The ability of the Pressure Aging Vessel (PAV) to properly simulate the long-term aging characteristics of asphalt binders has been questioned by researchers in the recent years. Several research efforts have indicated that the current PAV protocol may age the materials significantly less severely than the actual environmental field agents. Alternatively, updates on the current PAV testing procedures have been proposed to age the binders for 20 or even 60 h beyond the current 20 h. A protocol with very thin binder films, named as Universal Aging Test, has also been recommended by the Western Research Institute. Thermal aging with the combination of ultraviolet radiation exposition and heating has also been regarded as a possible more realistic route. This work aims to evaluate the cracking characteristics of nine unmodified and three modified (by SBS, ground tire rubber, and TLA) asphalt binders aged by different testing methodologies, i.e. a thermal route with changing exposition times and an ultraviolet route. The carbonyl index and the benzylic hydrogen content obtained by Fourier Transform Infrared Spectroscopy and Nuclear Magnetic Resonance, respectively, were evaluated to identify the chemical effects of the different aging strategies. The cracking resistance of the aged binders was evaluated by means of the Glover–Rowe (GR) parameter and of LAS test results. The GR results showed that the critical block-cracking zone could be reached by the two routes, being the oxidative effect that happens in the field more evident in the UV radiation route. Larger values of the benzylic hydrogen were observed for the materials deriving from a deasphalting residue process, resulting in higher susceptibility to aging. The carbonyl index was very sensitive to UV aging and presented in general larger values than the other aging strategies. The presence of an elastomeric modifier apparently protected the SBS and GTR samples against UV aging.

X-ray micro-computed tomography (micro-CT) is an advanced technique able to provide a comprehensive examination of the volumetric characteristics of asphalt mixtures. A key step for the air void (AV) quantification using micro-CT images is the segmentation, which is a stage of the digital image processing. The most common segmentation technique, the manual threshold (TH) selection, depends significantly on the operator skills, image homogeneity, and material complexity. These factors that can limit the reproducibility of the TH procedure. Machine learning and deep learning recently appeared as promising alternatives to solve this challenge. In this paper, images of an asphalt concrete (AC) specimen were acquired in a modern high-resolution micro-CT scanner to determine its AV content using four different segmentation tools, i.e. TH, watershed, machine learning, and deep learning. All methods presented similar results for the total AV content. The advantages and limitations of using each technique were discussed in terms of computational effort, user-friendliness, and accuracy of the results. Machine learning and deep learning were identified as powerful tools for AC segmentation, being accurate and easy to adjust, however taking longer data processing times.

Fine-grained lateritic soils, which are typically found in tropical regions and have been used successfully in low-cost pavements, are often considered inadequate for the base and subbase pavement layers when the material selection is based on the California bearing ratio (CBR). When analyzed in repeated load triaxial (RLT) test equipment, which is the most frequently used device to analyze the mechanical behavior of unbound pavement materials, fine-grained lateritic soils exhibit low levels of plastic deformation. Thus, to allow more appropriate analyses of the mechanical behavior of such soils compared to traditional CBR-based analyses, resilient modulus and permanent deformation tests using RLT test equipment were performed. Then, multifactorial regression analysis of the experimental results was performed to identify the parameters of the material models that are implemented in the Brazilian mechanistic-empirical pavement design software program, MEDINA. The experimental program included material characterization in accordance with the so-called miniature, compacted, tropical (MCT) methodology that is tailored specifically to classify tropical soils. For one of the lateritic soils, two key parameters, i.e., the stress level and compaction moisture content, were varied in the RLT permanent deformation tests. An additional numerical analysis using MEDINA was conducted to evaluate the structural characteristics of flexible pavements composed of the four lateritic soils analyzed in this study. In general, the results obtained from this study indicate that lateritic soils can potentially be used as base and subbase layers in flexible pavement structures.

In the last few years, there has been a great focus on human health and improving working conditions. Within this context, it is necessary to study the impact of the highway construction on the quality of life of workers and the environment. This paper aims to study polycyclic aromatic hydrocarbons (PAHs) emission from different bitumens commercialised in Brazil (conventional, modified by polymer or rubber and natural asphalt). The bitumens were submitted to conventional (Brazilian specifications) and rheological (SUPERPAVE classification) tests. The most usual application method is as a hot mixture. When heated, the bitumen releases volatile species and solid particles carried by gases, and this mixture is called bitumen emissions. In this fume, there are organic substances (PAHs), some of which may be carcinogenic. Therefore, the fume emitted during bitumen heating is harmful to health and should be considered both from the environmental sustainability and the worker health points of view. PAH studies were done alongside with other studies where the bitumen and the emission of some PAHs were correlated, which were measured through an experimental apparatus that generates and collects the bitumen fume. The equipment used was a nominated extraction and collection device (ECD) and the tests were conducted on laboratory benches. The fumes were collected in ECD and analysed by liquid chromatography–mass spectrometry to quantify the amount of emitted PAHs. From the research, it was possible to verify if bitumens with different behaviours at paving, from the perspective of sustainability and different impacts to the environment and human health. These emissions have an impact on health and the environment, which require further understanding.

Fracture damage mechanisms are some of the most significant causes of structural failure in asphalt mixtures. Ye t much research is still needed to understand properly the fracture process in such complex materials. The study reported in this paper investigated several experimental testing protocols available in the literature to characterize fracture properties of asphalt mixtures. Two bending tests (i.e., semicircular bending, single-edge notched beam) and one tension test (disk-shaped compact tension) were performed. An integrated approach that combined experimental tests and numerical simulations was applied to characterize fracture properties of a fine aggregate mixture. The experimental tests were simulated with a computational model on the basis of the finite element method, which was incorporated with material viscoelasticity and cohesive zone fracture. Two cohesive zone fracture parameters (i.e., cohesive strength, fracture energy) were determined through a calibration process until a good match between experimental and numerical results was observed. To illustrate the efficiency of the integrated numerical–experimental approach, fracture properties also were determined through a traditional methodology that used globally averaged material displacements far from the actual fracture process zone. The results indicated that different fracture properties at low temperatures might be obtained from simulations of a single test, regardless of the sample geometry or loading configuration. Through further testing and analysis, it is expected that the modeling approach employed in this work can provide meaningful insights into the effects of constituents on an overall mixture's performance, with significant savings in experimental cost and time.