In the oil sand industry, bitumen is separated from sands by aerating the heavy oil so that it can float out of a flotation vessel, leaving the unaerated sands behind. A bubble-against-plate apparatus equipped with a high-speed camera has been developed to record the optical interference patterns of the wetting films formed on a flat surface and subsequently obtain the temporal and spatial profiles of the films offline using the Reynolds lubrication theory. The technique has been used to study the interaction mechanisms between air bubbles and bitumen. It has been found that the film thinning kinetics increases in the order of asphaltene, bitumen, and maltene, and that the kinetics increases sharply with increasing temperature. In addition to obtaining kinetic information, the temporal and spatial profiles of the wetting films have been used to derive appropriate hydrodynamic information that can be used to determine the disjoining pressures (∏) in the wetting films. The results obtained in the present work show that ∏ < 0 for maltene and bitumen, while ∏ > 0 for asphaltene at temperatures in the range of 22 to 80 °C. The disjoining pressure data have been analyzed by considering the contributions from the hydrophobic and steric forces in addition to the classical DLVO forces. It has been found that the hydrophobic force increases with increasing temperature, which corroborates well with contact angle data. Dynamic contact angle measurements show that air bubbles attach on bitumen with relatively small contact angles initially but increase sharply to >90° . The extent and the kinetics of contact angle change increase sharply with increasing temperature. These findings suggest that the primary role of temperature may be to increase iii bitumen hydrophobicity and hence hydrophobic force, which is the driving force for bubblebitumen interaction. A thermodynamic analysis carried out on the basis of the Frumkin-Derjaguin isotherm suggests that the disjoining pressure will remain positive (and hence no flotation) until the hydrophobic force becomes strong enough (due to temperature increase) to overcome the positive disjoining pressure created during the course of bitumen liberation. / Ph. D.

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The pavement construction industry aims to reduce its Greenhouse Gas (GHG) emissions by investigating various energy efficient practices. The industry has focused on reducing energy consumption by producing Warm Mix Asphalt (WMA) surfacing materials that are workable at lower temperatures in relation to Hot Mix Asphalt (HMA), as a means to reduce carbon emissions. Half-Warm Foamed Bitumen Mixtures (HWF) is a relatively new material and is produced at temperatures below 100°C. This translates to large energy savings to overcome the latent heat of steam when exceeding 100°C. The characteristics of HWF mixes are a compromise between those of Foamed Bitumen Stabilised material (BSM-foam) and HMA characteristics. These include to a limited extent the improved tensile strength, particle coating and durability of HMA; and the shear strength of BSM-foam. The use of microwave technology as an efficient heating method to produce improved engineering properties of BSM-foam is proposed in this study. The benefits include energy saving due to its volumetric heating capability as well as rapid heating which improve productivity when using suitable materials. The aspect of recycling material brings forth further energy saving and emissions reduction when reusing materials. The portability of the in-plant recycling machines is an ideal candidate with logistical advantages to implement microwave generators to produce HWF mixes. This study is subdivided into four parts as it progressively investigates the potential to heat aggregates and produce HWF material. Firstly it investigates the heating potential of four aggregates, namely Hornfels, Quartzite, Eucrite, Granite and Reclaimed Asphalt (RA) at various moisture contents using a microwave apparatus. The second part discusses the thermodynamics of the preliminary investigation to provide insight into the third part, the Primary Investigation. The primary investigation evaluates the tensile strength and shear properties of two material blends by respectively implementing Indirect Tensile Strength (ITS) and monotonic triaxial tests on specimens. The two blends were a combination of RA and crushed hornfels. The fourth and final part evaluates the HWF properties in relation to those of the equivalent BSM-foam product by means of a pavement analysis. The highest laboratory production temperature achieved was depicted by the material properties, microwave power capability and production rates. This temperature was consistently recorded at 50°C which theoretically simulates an in-field production rate of approximately 25 tons per hour. ITS test results indicate 100% increase in tensile strengths and an increase in compaction density for the HWF mixes. Large reduction in moisture contents is also observed after curing in relation to BSM-foam. The benefits in improving a layer within a pavement structure have an effect on the pavement’s overall performance. This could assist in reducing the requirement for premium layers e.g. thickness of HMA within the structure, thereby further assisting energy conservation. The evaluation of the microwave heated HWF mixes can be considered economical if designed with a purpose to meet the thermal dynamic requirements of a material considering the microwaves volumetric potential. / AFRIKAANSE OPSOMMING: Die plaveisel konstruksie-industrie poog om hul kweekhuisgas (KHG) uitskeiding te verlaag deur verskeie energie doeltreffende metodes te ondersoek. Die industrie fokus op die vermindering van energie-verbruik deur middel van die produksie van Warm Mengsel Asfalt (WMA) oppervlak materiale wat werkbaar is in laer temperature in verhouding tot “Hete Mengsel Asfalt (HMA)” as `n metode om koolstof uitskeiding te verlaag. Half-Warm Skuim-Bitumen Mengsels (HWS) is `n relatief nuwe materiaal en word vervaardig onder 100 °C. Dit lei tot groot energie besparings en oorkom sodoende die latente hitte van stoom wanneer temperature van 100 °C oorskry word. Die karakter-eienskappe van HWS mengsels is `n kompromie tussen Skuim-Bitumen Gestabiliseerde materiaal (BSM-S) en HMA eienskappe. Dit sluit tot `n beperkte mate in die verbeterde spankrag, partikel bestryking; en die skeer krag van BSM-S. Die gebruik van mikrogolf-tegnologie as effektiewe verwarmingsmetode vir verbeterde ingenieurseienskappe van BSM-S word voorgestel in hierdie studie. Die voordele sluit in energie besparing as gevolg van die volumetriese verwarmingsvermoë sowel as snel verhitting wat produktiwiteit verbeter tydens die gebruik van gepaste materiale. Die gebruik van herwinde materiaal bring verdere energiebesparing en uitskeiding-vermindering mee. Die draagbaarheid van binne-aanleg herwinningsmasjinerie is ‘n ideale kandidate met logistieke voordele vir die installering van mikrogolf-opwekkers vir die produsering van HWS mengsels. Dié studie word onderverdeel in vier dele terwyl dit toenemend ondersoek instel na die potensiaal van hitte versameling asook die produksie van HWS stowwe. Eerstens ondersoek dit die verwarmingspotensiaal van vier versamelings naamlik horingsteen, kwartsiet, eukrite, graniet en Herwinde Asfalt (HA) teenoor verskeie vogskattings-mikrogolf aperate. Die tweede deel bespreek die termodinamika van die voorlopige ondersoek om insig te bied vir die derde deel, die primêre ondersoek. Die primêre ondersoek evalueer die rekbaarheid en skeereienskappe van twee materiaal-mengsels van ITS en monotoniese drieassige toetse onderskeidelik op verskillende monsters. Die twee mengsels was `n kombinasie van HA en gemaalde horingsteen. Die vierde en finale deel evalueer die HWS eienskappe in verhouding tot die van die ekwivalente BSM-S produk deurmiddel van `n sypad-analise. Die hoogste laboratoriumproduksie temperature wat bereik was, was uitgebeeld deur die materiaal-eienskappe, mikrogolf krag kapasiteit en produksiekoers. Hierdie temperature was deurlopend aangeteken teen 50 °C wat `n teoretiese voorstelling is van `n binneveld produksie tempo van ongeveer 25 ton per uur. ITS toets resultate wys `n 100 % verhoging in spankrag asook `n toename in kompakte vir die HWS mengsels. Groot afname in voginhoud is ook waargeneem na bewerking in verhouding tot BSM-S. Die voordeel verbonde aan die verbetering van `n lag binne `n plaveisel-struktuur, het `n impak op die plaveisel se algemene uithoubaarheid. Dit kan bydra tot `n verlaging in die vereiste binne die struktuur en verdere bydra tot energie besparing. Die evaluering van mikrogolf verhitte HWS stowwe kan as ekonomies beskou word wanneer dit doelgerig vervaardig word om te voldoen aan die termodinamika vereistes van `n materiaal, wanneer die mikrogolf volumetriese potensiaal in ag geneem word.

Polymer-modified bitumen (PMB) is a high-performance material for road construction and maintenance. But its storage stability and phase separation behaviour are still not sufficiently understood and need to be studied toward a more successful and sustainable application of PMB. In this thesis, the equilibrium thermodynamics and phase separation dynamics of PMB are investigated with the aim at a fundamental understanding on PMB storage stability and phase separation behaviour. The development of polymer modifiers for paving bitumen is reviewed. The phase separation process in unstable PMBs is captured by fluorescence microscopy at the storage temperature (180 °C). A coupled phase-field model of diffusion and flow is developed to simulate and predict the PMB storage stability and phase separation behaviour. The temperature dependency of PMB phase separation behaviour is modelled by introducing temperature-dependent model parameters between 140 °C and 180 °C. This model is implemented in a finite element software package and calibrated with the experimental observations of real PMBs. The results indicate that storage stability and phase separation behaviour of PMB are strongly dependent on the specific combination of the base bitumen and polymer. An unstable PMB starts to separate into two phases by diffusion, because of the poor polymer-bitumen compatibility. Once the density difference between the two phases becomes sufficiently significant, gravity starts to drive the flow of the two phases and accelerates the separation in the vertical direction. The proposed model, based on the Cahn-Hilliard equation, Flory-Huggins theory and Navier-Stokes equations, is capable of capturing the stability differences among the investigated PMBs and their distinct microstructures at different temperatures. The various material parameters of the PMBs determine the differences in the phase separation behaviour in terms of stability and temperature dependency. The developed model is able to simulate and explain the resulting differences due to the material parameters. The outcome of this study may thus assist in future efforts of ensuring storage stability and sustainable application of PMB. / Polymermodifierade bitumen (PMB) är ett högpresterande material för väganläggning och underhåll. Men PMB:s lagringsstabilitet och fassepareringsegenskaper är inte tillräckligt förstådda än och behöver studeras för en mer framgångsrik och hållbar användning av PMB. I denna avhandling studeras termodynamisk jämvikt och fasseparation av PMB med målsättning att uppnå en grundläggande förståelse av PMB:s lagringsstabilitet och fassepareringsegenskaper. Utvecklingen av polymermodifierade bitumen sammanfattas. Fasseparationsprocessen av instabil PMB:s studeras med hjälp av fluorescens mikroskopi vid lagringstemperatur (180 °C). En kopplad fas-fälts modell som beskriver diffusion och flöde har utvecklats för att simulera och förutsäga PMB:s lagringsstabilitet och fassepareringsegenskaper. Temperaturberoendet hos PMB:s fasseparation har beskrivits genom att införa temperaturberoende modellparametrar mellan 140 °C och 180 °C. Denna modell är införd i ett finit element program och kalibrerad med experimentella observationer på verkliga PMB. Resultaten indikerar att lagringsstabiliteten och fasseparationen hos PMB är starkt beroende av den specifika kombinationen av basbitumen och polymer. En instabil PMB börjar separera i två faser genom diffusion, beroende på dålig bitumen-polymer kompatibilitet. När skillnaden i densitet mellan de två faserna blir tillräckligt stor kommer gravitationen att driva flödet av de två faserna och accelerera separationen i vertikalled. Den föreslagna modellen, baserad på Cahn-Hilliards ekvation, Flory-Huggins teori och Navier-Stokes ekvation, kan beskriva stabilitetsskillnaderna mellan de undersökta PMB:erna och deras distinkta mikrostruktur vid olika temperaturer. De olika materialparametrarna hos PMB bestämmer skillnaden i fassepareringsegenskaper i termer av stabilitet och temperaturberoende. Den utvecklade modellen kan simulera och förklara de resulterande skillnaderna på grund av materialparametrarna. Resultatet av denna studie kan bidra till att säkerställa lagringsstabilitet och hållbara applikationer för PMB. / <p>QC 20161102</p>

For some time, sustainability has been the major principle of development across the globe, and all aspects of society are somehow affected by the concept. Companies are faced with stricter regulations and are forced to look for solutions to reduce their environmental impact. A key challenge in society is reducing dependence on fossil fuels in favour of renewable materials. The asphalt industry is a sector that has a substantial environmental impact where one of the main components of asphalt is the binder, bitumen, which is produced from petroleum. One prominent alternative with notable binding capabilities, which resembles the chemical structure of bitumen, is lignin. The work on substituting bitumen with lignin has come the furthest in the Netherlands, where they have been able to substitute 50 % of bitumen with lignin. Several demonstration roads have also been laid, and extensive research on the concept is ongoing. This study was conducted with the Research Institutes of Sweden (RISE) and the LignoCity initiative. The study aims to examine the current technical- and business market situation of lignin-based asphalt, and through this, present a roadmap for the introduction of lignin-based asphalt to the Swedish market. The research method is qualitative in the form of a case study with semi-structured interviews. The gathered data was analysed and presented through the processes of thematic analysis, and a systematic combining approach was utilized throughout the study. The study highlights both obstacles and potentials for the introduction of lignin-based asphalt to the Swedish market. The main obstacles were found to be the need for long-term testing and evaluation in Swedish climate and conditions. Passive manufacturers hesitant to invest in the concept, and buyers restrained by regulations also act as significant barriers. The findings suggest that projects and collaborations between actors on the market are necessary to encourage new developments. Procurement procedures and tax-policies should also be amended to favour sustainable solutions. Benefits such as carbon sequestration, noise reduction, and lower rolling resistance should be emphasized.

This dissertation presents the results of research undertaken for the characterization of bitumen and mastic which are constituents of Hot Mix Asphalt (HMA). The results of a large number of Dynamic Shear Rheometer (DSR) tests performed in the Laboratory of the Institute for Pavement Engineering at the TU Dresden form the background material for this work. The major objectives of this PhD research work were to gain a fundamental understanding about the mechanical behaviour of bitumen and mastic. The DSR tests undertaken included frequency sweeps for rheological behaviour, single stress creep recovery test (SSCR) for permanent deformation behaviour, Dresden cryogenic test (DDCT) for low temperature performance and fatigue testing with column cylindrical specimen. Selected tests were carried out on bitumen and mastic also to investigate the sensitivity of the materials to ageing. The frequency sweep data was also modelled using an appropriate rheological model to derive rheological data over a large frequency and temperature range. Based on the tests conducted, particular chosen parameters calculated were synthesized into a performance diagram which was developed within the framework of the dissertation. This was the main outcome of the PhD research work, which allows for optimum bitumen and mastic selection and ranking in terms of overall performance and specific desired criteria. Since this dissertation is a cumulative dissertation, it has been divided into three distinct parts. The first part forms a framework of the research undertaken and justifies the need and use of the dissertation in the future, along with explaining the test procedures in detail and resulting performance diagram developed using the data of three bitumen of the same penetration grade. The main part involves the published research – four journal papers and one chapter published in conference proceedings. The first paper uses the method developed to study one base bitumen and corresponding mastics with Limestone, Dolomite, Rhyolite and Granodiorite fillers. Other than understanding how fillers influence different mechanical properties, a main finding was that the specific surface area of the filler was the most sensitive parameter affecting the mechanical response of the mastics. Also, it was observed that the mastic prepared with Granodiorite filler showed the best fatigue and rutting resistance for this particular bitumen. Hence, the procedure could help identifying optimum filler-bitumen relations in advance. The second paper was about crumb rubber modified bitumen. This involved the study of four materials – one base bitumen and two different types of crumb rubber added different proportions. The results indicated an improvement in all performance-related properties by crumb rubber addition in bitumen and further allowing the ranking of materials. The third paper studied the feasibility of recycling a waste Ceramic powder as a filler alternative and it was found to have more superior performance than the commonly used Limestone filler. The fourth paper considers how addition of one filler, Limestone, to three differently-sourced bitumen of the same grade affects the properties of mastics. This study further emphasises the need to study mastics and predetermine the optimum filler-bitumen combinations that could avoid long-term maintenance costs. The fifth paper emphasises the need to move from current empirical testing to more specialised testing for bitumen by presenting different performance based results for three commonly used bitumen of penetration grade 50/70 that showed significant differences in the performance parameters. The third part of the dissertation is an additional section that includes the paper that was submitted to a journal and is currently in the second round of reviews under review. This paper studies fatigue behaviour of bitumen at different temperatures and frequencies using the Dissipated Energy (DE) approach. Fatigue functions were determined based on the relation between DE and the load cycle at failure. Based on these, a temperature was found to be a ‘frequency-free transition temperature’ for this bitumen as the failure lines at this temperature were overlapping at both frequencies tested. / Diese Dissertation präsentiert die Ergebnisse einer Forschungsarbeit zur Charakterisierung von Bitumen und Mastix, die als Bestandteil von Asphaltgemischen verwendet werden. Die Ergebnisse einer großen Anzahl von Dynamisches Scherrheometer (DSR) Versuche, die im Labor des Instituts für Stadtbauwesen und Straßenbau der TU Dresden durchgeführt wurden, bilden die Grundlage für diese Arbeit. Das Hauptziel dieser Dissertation bestanden darin, ein grundlegendes Verständnis über das mechanische Verhalten von Bitumen und Mastix zu gewinnen. Die durchgeführten DSR Versuche umfassten Frequenzsweeps für die Erfassung des rheologischen Verhaltens, Single Stress Creep Recovery Versuche (SSCR) für die Charakterisierung des permanenten Verformungsverhaltens, Dresden Cryogenic (DDCT) Versuche zur Erfassung des Verhaltes bei niedrigen Temperaturen und Ermüdungsversuche. Des Weiteren wurden ausgewählte Versuche am Bitumen und Mastix durchgeführt, um die Alterungsempfindlichkeit der Materialien zu untersuchen. Die Ergebnisse der Frequenzsweeps wurden ebenfalls mit einem geeigneten rheologischen Ansatz modelliert, um rheologische Charakteristiken über einen großen Frequenz- und Temperaturbereich abzuleiten. Schließlich wurde im Rahmen der Dissertation ein Performancediagramm für Bitumen und Mastix entwickelt. Auf der Grundlage der durchgeführten DSR-Versuche konnten Parameter für dieses Performancediagramm synthetisiert werden. Da es sich bei dieser Arbeit um eine kumulative Dissertation handelt, wurde erfolgte eine Aufgliederung in drei Teile. Der erste Teil der Arbeit umfasst eine Zusammenfassung der durchgeführten Forschungsarbeiten. Insbesondere werden die durchgeführten DSR Versuche detailliert erläutert und das entwickelte Performancediagramm am Beispiel von drei verschiedenen Bitumen 50/70 dargestellt. Der Hauptteil der Arbeit umfasst vier Veröffentlichungen in Fachzeitschriften sowie ein Konferenzbeitrag. Die erste Beitrag widmet sich der Untersuchung des Einflusses von verschiedenen Füllern (Kalkstein-, Dolomit-, Rhyolith- und Granodioritfüller) auf das Verhalten von Mastix unter Verwendung desselben Bitumens 50/70. Dabei hat sich gezeigt, dass die spezifische Oberfläche des Füllers der entscheidende Parameter ist, der das Verhalten von Mastix beeinflusst. Es wurde auch beobachtet, dass der mit Granodiorit-Füller hergestellte Mastix die beste Ermüdungs- und Spurrinnenbeständigkeit für dieses spezielle Bitumen zeigte. Daher könnte das in der Veröffentlichung vorgestellte Verfahren dazu beitragen, das optimale Verhältnis zwischen Füller und Bitumen im Voraus zu ermitteln. Die zweite Veröffentlichung befasst sich mit gummimodifiziertem Bitumen. Dabei wurden vier Materialien untersucht - ein Grundbitumen und zwei verschiedene Arten von Gummigranulaten mit unterschiedlichen Anteilen. Die Ergebnisse zeigten eine Verbesserung aller leistungsbezogenen Eigenschaften durch den Zusatz von Gummigranulat im Bitumen. Die dritte Veröffentlichung untersuchte die Eignung von Keramikmehl als Füller für Asphaltgemische. Dabei konnte festgestellt werden, dass dieser Keramikfüller zu besseren Eigenschaften des Mastix für das verwendete Bitumen im Vergleich zu einem Kalksteinfüller führt. Die vierte Veröffentlichung befasst sich hier mit der Frage, wie sich die Zugabe eines Füllers (Kalkstein-Füller) zu drei Bitumen unterschiedlicher Provenienz, jedoch derselben Sorte auf die Eigenschaften von Mastix auswirkt. Diese Studie unterstreicht weiter die Notwendigkeit, Mastix zu untersuchen um die optimalen Füller-Bitumen-Kombinationen zu bestimmen. Die fünfte Veröffentlichung betont die Notwendigkeit, von den derzeitigen empirischen Versuchen an Bitumen, wie z.B. Ring und Kugel Versuch zu performance-orientierten Versuchen für Bitumen überzugehen. Am Beispiel der Ergebnisse von DSR Versuchen an drei verschiedenen Bitumen 50/70 wird gezeigt, dass diese Bitumen sehr unterschiedliches mechanisches Verhalten aufweisen. Verdeutlicht wird dieser Sachverhalt in einem Performance-Diagramm, welches ausführlich in der Veröffentlichung diskutiert wird. Der dritte Teil der Dissertation beinhaltet eine Veröffentlichung, die bei Fachzeitschriften eingereicht wurde und sich derzeit im Review befindet. Zusätzlich wurde in dieser Arbeit das Ermüdungsverhalten von Bitumen bei verschiedenen Temperaturen und Frequenzen mit Hilfe des Dissipated Energy (DE)-Ansatzes untersucht. Die Versagenslinien wurden auf der Grundlage der Beziehung zwischen DE und der Lastwechselzahl beim Versagen entwickelt. Auf dieser Grundlage wurde eine Temperatur als 'frequenzfreie Übergangstemperatur' für dieses Bitumen ermittelt, da sich die Ermüdungsfunktionen bei dieser Temperatur bei beiden getesteten Frequenzen überlappen.

Asphalt is a material used to lay several different types of roads. It has been used in Sweden for more than 200 years. During these years, the work with asphalt has changed, ingredients have been replaced and manufacturing methods have been updated. In modern asphalt, bitumen is used as a binder. It is extracted from crude oil, which is a fossil substance that will not exist forever and also has a bad impact on the environment, therefore people have worked to find new ideas. This report will be about two methods of working for a more sustainable future. The construction and real estate company NCC works with asphalt recycling and the construction company Peab is researching if lignin can be used as a binder. The purpose of this report is to find out which of these methods leaves the least climate footprint. Asphalt is 100% recyclable, but to only use recycled asphalt in new production is not possible, as the quality does not measure up. Lignin is obtained from residual products from the forest industry, which means it is fossil-free. The work with lignin is currently at the research level, so it is not used as standard yet. In order to obtain a result, interviews with people who work at Peab and NCC have been conducted. These people have been able to answer our questions as they work on the topic. Recycling has been used for several decades, therefore the work has come significantly further than the work with lignin which has only been in progress since 2018. For this reason it is difficult to determine which method is most sustainable in the long run. What has been concluded is that when lignin is mixed with bitumen, the durability increases, hence the life-span. We have come to the conclusion that both companies think it is important with recycling, but also that they can see a future with a shortage of recycled asphalt. / Asfalt är ett material som används för att lägga flera olika typer av vägar. Den har använts i Sverige i mer än 200 år. Under dessa år har arbetet med asfalt förändrats, man har bytt ut innehåll och uppdaterat tillverkningsmetoder. I modern asfalt används bitumen som bindemedel. Den utvinns ur råolja vilket är ett fossilt ämne som inte kommer finnas för evigt och har även dålig påverkan på miljön, därför jobbar man för att hitta nya idéer. Denna rapport kommer handla om två metoder där man arbetar för en mer hållbar framtid. Återvinning av asfalt som bygg- och fastighetsföretaget NCC använder sig utav och lignin som bindemedel något som bygg- och anläggningsföretaget Peab forskar på. Syftet med denna rapport är att ta reda på vilken av dessa metoder som lämnar minst klimatavtryck. Asfalt är 100% återvinningsbar men att endast använda återvunnen asfalt i nyproduktion är inte möjligt, då kvaliteten inte håller måtten. Lignin får man fram ur restprodukter från skogsindustrin, den är alltså fossilfri. Arbetet med lignin är i nuläget på forskningsnivå, därför används den inte som standard ännu.  För att få fram ett resultat har bland annat intervjuer med personer som jobbar på Peab och NCC gjorts. Dessa personer har kunnat besvara på våra frågor då de arbetar med ämnet. Återvinning har använts i flera årtionden därför har arbetet kommit betydligt längre än arbetet med lignin som har pågått sedan 2018. Av denna anledning är det svårt att i nuläget avgöra vilken metod som är mest hållbar i längden. Det man har kommit fram till är att när lignin blandas med bitumen ökar hållbarheten, därmed livslängden. I slutsatsen kommer vi fram till att båda företag tycker det är viktigt med återvinning, men även att de kan se en framtid med brist på returasfalt.

Cold mix asphalt (CMA) emulsion technology could become an attractive option for the road industry as it offers lower startup and equipment installation costs, energy consumption and environmental impact than traditional alternatives. The adhesion between bitumen and aggregates is influenced by diverse parameters, such as changes in surface free energies of the binder and aggregates or the presence of moisture or dust on the surface of aggregates, mixing temperatures, surface textures (including open porosity), nature of the minerals present and their surface chemical composition, as well as additives in the binder phase. The performance of cold asphalt mixtures is strongly influenced by the wetting of bitumen on surfaces of the aggregates, which is governed by breaking and coalescence processes in bitumen emulsions. Better understanding of these processes is required. Thus, in the work this thesis is based upon, the surface free energies of both minerals/aggregates and binders were characterized using two approaches, based on contact angles and vapor sorption methods. The precise specific surface areas of four kinds of aggregates and seven minerals were determined using an approach based on BET (Brunauer, Emmett and Teller) theory, by measuring the physical adsorption of selected gas vapors on their surfaces and calculating the amount of adsorbed vapors corresponding to monolayer occupancy on the surfaces. Interfacial bond strengths between bitumen and aggregates were calculated based on measured surface free energy components of minerals/aggregates and binders, in both dry and wet conditions. In addition, a new experimental method has been developed to study bitumen coalescence by monitoring the shape relaxation of bitumen droplets in an emulsion environment. Using this method, the coalescence of spherical droplets of different bitumen grades has been correlated with neck growth, densification and changes in surface area during the coalescence process. The test protocol was designed to study the coalescence process in varied environmental conditions provided by a climate-controlled chamber. Presented results show that temperature and other variables influence kinetics of the relaxation process. They also show that the developed test procedure is repeatable and suitable for studying larger-scale coalescence processes. However, possible differences in measured parametric relationships between the bitumen emulsion scale and larger scales require further investigation. There are several different research directions that can be explored for the continuation of the research presented in this thesis. For instance, the rationale of the developed method for analyzing coalescence processes in bitumen emulsions rests on the assumption that the results are applicable to large-scale processes, which requires validation. A linear relationship between the scales is not essential, but it is important to be able to determine the scaling function. Even more importantly, qualitative effects of the investigated parameters require further confirmation. To overcome the laboratory limitations and assist in the determination of appropriate scaling functions further research could focus on the development of a three-dimensional multiphase model to study coalescence processes in more detail, including effects of surfactants, pH and other additives such as mineral fillers and salts. Additionally, better understanding of the breaking process and water-push out could help significantly to optimize CMA mix design. Different methods, both numerical and experimental could be explored for this. / Cold mix asphalt (CMA) eller kall asfaltbetong med hjälp av emulsionsteknik kan vara ett attraktivt alternativ för vägbyggnadsindustrin då det möjliggör lägre uppstart- och investeringskostnader, lägre energiförbrukning och mindre miljöpåverkan än traditionella alternativ. Adhesionen mellan bindemedel och stenpartiklarna påverkas av ett flertal parametrar, så som förändring i fri ytenergi hos både bindemedel och partiklar i närvaro av fukt eller damm på stenytorna, blandningstemperatur, yttextur (inklusive ytporositet), mineralegenskaper och ytornas kemiska sammansättning lika väl som tillsatsmedel i bindemedlen. Beteendet hos kall asfaltbetong är starkt påverkad av vätningsegenskaperna hos bindemedlet när det kommer i kontakt med stenmaterialet och detta i sin tur är beroende på bitumenemulsionens brytegenskaper och förmåga att blandas. Bättre förståelse av dessa processer är av största vikt. I detta arbete är avhandlingen baserad på fri ytenergi hos både mineraler/aggregat och bindemedel, baserat på kontaktvinkel och på ångabsorptionsmetoder. Den exakta specifika ytan hos fyra typer av aggregat och sju mineraler undersöktes med en metod baserad på BET (Brunauer, Emmett och Teller):s teorier genom att mäta den fysiska adsorptionen av utvalda gaser på ytorna och beräkna mängden adsorberad ånga som korresponderade mot ytlagret. Styrkan hos kontaktytornas bindning mellan bindemedlet och stenaggregaten beräknades baserat på mätningar av den fria ytenergin hos bägge ingående komponenterna, dels i torrhet dels i våta omgivningar. Som tillägg har en ny experimentell metod utvecklats för att studera bitumens blandbarhet genom att studera bitumendroppars relaxation i en emulsionsmiljö. Genom att använda denna metod har korelationen mellan sväriska droppar av bitumen undersökts mot förändringen i ytans area under blandningsprocessen. Testprotokollet utformades för att studera blandningsprocessen i varierande miljöer i en klimatkammare. Presenterade resultat visar att temperatur och andra variabler påverkar de kinetiska förhållandena vid relaxationsprocessen. De visar även att den utvecklade testmetoden är repeterbar och passar för studier av storskaliga blandningsprocesser. Det bör dock påpekas att vidare studier krävs för att påvisa skillnaderna mellan bitumenemulsionsskalan och större skalor. Framtida forskning kommer att koncentreras på utveckling av tredimensionella multifas­modeller för att studera blandningsförlopp på en mer detaljerad nivå, inkluderande effekter på ytaktiva ämnen, pH-värden och andra additativ så som mineralfiller och salt. Som tillägg kommer nyttan av nya karaktäriseringsmetoder att utvärderas, så som lågvikelspridning av neutroner eller kombinationer av röntgen, neutronradiologi och datortomografi, för att studera brytmekanismer hos bitumenemulsioner vid kontakt med mineraler och aggregat. / <p>QC 20160901</p>

Thesis (PhD)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: The increased use of reclaimed asphalt (RA) in Bitumen Stabilised Materials (BSMs), shortcomings in the existing design guidelines and manuals and ongoing developments in the concepts and understanding of these materials require further research into the fundamental properties and behaviour of BSMs. The state-of-the-art of foamed bitumen techniques is reviewed in the literature study. Current best practices in the design of BSMs and pavements incorporating such materials are also included in this literature study. Shortcomings and areas for further improvement of the design practice have been identified. With new environmental legislation, the importance of BSM technology including RA as an environmentally-friendlier and more sustainable construction technique is set to increase in the coming years. Changes in the behaviour of materials and failure mechanisms of BSM mixes are long-term phenomena. This implies that the study of the physico-chemical and mechanical properties of the mixes with increasing amount of RA is vital. Therefore, fundamental understandings of moisture damage and thermo-physical characteristics, which are related to material properties, are required. The main objective of this study is to advance BSM technology by assessing the influence of the selected materials on durability behaviour, temperature distribution and long-term performance in all phases of application (i.e. mix design, construction, and in-service condition). This study begins with a comprehensive literature review of research dealing with the interactions between RA and mineral aggregates. The properties of RA and mineral aggregates were reviewed. This was followed by a review into the mechanical properties of BSM-foam mixes with high percentage of RA and its durability performance. Factors influencing the temperature gradient of BSMs were then identified. Achieving a better understanding of the fundamental performance properties and temperature influence on the behaviour of BSMs with high percentage of RA is one of the key factors of this research, with a view to using the extended knowledge for improvements to current mix design and structural design practices. Finally, the fundamental theories on thermo-conductivity and the mechanical properties of the BSM were used to create a relationship between temperature and mechanical properties in a pavement section. A laboratory testing programme was set up to study the properties and behaviour of BSMs and to establish links with the compositional factors, i.e. the type of binder used, the percentage of RA in the mix and the addition of a small amount of cement as active filler. BSMs were blended in three different proportions of RA and good quality crushed stone materials: 100% RA (with 2 % bitumen content), 50% RA and 50% G2 Hornfels crushed stone (with 2.1% bitumen content) and 100% G2 (with 2.3 % bitumen content). Tri-axial testing was carried out to determine shear parameters, resilient modulus and permanent deformation behaviour, while brushing testing was carried out to determine the possible durability performance of the BSMs. The mixture durability in terms of moisture damage was investigated. Temperature data were collected and a model to accurately simulate the temperature distribution in the BSMs was identified and proposed for further investigation and validation. It was found from the laboratory temperature data collected in this study that the temperature gradient varied according to the depth of the BSMs. A considerable part of the efforts of this study were dedicated to characterise and model the temperature distribution in a pavement section, taking into account the mechanical properties and performance of the BSMs at different temperature layers. The study provides an insight into fundamental mechanical performance, material durability properties, and the thermal capacity and conductivity of the BSM-foam mixes with high percentage of RA. This will assist in improving the current procedure for selection, combining and formulation of the mix matrices for BSMs. In addition, the study provides guidelines that will enable practitioners to confidently understand the relationship between temperature gradient and mechanical behaviours of BSM-foam pavement section. The specific durability-related issues addressed in this study are substance for future research. / AFRIKAANSE OPSOMMING: Die toenemende gebruik van herwonne asfalt (Engels: reclaimed asphalt (RA)) in bitumen gestabiliseerde materiaal (Engels: Bitumen Stabilised Materials (BSMs)), tekortkominge in die bestaande ontwerpriglyne- en handleidings en deurlopende verbeteringe in die konsepte en begrip van hierdie material vereis verdere navorsing oor die fundamentele eienskappe en gedrag van BSM. In die literatuurstudie word die huidige stand van kennis van die ontwerp van skuimbitumentegnieke ondersoek. Die literatuurstudie dek ook die huidige beste praktyke in die ontwerp van BSM en plaveisels wat hierdie materiale insluit. Tekortkominge en areas van verdere verbetering in die ontwerppraktyke is geïdentifiseer. Onlangse omgewingswetgewing verhoog die belangrikheid van BSM tegnologie, insluitend RA, as ‘n meer omgewingsvriendelike en volhoubare konstruksie-tegniek. Hierdie faktor sal in die toekoms al hoe belangriker word. Die verandering in die gedrag van materiaal en die falingsmeganismes van BSM mengsels is langtermynverskynsels. Dit impliseer dat die studie van die fisio-chemiese en meganiese eienskappe van mengsels met toenemende verhoudings van RA van kardinale belang is’n Fundamentele begrip van die vogskade en temo-fisiese eienskappe, wat verwant is aan die materiale se eienskappe, word vereis. Die primêre doelwit van die studie is die bevordering van BSM tegnologie deur die invloed van die geselekteerde materiale op duursaamheid, temperatuurverspreiding en langtermyn gedrag in al die fases van toepassing (mengselontwerp, konstruksie en in-dienstoestand) te bepaal. Die verhandeling begin met ‘n omvattende literatuuroorsig van navorsing oor die interaksie tussen RA en mineraalaggregate. Die eienskappe van RA en die mineraalaggregate word bespreek. Dit word gevolg deur ‘n oorsig van die meganiese eienskappe van die BSM-skuimbitumenmengsels met ‘n hoë persentasie RA en die duursaamheidgedrag daarvan. Faktore wat die temperatuurgradient van BSM beïnvloed word dan aangetoon. ‘n Beter begrip van die fundamentele gedragseienskappe en die invloed van temperatuur op die gedrag van BSM met ‘n hoë persentasie RA is een van die sleutelfaktore van hierdie navorsing. Dit het ten doel om die uitgebreide kennis te gebruik om huidige mengselontwerp en strukturele ontwerppraktyke te verbeter. Laastens is die fundamentele teorie van termogeleiding en die meganiese eienskappe van BSM gebruik om ‘n verhouding tussen temperature en meganiese eienskappe in ‘n plaveiselsnit te ontwikkel. ‘n Laboratoriumtoetsprogram is opgestel om die eienskappe en gedrag van BSM te bestudeer en om verwantskappe tussen samestellende faktore soos die tipe bindmiddel gebruik, die persentasie RA in die mengsel en die toediening van klein hoeveelhede sement as aktiewe vuller te bepaal. BSM is in drie verskillende verhoudings van RA en goeie gehalte gebreekte klipmateriaal vermeng: 100% RA met 2 % bitumen, 50% RA en 50 % G2 Hornfels gebreekte klip met 2.1 % bitumen en 100% G2 met 2.3 % bitumen. Drie-assige druktoetse is gebruik om skuifsterkteparameters, elastiese modulus en permanente vervormingsgedrag te bepaal. Borseltoetse is gebruik om die duursaamheidgedrag van BSM te bepaal. Die mengsels se duursaamheid is ook in terme van vogskade ondersoek.

Thesis (MScEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Surface seals are widely used in South Africa. There are a number of reasons which include affordability, versatility and durability. There are, however, in some cases problems with stone loss that can lead to a shortened lifespan of the pavement. The loss of aggregate chippings in surface seals poses a major problem in the seal pavement industry. This study aims to identify the influencing factors that lead to these adhesive failures as well as to find optimum combinations of binders and aggregates at various conditions. Various binders commonly used in South African surface seal construction will be tested using the Bitumen Bond Strength (BBS) test method. The binders used in the study include 80/100 penetration grade bitumen, elastomer modified bitumen, bitumen rubber, elastomer modified emulsion and cationic rapid setting emulsion. Aggregates used in the study include dolerite, granite and quartzite. The test samples were cured and tested at two temperatures, 15 °C and 35 °C. The samples were also cured for 2, 6 and 24 hours respectively. The study tackles a wide range of variables in order to obtain a good understanding of adhesion properties of surface seals used in South Africa. Tests were repeated at least once to ensure repeatability and in some cases up to four repeats were performed. The loading rate at which the tests were performed had a significant influence on the BBS results. This rate varied which complicated the process of comparing the results. It was therefore decided to unify the loading rates. The BBS results exposed the difference between hot applied binders and emulsions. The former having significant stronger adhesion properties. It was also confirmed by the results that temperature plays a key role in the BBS results due to the visco-elastic properties of bitumen. These influences will be discussed along with others such as aggregate types and curing times. The type of failure is also discussed. Failure can either be adhesive or cohesive, the former being a failure between the aggregate and the binder while the later refers to a failure in the binder itself. The results of other students will also be discussed and compared to the results of this study. These include results of predecessors that tested emulsions as well as results from tests done on fractured aggregate surfaces and precoated aggregates. This study showed very similar results as these from other students, except for tests done with emulsions. It was discovered that the method of curing of the emulsions must be adapted to ensure proper curing of the emulsions. It was found that aggregates did not influence the BBS properties to the same extent as temperature and binder application type. The BBS results of hot applied binders also did not significantly increase as the curing time increased, but the results of emulsions showed some increase. However, the emulsions needed more time to cure properly. / AFRIKAANSE OPSOMMING: Oppervlak seëls word algemeen gebruik in Suid-Afrika. Daar is verskeie redes hiervoor waaronder bekostigbaarheid,veelsydigheid en duursaamheid. Daar is egter in sommige gevalle probleme met klipverlies wat kan lei tot n verkorte leeftyd. Hierdie klipverlies ontstaan as gevolg van verskeie redes of kombinasies daarvan. Die studie beoog om hierdie faktore wat die adhesie eienskappe beïnvloed te identifiseer sowel as om optimum kobinasies van bindmiddels en klipsoorte te bewerkstellig by verkeie kondisies. ‘n Verskeidenheid van bindmiddels wat algemeen in Suid-Afrika gebruik word, word in die studie getoets met die Bitumen Bond Sterkte (BBS) toets metode. Die bindmiddels wat in die studie gebruik word sluit 80/100 penetrasie graad bitumen, elastomeer gemodifiseerde bitumen, bitumen rubber, elastomeer gemodifiseerde emulsie en kationiese snel settende emulsie. Die klipsoorte wat vir die studie gebruikword is doleriet, graniet en kwartsiet. Hierdie gesteentes word algemeen in die praktyk gebruik. Die toets monsters word ook by twee temperature gekuur en getoets. Hierdie temperature is 15 °C en 35 °C. Die toets monsters word ook onderskeidelik vir 2, 6 en 24 uur gekuur. Die studie ondersoek 'n wye verskeidenheid van veranderlikes om sodoende 'n goeie begrip van adhesie eienskappe van die oppervlak seëls wat in Suid-Afrika gebruik word te verkry. Elke toets was ten minste een maal herhaal om herhaalbaarheid te verseker. Sommige toetse was tot 4 keer herhaal. Die belasting tempo van die toetse het ‘n beduidende uitwerking op die BBS resultate as gevolg van die visko-elastiese eienskappe van bitumen. Hierdie tempo het gewissel en dit moeilik gemaak om die resultate te vergelyk. Daarom was daar besluit om die tempo van die toetse te verander na ‘n gelykvormige tempo. Daar was ‘n duidelike verskil in BBS resultate van die warm toegepaste bindmiddels en die emulsies. Die warm bindmiddels het baie hoër BBS resultate gelwer. Dit was ook bevestig in die resultate dat temperatuur ‘n beduidende rol speel in die BBS. Hierdie invloede sal bespreek word tesame met ander, soos klipsoorte en kuring tye. Die tipe versaking word ook bespreek. Versaking kan plaasvind as gevolg van adhesie of cohesie, waar adhesie versaking 'n versaking is tussen die klip en die bindmiddel terwyl cohesie versaking verwys na 'n versaking in die bindmiddel self. Die uitslae van die ander studente sal ook bespreek word en vergelyking word met die resultate van hierdie studie. Dit sluit die resultate van voorgangers in wat emulsies getoets het sowel as die resultate van toetse wat gedoen is op gebreekte klipoppervlaktes en bitumen behandelde klippe. Hierdie studie het baie soortgelyke resultate getoon as dié van ander studente, behalwe vir die toetse wat gedoen was met emulsies. Daar is vasgestel dat die metode van kuring van die emulsies moet aangepas word om behoorlike kuring van die emulsies te verseker. Daar is ook gevind dat klipsoorte nie die BBS eienskappe in dieselfde mate as temperatuur en bindmiddel toepassingstipe beïnvloed het nie. Die BBS resultate van warm aangewende bindmiddels het ook nie aansienlik verhoog soos die kuringstyd toegeneem het nie, maar die resultate van emulsies het wel 'n toename getoon. Die emulsies het wel meer tyd nodig gehad om behoorlik te kuur.

Development of new asphalt technologies to reduce both energy consumption and CO2 production has attracted great interest in recent years. The use of foam bitumen, as one of them, is attractive due to the low investment and production cost. Formation and decay of foam bitumen is a highly dynamic temperature dependent process which makes characterization difficult. In this thesis, new experimental tools were developed and applied for characterizing the foam bitumen during the hot foaming process.  One of the main goals of this study was to improve understanding and characterization of the foam bitumen formation and decay. X-ray radiography was used to study the formation and decay of foam bitumen in 2D representation. The results demonstrate that the morphology of bubble formation depends on the types of bitumen used. Moreover, theoretical investigation based on the 3D X-ray computed tomography scan dataset of bubble merging showed that the disjoining pressure increased as the gap between the bubbles in the surface layer (foam film) decreased with time and finally was ruptured.   Examining the foam bitumen stream right at the nozzle revealed that foam bitumen at a very early stage contains fragmented pieces of irregular size rather resembling a liquid than foam. The result from thermogravimetric analysis demonstrated that residual water content depends on the initial water content, and was found to be between 38 wt% and 48 wt% of the initial water content of 4 wt% to 6 wt%. Moreover the influence of viscosity and surface tension on bubble shape and rise velocity of the bubbles using level-set method was implemented in finite element method. The modeling results were compared with bubble shape correlation map from literature. The results indicated that the bubble shapes are more dependent on the surface tension parameters than to the viscosity of the bitumen, whereas the bitumen viscosity is dominant for bubble rising velocity. / <p>QC 20160303</p>