clinker, such as porosity, water absorption and apparent density, have the greatest effect on the adhesion. The results of study can provide some reference for the selection of bauxite clinker, which is used in different types of highway construction, and a theoretical reference for the applicability research of bauxite clinker in asphalt mixture and the improvement of skid resistance and durability of pavement. Full article