The ability of titanium dioxide (TiO2) photocatalytic nanoparticles to trap and decompose organic and inorganic air pollutants render them a promising technology as a pavement coating to mitigate the harmful effects of vehicle emissions. This technology may revolutionize construction and production practices of hot-mix asphalt by introducing a new class of mixtures with superior environmental performance. The objective of this study was to assess the benefits of incorporating TiO2 into asphalt pavements. To achieve this objective, the photocatalytic effectiveness and durability of a water-based spray coating of TiO2 was evaluated in the laboratory. This study also presents the field performance of the country’s first air-purifying photocatalytic asphalt pavement, located on the campus of Louisiana State University. Laboratory evaluation showed that TiO2 was effective in removing NOx and SO2 pollutants from the air stream, with an efficiency ranging from 31–55% for NOx pollutants and 4–20% for SO2 ...

Self-healing microencapsulation in asphalt concrete is an emerging technology that would allow this particular material to resist cracking damage caused by vehicular and environmental loading. The objectives of this study were to evaluate the effects of asphalt rejuvenators on asphalt binder, to select a suitable healing agent for asphaltic materials, and to develop a synthesis procedure for the production of microencapsulation of asphalt rejuvenators. Produced microcapsules were characterized using scanning electron microscopy (SEM) to assess the effects of preparation parameters on the size and morphology of the microcapsules. Based on the results of the experimental program, it was concluded that the use of sunflower oil as a rejuvenator was effective in reversing the aging of asphalt binder and to positively affect both the high-temperature and low-temperature grades of the binder. In contrast, the use of PennzSuppress as a rejuvenator was not effective in reversing the aging of asphalt binder...

An accelerated wheel load testing program was conducted to evaluate the benefits of using geosynthetics to enhance the performance of pavement constructed over soft subgrade. Six full-scale test sections were constructed, among which two sections were reinforced by one or two layers of triaxial geogrids, and two sections were reinforced by one layer of high strength geotextile with different base layer thickness. The test sections were instrumented by a variety of sensors to measure the load- and environment-associated pavement response and performance. The results of full-scale accelerated load testing demonstrate the benefits of using geosynthetics in terms of reducing the permanent deformation in the pavement structure. The geosynthetics benefit to reducing the maximum stress on top of subgrade is more distinguishable at a higher load level. It was also found that the geosynthetic placed at the base-subgrade interface was able to improve the performance of both subgrade and base layers. By placing an additional layer of geogrid at the upper one-third of the base layer, the performance of the base layer was further enhanced. While the geosynthetic showed appreciable benefit to reducing the permanent deformation of subgrade in this study, it showed little effect on the resilient properties of subgrade.

The objective of this study was to compare the laboratory mechanistic properties of sulfur-modified warm-mix asphalt (WMA) with conventional asphalt mixtures. Three mixtures, two hot-mix asphalt (HMA) and one WMA, were prepared. Mixture One used an unmodified asphalt binder classified as PG 64-22, Mixture Two used a styrene-butadiene-styrene elastomeric modified binder classified as PG 70-22, and Mixture Three was a WMA that incorporated a sulfur-based mix additive and a PG 64-22 binder. A suite of tests was performed to evaluate the rutting performance, moisture resistance, fatigue endurance, fracture resistance, and thermal cracking resistance of the three mixtures. Results of the experimental program showed that the rutting performance of sulfur-modified WMA was comparable or superior to conventional mixes prepared with polymer-modified and unmodified asphalt binders. Results of the modified Lottman test showed that the moisture resistance of the sulfur-modified mixture was comparable to conventional m...

The Hamburg wheel tracking (HWT) test has been found to be a promising test to evaluate the field rutting performance of asphalt pavements and has been implemented as a material screening test during the mix design process by several state departments of transportation. However, the rutting performance of an asphalt pavement depends not only on the material properties, but also on many other factors such as pavement structure and traffic. To date, there are few performance models that have integrated the Hamburg rutting parameters for pavement rutting prediction. In addition, mechanistic-empirical–based prediction models have been found to have some difficulties in reasonably predicting field rut depth, especially when field variables and confounding factors have to be considered. Therefore, the objective of this paper is to evaluate the relationship between the HWT test results and the field rut depth, then develop a predictive model for field rut depth based on the HWT test results. Field projects consisting of 51 hot mix asphalt (HMA) and warm mix asphalt (WMA) pavements were included in the analysis. These projects were located in different climatic zones with varying traffic levels, pavement structures, and material properties. Through direct correlation, it was found that the field rut depth in general decreased with the increase of the rutting resistance index (RRI). However, HWT test results alone do not have a strong relationship with the field rut depth, and many other factors, such as climate and pavement structure, have to be considered. Further, statistical-based methods in conjunction with engineering interpretation were applied to identify critical influencing factors and develop a prediction model for field rut depth. The developed rutting predictive model indicated that (a) mixture property (rutting resistance index, a parameter developed based on the HWT test), pavement age (month), average annual daily truck traffic (AADTT), and pavement structure (total HMA thickness and overlay thickness) are critical influencing factors for field rut depth; (b) RRI, along with pavement age and traffic data, has the most significant effect on rut depth among the identified five key predictor variables; (c) no significant differences are observed between prediction results of HMA and WMA mixtures, and thus the prediction model can be applied for both; and (d) using the developed predictive model, the effect of the HWT RRI can be considered comprehensively with other factors including climate, traffic, and pavement structure to determine the suitability of a designed asphalt mixture for pavement construction.

The objective of this study was to evaluate the use of crumb rubber (CR) from waste tires and engineered additives as a rejuvenator to high reclaimed asphalt pavement (RAP) content asphalt mixtures. Six asphalt mixtures were prepared by mixing aggregate blends with four asphalt binders, an unmodified asphalt binder classified as performance grade (PG) 64-22, two polymer-modified binders classified as PG 70-22M and PG 76-22M, and a PG 76-22 crumb-rubber-modified binder. The RAP content was varied from 0–40% and crumb-rubber additives were blended with the unmodified binder by using wet and dry processes. Hot-mix asphalt (HMA) mixture testing included an evaluation of rutting susceptibility, moisture resistance, and resistance to cracking using the flow number test, the loaded-wheel tracking test, the dynamic modulus test, the modified Lottman test, the dissipated creep strain energy test, and the semi-circular bending test. Results of the experimental program indicated that the addition of the CR additives...