Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The increasing awareness of climate change causes a growing interest in pavement rehabilitation. Pavement rehabilitation by in-situ stabilisation with bitumen reduces the extraction of natural aggregate resources while enhancing flexibility and durability properties, which lowers maintenance costs over the design-life of the pavement structure. Incorporating Bitumen Stabilised Materials (BSMs) into a pavement structure can therefore have economic and environmental benefits, but more research is needed to fully understand the behaviour and potential of these materials. Stabilising materials with bitumen provides useful properties to pavement layers. The “TG2 2nd Edition, Bitumen Stabilised Materials” was published by the Academy of South Africa in May 2009, which provides a good understanding of the usage of Bitumen Stabilised Materials (BSMs). However, the shrinkage and flexible behaviour of these materials are still not fully understood and therefore more research on these materials is needed. The aim of this project is thus to determine the shrinkage and flexible behaviour of BSMs to incorporate these behavioural types in the revised design method for flexible pavements in the SAPDM. In addition, the influence of several additives on the shrinkage and flexible behaviour of BSMs have been evaluated to get an improved understanding of these properties. The additives included cement (1% and 2% content) and both bitumen emulsion (0.9% and 2.4% content) and foamed bitumen (only 2.4% content). Two linear shrinkage testing methods have been designed to test the shrinkage potential of BSMs, including a beam testing method and a cylindrical testing method. Based on the usage of the shrinkage measurements the applicable method can be used to determine the shrinkage potential of a BSM. The flexibility is a more complex property and was tested using a simple monotonic beam test. The strain-at-break parameter obtained from this test provided an indication of the material flexibility. Slight differences in the trends were observed between beam and cylindrical shrinkage due to specimen geometry, exposed surface area and shrinkage testing direction. Beam specimens initially show swelling when bitumen is added to the mixture and shrinks thereafter. Cylindrical specimens on the other hand show initial shrinkage followed by a slight length increase, where after shrinkage continues. The additives had the same influence on the shrinkage for both the beam and cylindrical specimens. Although all shrinkage measurements were small, an increase in bitumen reduced shrinkage and an increase in cement increased shrinkage. Stabilisation with foamed bitumen rather than bitumen emulsion proved to show less shrinkage, but only in combination with 2% cement. The strain-at-break, dissipated energy and material stiffness calculated from the monotonic beam tests provided a good indication of the flexibility behaviour of BSMs. Higher bitumen content increased the flexibility potential and an increase in cement decreased the flexibility potential of BSMs. This project has provided good insight on both the shrinkage and flexibility behaviour of BSMs, which can be used in the revised copy of the SAPDM. Increased bitumen contents decreases the shrinkage potential and increases the flexibility of a BSM. Increased cement contents on the other hand, increases shrinkage and decreases flexibility of BSMs. The correct combination of cement and bitumen in a BSM can thus provide a material with the wanted flexibility while keeping the shrinkage to a minimum. / AFRIKAANSE OPSOMMING: Die toenemende bewustheid van klimaatsverandering veroorsaak toenemende belangstelling in die rehabilitasie van plaveisels. Plaveisel rehabilitasie deur in-veld stabilisasie met bitumen verminder die ontginning van natuurlike hulpbronne, terwyl die verbetering van buigsaamheid en duursaamheid eienskappe die onderhoudskoste verlaag oor die ontwerp-lewe van die plaveiselstruktuur. Die inkorporasie van Bitumen Gestabiliseerde Materiale (BGM) in 'n plaveisel struktuur kan dus omgewings en ekonomiese voordele inhou. Meer navorsing word wel benodig om die gedrag van hierdie materiale beter te verstaan. Die stabilisering van materiale met bitumen verskaf nuttige eienskappe aan 'n plaveisellaag. Die "TG2 2de Uitgawe, Bitumen Gestabiliseerde Materiale" is gepubliseer deur die Akademie van Suid-Afrika in Mei 2009 en verskaf 'n goeie begrip van Bitumen Gestabiliseerde Materiale (BGM). Die krimpings en buigsaamheid gedrag van die materiaal word wel nog nie ten volle verstaan nie en daarom word meer navorsing oor hierdie materiaal benodig. Die doel van hierdie projek is dus om die krimpings gedrag sowel as die buigsaamheid gedrag van 'n BGM te bepaal en sodoende die kennis te gebruik in die hersiende ontwerp metode vir buigsame plaveisels in die SAPDM. Die invloed van verskeie bymiddels op die krimpings en buigsaamheid gedrag van 'n BGM is ook geëvalueer om 'n beter begrip van hierdie eienskappe te verkry. Die bymiddels sluit sement in (1% en 2% inhoud) asook beide emulsie bitumen (0,9% en 2,4% inhoud) en skuim bitumen (slegs 2.4% inhoud). Twee lineêre krimpings toets metodes was ontwerp om die krimping potensiaal van BGM's te bepaal, wat 'n balk toets metode en 'n silindriese toets metode insluit. Die metode wat gebruik sal word om die krimping van 'n BGM te bepaal moet baseer word op die toepassing waarvoor die krimpings resultate gebruik gaan word. Die buigsaamheid is 'n meer komplekse eienskap en was getoets met behulp van 'n eenvoudige monotoniese balk toets. Die spanning-by-breekpunt waardes wat verkry was vanuit die balktoetse, het 'n goeie aanduiding van die buigsaamheid van die materiaal verskaf. Klein verskille in krimpingstendense tussen balk en silindriese proefstukke is opgemerk tydens die projek en is veroorsaak deur die geometrie van die proefstuk, die blotgestelde oppervlakte asook die rigting van kimp toetsing. Balk proefstukke toon aanvanklike swelling wanneer bitumen bygevoeg is, gevolg deur krimping. Silindriese proefstukke aan die ander kant toon aanvanklike krimping gevolg deur 'n effense toename in lengte, waarna krimping weer plaasvind. Die bymiddles het dieselfde invloed op die krimping van beide die balk en silindriese proefstukke. Alhoewel al die krimpingswaardes baie klein was, het 'n toename in bitumen 'n vermindering in krimping voortgebring en 'n toename in sement het 'n toename in krimping voortgebring. Stabilisasie met skuim bitumen in plaas van emulsie bitumen toon verlaagde krimping, maar slegs in kombinasie met 2% sement. Die spanning-by-breekpunt, verkose energie en materiaal styfheid wat bereken is vanaf die monotoniese balk toets resultate, het 'n goeie aanduiding van die buigsaamheid gedrag van BGM's verskaf. 'n Hoër bitumen inhoud verhoog die buigsaamheid potensiaal van BGM‟s terwyl 'n toename in sement die buigsaamheid potensiaal van BGM's verlaag. Hierdie projek bied goeie insigte vir beide die krimpings en buigsaamheid gedrag van BGM's, wat in die hersiende ontwerp metode van die SAPDM gebruik kan word. Verhoogde bitumen inhoud verminder die krimping potensiaal en verhoog die buigsaamheid van 'n BGM. Verhoogde sement inhoud aan die ander kant, verhoog krimping en verminder buigsaamheid van BGM's. Die korrekte kombinasie van sement en bitumen in 'n BGM kan dus 'n materiaal produseer met die gewenste buigsaamheidseienskappe en terselfde tyd die krimping tot 'n minimum beperk.

Thesis (PhD (Civil Engineering))--Stellenbosch University, 2008. / The cold bituminous mixtures, which are the subject of this study, are obtained by mixing mineral aggregate with either bitumen emulsion or foamed bitumen at ambient temperatures. These techniques are frequently used in Cold In-Place Recycling whereby typically the top 150 – 250 mm of the existing pavement is reworked, as a rehabilitation measure when structural maintenance is required. To differentiate from the cold mixes for surfacing layers the term Bitumen Stabilised Materials (BSM’s) is adopted here. The increased use of BSM’s, 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 BSM’s. Achieving a better understanding of the fundamental performance properties of BSM’s is the main objective of this study, with a view to using the extended knowledge for improvements to current mix design and structural design practices. The state-of-the-art of bitumen emulsion and foamed bitumen techniques is reviewed in a literature study. Current best practices in the design of BSM’s and pavements incorporating such materials is also included in this literature study. Shortcomings and areas for further improvement of the design practice have been identified. With new environmental legislation that recently came into effect in South Africa, the importance of BSM technology as an environmentally-friendlier and more sustainable construction technique is set to increase in the coming years. A laboratory testing programme was set-up to study the properties and behaviour of BSM’s and to establish links with the compositional factors, i.e. the type of binder used, the percentage of Reclaimed Asphalt Pavement (RAP) in the mix and the addition of a small dosage of cement as active filler. The mineral aggregates used were sourced in the USA and consisted of crushed limestone rock and RAP millings. These were blended in two different proportions of crushed rock : RAP, i.e. 3:1 (with 3.6 % residual binder) and 1:3 (with 2.4 % residual binder). Tri-axial testing (150 mm diamter) was carried out to determine shear parameters, resilient modulus and permanent deformation behaviour, while four-point beam testing was carried out to determine strain-at-break, flexural stiffness and fatigue behaviour. It was found that the process of bitumen stabilisation improves the shear strength of the material, particularly in case 1 % of cement is added as active filler. This increase in shear strength is entirely the result of increased cohesion. There is a good correlation between the shear strength and the resilient modulus of BSM’s. The resilient modulus of BSM is stress-dependent and the Mr-θ model is adequate to model the resilient modulus of the blends with a low percentage of RAP. For the blends with a higher percentage of RAP this model cannot be applied and the resilient modulus reduces in stiffness at higher deviator stress ratios. A considerable part of the efforts of this study were dedicated to characterise and model the permanent deformation behaviour. The General Permanent Deformation Law as originally developed by Francken applies also to BSM’s. An improved nonlinear method to converge at a solution for the model parameters that describe the tertiary flow part of this deformation law was developed as part of this study. Parameters that can be derived from the first stage of the permanent deformation test, i.e. initial strain and initial strain rate as defined in this study, were found that correlate well with the model parameters that describe the first linear part of the deformation law. Critical deviator stress ratios for the several mixes tested were determined. When BSM’s are subjected to loading below these ratios, tertiary flow is unlikely to occur. A high variability was generally found in the four-point beam test results, especially for the strain-at-break. Specimen preparation protocols and the quality of the beam specimens are of utmost importance when performing four-point beam tests on BSM’s. This limits the practical applications of the strain-at-break test. Trends observed in the strain-at-break were also inconsistent and sometimes not in line with the other type of tests. BSM’s exhibit a visco-elastic behaviour, which was determined by flexural stiffness testing, however, to a lesser extent than HMA. Phase angles and Black Diagrams were developed for the BSM’s tested, which also made it possible to determine the parameters of the Burgers Model, which is a mechanical model describing viscoelastic behaviour. Fatigue relationships were also developed for the BSM’s tested. The fatigue performance of these mixes is lower than for selected HMA mixes. The foamed BSM generally showed better fatigue life than emulsion BSM, however, the lower initial stiffness of the foamed BSM’s may contribute to a perceived longer fatigue life. For the mixes tested, the flexural stiffness of foamed BSM’s is generally also lower than that of emulsion BSM’s It is recommended that the mix design of BSM’s be split into two phases. During the first phase the usually large number of variables could be reduced to a selected few by means of UCS and ITS indicator testing. Subsequently, more fundamental parameters should be determined during the second phase, such as shear strength and resilient modulus, as well as permanent deformation behaviour. The fact that commercial laboratories in South Africa do not have tri-axial testing facilities is currently a practical limiting factor. Initiatives currently underway to develop “simple” shear tests are welcomed in this regard. It is proposed that classification of BSM is based on shear strength. There are indications that shear failure in BSM is more critical than failure as a result of fatigue. The effect of curing resulting in an increase in BSM stiffness in the period after construction, i.e. typically 6 to 18 months, is currently ignored in structural design models. The rapid stiffness reduction of BSM’s during the first period after construction in the current structural design models and also found during Accelerated Pavement Testing is not being observed in Long-Term Pavement Performance (LTPP). On the contrary, an increase in stiffness is observed in LTPP. This would indicate that stiffness reduction as a result of fatigue does not occur or is overshadowed by the effect of curing and that fatigue as a failure mechanism of BSM’s is currently over-emphasized.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2009. / The need for a more reliable testing procedure for the characterisation and Quality Assurance/ Control of Bitumen Stabilised Materials (BSMs), besides UCS and ITS testing, has long been recognised by the roads industry. In fact, at CAPSA 2004 and CAPSA 2007, discussions of improved test methods for granular materials, i.e. possible replacement tests for CBR procedures, were conducted in workshops. Triaxial testing for the evaluation of shear parameters is widely recognised as a reliable method of measuring these critical performance properties of granular and Bitumen Stabilised Materials (BSMs). However, the triaxial test in its current state as a research test has little chance of extensive use by practitioners and commercial laboratories, because of complexity, cost and time issues. Major adaptations to the research triaxial test are necessary, before this useful test can have a chance of being accepted by road practitioners. The main aim of this study is to investigate possibilities of developing a simple, affordable, reliable and robust test for characterizing granular and bitumen stabilized materials thus linking test outcome with in-situ performance. This is achieved through the innovative design and manufacture of a prototype triaxial cell capable of accommodating 150 mm diameter by 300 mm deep specimens. The cell is simpler than the research (geotechnical) triaxial cell and the operational protocols have been streamlined, thereby reducing the time and steps required in assembling specimens and testing them. In order to ensure the development of an appropriate triaxial cell for industry, a survey was conducted aimed at investigating currently available facilities, testing capacity and resources within civil engineering laboratories in South Africa. Findings of the survey (Appendix 4) have provided guidance with regard to the nature and sophistication of any new tests to be developed. The survey highlighted some of the limitations and lack of sophistication of the current loading frames used for CBR and UCS testing such as lack of electronic LVDTs, limited overhead space, limited loading capacity and others. Most laboratories would need to invest in new loading facilities to carry out triaxial tests. A review of the test procedure for monotonic triaxial test showed that two main factors contribute to the complexity of the research (geotechnical) triaxial cell namely, time taken to assemble the specimen accurately in the cell and secondly the inherent design of the cell which makes it water and/or air tight at relatively high pressures. The design of the Simple Triaxial Test, therefore, was aimed at overcoming the drawbacks of research triaxial test e.g. fitting a membrane to each specimen to be tested, through considerable simplification by means of a new structure design and procedure of assembly of specimen into the cell. The advantage of addressing these issues would be reduction in the number of steps required in the test procedure and therefore reduction in testing time. The design of the cell particularly was preceded by a conceptualization process that involved investigation of numerous options. Concepts such as the bottle, encapsulated-tube, bottle and sandwich concepts were considered and given reality checks. In addition, available triaxial procedures of a similar nature e.g. Texas Triaxial, were evaluated and analyzed. Ultimately, with some trials and innovation, a design was developed for a simple triaxial cell comprising a steel casing with a latex tube which is then introduced around the specimen sitting on a base plate. It is based on the ‘tube concept’ in which the specimen acts like a ‘rim’ and the cell acts like a ‘tyre’ providing confinement to the triaxial specimens for testing, within the tube. This approach eliminates the use of O-rings and membranes for the specimen and tie-rods for the triaxial cell, thus reducing testing time considerably. The overall dimensions of the cell are 244 mm diameter by 372 mm height (Appendix 5). The cell was manufactured at Stellenbosch University Civil Engineering workshop and preliminary tests were conducted under this study. Parallel tests were also conducted with the Research Triaxial Test setup at Stellenbosch University in order to determine if preliminary results obtained with the Simple Triaxial Test setup were comparable therefore providing a means of validating the data. Results of analysis of variance (ANOVA) show that variability between Simple Triaxial Test (STT) and Research Triaxial Test (RTT) results is less significant whilst that within samples of STT and RTT results is quite significant. Comparisons also show that good correlation were obtained from Reclaimed Asphalt Pavement (RAP) Hornfels + 3.3 % Emulsion + 0 % Cement mix and mixes with the G2 base course aggregate whilst completely different correlation was obtained from RAP + 3.3 % Emulsion + 1% Cement. It is evident however that the differences observed stem from material variability i.e. random variability to one degree or the other and not to the STT apparatus. It is recommended for future research that more STT versus RTT testing be done especially on a mix with known mechanical properties when compacted to a specified dry density, e.g. graded crushed stone (G1) compacted to 100% mod. AASHTO. In summary, a locally made, low cost, relatively durable triaxial cell with relatively easy and quick specimen assembly procedures has been developed. It is now possible to perform triaxial tests on 150 mm diameter by 300 mm high specimen relatively easily and quickly. However, the challenge of validating results obtained, as well as improving the manufacture process of its main component, the tube, still remains.

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.

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: This research investigates the flexibility and the performance properties of bitumen stabilised materials under the influence of mix variables. The laboratory testing consisted of two main phases. During the first phase (mix design), the strength and the flexibility of the mixes were assessed through ITS (Indirect Tensile Strength), UCS (Unconfined Compressive Strength), displacement at break, strain at break and fracture energy. The second phase consisted of a series of triaxial tests done to assess the performance properties (shear strength: cohesion and angle of internal friction; and stiffness: resilient modulus) of the mixes. The mineral aggregates used in this study were milled from different locations of the R35, near Bethal. This was a blend of granular material (dolerite, from various locations of the existing base and subbase layer of the R35) and Reclaimed Asphalt (RA) milled from the existing surfacing. During the mix design phase, two types of bituminous binders were used (bitumen emulsion and foamed bitumen) at bitumen content ranges of 2%, 2.4% and 2.8% each. Two types of active filler were used separately and in combination at a proportion of 1% and 2%. Finally, specimens were tested in wet and dry conditions for each mix combination. During the triaxial testing phase, only the optimum bitumen content of 2.4% was used, both for bitumen emulsion and foamed bitumen, with only cement as active filler in a proportion 1% and 2%. The specimens were tested at different ranges of densities and saturation levels. The flexibility of the mix was assessed through the fracture energy, the strain and the displacement at break parameters. An analysis of variance (ANOVA) was conducted on the data to assess the significance of experimental variables on this property. This property was found to be very sensitive to bitumen and cement content added to the mix. When assessing the combined effect and the significance of the variables on the flexibility of the mixes, it was found that fracture energy is mostly influenced by the cement content, followed by the bitumen content, then the type of treatment and finally the testing condition. However, the level of significance was not in the same order for the other two parameters (displacement and strain at break). It was also found that the combined effect of some independent variables (cement content + testing condition, type of treatment + cement content + bitumen content) had a significant effect on the fracture energy and the strain at break respectively. From the ITS and UCS tests, an increase in strength was noticed with the increase of cement content. On the other hand, the increase in bitumen content led to a decrease in strength of the material. The statistical analysis on the ITS and UCS values show that the independent variable with the most significant effect on the ITS is the cement content, followed by the testing conditions, then the bitumen content and finally the type of treatment. The combined effect of cement content + bitumen content was found to be significant both for ITS and UCS. In the second phase triaxial tests were performed in order to evaluate the performance properties of the mixes. It was found that the increase of the active filler content significantly improves the shear strength of the material. It was also found that at a fixed cement content, specimens tested at low density and/or high level of saturation show low shear strength. The Mr-θ model was used to model the resilient modulus of the mixes and the model coefficients used to evaluate the effect of experimental variables on the resilient modulus. It was found that the resilient modulus of the mixes increases as the bulk stress increases. This confirms the stress dependent behaviour of bitumen stabilised materials. The analysis show that increasing the percentage of active fillers content results in a significant increase in the resilient modulus values. An increase in relative density also resulted in an increase in the resilient modulus of the mixes, while the opposite effect was observed with the increased of the saturation level. Besides the engineering properties and the mechanical test parameters, other parameters such as the Tensile Strength Ratio (TSR) was calculated in order to evaluate the moisture sensitivity of the mixes. Weakening due to moisture was found to be more predominant in the mixes with less active filler. In addition, bitumen emulsion mixes were found to have a better resistance to moisture weakening effects compared to foamed bitumen. In addition, a comparison between the rapid curing and the accelerated curing was done. Higher ITS and UCS results were obtained for specimens cured using long term curing compared to specimens cured using the accelerated curing method. In conclusion, flexibility is an important property of bitumen road construction material (bitumen stabilised material include) however, it is not an easy property to measure. Although, displacement/strain at break and fracture energy from ITS and UCS were able to give us some indications on the main factors governing the flexibility of bitumen stabilised materials (the bitumen and active filler content), more accurate and adequate tests are required to evaluate the parameter. / AFRIKAANSE OPSOMMING: Die buigsaamheid en gedragseienskappe van bitumen gestabiliseerde materiale was getoets om sodoende die invloed van verskeie mengselveranderlikes te evalueer. Die ondersoek het uit twee fases bestaan. Tydens die eerste fase (mengfase) is die sterkte en buigsaamheid deur middel van indirekte treksterkte toetse (ITS), onbegrensde druksterkte toetse (UCS), verplasing – en vervorming by breekpunt sowel as breek-energie toetse gedoen en ondersoek. Die tweede fase het bestaan uit ʼn reeks drie-assige triaksiaal toetse. Triaksiaaltoetse is uitgevoer om die gedragseienskappe soos die skuifsterkte, kohesie, hoek van interne wrywing, styfheid en weerstand modulus te ondersoek. Die gemaalde mineraal-aggregaat wat in hierdie ondersoek gebruik is, was verkry op verskeie areas van die R35, geleë naby Bethal. Die materiaal is ʼn mengsel van granulêre materiaal (van die bestaande kroonlaag en stutlaag van die pad) en herwonne asfalt (RA). Tydens die mengontwerp fase is twee tipes bitumen gebruik naamlik bitumenemulsie en skuimbitumen in hoeveelhede van 2%, 2.4% en 2.8%. Twee tipes aktiewe vulstof (hoeveelhede van onderskeidelik 1% en 2%) was saam met elk van die verskeie bitumen-hoeveelhede gebruik. Proefstukke van elk van hierdie mengsel kombinasies is onder beide nat en droë kondisies getoets. Tydens die tweede fase, is slegs die optimum binder inhoud (2.4%) gebruik vir beide emulsie- en skuimbitumen, gekombineer met 1% en 2% aktiewe vulstof. Proefstukke was getoets by ʼn reeks van verskillende digthede en versadigingvlakke. Die buigsaamheid was ondersoek deur middel van breek-energie, vervorming en die verplasing by breekpunt. ʼn Analise van variasie (ANOVA) is uitgevoer op die toetsdata om sodoende die te evalueer of die veranderlikes beduidend is ten opsigte van buigsaamheid. Daar is gevind dat die buigsaamheideienskap sensitief is vir beide bitumen en sement inhoud. Met assessering van die gekombineerde effek en betekenis van die veranderlikes op die buigsaamheid van die mengsels, is daar gevind dat die hoogste beduidende veranderlike t.o.v breek-energie die sement inhoud is, gevolg deur die bitumeninhoud, tipe behandeling en laastens die toetskondisie. Die orde van belangrikheid verskil vir die ander twee parameters (verplasing en vervorming by breekpunt). Daar is ook gevind dat die gekombineerde effek van sommige veranderlikes (sement inhoud en toets kondisie, tipe behandeling en sement inhoud tesame met bitumen inhoud) ook beduidend was t.o.v breek-energie en vervorming by breekpunt. Vanuit die ITS en UCS toetse was daar ʼn toename in sterkte waargeneem soos die sementinhoud toeneem. Aan die anderkant, het ʼn toename in bitumeninhoud ‘n afname in sterkte veroorsaak. Die statistiese analise van ITS en UCS resultate, toon dat die grootste beduidende onafhanklike t.o.v ITS waardes ook die sement inhoud was, gevolg deur toets kondisies die grootste effek, bitumen inhoud en die tipe behandeling. Die gekombineerde effek van sementinhoud en bitumeninhoud, was betekenisvol vir beide ITS en UCS. Drie-assige triaksiaaltoetse was uitgevoer om die gedragseienskappe van die mengsels te evalueer. Daar is gevind dat die toename in sement inhoud, die skuif sterkte van die materiaal grootliks verbeter. By ʼn konstante sementinhoud, wys toetsresultate van proefstukke wat getoets is by lae digthede en hoë vlakke van versadiging, lae skuif sterkte. Die Mr – θ model was gebruik om die veerkragsmodulus van die mengsels te moduleer en die modelkoëffisiënte is gebruik om die effek van eksperimentele veranderlikes op die weerstand modulus te evalueer. Met toename in die omhullende spanning is ‘n toename in die veerkragsmodulus waargeneem, wat bevestig dat die gedrag van bitumen gestabiliseerde materiale spannings afhanklik is. ʼn Toename in die sement en relatiewe digtheid het ʼn merkwaardige toename in die veerkragsmodulus tot gevolg gehad, terwyl die teenoorgestelde waargeneem is met toename in versadigingsvlakke. Buiten die ingenieurseienskap en meganiese toetsfaktore, is ander faktore (soos die trekspanning verhouding) bereken om die vogsensitiwiteit van die mengsels te evalueer. Mengsels met laer sement inhoud het groter verswakking ervaar met blootstelling aan water. Bitumenemulsie proefstukke toon beter weerstand teen water as skuimbitumen. Vergelyking tussen versnelde en korttermyn nabehandelingsprosedure van proefstukke, toon hoër ITS en UCS waardes vir die versnelde nabehandelingsprosedure prosedure. Buigsaamheid is ‘n belangrike eienskap van bitumen in padkonstruksie materiale (insluitend bitumen gestabiliseerde materiale), maar word moeilik gemeet. Alhoewel verplasing/vervorming by breekpunt en breek energie, bepaal vanaf ITS en UCS, ‘n indikasie toon van die hooffaktore (binder en sement) wat buigsaamheid van bitumen gestabiliseerde materiaal beïnvloed, word meer akkurate toetse benodig om die eienskap te ondersoek.