Rheology of bituminous mastics and mortars containing crumb rubber from tyres: a novel dry-hybrid technology

This report studied the effect of crumb rubber in the asphalt mixture. The mixtures were also having limestone filler as a modifier. Mastic and mortar (mastic-fine aggregate system) mixture having different quantities of crumb rubber and limestone filler modifiers have been tested in order to find the best rutting resistance combination with an acceptable stiffness. The rheological tests on bituminous mastics and mortars have done in the laboratories in Nottingham Transport Engineering Centre (NTEC) and University of Bologna (DICAM). In the second chapter, an extensive literature review about the binders, additives, asphalt mixtures, various modelling and testing methods have been reviewed. In the third chapter, the physical and rheological properties of the binders have been investigated using both traditional devices and DSRs. The forth chapter is dedicated to finding the behaviour of the modified mastics (Binder-modifier system) with different combinations. Five different combinations of crumb rubber and limestone filler mastic tested with various methods using Dynamic Shear Rheometers. In the fifth chapter, in order to find the effect of the modifiers in the rheological properties of the complete asphalt mixture, the fine aggregates added to the same mastic combinations. In this phase, the behaviour of the system so-called mortar; binder, rubber, filler and fine aggregates) has been studied using the DSR device and the traditional tests. The results show that using fine crumb rubber reduces the thermo sensibility of the mastic (Binder Bitumen System) and improves its elasticity. Limestone filler in the other hand increases the mixture stiffness at high Frequencies. Another important outcome of this research was that the rheological properties of the mortars were following the same trend of the mastics, therefore study the rheological properties of the mastic gives an upright estimation of the mortar.

Rheological Characterization of Bitumen and Asphalt including the effect of Added-recycled Material

This thesis evaluates the rheological behaviour of asphalt mixtures and the corresponding extracted binders from the mixtures containing different amounts of Reclaimed Asphalt (RA). Generally, the use of RA is limited to certain amounts. The study materials are Stone Mastic Asphalts including a control sample with 0% RA, and other samples with RA rates of 30%, 60% and 100%. Another set of studied mixtures are Asphalt Concretes (AC) types with again a control mix having 0% RA rate and the other mixtures designs containing 30%, 60% and 90% of reclaimed asphalt which also contain additives. In addition to the bitumen samples extracted from asphalt mixes, there are bitumen samples directly extracted from the original RA. To characterize the viscoelastic behaviour of the binders, Dynamic Shear Rheometer (DSR) tests were conducted on bitumen specimens. The resulting influence of the RA content in the bituminous binders are illustrated through master curves, black diagrams and Cole-Cole plots with regressing these experimental data by the application of the analogical 2S2P1D and the analytical CA model. The advantage of the CA model is in its limited number of parameters and thus is a simple model to use. The 2S2P1D model is an analogical rheological model for the prediction of the linear viscoelastic properties of both asphalt binders and mixtures. In order to study the influence of RA on mixtures, the Indirect Tensile Test (ITT) has been conducted. The master curves of different mixture samples are evaluated by regressing the test data points to a sigmoidal function and subsequently by comparing the master curves, the influence of RA materials is studied. The thesis also focusses on the applicability and also differences of CA model and 2S2P1D model for bitumen samples and the sigmoid function for the mixtures and presents the influence of the RA rate on the investigated model parameters.

Laboratory verification of predicted permanent deformation in asphalt materials following climate change.

In the past a change in temperature of 5°C most often occurred over intervals of thousands of years. According to estimates by the IPCC, in the XXI century is expected an increase in average temperatures in Europe between 1.8 and 4.0°C in the best case caused by emissions of carbon dioxide and other GHG from human activities. As well as on the environment and economic context, global warming will have effects even on road safety. Several studies have already shown how increasing temperature may cause a worsening of some types of road surface damages, especially rutting, a permanent deformation of the road structures consisting in the formation of a longitudinal depression in the wheelpath, mostly due to the rheological behavior of bitumen. This deformation evolves during the hot season because of the heating capacity of the asphalt layers, in fact, the road surface temperature is up to 24°C higher than air. In this thesis, through the use of Wheeltrack test, it was studied the behavior of some types of asphalt concrete mixtures subjected to fatigue testing at different temperatures. The objectives of this study are: to determine the strain variation of different bituminous mixture subjected to fatigue testing at different temperature conditions; to investigate the effect of aggregates, bitumen and mixtures’ characteristics on rutting. Samples were made in the laboratory mostly using an already prepared mixtures, the others preparing the asphalt concrete from the grading curve and bitumen content. The same procedure was performed for each specimen: preparation, compaction using the roller compactor, cooling and heating before the test. The tests were carried out at 40 - 50 - 60°C in order to obtain the evolution of deformation with temperature variation, except some mixtures for which the tests were carried out only at 50°C. In the elaboration of the results were considered testing parameters, component properties and the characteristics of the mixture. Among the testing parameters, temperature was varied for each sample. The mixtures responded to this variation with a different behavior (linear logarithmic and exponential) not directly correlated with the asphalt characteristics; the others parameters as load, passage frequency and test condition were kept constant. According to the results obtained, the main contribution to deformation is due to the type of binder used, it was found that the modified bitumen have a better response than the same mixtures containing traditional bitumen; to the porosity which affects negatively the behavior of the samples and to the homogeneity ceteris paribus. The granulometric composition did not seem to have interfered with the results. Overall has emerged at working temperature, a decisive importance of bitumen composition, than the other characteristics of the mixture, that tends to disappear with heating in favor of increased dependence of rutting resistance from the granulometric composition of the sample considered. In particular it is essential, rather than the mechanical characteristics of the binder, its chemical properties given by the polymeric modification. To confirm some considered results, the maximum bulk density and the air voids content were determined. Tests have been conducted in the laboratories of the Civil Engineering Department at NTNU in Trondheim according to European Standards.

Innovative Infrastructures for Sustainable Mobility in Urban Areas: Protective Asphalt to Prevent Vulnerable Road Users Injuries.

Nell’elaborato viene studiato il fenomeno dell’incidentalità singola delle utenze deboli sulla strada (perdita di controllo, scivolamento ecc..ecc..), con particolare enfasi nell’analizzare le conseguenze traumatiche dovute all’impatto con la superficie stradale. Una nuova tecnologia viene sviluppata per rendere le pavimentazioni di piste ciclabili, marciapiedi e zone pedonali con capacità di assorbimento degli impatti, prevenendo, o riducendo drasticamente, la probabilità e entità di eventi traumatici a seguito di una caduta. Attraverso una stesa di prova avvenuta ad Imola (BO), si sono analizzate e risolte le problematiche dovute alle discrepanze riscontrate fra “costruzione” in laboratorio e costruzione nella realtà urbana. La nuova tecnologia, infatti, è stata studiata come “construction-friendly”, permettendo alle società di costruzione e pavimentazione di stendere il nuovo manto protettivo con strumenti e macchinari tradizionali. Infine l’asfalto modificato è stato testato nei laboratori svedesi del KTH – Royal Institute of Technology per provarne l’efficacia in termini di assorbimento degli impatti. Nel “Drop Impact Test”, test specifico per l’approvazione dei caschi protettivi da bicicletta, l’asfalto modificato ha performato ben al di sotto della soglia di approvazione dei caschi da ciclista, e si colloca in un range di valore di accelerazione lineare perfino al di sotto della soglia di “Low Risk of Injuries”. La nuova tecnologia, inoltre, fa utilizzo di gomma granulata riciclata da pneumatici fuori uso. Tale dettaglio conferisce maggiore sostenibilità al progetto: oltre all’utilizzo di legante a freddo, che diminuisce le emissioni di CO2, e di incentivare l’utilizzo della mobilità dolce attraverso una più sicura rete infrastrutturale, l’utilizzo di gomma riciclata dà nuova vita al materiale che altrimenti andrebbe in discarica e prolunga, così, la vita utile del materiale.