Federico Autelitano

The odour fingerprint of bitumen

Bitumen is a very complex material with chemical composition and properties highly dependent on the crude oil source and refinery processes. Several analytical procedures were developed to understand the relationship between bitumen composition, microstructure and physical properties. Nevertheless, these techniques are expensive, time-consuming and involve significant drawbacks. Moreover, advanced research and industrial research have often different purposes and timing perspectives. Several bitumen operators require simpler and more suitable techniques for research and technology development, production and acceptance control and above all polymer modification. This necessity has led the authors to propose a new approach based on the artificial olfactory system (AOS), also known as electronic nose or e-nose. AOS is an instrument consisting of an array of partially selective sensors coupled to a suitable pattern-recognition system capable of recognising complex odours. The warm-up study highlighted the possibility of AOS to discriminate, already at room temperature without the need of sample pre-treatments, between bitumen produced with different origin crude oils and to verify the production stability in the same plant. Thus, these results indicate that the e-nose method may be used for quality assurance and quality control applications and for the fingerprinting of bitumen, showing a number of advantages over classical analytical instruments.

DEM modelling analysis of tree root growth in street pavements

The coexistence of urban green spaces and infrastructure is often difficult. Trees find inhospitable environments in urban areas, whereas tree root systems can damage sidewalk, street and parking lot. The main form of failure concerns the growing of tree roots beneath the pavements, which produce upheavals and displacements on wearing course. The main objective of this study was a distinct element method modelling analysis of the potential interactions between tree root systems and street pavements. This calculation code allowed us to simulate the dynamic behaviour of the ground-pavement system as result of the roots growth. The performed modelling, representative of various planting strategies commonly used in urban contexts, have highlighted the progressive reduction of deformations with the increase of the roots penetration depth. Such displacements were strongly influenced by other factors such as the porosity and the grain-size distribution of the soil and the type of pavement considered.

Thermomechanical behaviour of airfield concrete pads supporting joint strike fighter F-35B

The Lockheed Martin F-35B Lightning II is the Short Take-Off/Vertical Landing (STOVL) aircraft variant of the joint strike fighter. The new dual-cycle propulsion system, which permits the STOVL operations, exposes the airfield pavements to extremely critical thermal conditions (temperatures exceeding 930°C and heating rate of about 85°C s−1). This study permitted to analyse the thermomechanical behaviour of an ordinary concrete pad during the F-35B aircraft vertical landing. The numerical analysis provided a detailed picture of the pavement stress state generated by the jet gases, opening the scenario to different planning solutions. The results highlighted how the damage, in the form of thermomechanical spalling, occurred in the top 2–5 mm of the pavement surface. One of the possible design solutions for high-performance vertical landing pads, supporting the F-35B aircraft, could be a two-layered pavement characterised by a thin (2.5 cm) fibre-reinforced Very High-Strength Concrete overlay. GRAPHICAL ABSTRACT