Experimental study of bitumen emulsion–cement mortars: mechanical behaviour and relation to mixtures

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Correction to: Experimental study of bitumen emulsion–cement mortars: mechanical behaviour and relation to mixtures

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Rheological characterisation of cold bitumen emulsion slurries

The performance of cold bitumen emulsion (CBE) mixtures is strongly linked to an optimised design of the binder blends and mastics. Types and dosages of bitumen, mineral additions and the workability must be characterised and optimised. This study aims at providing an approach for the fundamental characterisation of CBE materials using rotational viscometry. Firstly, a procedure for measuring the viscosity of CBE slurries using the Brookfield viscometer was investigated by comparing results obtained by using a traditional spindle geometry and a novel impeller engineered to avoid phase separation: the dual helical ribbon (DHR). Afterwards, the effect of mineral additions and bitumen emulsions types was measured and modelled, also considering the influence of their concentration. The Krieger-Dougherty model proved to be a powerful tool to fit results and provide fundamental parameters for improved CBE materials engineering characterisation. Overall, the DHR was found a promising tool for CBE slurries rheological characterisation

Dopamine receptors and transporters sensitivity to trimethyltin in rat hippocampus and facial nucleus

Trimethyltin (TMT) is considered a useful tool to obtain an experimental model of neurodegeneration. TMT is known to cause neurotoxicant effects especially marked in the hippocampus. Despite many studies are published, there are poor literature on the interaction of this xenobiotic with dopaminergic system. In the present work, we investigate in rat brain, after 21 days following TMT intraperitoneal administration, the cells viability (N-NEU) and the animal behaviour in association with the immunohystochemical expression of dopamine receptors (D1- and D2-like) and transporters membrane (DAT) and vesicular monoamine trasporters (VMAT-1 and -2) in rat hippocampus and facial nucleus. The animal behaviour shows a significant reduction of spatial reference memory in a Morris water maze task according with the reduction (70% Vs control) of hippocampus dopaminergic system expression, despite the cell viability is maintained at about 50%. In the facial nucleus, a different reduction of dopamine receptors and trasporters (30% against 60%) was observed while the N-NEU reduction was 40%. These results suggest that the toxic interaction of TMT with the dopaminergic system in rat hippocampus may be responsible for learning and memory deficits. Data obtained in facial nucleus demonstrate different sensitivity of dopamine receptors and dopamine transporters to xenobiotic. Supported by PRIN 2008 - prot. 20089MANHH_00

Guidelines for the implementation of SMARTI: Sustainable Multifunctional Automated Resilient Transport Infrastructure

The World's transport infrastructures (TI) network is facing fast changes due to population growth, mobility, business trades and globalization. More challenges are coming from unforeseen natural and human-induced hazards, including climate change's effects. Meanwhile, technology development continues apace, and new solutions from multi-disciplinary sectors could help solve the main challenges faced by the TI industry. This work presents “SMARTI”, a vision that aims at engineering and implementing concepts such as Sustainability, Multifunctionality, Automation and Resilience within the design, construction and management of TI. As a result, the paper provides roadmaps for each of the above-mentioned pillars, identifying aims, current practices and stepping stones that infrastructure managers, policymakers and governors should consider toward more sustainable TI within 2030

Multiscale approach for characterising the behaviour of cold bitumen emulsion materials

I materiali a freddo prodotti con emulsione bituminosa rappresentano tecnologie sostenibili nel campo della costruzione e riabilitazione delle pavimentazioni. Si ottengono utilizzando l'emulsione bituminosa come legante principale. Come co-leganti o agenti stabilizzanti secondari possono essere impiegati cemento o altri tipi di aggiunte. Spesso, i materiali a freddo con emulsione vengono prodotti utilizzando quantità elevate di conglomerato bituminoso di recupero, massimizzando i loro benefici in termini di sostenibilità. Tuttavia, i materiali a freddo possono apportare reali vantaggi economici solo se le loro prestazioni sono paragonabili a quelle del tradizionale conglomerato bituminoso. L’ottenimento di materiali a freddo con emulsione bituminosa aventi prestazioni soddisfacenti è fortemente legato ad una progettazione avanzata della loro composizione e ad una profonda consapevolezza dei meccanismi che influenzano il loro comportamento meccanico. Di conseguenza, il tipo e i dosaggi dei componenti, ma anche la loro interazione, sono caratteristiche chiave da studiare e ottimizzare. In quest’ottica, la presente tesi mira a fornire alla comunità scientifica un approccio multiscala per la caratterizzazione fondamentale dei materiali a freddo prodotti con emulsione bituminosa. L'approccio multiscala qui presentato considera i materiali a freddo con emulsione bituminosa come compositi multifase e indaga quattro scale di interesse ingegneristico: le miscele, la malte, i mastici allo stato fresco e l’emulsione bituminosa. Nello specifico, l'indagine sperimentale ha tentato di definire il concetto di malta. È stato poi valutato il comportamento evolutivo di miscele e malte, nonché le loro proprietà viscoelastiche lineari (LVE). Quindi, è stata studiata una procedura per misurare la viscosità dei mastici allo stato fresco. Parallelamente, è stata valutata anche l'adozione di componenti innovative per migliorare le prestazioni dei materiali a freddo. I risultati hanno mostrato che l'approccio multiscala sviluppato è uno strumento efficace per caratterizzare i materiali a freddo con emulsione bituminosa. Le malte hanno evidenziato una soddisfacente capacità predittiva del comportamento evolutivo delle miscele. Inoltre, malte e miscele hanno mostrato una sensibilità simile in termini di risposta LVE. È stata proposta una nuova metodologia affidabile per caratterizzare il comportamento reologico dei mastici freschi. Infine, l'uso di materiali innovativi si è dimostrato utile per migliorare le proprietà meccaniche dei materiali CBE.Cold bitumen emulsion (CBE) materials are sustainable pavement construction and rehabilitation technologies. They are obtained using bitumen emulsion as the main binder. Cement or other types of mineral additions can be employed as co-binders or secondary stabilising agents. Frequently, CBE materials are produced using high amounts of reclaimed asphalt aggregate, maximising their sustainable benefits. However, CBE materials can lead to real economic advantages only if their performance is comparable to traditional hot mix asphalt. The achievement of CBE materials with satisfactory performances is strongly linked to a superior design of their composition and to a deep awareness about the mechanisms influencing their mechanical behaviour. Hence, type and dosages of the constituents, and their interaction, are key features to be investigated and optimised. Within this framework, this thesis aims to provide the scientific community with a multiscale approach for the fundamental characterisation of CBE materials. The multiscale approach here presented considers CBE materials as multiphase composites and investigates four scales of engineering interest: mixtures, fine aggregate matrix (FAM) mortars, fresh mastics (i.e. slurries) and bitumen emulsions. Specifically, the experimental investigation first attempted to define the FAM mortar concept. The evolutive behaviours of mixtures and FAM mortars were evaluated, as well as their linear viscoelastic (LVE) response. Then, a procedure for testing the viscosity of CBE slurries was investigated. In parallel, the adoption of innovative constituents for enhancing the CBE materials performances was assessed as well. Results showed that the developed multiscale approach is an effective tool for characterising CBE materials. FAM mortars showed a satisfactory predicting ability of CBE mixtures evolutive behaviour indeed. Besides, mortars and mixtures exhibited a similar sensitivity in terms of LVE response. A reliable novel methodology for characterising the rheological behaviour of CBE slurries was proposed. Finally, the use of innovative materials was found beneficial for enhancing the mechanical properties of CBE materials

The role of fine aggregate matrix in the linear viscoelastic behaviour of cement-bitumen treated materials

The use of cold recycling technologies, including cement-bitumen treated materials (CBTM), is rising to address the environmental and economic challenges required for implementing sustainable road pavements. However, to obtain performances comparable to those of hot bituminous mixtures, the advanced study of these relatively new materials is essential, also considering the analysis of the linear viscoelastic (LVE) behaviour. This research studies the complex modulus of fine aggregate matrix (FAM) mortars, representative of the binding matrix of CBTM mixtures, characterised by several compositions. The experimental results were modelled considering both viscous and time- and temperature-independent dissipation components. Findings showed that the LVE behaviour of FAM mortars strongly depends on their composition, especially in terms of bituminous components, i.e. fresh and aged bitumen, and cement. Besides, the aged bitumen coating the reclaimed asphalt aggregate plays a role in the LVE response of CBTM mortars and mixtures

FIELD BEHAVIOUR OF COLD-RECYCLED ASPHALT MIXTURES FOR BINDER COURSES

A new awareness on sustainable materials and construction techniques is promoting field applications of cold bitumen emulsion mixtures. Cold in-plant recycling (CPR) techniques with bitumen emulsion ensure important benefits in terms of energy saving and amount of recycled materials while maximising the performance and production stability of mixtures. This study describes the construction of a pavement trial section where a cold-recycled asphalt mixture (CRAM) was placed as binder course. The CRAM was manufactured in-plant, using about 90% of reclaimed asphalt, bitumen emulsion and cement. The evolution of indirect tensile stiffness modulus (ITSM) was monitored on both laboratory-compacted specimens and cores extracted from the pavement. From the analysis of results, it can be affirmed that the increase of ITSM due to the curing process was faster for laboratory specimens with respect to fiel

Complex Modulus Testing and Rheological Modeling of Cold-Recycled Mixtures

This research compares the rheological behavior of different cold-recycled mixtures (CRMs) produced in-place through full-depth reclamation. Reclaimed asphalt pavement (RAP) obtained from the milling of the old asphalt layers was blended with reclaimed unbound aggregate from the existing subgrade. Asphalt emulsion, foamed asphalt, and portland cement were employed as stabilizing agents. The complex modulus was measured on cylindrical cores, applying a sinusoidal strain with an amplitude of 30 microstrain at testing temperatures ranging from 0°C to 50°C and frequencies ranging from 0.1 to 20 Hz. The Huet-Sayegh (HS) rheological model was applied to simulate the experimental data. The results showed that the behavior of CRM is thermo- and frequency-dependent and that the time-temperature superposition principle can be applied. The HS model provides an excellent fitting of the dynamic modulus data, whereas fitting of the loss angle data was improved, introducing a temperature- and frequency-independent correction. The RAP influences the rheological behavior, but viscous dissipation is mainly due to the asphalt-stabilizing agents (emulsion residue or foamed asphalt)

EVALUATING THE CRACKING RESISTANCE OF CEMENT-BITUMEN TREATED MATERIALS USING THE SEMI-CIRCULAR BENDING TEST

Cement-bitumen treated materials (CBTM) are produced using cold recycling technologies for the rehabilitation of bituminous pavements. Bitumen emulsion and cement are used as binders, and thus jointly contribute to the mechanical performance of the mixtures. This paper focuses on the cracking resistance of CBTM, which is related to the presence and relative effect of bituminous and cementitious bonds within the mixtures. The objective is to evaluate the influence of different cement types, bitumen-to-cement ratios (1.3 and 0.8) and curing conditions (free and restricted evaporation). The semi-circular bending (SCB) test was used to evaluate the cracking resistance of mortar specimens whose composition was derived from the mixtures’ composition removing the coarse aggregates. The SCB specimens cut from gyratory compacted specimens were tested at 10 °C after 28 days of curing at 25 °C. The results analysis indicates that in the crack initiation phase, the behaviour of CBTM mortars depends on the combined presence of cementitious and bituminous bonds, whereas, in the crack propagation phase, the effects of cement type and dosage prevail and may lead to a brittle behaviour