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Pavement preservation is playing an increasingly significant role in maintaining our aged pavement infrastructure under severe budget constraints. One important component is the use of surface treatments based on application of sealants. Recently, a number of new products, called bio sealants, have been used to treat aging pavement surfaces. The objective of this study is to investigate rheological properties of the binders treated with these materials to understand the mechanism by which they may improve pavement performance. One plain asphalt binder and four types of sealants, two oil-based sealants, one water-based sealant, and one traditional emulsion were used in the experimental work. The results obtained using a dynamic shear rheometer and a bending beam rheometer were used to determine the changes in rheological properties and the change in performance grade. It was observed that the oil-based sealants have a significant softening effect of the control binder compared to the water-based sealants. The transverse cracking histories from field investigation were used to verify the laboratory findings. [ABSTRACT FROM AUTHOR]

Rutting is one of the most important issues associated with asphalt pavements. This defect leads to the accelerated degradation of the pavement and considerably reduces the level of road safety. This paper reports on the results obtained in the optimization of nanocomposite asphalt containing carbon nanotubes (CNTs) with regard to the resistance to permanent deformation. Nanocomposite asphalts were prepared with the addition of different proportions of CNTs. Based on a study on the empirical and rheological properties of the nanocomposites developed, optimization of the CNT content incorporated into the conventional asphalt binder was carried out. Then two asphalt mixtures were investigated, a reference mixture and a nanomodified mixture with CNTs (optimal content). The rheological evaluations were carried out on four-point fatigue equipment and the resistance to permanent deformation was tested in a traffic simulator (wheel tracking test). The results demonstrate the efficient contribution of the nanocomposite to the resistance to permanent deformation. [ABSTRACT FROM AUTHOR]

Crumb rubber is the recycled rubber particle obtained from mechanical shearing or grinding scrap tires into small particle sizes less than 6.3 mm (or approximately 1/4'). The rheological properties of asphalt binder have an important effect on the field performance of asphalt mixtures and the long-term serviceability of asphalt pavement. The objective of this research is to evaluate the high temperature rheological performance of rubber asphalt binder based on the complex shear modulus (| G*|) and the phase angle ( δ) values using the dynamic shear rheometer. Five rubber asphalt dosages at 0, 10, 15, 20, and 25% by weight of asphalt (Superpave PG 64-22), respectively, were used to modify asphalt binder; and three rubber particle meshes, 20#, 30#, and 40#, were utilized in this research. The | G*| at various temperatures and frequencies were tested on each sample, including original and short-term aging binder using the rolling thin-film over. The master curves of | G*|/sin( δ) for each type of rubber asphalt was generated to investigate its rheological properties over a broad range of temperatures and frequencies. Based on the testing results, it was found that the addition of crumb rubber significantly increases the | G*| of asphalt binder, which is desirable to potentially improve the anti-rutting performance of asphalt mixtures. It was also found that the addition of 10% mesh crumb rubbers bumps up the high temperature grade of asphalt, from PG64 to PG76 in this case. The master curve using the | G*|/sin( δ) of rubber asphalt shows a substantial improvement in rutting resistant at each testing temperature and loading frequency. However, it was noteworthy that the rutting resistance enhancement of crumb rubber was affected by the percentage of rubber used, the rubber particle size and its aging condition. [ABSTRACT FROM AUTHOR]

Traditionally, moisture damage in asphalt is determined by laboratory testing of liquid asphalt binder, loose mix, and (or) solid asphalt concrete samples under wet and dry conditions. Yet some asphalt mixes pass such laboratory moisture damage tests but show poor moisture damage potential in the field. To this end, this study presents asphalt constituents such as mastic and matrix testing for true evaluation of field moisture damage in asphalt concrete. Three mixes included in this study have almost identical laboratory moisture damage potential, but coarse mix (SP-III) has higher field moisture damage potential than two fine mixes (SP-B, SP-C). Related to these mixes, three mastics namely natural fines (NF), crushed fines (CF), and combined natural and crushed fines (NF+CF) are tested using a dynamic shear rheometer (DSR) at varying temperature and frequency. Also, matrix materials passing #4 sieve is tested in DSR, tension, pull-off, and direct shear loadings. It is shown that mastic and matrix test results can better identify field moisture damage of asphalt concrete. Fine mastic and matrix have low moisture damage potential than the coarse matrix and mastic. At high temperature (above 25 °C), shear modulus converges to a small number irrespective of mastic type. Due to moisture conditioning, matrix ultimate stress decreases in tension and pull-off tests but not in shear test. [ABSTRACT FROM AUTHOR]

The main objective of using warm mix asphalt (WMA) is to reduce emissions and improve the workability by lowering the mixing and compaction temperatures of asphalt mixes through different mechanisms. Since warm asphalt is a relatively new technology, not much research has been conducted on various mix compositions. While some of the concerns about WMA have been addressed, the interaction of warm mix additives with modified binders, especially crumb rubber modified (CRM) binder, is not known in great detail. This paper presents the data on rheological tests conducted on rubberized binders containing warm asphalt additives. Binders from five different sources were modified using 10% crumb rubber by weight of the virgin binders. Two of the available warm asphalt technologies, Aspha-min® and Sasobit®, were used to produce the warm asphalt binders. From the tests, it was observed that the addition of the warm asphalt additives significantly reduce the permanent deformation of the binders, increase the viscosity at 60 °C and the complex modulus, G*, and decrease the phase angle, δ, at high frequencies and low temperatures compared with the CRM binders. L’objectif principal derrière l’utilisation de mélanges bitumineux tièdes (WMA) est de réduire les émissions et d’améliorer la maniabilité en abaissant les températures de mélange et de compaction des mélanges bitumineux par l’utilisation de divers mécanismes. Toutefois, puisque le bitume tiède représente une technologie relativement nouvelle, peu de recherche a été réalisée sur les différentes compositions de mélanges. Bien que certains problèmes aient été abordés à propos des WMA, l’interaction d’adjuvants de mélanges bitumineux chauds avec des liants modifiés, plus particulièrement le liant modifié de caoutchouc granulaire, n’est pas vraiment bien connue. Cet article présente les données d’essais rhéologiques réalisés sur des liants caoutchoutés contenant des adjuvants de mélanges bitumineux tièdes. Les liants de cinq sources différentes ont été modifiés en utilisant 10 % de caoutchouc granulaire par poids de liant vierge. Deux technologies de bitume chaud disponibles, Aspha-min® et Sasobit®, ont été utilisées pour produire des liants bitumineux tièdes. Les essais ont montré que l’ajout d’adjuvants bitumineux chauds réduit de manière significative la déformation permanente des liants, augmente la viscosité à 60 °C et le module complexe, G*, et diminue l’angle de phase, δ, à de hautes fréquences et faibles températures par rapport aux liants CRM. [ABSTRACT FROM AUTHOR]

The behavior of asphalt mixtures is very complicated due to structural configuration and interfacial friction of aggregates as well as chemical and rheological reactions of the asphalt binder itself or with the aggregates. Furthermore, this complex response is more complicated under various loads, temperatures, and other environmental factors. To control the complex responses and reduce the complex factors, a DSR moisture damage test using small rock disks was developed. This paper focuses on the more fundamental concepts to explain asphalt and asphalt-aggregate bond behavior exhibited under the newly-developed DSR moisture damage test. The traditional model of asphalt structure is based on the theory of colloid and surface chemistry. Although this traditional model can explain many physical phenomena of asphalt structure, it cannot explain all the asphalt behaviors, such as steric hardening. Therefore, more general, but fundamental concepts may be required to attain insight of the material. As one of the possible concepts, a self-assembly concept in supramolecular chemistry is proposed and phenomena and results of the DSR moisture damage test are explained by the concept. [ABSTRACT FROM AUTHOR]