1,721,121 research outputs found
Airey, G J, VX44578
No full textThis record was harvested from a previous catalogue system and will be withdrawn in 2025. Information in this record may be superseded or incomplete. Visit this record in UMA's new catalogue at: https://archives.library.unimelb.edu.au/nodes/view/367990Surname: AIREY
Given Name(s) or Initials: G J
Military Service Number or Last Known Location: VX44578
Missing, Wounded and Prisoner of War Enquiry Card Index Number: 23725178037
Item: [2016.0049.00322] "Airey, G J, VX44578
Influence of processing conditions on rheology of tyre rubber modified bitumens
No full textTyre Rubber Modified Binders (TR-MBs), produced through McDonald wet process and used worldwide (e.g. asphalt rubber), have been demonstrated to provide various benefits to pavements and, moreover, they represent a good opportunity for recycling tyre rubber. However this technology is still struggling to be fully adopted in Europe, mainly because of their poor stability during high temperatures storage, which leads to high initial costs in modifying existing asphalt plants. NO-agitation TR-MBs (also known as terminal blends) is proving to be a great option and its development could also be the key to spreading the recycling of tyre rubber in paving applications in Europe. This paper aims to enrich this field of research by presenting the results of a study focused on the optimisation of laboratory procedures to better understand the effect of varying processing conditions on the rheology TR-MBs. The experimental programme has been carried out by a preliminary selection of materials, followed by the production of the TR-MBs, via practical laboratory protocols. A continuous comparison between two commercially used SBS-MBs, with high and medium levels of modification, and the produced TR-MBs, helped to understand the effect of varying the selected processing conditions on binder properties. Results have shown that TR-MBs are a very effective alternative to commercially used SBS-MB. Although the rheology of TR-MBs is very sensitive to the varying of processing conditions, therefore an appropriate selection of materials and a superior binder design are mandatory to optimise the modification process to achieve the desired level of modification
Tyre rubber-modified bitumens development: the effect of varying processing conditions
No full textTyre rubber-modified binders (TR-MBs), produced through McDonald's wet process and used worldwide (e.g. asphalt rubber), have been demonstrated to provide various benefits to pavements and, moreover, they represent a good opportunity for recycling tyre rubber (TR). However, this technology is still struggling to be fully adopted in Europe, mainly because of their poor stability during high temperatures storage, which leads to high initial costs in modifying existing asphalt plants. Storage stable TR-MBs are proving to be a great option and their development could be the key to spread the recycling of TR within paving applications in Europe. This paper aims to enrich this field of research by presenting the results of a study focused on the optimisation of laboratory procedures to better understand the effect of varying processing conditions on the rheology of TR-MBs. The experimental programme has been carried out by a preliminary selection of materials, followed by the production of the TR-MBs, via practical laboratory protocols. A continuous comparison between two commercially used styrene-butadiene-styrene (SBS)-MBs, with high and medium levels of modification, and the produced TR-MBs helped to understand the effect of varying the selected processing conditions on binder properties. Results have shown that TR-MBs are a very effective alternative to commercially used SBS-MB. Nevertheless, the rheology of TR-MBs is very sensitive to the variation of the processing conditions, so appropriate selection of materials and a superior binder design are mandatory to achieve the desired level of modification
Manufacturing reclaimed asphalt test specimens using gyratory compactor
No full textThis paper presents a laboratory investigation aiming to provide a protocol that
allows to confidently using gyratory compaction for the production of reclaimed asphalt test
specimens. The presented investigation is part of a wider experimental programme aiming at
obtaining input parameters for modelling purposes. For this reason, it has been necessary to
define a quick and reliable and repeatable procedure to manufacture a high number of
specimens with a limited amount of material. Gyratory specimens were compacted by
targeting to densities defined in previous Marshall mix design and with the final aim of
obtaining specimens with a fixed and homogeneous distribution of air voids content. The
study has been developed by comparing results of two Stone Mastic Asphalt mixtures, a
control mix with virgin material and a reclaimed asphalt mix with 30% of RA. The mixtures
had almost identical air void contents, aggregate grading curves and the binders had similar
conventional binder properties. Homogeneity of air void distribution was investigated by X-ray
Computed Tomography (CT), image analysis techniques and buoyancy tests. Coring and
trimming of the compacted specimens were used to obtain the final test specimens with fixed
homogeneous properties. The study concluded that gyratory compaction is suitable to
produce homogeneous test specimens also for mixtures containing high amount of reclaimed
asphalt. Nevertheless final coring and trimming of the specimens are mandatory as well as
performing a preliminary investigation for each material consisting in the compaction, and the
further buoyancy tests, of few specimens having densities ranging from 100 to 90% of the
initial target. The presence of high percentage of RA did not present remarkable issues apart
making the compaction harder. This study has been developed within the FP7 European
Project Re-Road
Rubberised stone mastic asphalt mixtures: a performance-related evaluation
No full textThe binder content of rubberised asphalt mixtures is usually increased compared to that used in conventional asphalt. This increase is deemed important to compensate for the reduction in the actual bitumen due to the existence of rubber particles. This study presents the results of performance evaluation conducted on different rubberised Stone Mastic Asphalt (SMA) mixtures produced using different types and contents of rubberised bitumen. The energy ratio (ER) computed from Superpave Indirect Tensile (IDT) tests was used to evaluate the cracking resistance of asphalt mixtures while the rutting behaviour was evaluated using the Repeated Load Axial Test (RLAT). The indirect tensile stiffness and strength were used to evaluate the moisture susceptibility. Using the same binder content for rubberised SMA mixtures as used in the conventional mixtures can still give superior performance properties. Adding crumb rubber to softer base bitumen can produce asphalt mixtures with superior cracking and rutting resistance
Rheological characterisation of cold bitumen emulsion slurries
No full textThe 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
Effects of ageing on the damage tolerance of polymer modified bitumens investigated through the LAS test and fluorescence microscopy
No full textThe effects of polymer modification on the durability of Polymer Modified Bitumens (PMBs) still remain relatively unclear due to partial understanding of the combined effects of ageing and loading on damage accumulation. This paper investigates the effects of laboratory ageing on the damage tolerance of cross-linked SBS and EVA modified bitumens measured using the Linear Amplitude Sweep (LAS) test and corroborated with the morphology of the PMBs. The PMBs were prepared with three polymer concentrations (i.e. 2%, 4% and 6%). In general, ageing affects the capacity of bitumens to maintain integrity to damage and reduces their time-temperature susceptibility. The damage tolerance is derived from the combination of the two mechanisms as a function of the bitumen’s strain level. At low strain levels, typical of thick pavements, ageing enhances the damage tolerance. Contrarily, at higher strain levels, it provides the opposite effect. SBS improves the damage tolerance of the base bitumen as a function of polymer concentration and dispersion. However, the polymer chain undergoes oxidative degradation and its effect reduces with ageing. EVA forms a polymer network with a low oxidative susceptibility that contributes, at low strain, to maintaining or improving the damage tolerance with ageing as a function of the polymer concentration
Effects of mineral fillers on bitumen mastic chemistry and rheology
No full textAge hardening of bitumen is one of the key factors determining the lifetime of an asphalt pavement. This study attempts to investigate the effect of different fillers including hydrated lime on mastic ageing. The Thin Film Oven Test (TFOT) was used for short-term ageing, and the Pressure Ageing Vessel (PAV) was used to simulate long-term ageing. The changes due to the ageing are measured by the changes in complex modulus |G*| of the mastics. Chemical changes in the binder were evaluated by the means of Fourier Transform Infrared Spectroscopy (FTIR). Results indicated that different filler mineralogy and properties can significantly affect the rate of oxidative ageing, and this depends mainly on the filler type and concentration. It also showed that hydrated lime reduces the hardening rate more than limestone and granite filler and this correlated with the chemical changes measured by FTIR in terms of rate of change of the carbonyl oxidative products
Thermo-rheological analysis of WMA-additive modified binders
Get PDFThermo-rheological characteristics of unmodified and modified bitumen have significant impacts on the mechanical response of asphalt. This study investigates the impacts of an organic and a chemical Warm Mix Asphalt additive on bitumen thermo-rheological and mechanical characteristics. Modified binders with different concentrations of each additive were studied and analysed comparatively to a 40/60 penetration grade bitumen. Frequency sweep tests were performed at different ageing levels to characterise the Linear Viscoelastic properties. The multiple stress creep and recovery, linear amplitude sweep (LAS) and low temperature creep stiffness tests, together with the Glover–Rowe (G–R) fatigue parameter (determined from fitting of the 2S2P1D model to the complex shear modulus and phase angle master curves) were used to analyse the performance of the binders at critical operating temperatures. The results demonstrated the necessity to analyse the behavior of the studied binders beyond the limits of linear viscoelasticity to better characterise these types of bitumen. The results also indicated that both additives retarded bitumen ageing with the organic additive increasing bitumen elastic response while the chemical additive increased its viscous response. The results also showed an excellent correlation between the G–R parameter and LAS results which suggests the ability to use this parameter in characterising fatigue performance of the studied binders. This also suggests that bitumen fatigue life may be improving over time due to the increased elastic behahviour during ageing so long as a certain critical level of ageing is not reached
Comparison between various bituminous binders modified with crumb tyre rubber
No full textThe aim of this paper is to show how the rheology, the performance and the storage
stability of different bituminous binders, obtained from two bitumens with different
asphaltenes content, change their properties when they are modified with recycled tyre crumb
rubber. Physical, chemical and performance characterisation followed by rheological and
storage stability analyses have been undertaken as the basis for the comparison. The results
of the investigation indicate that bitumen with lower asphaltenes content is more influenced
by the modification with the rubber. However, the modification of the bitumen with the higher
asphaltenes content gives a binder with better performance and storage stability. Moreover,
results shows that the addition of a certain amount of oil extender to the bitumens reduces the
effect of the modification and has no positive effect on storage stability
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