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

The high friction surface treatment (HFST) is an effective countermeasure to roadway departure crashes. The field performance of the HFST system was evaluated from seven field monitoring trials on six HFST sites in Oklahoma from 2015 to 2017. HFST sections have statistically significant higher pavement friction and macrotexture in contrast to the adjacent untreated pavements. Meanwhile, distresses including patching, reflective cracking, raveling, and delamination have been observed on these HFST sites. The number of property damage crashes and injured crashes before and after the HFST installation are queried from the Oklahoma safety database. The HFST results in 29% to 100% reductions of annual property damage crashes and 100% reduction of annual injured crashes. The benefit-cost ratios of the HFST sites range from 6.9 to 27.9. In addition, HFST sites constructed with bauxite show higher friction numbers and better polishing resistance performance than sites using the local mine chat aggregates.

Performance of optimized composition of epoxy resin adhesive used in High Friction Surface Treatment

The pavement skid resistance, namely the vehicle tire-road contact friction, plays important roles on pavement response, pavement deterioration, traffic operation, and traffic safety. One may find higher tire-road friction surface course is needed or applicable as an effective safety countermeasure for reducing potential traffic crashes and/or collision severity at certain roadway locations, in particular, the ramp emerging or weaving area where foreseeable sideswipe or rear-end collisions might take place between a merging vehicle and another vehicle from the outside lane. A driver should decelerate when merging become difficult as trained in a licensing procedure for avoiding potential collisions. If the required deceleration length is shortened upon avoiding a potential collision, the number of collisions at the onramp should decrease and the collisions if occurred would be less severe. The tire-road frictional coefficient if raised high enough could dramatically reduce the required deceleration length prior to collision, and the high friction surface treatment (HFST) has been introduced in practice for the last decade to shorten the required distance to stop a moving vehicle for both wet and dry road surface conditions. It is of significant interest to examine quantitatively, based on a proposed integrated framework, the effect of a high frictional surface course on reducing the needed deceleration distance, in particular, on an onramp merging/weaving section constructed with limited right of way.

Calcined Bauxite (CB) is a common aggregate used in high friction surface treatment. Due to the high price of CB, six aggregates were investigated as alternatives to CB. These aggregates were Steel Slag, Meramec River Aggregate, Rhyolite, Earthworks, and Potosi Dolomite. Correlations between the frictional performance of these aggregates were scrutinized using an aggregate image measurement system (AIMS), British pendulum (BP), and dynamic friction tester (DFT). Micro-Deval (MD) was utilized, and its results correlated with the frictional testing results. A stronger correlation was observed between the angularity and sphericity indices when compared with the correlation between the texture and sphericity indices or when compared with texture and angularity indices. Inverse correlations were found between the MD percentages and texture or angularity indices. No correlations were found between AIMS and BP or between AIMS and DFT results. A direct linear correlation was distinguished between DFT and BP results.

Chip seal construction has received increased attention recently because of rising construction costs and reduced funding for new asphalt pavement projects. The cost and carbon footprint of chip seal applications can be reduced using reclaimed asphalt pavement (RAP). In this paper, the suitability of RAP material for chip seal applications was evaluated through laboratory experiments. Aggregate retention performance and bleeding susceptibility of chip seal samples were investigated using two different aggregate sources and emulsion types. The gradation of the collected aggregates was matched with RAP aggregates using sieving and batching. Modified sweep, Vialit, and pull-off tests were conducted to determine the aggregate retention performance of RAP-modified chip seal samples. To evaluate the effect of RAP on bleeding susceptibility, a Hamburg wheel tracker (HWT) device with a rubber wheel was used. Macrotexture values were measured at specific HWT passes using a laser texture scanner, and the number of passes until chip seal failure was iterated. According to the results, the aggregate retention performance of RAP was found to be comparable with that of natural aggregates when a binder with an appropriate charge was used. RAP material showed higher aggregate retention with the cationic binder compared to the anionic binder. The bleeding test results indicated that RAP is more susceptible to bleeding. Overall, laboratory test results showed that RAP can be a good alternative to virgin aggregate and may reduce the need for virgin binders used in chip seal construction.

Comparative life cycle assessment of chip seal preventive maintenance techniques: Cost and environmental implications

Slag as waste material of steel-making process has similar characteristics with aggregate that has been widely used in pavement construction. The use of slag as chip seal aggregate to provide skid resistance needs to be analyzed. In this laboratory study, the chip seal samples are made using steel slag and natural aggregate. The bonding materials used are asphalt and epoxy resin. Skid resistance tests for all chip seal samples and also hot rolled sheet pavement without chip seal application are performed using the Portable British Pendulum Tester. The results show the variations of chip seal aggregate weight are inconsistent. The natural aggregate used as chip seal material could produce high skid resistance value of 10.3% higher than that using steel slag. Also the skid resistance of chip seal with the ALD 3 mm are not significantly different with that of ALD 6 mm. Similar results occur on the skid resistance of chip seals using epoxy resin and asphalt. Keywords: steel slag, waste material, chip seal, the Portable British Pendulum Tester, skid resistance.

There is limited information on the characteristics and performance of paving mixtures made with 100% bio-binders. Moisture damage resistance of this type of mixture is a concern since the components of the bio-binder may have a higher affinity with water than asphalt binders. In this context, this paper presents a moisture damage susceptibility evaluation of wood-based bio-binder-aggregate interfaces in terms of energy parameters calculated from surface free energy components. The bio-binder was used as a total replacement for asphalt binders, and the responses were compared to a neat- and a highly modified-asphalt binder, considering different aggregate sources. Results suggest the bio-binder has similar moisture damage resistance to the neat asphalt binder and higher resistance than the highly modified asphalt binder, providing a first indication for the potential use of this bio-binder as 100% asphalt binder replacement. However, additional research is still required to validate these findings at the mixture level.

Open-graded friction course (OGFC) is a thin asphalt mixture surface layer. It is gap-graded with a high percentage of coarse aggregates that are nearly uniform in size, resulting in a high percentage of interconnected air voids and asphalt binder, which provides improved skid resistance, visibility, and decreased pavement–tire noise. However, construction personnel at the Louisiana Department of Transportation and Development reported that conventional OGFC mixtures have durability issues and shorter service life, compared with thin asphalt mixture lifts. Hence, effects of different asphalt binder types on the performance of OGFC mixtures were evaluated. Five types of asphalt binder were utilized: conventional styrene-butadiene-styrene (SBS) asphalt binder PG 76-22M; high SBS content asphalt binder PG 88-28; diluted epoxy asphalt (EA) binder with two different dosages (25% and 50%); and a hybrid modified asphalt binder prepared with SBS and crumb rubber modifier PG 76-22G. The optimal aggregate structures were determined based on minimum required air voids and voids in coarse aggregate. Physical and mechanical tests were conducted to assess the performance of OGFC mixtures, including draindown, permeability, loaded wheel track, and Cantabro abrasion loss. Results indicate that OGFC mixtures incorporating diluted EA binder exhibited lower draindown values than mixtures containing PG 76-22M and PG 88-28. Moreover, mixtures with PG 88-28 and 50% EA binders demonstrated improved resistance to rutting. Mixtures with 50% EA and PG 88-28 binders demonstrated improved durability, compared with mixtures with PG 76-22M for unaged and aged conditioning, as measured by Cantabro abrasion loss values.

The interaction between asphalt binder and aggregate is fundamental to ensure adequate performance of asphalt mixtures, mainly in the presence of water. The work of adhesion generated between both materials directly affects the resistance of asphalt mixture to moisture damage, because it measures the ease with which water can displace asphalt binder from the aggregate surface. The objective of this study was to characterize the bond strength between asphalt and several aggregate sources. A PG 64-22 neat binder was modified with several additives to determine the effect on adhesion: polymers, nanomaterials, and adhesion promoters. To measure the strength of adhesion, the bitumen bond strength (BBS) test and contact angle measurements between asphalt binder and the aggregate surface by means of goniometry were used. The surface energy of the asphalt and the aggregate, with and without the presence of water, was estimated also. Testing was performed on all binders and on each binder–aggregate combination after ( a) rolling thin-film oven (RTFO) aging and ( b) RTFO and pressure aging vessel aging. The BBS results identified differences in bond strength as a result of moisture conditioning and aging. The differences depended on the aggregate source and binder type. Different failure modes were also observed (i.e., cohesive, adhesive). The results also indicated an increase in strength of adhesion associated with the aging process: the main resistance gain was observed after RTFO aging. Finally, changes in bond strength were compared with functional composition changes associated with the aging process and related to changes in performance.

Rutting is one of the main asphalt pavement distresses, and it is believed that binder properties play an important role in mixture’s potential rutting resistance. Generally, in the Superpave design system asphalt binder is selected based on the binder PG grade required for the climate. However, to implement performance control through the traditional Superpave PG system during mix design faces more challenges due to the changes of oil refinery, asphalt binder modification, and the use of recycled materials in the mixture. This paper aims to investigate the role of asphalt binders and mix designs in the rutting resistance of asphalt mixtures. A total of 22 plant-produced mixtures from 10 states and 5 laboratory-produced mixtures were investigated for their rutting performance in this study. Those tested mixtures include various binder grades, aggregate sources, RAP contents, and mix designs. The Superpave binder rutting parameter G*/sinδ and Multiple Stress Creep and Recovery (MSCR) grade parameter Jnr3.2 are correlated with the mixture dynamic modulus and Hamburg Wheel Tracking (HWT) rutting parameters. In addition, the effects of other mix design variables on the rutting resistance are evaluated using a statistical analysis. The results show that by incorporating the binder properties and mix design variables, the stepwise regression fitting provides a much better prediction for HWT rutting parameters as compared to using only the binder properties. This indicates the importance of proper selection of the binder grade for mixture performance, and it also calls for justifying more focus on including mixture design variables to ensure acceptable mixture rutting performance. The statistical analysis can provide an insight into the use of artificial intelligence and machine learning by generating mathematical models for evaluating which mixture design variables are needed for better prediction of rutting performance.

The chip seal refers to the technology of using the layer-pave method to directly spread asphalt binder and crushed stone with single particle size, and then form a thin layer after rolling. The asphalt in the chip seal is covered with a continuous film on the surface of the underlying layer, so it can effectively prevent the road surface from seeping underwater and reduce road water damage; it has a good follower deformation ability and can adapt to the relatively poor underlying layer conditions; The stone in the gravel seal is directly exposed on the road surface, so it has excellent anti-sliding performance and abrasion resistance. Fiber seal is an upgraded version of the chip seal. It refers to the use of synchronous fiber seal construction equipment, spraying two layers of asphalt cement and a layer of glass fiber at the same time, and then spread the crushed stones on it, forming new wear after rolling. Layer or stress-absorbing layer (SAMI) is a rapid pavement maintenance technology. Compared with the crushed stone seal layer, the fiber seal has a better ability to prevent reflection cracks due to the addition of glass fiber. This chapter mainly introduces the material, construction, construction equipment, construction process, use conditions, quality inspection and acceptance of chip seal and fiber seal.

This study evaluated the effect of different aggregate sources along with their Corresponding change in mixture characteristics to determine the influence of both on binder oxidation rates and changes in mixture stiffness when compacted mixtures were exposed to laboratory aging conditions. The two aggregate sources, Colorado and Nevada, had different gradations and different water absorption rates, which led to differences in the calculated asphalt binder apparent film thicknesses (AFT) for each mixture. Two asphalt binders, an unmodified PG 64-22 and a styrene–butadiene–styrene–modified PG 64-28, were used. The overall findings of the study indicated that both the aggregate and mixture characteristics influenced the oxidation rates of the binder, with the two binders oxidizing by similar amounts when aged in mixtures with the same characteristics (AFT and mixture air voids). The oxidation changes in the binder had differing effects on the stiffness of the mixture as a function of age. Not only were the aggregate and mixture characteristics important to the mixture stiffness and aging relationship, but the binder characteristics themselves, in particular polymer modification, influenced the aging and stiffness relationships of mixtures with age.

Chip seal is a widely used preventive maintenance treatment for flexible pavements. However, a major problem with chip seal is the damage caused by loose aggregates from newly placed seals, partly because of a lack of compatibility between aggregate and asphalt emulsion. In this study, limestone, crushed gravel, synthetic lightweight aggregates, and recycled asphalt pavement materials were studied in the laboratory with two polymer-modified asphalt emulsions to find the aggregate–emulsion combination that would result in maximum chip retention. Replicate specimens were tested in the ASTM D7000 sweep test for each aggregate–emulsion combination. Lightweight aggregates and gravel were also tested in a newly developed test setup for simulating the sweep test. Test results show that lightweight aggregates perform better than gravel. However, lightweight aggregate sources play an important role in chip retention. Emulsion is the most significant factor that affects chip loss. Statistical analysis identified the influential design factors affecting chip retention. Analysis of variance shows that aggregate and emulsion types and aggregate–emulsion interaction are significant factors affecting chip retention. Aggregate precoating and its interaction with emulsion type are insignificant factors as far as chip retention is concerned.

Reflective cracking through jointed concrete pavement overlays has been a persistent problem. Several different rehabilitation strategies have been used in Texas. This paper is a summary of the performance of strategies used in the past 10 years. The performance of the crack-retarding grid has been disappointing as it has been related to several premature failures. Only one project has realized a benefit of the crack-retarding grid, where the reflective cracking was delayed by about 1 year. The writers believe the small openings in the crack-retarding grid and the lack of an effective bond may be the causes of the layer separation. A proprietary crack-retarding asphalt material has been performing well over two years of monitoring. In one experimental project, 100% of the cracks reflected through conventional overlay material in the first year. Both Petromat fabric underseal and crack-retarding asphalt material have been performing satisfactorily to retard reflective cracking. However, there is a large cost difference between these two treatments. Seven experimental treatments on a major section of US 59 were evaluated. The worst-performing section on the US 59 project was the break-and-seat method, which failed due to weak subgrade support. The weak subgrade is unable to support cracked concrete, which leads to a rocking action under traffic loads. It is concluded that for future projects, the break-and-seat method should not be applied on subgrade with a dynamic cone penetrometer penetration rate exceeding 25 mm per blow. A flexible base overlay with thin asphalt surfacing and the Arkansas (large stone) mix have performed well. Flexible base overlays were able to absorb the joint movement and eliminate the reflective cracking. The flexible base should be of top quality with very low moisture susceptibility. In Texas, this involves specifying a Texas triaxial Class 1 material with classification of "good" in suction/dielectric tests. It is also critical to provide an effective seal for the flexible base. A chip seal followed by a thin 75-mm hot mix layer is recommended.