CHIARA MIGNINI

Pubblicazioni

CHIARA MIGNINI

 

16 pubblicazioni classificate nel seguente modo:

Nr. doc. Classificazioni
8 1 Contributo su Rivista
7 4 Contributo in Atti di Convegno (Proceeding)
1 8 Tesi di dottorato
Anno
Risorse
On the densification of cold recycled asphalt mixtures
JOURNAL OF TESTING AND EVALUATION
Autore/i: Mignini, C.; Virgili, A.; Graziani, A.
Classificazione: 1 Contributo su Rivista
Abstract: The mechanical behavior of cold recycled asphalt mixtures (CRAMs) is directly connected to their volumetric properties. Therefore, the objective of the present research was to investigate the effect of different composition factors on the densification of CRAMs. To this aim, a new empirical modeling approach for characterizing and comparing the densification of CRAMs using the gyratory compactor was proposed. The methodology was then applied to CRAMs produced using four gradations, two asphalt emulsions, two cements, various water contents, and several superplasticizer dosages. The densification curves were analyzed using three parameters representing the self-densification, the compactability, and the compaction energy. These parameters were linked using a mathematical model, which was represented using three interrelated pairwise relationships. The results showed that the grading distribution of the CRAMs was the main parameter controlling their densification behavior, whereas the water content and other composition factors played a minor role.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/292744 Collegamento a IRIS

Experimental Study on the Grading Distribution of Cold Recycled Asphalt Mixtures Produced with Bitumen Emulsion and High Strength Cement
RILEM Bookseries
Autore/i: Mignini, C.; Cardone, F.; Graziani, A.
Editore: Springer Science and Business Media B.V.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Cold recycled asphalt mixtures (CRAM) can lead to real economic advantages only if their performance is comparable to that of traditional hot mix asphalt. This experimental study aims to investigate the effect of the grading distribution on the volumetric and mechanical properties of CRAM produced with high reclaimed asphalt dosage (>70%), bitumen emulsion and high strength cement. Four grading distributions were analysed: two continuously graded curve (derived from the Fuller-Thompson maximum density curve) with nominal maximum aggregate size (NMAS) 16 and 10 mm. The third was obtained increasing the filler dosage, and the fourth grading distribution was a gap-graded type, with NMAS 16 mm. Workability and compactability of the fresh CRAM were evaluated using the gyratory compactor. CRAM long-term complex modulus was measured using cyclic compression tests. Results showed that the gap-graded and the high-filler grading distributions allowed obtaining the lower voids in the mixture. Having fixed the number of voids in the mixture, the gap-graded CRAM showed a higher stiffness modulus and lower phase angle if compared to CRAM produced with the continuously graded curve.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/292642 Collegamento a IRIS

Interphase Relations in the Characterisation of Bitumen Emulsion-Cement Composites
Proceedings of the RILEM International Symposium on Bituminous Materials. ISBM 2020
Autore/i: Miljkovic, M.; Graziani, A.; Mignini, C.
Editore: Springer Science and Business Media B.V.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Strategic research on bitumen emulsion-based materials is substantial for addressing numerous environmental effects of road infrastructure. The present specifications for bitumen emulsions are based on properties that are insufficient for a fundamental understanding of their relation to the physicomechanical behaviour of realistic coarse-graded materials for structural layers. The aim of the interlaboratory testing (ILT) of RILEM TC 280-CBE Task group 1 is to investigate the link between the intrinsic interphase relations and macroscopic physicomechanical behaviour of bitumen emulsion-cement composites. Thus, the objective of this individual research was creating the basis for the above ILT by experimental and analytical evaluation of mortar-based model systems, by investigating their physicomechanical behaviour, and by conducting the sensitivity analysis of the relations between phases. The experimental evaluation comprised compactability and volumetric evaluation of fresh mixtures, indirect tensile-based testing at different stages of curing, as well as the temporal measurement of the evaporation of water from specimens.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/292647 Collegamento a IRIS

2021
Using fine aggregate matrix mortars to predict the curing behaviour of cement bitumen treated materials produced with different cements
CONSTRUCTION AND BUILDING MATERIALS
Autore/i: Mignini, C.; Cardone, F.; Graziani, A.
Classificazione: 1 Contributo su Rivista
Abstract: Cold recycling is a sustainable pavement rehabilitation technology. Among the different techniques, cement-bitumen treated materials (CBTM) take advantage of the presence of the two co-binders to achieve satisfying performance. A multiscale study addresses the effect of different cementitious binders on the mechanical behaviour of CBTM mixtures and fine aggregate matrix mortars produced with bitumen emulsion. The evolution of stiffness and strength during curing is measured and compared. Results show that the cement type has a critical effect on the mechanical behaviour and, under fixed curing conditions, changing the strength is equivalent to changing the dosage. Finally, fine aggregate matrix mortars offer an excellent prediction of mixture mechanical properties.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/286839 Collegamento a IRIS

2021
Multiscale approach for characterising the behaviour of cold bitumen emulsion materials
Autore/i: Mignini, Chiara
Classificazione: 8 Tesi di dottorato
Abstract: 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.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/289668 Collegamento a IRIS

2021
Rheological characterisation of cold bitumen emulsion slurries
ROAD MATERIALS AND PAVEMENT DESIGN
Autore/i: Mignini, C.; Lo Presti, D.; Airey, G.; Graziani, A.
Classificazione: 1 Contributo su Rivista
Abstract: 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.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/292641 Collegamento a IRIS

2020
Comparing the field and laboratory curing behaviour of cold recycled asphalt mixtures for binder courses
MATERIALS
Autore/i: Ferrotti, G.; Grilli, A.; Mignini, C.; Graziani, A.
Classificazione: 1 Contributo su Rivista
Abstract: The cold recycling of reclaimed asphalt (RA) for the rehabilitation of end-of-life pavements is becoming very common. Cold recycled asphalt mixtures (CRAMs) are characterised by a curing time, required to reach the material design mechanical performance. Since the laboratory simulation of the long-term field curing is not yet a standardised procedure, a CRAM was laid as binder course in a full-scale trial section that was monitored for more than two years. The comparison between field curing and oven-curing in laboratory at 40◦C was performed by carrying out indirect tensile stiffness modulus (ITSM), indirect tensile strength (ITS) and complex modulus tests, as well as measurements of the air voids content. The evolution of the ITSM as a function of the curing time (field/oven-curing) was obtained for both gyratory specimens and cores taken from the trial section at different time periods. Results showed that the material stiffness development can be accelerated with a small effect on its long-term value if oven-curing is applied a few days/weeks after compaction. A linear relationship was found between the ITS measured on the cores and their air voids content. Finally, the complex modulus tests confirmed that CRAMs provide an intermediate behaviour between asphalt concrete mixtures and cement-bound mixtures.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/286852 Collegamento a IRIS

2020
Mechanical Behaviour of Cold Recycled Asphalt Mixtures for Binder Courses Produced with Bitumen Emulsion and High Strength Cement
Lecture Notes in Civil Engineering
Autore/i: Mignini, C.; Cardone, F.; Graziani, A.
Editore: Springer
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Cold recycled asphalt mixtures (CRAM) are sustainable solutions for maintenance and rehabilitation of road pavements. Notwithstanding the environmental benefits, CRAM may exhibit lower performances compared to traditional hot mix asphalt. Besides, CRAM require a curing period to reach their long-term properties, and thus, they are usually employed in base courses. This work investigates the mechanical behaviour of CRAM with bitumen emulsion and high strength cement to verify if they are suitable for binder courses. Six CRAM were produced using 80% of reclaimed asphalt, modified emulsion and two high strength cement: sulfo-aluminous and Portland-slag cement. For comparison, two additional mixtures were produced using traditional emulsion. The CRAM had an emulsion content of 4.2% or 5.0%, and residual bitumen to cement ratio of 1.0 or 1.2. After curing periods from 6 h to 1 year, the indirect tensile stiffness modulus (ITSM) and indirect tensile strength (ITS) were assessed. Their thermal sensitivity was evaluated as well, measuring ITSM at different temperatures. Results indicate that high strength cement leads to satisfactory mechanical behaviour in the long-term. Compared to Portland-slag cement, sulfo-aluminous cement increases the rate of development of ITS and ITSM in the early stage of about 50% and 25%, respectively.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/286842 Collegamento a IRIS

2020
Use of fine aggregate matrix to analyze the rheological behavior of cold recycled materials
MATERIALS AND STRUCTURES
Autore/i: Graziani, A.; Raschia, S.; Mignini, C.; Carter, A.; Perraton, D.
Classificazione: 1 Contributo su Rivista
Abstract: Nowadays, one of the main challenges to a wider application of cold recycling techniques is the lack of reliable information on the mechanical behavior of cold recycled materials (CRM). In this context, measurement and modelling of the complex modulus of CRM mixtures may give an important contribution to the design and analysis of pavements including cold recycled layers. In this study, we analyzed the rheological behavior of CRM mixtures produced using bitumen emulsion and cement through the study of their fine aggregate matrix (FAM). Starting from a fixed CRM mixture composition, we compared different FAM mortars, focusing on the effect of water and air content. Then, we selected a composition as representative of the FAM in the mixture and investigated the evolution of both materials during a fixed curing period. Next, we measured the complex modulus of the CRM mixture and FAM at two curing stages and applied a rheological model to simulate and compare their behavior. Results showed that the properties of CRM mixtures are comparable to those of FAM mortars produced using all the binding agents (bitumen emulsion and cement) and a fraction of the voids contained in the mixture. Despite the huge difference in volumetric compositions, the FAM mortar controlled the curing and the thermo-rheological behavior of the CRM mixture, while the coarse reclaimed asphalt aggregate fraction and the voids mainly affected the asymptotic properties (equilibrium and glassy moduli) and the non-viscous dissipation component.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/286841 Collegamento a IRIS

2019
EVALUATING THE CRACKING RESISTANCE OF CEMENT-BITUMEN TREATED MATERIALS USING THE SEMI-CIRCULAR BENDING TEST
New generation of construction materials
Autore/i: Mignini, Chiara; Cardone, Fabrizio; Morbi, Alessandro; Setti, Luca; Graziani, Andrea
Editore: RILEM sarl
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: 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.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/267169 Collegamento a IRIS

2019
FIELD BEHAVIOUR OF COLD-RECYCLED ASPHALT MIXTURES FOR BINDER COURSES
New generation of construction materials
Autore/i: Grilli, Andrea; Mignini, Chiara; Graziani, Andrea
Editore: RILEM sarl
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: 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 field
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/267168 Collegamento a IRIS

2019
Complex Modulus Testing and Rheological Modeling of Cold-Recycled Mixtures
JOURNAL OF TESTING AND EVALUATION
Autore/i: Graziani, Andrea; Mignini, Chiara; Bocci, Edoardo; Bocci, Maurizio
Classificazione: 1 Contributo su Rivista
Abstract: 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).
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/268080 Collegamento a IRIS

2019
Effect of curing on the indirect tensile failure energy of cement-bitumen treated materials
7th International Conference "Bituminous Mixtures and Pavements"
Autore/i: Mignini, Chiara; Cardone, Fabrizio; Graziani, Andrea; Morbi, Alessandro; Setti, Luca
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Cold recycling technologies allow the use of high percentage of reclaimed asphalt (RA) through mixing at ambient temperature and thus, they represent a sustainable solution for road construction and rehabilitation. Specifically, cement-bitumen treated materials (CBTM) are produced using both bituminous and cementitious binders. Consequently, they require a curing time to reach adequate mechanical properties. This study focuses on CBTM manufactured using bitumen emulsion (2.0% of residual bitumen), cement (1.5% and 2.5%) and 80% of RA. Indirect tensile strength (ITS) was evaluated at times ranging from 1 to 90 days after sealed and unsealed curing. The transverse deformation of the specimens was measured to calculate the failure energy. Results show that ITS and failure energy increase with curing time and are higher in unsealed conditions. The horizontal strain in the early stage depends on the binders’ dosage and curing conditions whereas, in the long term it is similar for all the mixtures investigated.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/263584 Collegamento a IRIS

2019
Effect of gradation on volumetric and mechanical properties of cold recycled mixtures (CRM)
ROAD MATERIALS AND PAVEMENT DESIGN
Autore/i: Raschia, S.; Mignini, C.; Graziani, A.; Carter, A.; Perraton, D.; Vaillancourt, M.
Classificazione: 1 Contributo su Rivista
Abstract: In recent times, recycling using cold bituminous mixtures has become one of the most interesting techniques in pavement engineering from sustainability aspect. This study focuses on the clarification of the steps concerned with the cold mixture mix design to determine the initial aggregate gradation of the mixture. The study has been developed involving procedures followed in Canada and Italy. In both the cases, three different gradations, normally employed in the production of traditional bituminous mixtures, were compared. The effect conferred by the gradation type has been studied in terms of workability, compactability and mechanical properties. Results show that in both the procedures the gradation influenced the workability and the compaction behaviour of the mixtures studied. At the same time, in terms of mechanical properties, the gradation influenced the strength of the final mixture in only one of the procedures applied.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/271214 Collegamento a IRIS

2018
Complex Modulus of Cold Recycled Mixtures: measurement and modelling
2018 ISAP Conference
Autore/i: Graziani, Andrea; Mignini, Chiara; Bocci, Edoardo; Bocci, Maurizio
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: In the present study, the complex modulus E* of three types of cold recycled mixtures was measured in the laboratory using cyclic compression tests. The mixtures, that were produced in situ using the full-depth reclamation technique, were characterised by the same 100% reclaimed aggregate composition, whereas bitumen emulsion, foamed bitumen and portland cement were employed as binding agents. Complex modulus testing was carried out on cylindrical specimens cored from the pavement seven years after construction. A sinusoidal strain with amplitude of 30 microstrain was applied at testing temperatures ranging from 0 to 50 °C and frequencies ranging from 0.1 to 20 Hz. Results showed that the time-temperature superposition principle was fully verified for the stiffness modulus whereas some discrepancy was highlighted by the loss angle. The Huet-Sayegh rheological model was applied to simulate the experimental data. Model fitting based only on the stiffness modulus provided excellent results. Indeed, the fitted rheological model was also able to simulate the loss angle variation quite well, but with some underestimation (about 3°) of the measured values. It can be concluded that other dissipation mechanism, in addition to the “classical” viscous type, were influent for behaviour of the studied cold recycled mixtures.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/259785 Collegamento a IRIS

2018
Experimental study of bitumen emulsion–cement mortars: mechanical behaviour and relation to mixtures
MATERIALS AND STRUCTURES
Autore/i: Mignini, Chiara; Cardone, Fabrizio; Graziani, Andrea
Classificazione: 1 Contributo su Rivista
Abstract: Cold bitumen emulsion mixtures are ecofriendly materials for road pavement construction. Portland cement and other supplementary cementitious materials are added to the mixtures to improve their performance. In bitumen emulsion–cement (BEC) mixtures, the two binders affect the mechanical behaviour and the curing process. In this research, BEC mixtures are considered as multiphase composite materials consisting of a mortar matrix and coarse aggregate inclusions. The main objectives are to identify the composition of BEC mortar phase and to compare mixtures and mortars throughout the curing process. Starting from two BEC mixtures containing 80% reclaimed asphalt, eighteen mortars were manufactured by changing their water and air voids content. Then, two design composition were selected to analyse the curing process by monitoring indirect tensile strength (ITS), indirect tensile stiffness modulus (ITSM) and moisture loss. Results showed that the short-term ITS of mortars (1 day of curing) increased by reducing their water and their air voids content. During curing (from 1 to 28 days), the mechanical properties (ITS and ITSM) of mixtures and mortars increased in a similar way. Unique relationships were identified between mortar and mixture properties, regardless of bitumen to cement (B/C) ratio, curing time and curing condition. In terms of predictive behaviour, the design composition slightly underestimated mixture stiffness and overestimated mixture strength.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/263585 Collegamento a IRIS




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