Unlocking the Dual Helical Ribbon for rotational viscosity measurements of highly heterogeneous fluids

Road bituminous binders are becoming more complex since, to enhance properties and/or engineer circular economy, the conventional binder is enriched with modifiers of different nature giving birth to a final-product recognisable as highly heterogeneous fluid. The assessment of these materials relies on rheological measurements; however, existing testing equipment are designed for homogeneous fluids, proving to be often inadequate. In fact, rotational testing lacking mixing efficiency during measurements, can compromise sample stability, resulting in non-representative results Lo Presti et al. (2014). To address these challenges, a dual helical ribbons (DHR) was purposefully created and successfully employed in prior studies to measure the rotational viscosity of highly heterogeneous asphalt materials Giancontieri et al. (2019). While the DHR effectiveness has been extensively discussed in earlier investigations, this study aims to contribute to the scientific community at large by providing: state-of-the-art on improving mixing efficiency of highly heterogeneous fluids, rationalizing the choice of the DHR geometry comprehensive technical details for realising any DHR, verified through numerical modelling Calibration with model input parameters achieved by adopting the Rieger and Novak method, and finally design validation. The authors aim for the broader material science community to benefit from this investigation, enabling technologists to independently develop DHR devices and explore new applications

Rheological Behaviors of Waste Polyethylene Modified Asphalt Binder: Statistical Analysis of Interlaboratory Testing Results

This article investigated the effect of waste polyethylene (PE) on the modified asphalt binders' rheological behavior from a statistical point of view. The interlaboratory testing results from the RILEM Technical Committee 279 Valorization of Waste and Secondary Materials for Roads Task Group 1 were used for this purpose. First, an unaged 70/100 penetration graded neat binder was selected as the reference material. Next, a single 5 % content of waste PE additives (PE-pellets and PE-shreds) was mixed with a 95 % neat binder to prepare two PE modified binders. Then, dynamic shear rheometer-based temperature-frequency sweep tests were performed over a wide range of temperatures and frequencies to evaluate the rheological properties of these three binders. Different rheological behaviors were observed in the isochronal plots at high temperatures. Based on a reproducibility precision requirement proposed for phase angle, 28 degrees C was set as the transition temperature across the rheological behaviors. Next, according to the three rheological behaviors defined in a previous study by the authors, statistical analysis was introduced to identify sensitive rheological parameters and determine the thresholds. Results indicate that the phase angle measured above 28 degrees C and 1.59 Hz can be used as a sensitive parameter to discriminate the three rheological behaviors of PE modified binders. The thresholds among different behaviors were also calculated as an example for phase angle measured at the highest common testing temperature of 70 degrees C. Additional experimental evaluations on more types of PE modified binders, especially at intermediate and high temperatures, are recommended to better understand their influence on the rheological behavior of PE modified binders

Improving the rheometry of rubberized bitumen: experimental and computation fluid dynamics studies

Multi-phase materials are common in several fields of engineering and rheological measurements are intensively adopted for their development and quality control. Unfortunately, due to the complexity of these materials, accurate measurements can be challenging. This is the case of bitumen-rubber blends used in civil engineering as binders for several applications such as asphalt concrete for road pavements but recently also for roofing membranes. These materials can be considered as heterogeneous blends of fluid and particles with different densities. Due to this nature the two components tends to separate and this phenomenon can be enhanced with inappropriate design and mixing. This is the reason behind the need of efficient dispersion and distribution during their manufacturing and it also explains while realtime viscosity measurements could provide misleading results. To overcome this problem, in a previous research effort, a Dual Helical Impeller (DHI) for a Brookfield viscometer was specifically designed, calibrated and manufactured. The DHI showed to provide a more stable trend of measurements and these were identified as being ‘‘more realistic” when compared with those obtained with standard concentric cylinder testing geometries, over a wide range of viscosities. However, a fundamental understanding of the reasons behind this improvement is lacking and this paper aims at filling these gaps. Hence, in this study a tailored experimental programme resembling the bitumen-rubber system together with a bespoke Computational Fluid Dynamics (CFD) model are used to provide insights into DHI applicability to perform viscosity measurements with multiphase fluids as well as to validate its empirical calibration procedure. A qualitative comparison between the laboratory results and CFD simulations proved encouraging and this was enhanced with quantitative estimations of the mixing efficiency of both systems. The results proved that CFD model is capable of simulating these systems and the obtained simulations gave insights into the flow fields created by the DHI. It is now clear that DHI uses its inner screw to create a vertical dragging of particles within a fluid of lower density, while the outer screw transports the suspended particles down. This induced flow helps keeping the test sample less heterogeneous and this in turns allows recording more stable viscosity measurements

Towards low-cost pavement condition health monitoring and analysis using deep learning

Governments are faced with countless challenges to maintain conditions of road networks. This is due to financial and physical resource deficiencies of road authorities. Therefore, low-cost automated systems are sought after to alleviate these issues and deliver adequate road conditions for citizens. There have been several attempts at creating such systems and integrating them within Pavement management systems. This paper utilizes replicable deep learning techniques to carry out hotspot analyses on urban road networks highlighting important pavement distress types and associated severities. Following this, analyses were performed illustrating how the hotspot analysis can be carried out to continuously monitor the structural health of the pavement network. The methodology is applied to a road network in Sicily, Italy where there are numerous roads in need of rehabilitation and repair. Damage detection models were created which accurately highlight the location and a severity assessment. Harmonized distress categories, based on industry standards, are utilized to create practical workflows. This creates a pipeline for future applications of automated pavement distress classification and a platform for an integrated approach towards optimizing urban pavement management systems

Are we correctly measuring the rotational viscosity of heterogeneous bituminous binders?

Modified bituminous binders allow asphalt technologists to design asphalt mixtures with superior performance. However, several recent studies highlighted that due to the complexity of these material, their characterisation can be challenging since common procedures used to characterise neat bitumen might not be adequate. For instance, during high temperature rotational viscosity testing of recycled tyre rubber modified binders (RTR-MB), a number of changes may occur to the sample leading to the here-defined sample stability which in turn provides misleading results. In this study the authors want to first provide a deeper understanding of this phenomenon by a numerical analysis using a bespoke Computational Fluid Dynamics (CFD) model to simulate the laboratory tests and use innovative visual aids to monitor the sample stability of heterogeneous bituminous binders during the rotational test. The numerical analysis was complemented by a laboratory campaign aiming at proving the occurring of sample stability during viscosity measurement of heterogeneous bituminous binders with a standard testing setup (SC-27). Furthermore, a dual helical ribbon (DHR) is here introduced as a solution to overcome the issue. Hence, laboratory tests were undertaken also with DHR and differences in viscosity measurements of neat bitumen, SBS-MB and RTR-MB were recorded. Results of this combined numerical and empirical approach proved that the standard setup for rotational viscosity measurements seems not be adequate for RTR-MB and depending on the level of modification and test temperatures, might not be best suited for SBS-MB either. The DHR seems to solve the issue and authors strongly recommend the adoption of this testing geometry to obtain more realistic high-temperature viscosity measurement of heterogeneous bituminous binders

Improved Testing Setup for Real-Time Monitoring of PMBs During Manufacturing and Rotational Viscosity Measurements

Polymer modified binders (PMBs) are a practical solution to design asphaltmixtures with superior performance. Although these polymers often improve bitumen properties to some extent, their final performance are linked to the accurate control of the properties during manufacturing and storage. However, some of the common procedures used to characterise neat bitumen are not suitable with these binders making their characterisation challenging. This study presents a novel laboratory procedure to produce SBS-MB through a real-time monitoring of the rotational viscosity, as well as an attempt to understand the suitability of current testing geometries to measure viscosity of such a complex bituminous binder. The proposed innovation lies in the adoption of a Dual Helical Ribbon (DHR), as a novel mixing/measuring device for rotational viscometers. The laboratory tests were undertaken by using the DHR and a standard coaxial cylinder configuration with a spindle geometry (SC27) as a control to record eventual differences in viscosity measurements of PMBs. As a result, the real-time monitoring procedure improved the governing of the modifications process, furthermore, it was proven that when blends with high polymer content and no cross linker are tested, the conventional coaxial cylinder setup for rotational viscosity measurements might not be adequate and spindle geometries should be replaced with the DHR

Controllo delle Polveri Derivanti dalla Lavorazione di Legni Duri

In questo studio sono state affrontate le problematiche riguardanti la produzione di polveri generate durante diverse fasi di lavorazione di legno duro

Morphological and Morphometrical Characteritics of Ornamental Stone Airborne Dusts: Capture and Filtration

Dust generated during ornamental stone transformation process is considered one of the most dangerous factors affecting the health of workers employed in the stone industry. Workers are exposed to very-high dust generation during manual work actions, especially during the finishing stage of the production cycle. During such operations tools are handled directly by the workers without using water. This particulate matter (dust) presents different composition and different morphological and morphometrical attributes which strongly influence capture and filtering system behavior. As a consequence, the quantity and the quality of the dust circulating in the work environment directly influences the air being breathed by the workers causing considerable variation in quality. In this paper, results obtained from a dust collection analysis campaign, carried out in an ornamental stone conversion industry, are analyzed and discussed in order to obtain the best dust reduction adopting an innovative captioning-filtering device. The study was particularly addressed to identify possible correlation between working actions performed, tools utilized, concentration of produced dusts in order to define the best strategy to reduce its production during hand working actions and to improve the air quality of working environment, through the adoption of efficient dust collection devices. All the tests have been carried out in a controlled environment, directly installed in the factory, equipped with an innovative filtration system and an “on-line” control logic for dust collection. Different types of ornamental stones have been selected for the tests (granite, limestone, sandstone, etc.)

Investigating Tools for Sustainability Assessment of Road Pavements in Europe

Sustainability assessment (SA) is a method to support decision making processes through the evaluation of system effectiveness, environmental integrity, economic valuation, and social implications [1]. SA can be carried out through the application of life-cycle-based techniques for quantitative assessment, or by performing a mainly qualitative approach via sustainability rating systems (SRS). In the field of civil engineering, many SRS have been proposed, all based on assigning point values to actions that are determined to contribute to the overall sustainability of the project. However, only few of these systems can be applied specifically to compare road pavement technologies and/or maintenance and rehabilitation strategies. This study focuses on adapting two of these tools: GreenPave [2], developed in the US, and BE2ST (Building Environmentally and Economically Sustainable Transportation–Infrastructure–Highways) [3], developed in Canada. The investigation consisted of evaluating the feasibility of increasing the amount of reclaimed asphalt (RA) in European wearing courses by carrying out a comparative analysis of eight different mixtures, containing up to 90% of RA