Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The research conducted in this study forms part of the Phase II process of the Bitumen Stabilized Materials (BSMs) Guideline improvement initiative. The initiative aims to address areas of concern in the cold mix design procedures for BSMs. Current road rehabilitation using the bitumen stabilization process requires testing of representative specimens as means to evaluate pavement performance over time. In order to adequately acquire specimens representative of field conditions, it is necessary to condition the materials in a process called curing. Although curing procedures have been standard in many countries on different continents, the protocols are varied and an acceptable procedure is currently not available. In order to develop an acceptable curing protocol for BSMs, both field and laboratory environments were investigated. Considering that curing takes time in the field, production of representative samples intended for laboratory testing must undergo accelerated curing in the laboratory. Given the complexities involved in achieving close correlations between field and laboratory environments, the research strived to reconcile field and laboratory material behaviour. In particular, the main objective of the research was to unify the curing protocol for BSMs, with the standardization of the curing protocol being top priority. In this study, laboratory results have confirmed that the different natures of curing mechanisms inherent in a BSM-foam and BSM-emulsion contribute to irreconcilable material behaviour(s). Results have confirmed that curing of BSM-foam is largely a function of water repulsion, with the addition of active filler dominating material performance almost immediately. Unlike BSM-foam, curing of BSM-emulsion is both a function of the breaking of emulsion during the initial phase and the gradual release of moisture with time. In this instance, BSM-emulsion material performance resembled active filler influences past the breaking of the emulsion cycle. Consequently, given the observed differences regarding material behaviour(s), the unification of the curing protocol for BSMs has not been successful. In terms of accommodation of active filler in the final curing protocol for BSMs, findings in this research have revealed that active filler’s tendency to absorb moisture in the initial stages requires longer curing time to help extract the absorbed moisture during the curing process. Although the use of active filler has an impact on curing, its inclusion in a BSM does not justify its extension in the curing time as cementation is not one of the desired properties of these materials. BSMs are primarily desirable for their flexibility in pavement structures. For this reason, active filler was omitted in the final curing protocol due to reasons of simplifying the mix design process. In conclusion, different curing protocols were tested and developed to help produce reconcilable material behaviour in both the field and laboratory environments. Through the reconciliation of key material properties such as the resilient modulus, long term equilibrium moisture conditions and shear parameters, an acceptable standardized curing protocol for BSM-foam and BSMemulsion intended for application in industrial laboratories across South Africa was successfully developed. / AFRIKAANSE OPSOMMING: Die navorsing tydens hierdie studie gedoen, vorm deel van die Tweede fase van die Bitumen Gestabiliseerde Materiale Riglyne verbeteringsinisiatief. Die inisiatief het ten doel om areas van bekommernis in die kouemengsel-ontwerp-prosedures vir Bitumen Gestabiliseerde Materiale aan te spreek. Huidige padrehabilitasie wat gebruik maak van die Bitumen Gestabiliseerde Materiale proses, vereis toetsing van verteenwoordigende monsters om sodoende plaveiselgedrag oor ‘n tydperk te evalueer. Materiale moet deur die verouderingsproses gekondisioneer word, om sodoende monsters te verkry wat akkuraat verteenwoordigend van veldtoestande is. Alhoewel verouderingsprosesse in meeste lande - op verskillende kontinente - gestandariseerd is, is die protokol verskillend en ‘n aanvaarbare prosedure is nie tans beskikbaar nie. Beide veld- en laboratoriumomgewings is ondersoek, om sodoende ‘n aanvaarbare verouderings-protokol vir Bitumen Gestabiliseerde Materiale te ontwikkel. Wanneer in ag geneem word dat veroudering in die veld tydrowend is, moet vervaardiging van verteenwoordigende monsters vir laboratoriumgebruik versnelde veroudering in die laboratoruim ondergaan. Gegee die kompleksiteite betrokke om goeie korrelasie tussen velden laboratoriumomgewings te verkry, het die navorsing daarna gestreef om die veld- en laboratoriummateriaalgedrag te verenig. Die hoofdoel van die navorsing was om die verouderingsprotokol vir Bitumen Gestabiliseerde Materiale te verenig met die stardaardisering van die verouderingsprotokol as top prioriteit. In hierdie studie het laboratorium resultate bevestig dat die verskillende aard van voorbereidings- meganismes inherent in BSM-skuim en BSM-emulsie bydra tot onversoenbare materiaalgedrag. Resultate het bevestig dat voorbereiding van BSM-skuim ’n funksie van waterrepulsie het en met die byvoeging van aktiewe vullers dominieer dit die materiaalgedrag byna onmiddelik. Anders as BSM-skuim is die voorbereiding van BSM-emulsie beide ’n funksie vir die breek van emulsie tydens die begin fase en die geleidelike vrystelling van vog oor tyd. In hierdie geval het BSM-emulsie se materiaalgedrag die invloed van aktiewe vuller getoon nadat die emulsie gebreek het. Gevolglik, weens die waargenome verskille rakende materiaalgedrag is die vereniging van die voorbereidings- protokols vir BSMs nie suksesvol nie. In terme van inagneming van aktiewe vullers in die finale voorbereidingsprotokol vir BSM’s, is deur navorsing bevind dat aktiewe vullers neig se neiging om vog te absorbeer in die beginstadia dit benodig dus ‘n langer verouderingstyd vir die ontrekking van die geabsorbeerde vog. Hoewel die gebruik van aktiewe vullers ’n impak het op die voorbereiding, reverdig dit nie die verlenging van die verouderingstyd vir die insluiting daarvan in BSM nie, siende dat sementering nie een van die gewenste eienskappe van hierdie materiaal is nie. BSMs word hoofsaaklik verkies vir sy buigsaamheid in paveiselsturkture. Om die mengselontwerp prosesse te vereenvoudig, was aktiewe vullers dus weggelaat in die finale voorbereidingsprotokol. Ter afsluiting was verskeie voorbereidings protokolle getoets en ontwikkel om te help met die vervaardiging van versoenbare materaalgedrag in beide veld-en-laboratoriumomgewings. Deur die versoening van kern materiaal eienskappe soos die elastisiteitsmodulus, lang termynewewigvog kondisies en skuifparameters, is ’n aanvaarbare gestandariseerde voorbereidingsprotokol vir BSM-skuim en BSM-emulsie bedoel vir aanwending in industriele laboratoriums regoor Suid Afrika suksesvol ontwikkel.

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Factors influencing surface run-off of bitumen emulsions were studied in order to understand binders for use in the construction of surfacing seals. Run-off of the binder from the road surface causes an inconsistent film thickness leading to ravelling (Johannes, Hanz & Bahia n.d.) and bleeding at the upstream and downstream regions, respectively. There is currently no accepted specification for surface run-off viscosity. Practice mainly relies on empirical tests and experience. As the establishment of such a specification encompasses performance of the binder in various environments or field conditions, this study was undertaken to determine performance of the selected binder. Viscosity was kept constant by spraying the emulsion at a constant temperature and also holding the pavement temperature constant. In order to study the run-off behaviour of the binder, run-off tests were conducted at various gradients, texture depths and spray rates. Surfacing seals of various texture depths were constructed in the laboratory. Using a spray bar, the emulsion was sprayed at various spray rates. The sample surfaces were tilted to various gradients. Results portrayed the effects of the three factors (spray rate, gradient and texture depth) on the amount of runoff. An increase in the magnitude of the factors resulted in a variation in the runoff (increase or decrease). One notable finding was that the runoff from the 9.5 mm seal was less than that from the 13.2 mm seal. The other significant finding was that spray rate had the largest effect on runoff, followed by texture depth, and gradient. / AFRIKAANSE OPSOMMING: Sekere eienskappe wat oppervlakdreinering van bitumen emulsies op paaie beinvloed, is bestudeer om sodoende binders wat gebruik word in die konstruksie van die seëls beter te verstaan. Afloop van die binder vanaf die padoppervlak kan lei tot die vorming van ‘n laag met ongelyke dikte wat moontlike rafeling (Johannes, Hanz & Bahia nd) en bloeing vanuit die onderkant van die pad tot gevolg kan hê. Daar is tans geen aanvaarde spesifikasies wat hierdie verskynsels inperk nie. Konstruksie praktyk berus hoofsaaklik op empiriese toetse en ondervinding. Hierdie studie is dus onderneem om prestasie van die geselekteerde binder vas te stel. Viskositeit was konstant gehou deur die aangewende emulsie en padtemperatuur konstant te hou. Ten einde die afloopgedrag van die binder te bestudeer, is toetse uitgevoer op verskeie hellings, tekstuurdieptes en aanwendingskoerse. Seëls van die verskillende tekstuurdieptes is gebou in die laboratorium, en emulsies op hierdie oppervlaktes aangewend. Die toetsoppervlakte is gekantel om die vereiste helling te kry. Resultate vir die drie faktore wys die invloed op afloop. ‘n Toename in die grootte van die faktore het gelei tot 'n variasie in die afloop (toename of afname). Een noemenswaardige bevinding was dat die afloop van die seël van 9,5 mm minder was as dié van die seël van 13,2 mm. Belangrike bevindinge sluit ook in dat die spuitkoers die grootste invloed het op afloop, gevolg deur die tekstuur diepte en die gradiënt.

Thesis (MEng)-- Stellenbosch University, 2013. / ENGLISH ABSTRACT: Two common methods of road pavement, granular material stabilisation used in road construction throughout South Africa today include Cold in Place Recycling (CIPR) and stabilisation with cement or bitumen and an active filler to create Bitumen Stabilised Materials (BSM). As part of the updating of the South African Pavement Design Method (SAPDM) an experimental section, investigating the structural capacity of cement and lime stabilised and BSM pavement layers, was constructed and will be monitored over a two year period. As part of this study Falling Weight Deflectometer (FWD) measurements were taken on the various experimental stabilised pavement layers constructed. The FWD deflection data, measured at various time intervals over a 360 day period, forms the basis of the study presented here. The objective of this thesis was to identify typical back-calculated layer stiffnesses and their variability over time for the various in-situ recycled and stabilised base layers constructed within the experimental section. Stabiliser type, content and layer thicknesses were varied across experimental sub-sections. Trends in back-calculated stiffness of cement stabilised base layers consistently showed significant reductions in layer stiffness subsequent to construction traffic loading. Subsequent to the initial reduction in stiffness little change in stiffness was noted under normal traffic loads. Observations on the trends in back-calculated stabilised layer stiffness per material type over time indicated that seasonal moisture and temperature fluctuations have an effect on the stiffness of the pavement structure as a whole. BSM materials showed significant variability over time in-line with seasonal variability in the supporting subgrade stiffness in the southbound lane. BSM materials with 1% cement added in the northbound lane show initial stiffness reductions due to direct rainfall application however a significant increase in layer stiffness occurs up to 360 days after construction. BSMs with 2% cement in the northbound lane show significant increases in layer stiffness over the 360 day observation period. No significant difference in stiffness trend was observed between BSM emulsion a BSM foam materials. The BSM emulsion with 0.9% residual bitumen and 1% cement was observed to show rapid reduction in stiffness upon opening to traffic and reverting to stiffness values similar to an unbound material of approximately 350 MPa. Cement and lime stabilised materials showed typical post 28 –day average stiffnesses per sub-section ranging between 600 MPa and 1800 MPa. BSM foam with 1% cement added were observed to have average stiffnesses per sub-section in the range of 400MPa to 2200 MPa and BSM emulsion with 1% cement with stiffnesses between 400 MPa to 1700 MPa over the 360 day period. BSMs with 2% cement added showed stiffness ranges between 900 MPa to 4300 MPa for BSM foam and 900 MPa to 3900 MPa for BSM emulsions over the 360 day period. The spatial variability of back-calculated stiffness per sub-section of a particular stabilisation design was significant and was observed, through the Co-efficient of Variation (COV), to increase over time. The effect of the observed variability when incorporated into a pavement design scenario, requiring a design reliability of 90%, showed 50% of the pavement structure would be overdesigned by a factor of 4. With respect to the current philosophies on the development of stiffness over time of cement and lime stabilised and BSM pavement layers some useful observations were made. Cement stabilised materials correlate well with stiffness development theories predicted by previous studies. Theories relating to the stiffness development of BSMs however did not predict the levels of variability in base layer stiffness observed on the experimental section. The continued observation of the experimental section for another year will give greater insight to the stiffness trends of the stabilised materials discussed above.

M. Tech. Civil Engineering.. / Investigates the feasibility of recycling construction waste for re-use as raw material in rehabilitation of roads in Bethal (Govan Mbeki Municipality). Specific Objectives: (a) To identify the causes of roads failure within the study area.(b) To assess feasibility of reuse of construction waste and propose method of road rehabilitation.(c) To recycle unsuitable material through characterisation of the construction waste. (d) To compare the cost implications when recycled construction waste is used with that of normal roads' rehabilitation.

Bitumen acts as a binding agent in asphalt mixtures where it binds the aggregates together. It is known for its potential to heal small cracks and recover its mechanical properties under the right conditions. Though this self-healing property is known, there is currently a lack of knowledge about the mechanisms that drive the process. To optimize the use of this material for pavement design, the healing ability should be better understood and controlled. In this work, it is investigated how neutron imaging can be used to increase the understanding of the mechanisms behind the self-healing in bitumen. As a first step, the sample size requirement set by the measurement technique was determined. In order to detect micro cracks in bitumen by using this technique, the sample must be sufficiently small to allow neutron transmission. On the other hand, too small samples would complicate the structural analysis of the material since less information would be possible to obtain. Bitumen with different dimensions were scanned with neutrons to determine the maximum sample thickness. This work was followed by evaluating the healing capability of fractured bitumen and mastic samples, by using time series neutron tomography. The studied samples had a varying combination of hydrated lime (HL) filler concentration, crack volume, and contact area between the broken pieces. The data acquired from the time series tomography scans was analyzed using a three-dimensional analysis procedure including denoising, segmentation and volume measurements. From the volumetric analysis, it appeared that the initial crack size and crack shape have a large impact on the healing rate. It was found that bitumen, mastic with 20%, and 30% filler content had a similar healing behavior for relatively small crack volumes. When increasing the content of HL in the mastic, the healing rate decreases exponentially, with a drastic decrease after reaching a filler content of about 30%. / Bitumen fungerar som bindemedel i asfaltsblandningar där det binder ihop stenaggregaten. Bitumen är känd för sin förmåga att läka små sprickor och återfå sina mekaniska egenskaper under rätt förutsättningar. Trots att den självläkande egenskapen är välkänd, råder det idag en brist på kunskap om de mekanismer som ligger bakom denna process. För att optimera användandet av bitumen för vägbeläggningar behövs en bättre förståelse kring denna läkande egenskap. I detta projekt undersöks det hur neutronavbildning kan användas för att öka förståelsen kring de mekanismer som ligger bakom den självläkande egenskapen hos bitumen. Som ett första steg bestämdes provstorlekskravet för denna analysteknik. För att möjliggöra detekteringen av små sprickor i bitumen genom att använda denna teknik måste provmaterialet vara tillräckligt tunt för att neutronerna ska kunna transmitteras genom materialet. Allt för små provstorlekar skulle, å andra sidan, försvåra analysen av materialets struktur då informationen man kan erhålla blir mer begränsad. Bitumen med olika provstorlekar skannades med neutroner för att bestämma den maximala provtjockleken. Därefter analyserades den självläkande förmågan hos brutna bitumen- och bitumenmastixprover med tidsserie neutrontomografi. Prover med olika mängder av kalciumhydroxidfiller i bitumenblandningen, olika storlek på sprickvolymen och kontaktytan mellan de brutna provdelarna studerades. Data erhållna från experimenten användes för att göra en 3-dimensionell analys som inkluderade brusreducering av bilder, segmentering och volymmätningar. Från volymanalyserna konstaterades det att den initiala sprickstorleken och sprickformen har en stor inverkan på läkningstakten. Bitumen, mastix med 20%, och 30% filler-additiv uppvisade liknande läkningsegenskaper för relativt små sprickstorlekar. Vid en ökning av mängden filler material i mastixen minskar läkningstakten exponentiellt, med en drastisk minskning när man passerar en filler-koncentration på runt 30%. / <p>QC 210303</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, 2012. / ENGLISH ABSTRACT: Chip and spray surfacing seals has been widely used in South Africa as the preferred surface treatment for rural roads. The design of these seals has also experienced renewed interest and continuous development in several other countries over the past two decades. In South Africa seals are continually used as increasing attention is given to the periodic maintenance of existing surfaced roads. There is also a significant increase in the use of surfacing seals in North America as the need to develop more energy and resource efficient surfacing options becomes a priority. Despite this growing use of surface seals, the seal design and especially the selection of binder type and grade does not always follow scientific processes. Seals are often designed based on client preference, previous experience, material availability and industry trends. With an ageing road network and limited funding to ensure timeous maintenance, the focus in South Africa is moving towards more stringent and scientific design processes. The USA and Europe, forced by increasing traffic volumes and heightened performance demands, are moving towards performance- based specification to account for deficiencies in their current surface seal design methods. One of the major failure mechanisms of surface seals is ravelling which takes place when the binder and the aggregate bond becomes weak and are broken by the forces generated by traffic. This leads to loose aggregate on the road which in turns leads to bare surface patches and broken windscreens. To prevent and address this as part of the development of performance-based specifications, the need for a simple and inexpensive technique for evaluating bitumen and bitumen emulsion bond strength development over time, as well as binder-aggregate compatibility, was identified. Although various tests exist for investigating adhesion between bituminous emulsions and aggregate chips most of the tests does not deliver the level of information required by the performance-based specifications. The Bitumen Bond Strength (BBS) test method was therefore developed with the aim to address some of the limitations encountered in evaluating bond strength between binders and aggregates. The BBS test (AASHTO TP-91, 2011) was developed by the University of Wisconsin – Madison (UWM) in partnership with the University of Ancona – Italy (UAI) and the University of Stellenbosch – South Africa (US) specifically for evaluating bond strength between aggregates and hot applied binders and emulsions, respectively. US became involved in BBS test efforts in 2008 to assist in the development and practical evaluation of the BBS test method. UAI contributed significantly to the development of the test apparatus through their work in conjunction with UWM. Due to time and resources available, the involvement of the US was limited to various discussion sessions, a study tour, the evaluation of the BBS test, and conducting a series of control tests. By using the Bitumen Bond Strength test it was possible to evaluate the practicality and repeatability of the developed procedure and the results measured was successfully used to evaluate the bond strength development of modified and unmodified bitumen emulsions on tillite and granite aggregates. It was also possible to correlate the results achieved at the University of Stellenbosch with results from the University of Wisconsin-Madison due to the fact that testing took place at both institutions. The development of the test and the inter-laboratory test results in essence reinforced the hypothesis that the BBS test protocol can be used to effectively evaluate bond strength of different emulsion types and aggregate types. Except for the loading rate which is a known critical influence, the emulsion type and curing intervals are both identified as the most significant other factors contributing to bond strength development. Aggregate type is also identified as a significant factor that will influence the bond strength development. Interactions between emulsion type and curing interval are identified as the most significant interaction. A lot of further validation test on the BBS test method is still required for the test to be integrated into a performance-based specification system for surface seals. / AFRIKAANSE OPSOMMING: “Chip and Spray” oppervlak seëls is die verkose seël tipe vir gebruik op Suid Afrikaanse plattelandse paaie. Die ontwerp van hierdie tipe seëls is ook tans besig om hernude aandag te trek in heelwat lande. In Suid Afrika word die tipe seël al meer gebruik soos die behoefte na herseël projeke op die verouderde pad netwerk groei . Daar is ook heelwat groei in die gebruik van “Chip en Spray” seëls in Noord Amerika aangesien daar n behoefte is om n meer energie en materiaal effektiewe seëls te gebruik. Ten spyte van die groeiende gebruik van hierdie seëls het daar min wetenskaplike ontwikkeling plaasgevind in the ontwerp daarvan. Seëls word meestal ontwerp gebaseer op klient voorkeur , ondervinding, materiaal beskikbaarheid en ook industrie norms. ‘n Verouderde pad netwerk dwing die Suid Afrikaanse industrie om meer deeglike en wetenskaplike ontwerp prosedures te volg. Die VSA en Europa word deur vinnig groeiende verkeersvolumes en verhoogte kwaliteits behoeftes gedwing om prestasie gebaseerde spesifikasies te ontwikkel. Een van die hoof defekte op seëls is klipverlies wat plaasvind as die verbinding tussen die bitumen en aggregaat verswak en gebreek word deur die kragte wat deur verkeer oorgedra word. Dit lei tot los klip op die pad wat weer tot skade aan voertuie lei. Om dit te voorkom en aan te spreek het die behoefte laat ontwikkel vir n maklike en goedkoop tegniek om te meet hoe sterk die verbinding is wat ontwikkel tussen verskillende bitumen, bitumen emulsies en aggregaat monsters. Alhoewel daar alreeds toetse bestaan wat kan toets hoe sterk die verbinding is , gee die meeste van die toetse nie die informasie wat benodig word deur die voorgestelde prestasie gedrewe spesfikasies nie. Die “Bitumen Bond Strength” (BBS) toets metode is daarom ontwikkel om die tekortkoming in die toets van die bitumen en aggregaat verdindinge aan te spreek. Die BBS toets (AASHTO TP-91, 2011) is ontwikkel by die Universiteit van Wisconsin – Madison (UWM) in vennootskap met die Universiteit van Ancona – Italy (UAI) en die Universiteit van Stellenbosch (US) , spesifiek om die die sterkte van die verbinding wat vorm tussen aggregaat en bitumen te meet. Die US het in 2008 betrokke geraak by die BBS toets studie om hulp te verleen met die ontwikkeling en praktiese evalueering van die BBS toets metode. As gevolg van tyd en personeel tekorte is die betrokkendheid by die US beperk tot verskeie besprekings sessies, n studie toer, die evalueering van die BBS toets sowel as die voltooing van n uitgebreide stel toetse. Deur die voltooing van eksperimente met die BBS toets was dit moontlik om die uitvoerbaarheid en herhaalbaarheid van die ontwikkelde prosedure te toets. Die resultate van die toetse is suksesvol gebruik om die ontwikkeling van die verbinding sterkte tussen gemodifiseerde en ongemodifiseerde bitumen emulsies en tilliet en graniet te definïeer en te evalueer. Dit was ook moontlik om die resultate van die Universiteit Stellenbosch en die Universiteit of Wisconsin-Madison suksesvol met mekaar te vergelyk aangesien toetse by beide die instansies voltooi is. Die ontwikkeling van die toets en die inter laboratorium toets resultate het dit moontlik gemaak om die hipotese te bevestig dat die BBS toets prosedure effektief gebruik kan word om die bitumen en aggregaat verdindinge te toets en te evalueer. Behalwe vir die tempo van die lading waarteen die aftrek sterkte getoets word , is die emulsie tipe en die nabehandeling tydperk beide geidentifiseer as die mees beduidende invloede wat bydrae tot die ontwikkeling van die verbinding sterkte. Die aggregaat tipe is ook geidentifiseer as n belangrike faktor wat die verbinding sterkte ontwikkeling sal beïnvloed. Die interaksie tussen die emulsie tipe en nabehandeling tydperk was geïdentifiseer as die mees beduidende interaksie. Daar sal wel nog heelwat eksperimente voltooi moet word met die BBS toets prosedure voordat dit volkome geïntegreer kan word as deel van n prestasie gebaseerde spesifikasie stelsel vir die ontwerp van seëls.

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.

M. Tech. Civil Engineering. / Evaluates various laboratory test methods to assess rutting potential in the hot-mix asphalt (HMA) and the effects of compaction methods. To achieve this objective, rutting potential of HMA samples prepared and compacted in the laboratory, and in the field was evaluated using different laboratory test methods under a range of temperatures and loads.

La fatigue est un des principaux mécanismes de dégradation des chaussées. En laboratoire, la fatigue est simulée en utilisant des essais de chargement cyclique, généralement sans période de repos. L’évolution du module complexe (une propriété du matériau utilisée dans la caractérisation de la rigidité des matériaux viscoélastiques) est suivie de manière à caractériser l’endommagement. Son changement est généralement interprété comme étant dû au dommage, alors que d’autres phénomènes (se distinguant du dommage par leur réversibilité) apparaissent. Des effets transitoires, propres aux matériaux viscoélastiques, apparaissent lors des tout premiers cycles (2 ou 3) et produisent une erreur dans la détermination du module complexe. La non-linéarité (dépendance du module complexe avec le niveau de déformation) est caractérisée par une diminution réversible instantanée du module et une augmentation de l’angle de phase qui est observée avec l’augmentation de l’amplitude de déformation. De plus, pendant le chargement, de l’énergie mécanique est dissipée en raison du caractère visqueux du comportement du matériau. Cette énergie se transforme principalement en chaleur ce qui induit une augmentation de température. Cela produit une diminution de module liée à cet auto-échauffement. Quand le matériau revient à la température initiale, le module initial est alors retrouvé. La partie restante du changement de module peut être expliquée, d’une part par un autre phénomène réversible, appelé dans la littérature « thixotropie », et d’autre part par le dommage « réel », qui est irréversible. Cette thèse explore ces phénomènes dans les bitumes, mastics (bitume mélangé avec des particules fines, dont le diamètre est inférieur à 80μm) et enrobés bitumineux. Un chapitre (sur la nonlinearité) présente des essais de « balayage d’amplitude de déformation » avec augmentation ou/et diminution des amplitudes sont présentés. Un autre se concentre sur l’auto-échauffement. Il comprend une proposition de procédures de modélisation dont les résultats sont comparés avec des résultats des cycles initiaux d’essais de fatigue. Finalement, un chapitre est dédié à l’analyse du module complexe mesuré pendant le chargement et les phases de repos. Des essais de chargement et repos ont été réalisés sur bitume (où le phénomène de thixotropie est supposé avoir lieu) et mastic, de manière à déterminer l’effet de chacun des phénomènes identifiés sur l’évolution du module complexe des matériaux testés. Les résultats de l’étude sur la nonlinearité suggèrent que son effet vient principalement du comportement non linéaire du bitume, qui est déformé de manière très non-homogène dans les enrobés bitumineux. Il est démontré qu’un modèle de calcul thermomécanique simplifié de l’échauffement local, ne considérant aucune diffusion de chaleur, peut expliquer le changement initial de module complexe observé au cours des essais cycliques sur enrobés. Néanmoins, la modélisation de la diffusion de chaleur a démontré que cette diffusion est excessivement rapide. Cela indique que la distribution de l’augmentation de température nécessaire pour expliquer complètement le module complexe observé ne peut pas être atteinte. Un autre phénomène réversible, qui a des effets sur le module complexe similaires à ceux d’un changement de température, doit donc avoir lieu. Ce phénomène est considéré être de la thixotropie. Finalement, à partir des essais de chargement et repos, il est démontré qu’une partie majeure du changement de module complexe au cours des essais cycliques vient des processus réversibles. Le dommage se cumule de manière approximativement linéaire par rapport au nombre de cycles. Le phénomène de thixotropie semble partager la même direction sur l’espace complexe que la nonlinéarité. Cela indique que les deux phénomènes sont possiblement liés par la même origine microstructurelle. Des travaux supplémentaires sur le phénomène de thixotropie sont nécessaires. / Fatigue is a main pavement distress. In laboratory, fatigue is simulated using cyclic loading tests, usually without rest periods. Complex modulus (a material stiffness property used in viscoelastic materials characterisation) evolution is monitored, in order to characterise damage evolution. Its change is generally interpreted as damage, whereas other phenomena (distinguishable from damage by their reversibility) occur. Transient effects, proper to viscoelastic materials, occur during the very initial cycles (2 or 3) and induce an error in the measurement of complex modulus. Nonlinearity (strain-dependence of the material’s mechanical behaviour) is characterised by an instantaneous reversible modulus decrease and phase angle increase observed when strain amplitude increases. Moreover, during loading, mechanical energy is dissipated due to the viscous aspect of material behaviour. This energy turns mainly into heat and produces a temperature increase. This produces a modulus decrease due to self-heating. When the material is allowed to cool back to its initial temperature, initial modulus is recovered. The remaining stiffness change can be explained partly by another reversible phenomenon, called in the literature “thixotropy”, and, then, by the “real” damage, which is irreversible. This thesis investigates these phenomena in bitumen, mastic (bitumen mixed with fine particles, whose diameter is smaller than 80μm) and bituminous mixtures. One chapter (on nonlinearity) presents increasing and/or decreasing strain amplitude sweep tests. Another one focuses on selfheating. It includes a proposition of modelling procedures whose results are compared with the initial cycles from fatigue tests. Finally, a chapter is dedicated to the analysis of the measured complex modulus during both loading and rest periods. Loading and rest periods tests were performed on bitumen (where the phenomenon of thixotropy is supposed to happen) and mastic in order to determine the effect of each of the identified phenomena on the complex modulus evolution of the tested materials. Results from the nonlinearity investigation suggest that its effect comes primarily from the nonlinear behaviour of the bitumen, which is very non-homogeneously strained in the bituminous mixtures. It was demonstrated that a simplified thermomechanical model for the calculation of local selfheating (non-uniform temperature increase distribution), considering no heat diffusion, could explain the initial complex modulus change observed during cyclic tests on bituminous mixtures. However, heat diffusion modelling demonstrated that this diffusion is excessively fast. This indicates that the temperature increase distribution necessary to completely explain the observed complex modulus decrease cannot be reached. Another reversible phenomenon, which has effects on complex modulus similar to the ones of a temperature change, needs to occur. That phenomenon is hypothesised as thixotropy. Finally, from the loading and rest periods tests, it was demonstrated that a major part of the complex modulus change during cyclic loading comes from the reversible processes. Damage was xivfound to cumulate in an approximately linear rate with respect to the number of cycles. The thixotropy phenomenon seems to share the same direction in complex space as the one of nonlinearity. This indicates that both phenomena are possibly linked by the same microstructural origin. Further research on the thixotropy phenomenon is needed.