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This work presents the results of RILEM TC 237-SIB (Testing and characterization of sustainable innovative bituminous materials and systems). The papers have been selected for publication after a rigorous peer review process and will be an invaluable source to outline and clarify the main directions of present and future research and standardization for bituminous materials and pavements. The following topics are covered: - Characterization of binder-aggregate interaction - Innovative testing of bituminous binders, additives and modifiers - Durability and aging of asphalt pavements - Mixture design and compaction analysis - Environmentally sustainable materials and technologies - Advances in laboratory characterization of bituminous materials - Modeling of road materials and pavement performance prediction - Field measurement and in-situ characterization - Innovative materials for reinforcement and interlayer systems - Cracking and damage characterization of asphalt pavements - Recycling and re-use in road pavements This is the proceedings of the RILEM SIB2015 Symposium (Ancona, Italy, October 7-9, 2015).
The use of phase-change materials (PCMs) in asphalt mixture is expected to solve some problems related to asphalt-pavement temperature, such as rutting behaviors and urban heat island effect. This study mainly evaluated the thermal and mechanical properties of asphalt mixtures with and without various PCMs (PCM-L, PCM-Z) using laboratory performance tests. The experimental tests included thermal conductivity and diffusivity, volumetric heat capacity, indoor temperature changes versus time when heated or cooled, indirect tensile strength, high-temperature rutting, and low-temperature cracking. In addition, a hot disk thermal constants analyzer was used to measure the thermal constants of asphalt mixtures. The results showed that different PCMs had different effects on the thermal constants of asphalt mixtures. Compared with control sample, the sample with PCM-L showed a higher thermal conductivity, whereas the sample with PCM-Z had a lower thermal conductivity. Moreover, PCM-Z exhibited a more-significant phase-change adjusting-temperature effect on asphalt mixtures than PCM-L. However, the addition of PCM to asphalt mixtures resulted in a decreased indirect tensile strength and a weakened rutting resistance, but the effect of PCM-Z was smaller than that of PCM-L. In addition, the asphalt mixture with PCM-Z exhibited better cracking resistance than the mixture with PCM-L and control mixture. Therefore, it is recommended to use PCM-Z in asphalt mixtures to solve the problem of pavement at high temperatures.
Asphalt oxidation causes major changes to binder properties and is hypothesized to be a major contributor to age-related pavement failure such as fatigue cracking. Extensive laboratory aging research has been done to assess the effects of oxidation on binder properties. Previous work shows binder oxidation makes the binder stiffer and more brittle, leading to higher binder stresses under a given deformation. Failure occurs when these stresses exceed the strength of the binder. However, binder oxidation in pavements has not been studied in the same detail as laboratory aging of neat binders. The impact of binder oxidation on long-term pavement performance has been either underestimated or ignored. This research includes studies of binder oxidation in Texas pavements to compare the field aging with laboratory neat binder aging, the impact of binder oxidation on HMAC mixture aging and HMAC mixture fatigue performance, and fundamental rheological property changes of the binder and the mixture. Binder oxidation is studied in fifteen pavements from locations across Texas. Results indicate that unmodified binders in pavements typically oxidize and harden to a degree that exceeds generally accepted pavement aging assumptions. This hardening may also extend much deeper into the pavement than has been previously assumed or documented. Data suggest that pavements can oxidize at rates surprisingly uniform with depth once early oxidation occurs, and that these rates continue for an extended time. Laboratory-aged HMAC mixtures and binders were tested and analyzed for fatigue resistance and their rheological properties. Mixture aging shows the same aging mechanisms as neat binder aging. Both binder and mixture have a higher modulus with aging and a good rheological correlation. The decline in mixture fatigue life (determined using the calibrated mechanistic fatigue analysis approach with surface energy measurement) due to oxidation is significant. Pavement service life is dependent on the mixture, but can be estimated by a cumulative damage approach that considers binder oxidation and pavement loading rate simultaneously. The differences in expected pavement life arise from differences in the rate of binder stiffening due to oxidation and the impact of this stiffening on the decline of fatigue life.
This volume highlights the latest advances, innovations, and applications in the field of asphalt pavement technology, as presented by leading international researchers and engineers at the 5th International Symposium on Asphalt Pavements & Environment (ISAP 2019 APE Symposium), held in Padua, Italy on September 11-13, 2019. It covers a diverse range of topics concerning materials and technologies for asphalt pavements, designed for sustainability and environmental compatibility: sustainable pavement materials, marginal materials for asphalt pavements, pavement structures, testing methods and performance, maintenance and management methods, urban heat island mitigation, energy harvesting, and Life Cycle Assessment. The contributions, which were selected by means of a rigorous international peer-review process, present a wealth of exciting ideas that will open novel research directions and foster multidisciplinary collaboration among different specialists.
Heating of asphalt during production and construction causes the volatilization and oxidation of binders used in mixes. Volatilization and oxidation causes degradation of asphalt pavements by increasing the stiffness of the binders, increasing susceptibility to cracking and negatively affecting the functional and structural performance of the pavements. Degradation of asphalt binders by volatilization and oxidation due to high production temperature occur during early stages of pavement life and are known as Short Term Aging (STA). Elevated temperatures and increased exposure time to elevated temperatures causes increased STA of asphalt. The objective of this research was to investigate how elevated mixing temperatures and exposure time to elevated temperatures affect aging and stiffening of binders, thus influencing properties of the asphalt mixtures. The study was conducted in two stages. The first stage evaluated STA effect of asphalt binders. It involved aging two Performance Graded (PG) virgin asphalt binders, PG 76-16 and PG 64-22 at two different temperatures and durations, then measuring their viscosities. The second stage involved evaluating the effects of elevated STA temperature and time on properties of the asphalt mixtures. It involved STA of asphalt mixtures produced in the laboratory with the PG 64-22 binder at mixing temperatures elevated 25OF above standard practice; STA times at 2 and 4 hours longer than standard practices, and then compacted in a gyratory compactor. Dynamic modulus (E*) and Indirect Tensile Strength (IDT) were measured for the aged mixtures for each temperature and duration to determine the effect of different aging times and temperatures on the stiffness and fatigue properties of the aged asphalt mixtures. The binder test results showed that in all cases, there was increased viscosity. The results showed the highest increase in viscosity resulted from increased aging time. The results also indicated that PG 64-22 was more susceptible to elevated STA temperature and extended time than the PG 76-16 binders. The asphalt mixture test results confirmed the expected outcome that increasing the STA and mixing temperature by 25oF alters the stiffness of mixtures. Significant change in the dynamic modulus mostly occurred at four hour increase in STA time regardless of temperature.
Bituminous Mixtures and Pavements VIII contains 114 papers as presented at the 8th International Conference ‘Bituminous Mixtures and Pavements’ (8th ICONFBMP, 12-14 June 2024, Thessaloniki, Greece). The contributions reflect the research and practical experience of academics and practicing engineers from thirty-four (34) different countries, and cover a wide range of topics: Session I: Bitumen, Modified binders, Aggregates, and Subgrade Session II: Bituminous mixtures (Design, Construction, Testing, Performance) Session III: Pavements (Design, Construction, Maintenance, Sustainability, Energy and Environmental consideration) Session IV: Pavement management and Geosynthetics Session V: Pavement recycling Session VI: Pavement surface characteristics, Pavement performance monitoring, Safety Session VII: Biomaterials in pavement engineering Session VIII: Prediction models of pavement performance Bituminous Mixtures and Pavements VIII covers recent advances in highway materials technology and pavement engineering, and will be of interest to scientists and professionals involved or interested in these areas. The ICONFBMP-conferences have been organized every four years since 1992. This 8th conference was jointly organized by: Laboratory of Highway Engineering, Aristotle University of Thessaloniki, Greece; Built Environment Research Institute (BERI), University of Ulster, UK; University of Texas San Antonio (UTSA), USA; Laboratory for Advanced Construction Technology (LACT), Technological Institute of Iowa, USA; Technological University of Delft (TUDelft), The Netherlands, and University of Antwerp, (UA), Belgium.
Construction materials are the most widely used materials for civil infrastructure in our daily lives. However, from an environmental point of view, they consume a huge amount of natural resources and generate the majority of greenhouse gasses. Therefore, many new and novel technologies for designing environmentally friendly construction materials have been developed recently. This Special Issue, “Environment-Friendly Construction Materials”, has been proposed and organized as a means to present recent developments in the field of construction materials. It covers a wide range of selected topics on construction materials.
Sustainable road construction and maintenance could be supported when excellent warm-mix additives are employed in the modification of asphalt. These warm-mix additives provide remedies for today's requirements such as fatigue cracking resistance, durability, thermal cracking resistance, rutting resistance and resistance to moisture damage. Warm-mix additives are based on waxes and surfactants which reduce energy consumption and carbon dioxide emissions significantly during the construction phase of the pavement. In this study, the effects of two warm mix additives, siloxane and oxidised polyethylene wax, on roofing asphalt flux (RAF) and asphalt modified with waste engine oil (655-7) were investigated to evaluate the rheological, aging and failure properties of the asphalt binders. In terms of the properties of these two different asphalts, RAF has proved to be superior quality asphalt whereas 655-7 is poor quality asphalt. The properties of the modified asphalt samples were measured by Superpave(TM) tests such as Dynamic Shear Rheometer (DSR) test and Bending Beam Rheometer (BBR) test as well as modified protocols such as the extended BBR (eBBR) test (LS-308) and the Double-Edge-Notched Tension (DENT) test (LS-299) after laboratory aging. In addition, the Avrami theory was used to gain an insight on the crystallization of asphalt or the waxes within the asphalt binder. This study has however shown that the eBBR and DENT tests are better tools for providing accurate specification tests to curb thermal and fatigue cracking in contemporary asphalt pavements.