Dissertation (PhD)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: The use of foamed bitumen and bitumen emulsion as binders for use in road
rehabilitation is gaining favour globally. High-level road facilities through to unpaved
roads requiring attention are being treated with these binders due to environmental,
economic and practical benefits in the use of cold bituminous mixes. In addition,
static and mobile plant with the capability of performing stabilisation using bitumenemulsion
and foamed bitumen has become commercially available and widely
utilised, as a result of development in recycling technology and lapse in patent rights
on foam nozzles.
An understanding of the behaviour and failure mechanisms of these cold mixes, as
well as sound guidelines for the mix design procedures of cold mixes, especially
foamed bitumen, and design guidelines for pavements structures incorporating these
materials, are lacking however. Mix designs are carried out primarily on the basis of
experience and pavement designs are empirically based.
The main objective of this dissertation is to address the need for a fundamental
understanding of foamed bitumen and foamed bitumen mixes, and in so doing to
develop techniques for adjudicating mixes, optimising their composition and
rationalising their design both as mixes and as layers in road pavements. At the
same time the exploration of new applications for foamed bitumen and the
possibilities for progressive related technology, is a priority.
To commence, this study includes an appraisal of most of the literature available on
foamed bitumen. This is followed by a fundamental investigation of the colloidal mass
of foam that is produced when small quantities of cold water are added to hot
bitumen. Factors influencing the quality of the foam are identified and a Foam Index
is developed for characterisation and optimisation of the foam.
The spatial composition of a cold foamed bitumen mix, including Interaction of the
foam with moist mineral aggregate, is also addressed in this dissertation. In
particular, the stiffening of the filler mastic using foamed bitumen as binder is
analysed. Techniques of optimising the sand type and content in the mix are also
developed and guidelines for desired aggregate structures for foam treatment are
established.
The temperature of the mineral aggregate has been shown to have a profound
influence on the behaviour and performance of a foamed bitumen mix. This has been
selected as a focal area of further investigation and the research has lead to the
development of a new process called "The half-warm foamed bitumen treatment
process" that can produce mixes with almost the quality of hot mix asphalt with up to
40% less energy consumption.
Other processes developed in this research include the use of cold mix asphaltic
blocks for construction of road pavements in developing areas. This technology
enhances the use of a high labour component in road construction in an
economically competitive manner. The dissertation provides details for mix design
and construction of the cold mix blocks. Finally, the study includes models for the performance prediction of foamed bitumen
mixes. In particular, foamed mixes that exhibit stress-dependent behaviour have
been investigated and models established on the basis of triaxial testing and
accelerated pavement testing for the prediction of permanent deformation of such
layers under repeated loading.
Practical applications of the research findings are summarised in Appendix F. This
includes:
• methods for optimisation of the foamed bitumen properties,
• guidelines for the selection of the ideal aggregate structure for cold foamed
mixes,
• procedures for carrying out cold mix design in the laboratory (including mixing,
compaction and curing),
• procedures for manufacturing half-warm foamed mixes in the laboratory,
• methods for manufacturing cold mix blocks, and
• pavement design methods for road structures incorporating foamed mix layers.
Appendix G outlines statistical techniques that are relevant to the design of
experiments in pavement engineering including examples of applications of these
procedures. The techniques are applied selectively in the relevant chapters of the
dissertation. / AFRIKAANSE OPSOMMING: Die gebruik van skuim bitumen en bitumen emulsie as bindmidel in pad rehabilitasie
begin groter voorkeur wêreldwyd geniet. Van hoë vlak padfasiliteite tot ongeplaveide
paaie wat aandag benodig, word met hierdie binders behandel vanweë die
omgewings-, ekonomiese en praktiese voordele wat hierdie koue bitumen mengsels
inhou. Voorts is statiese en mobiele masjinerie wat die vermoë het om stabilisasie in
die gebruik van bitumenemulsie en skuimbitumen te bewerkstellig, in die handel
verkrygbaar. Dit word algemeen gebruik as 'n uitvloeisel van ontwikkelings in
herwinningstegnologie en die verslapping van patenteregte op skuim sproeikoppe.
'n Leemte bestaan in die begrip van die gedrags- en swigtingsmeganismes van
hierdie koue mengsels, asook goeie riglyne vir die mengselontwerp van koue
mengsels en in besonder skuimbitumen, en ontwerpriglyne vir plaveisel strukture
waar hierdie materiaal geinkorporeer is. Mengselontwerpe word hoofsaaklik
uitgevoer op grond van ondervinding, terwyl plaveiselontwerpe empiries gebaseer is.
Die hoofdoel van die verhandeling is om die behoefte vir 'n fundamentele begrip van
skuim bitumen en skuimbitumen mengsels aan te spreek, en daardeur tegnieke te
ontwikkel vir die be-oordeling van mengsels, optimsering van hul samestelling en
rasionalisering van hulontwerp vir beide mengsels en plaveisellae. Terselfdertyd is
die ondersoek na nuwe toepassings van skuim bitumen en die moontlikhede van
nuwe tegnologie 'n prioriteit.
As beginpunt sluit hierdie studie 'n waardeskatting van die meeste literatuur
beskikbaar op skuim bitumen in. Dit word gevolg deur 'n basiese ondersoek na die
kolloidale massa van skuim wat geproduseer word wanneer klein hoeveelhede koue
water by warm bitumen gevoeg word. Faktore wat die gehalte van die skuim
beinvloed word uitgewys en 'n Skuim Indeks is ontwikkel vir die karakterisering en
optimisering van die skuim.
Die ruimtelike samestelling van 'n koue bitumen mengsel, wat die interaksie van die
skuim met vogtige minerale samevoegings (aggregate) insluit, word ook
aangespreek. Besondere aandag word gewy aan die verharding van die vuiler
mastiekgom wat gebruik word as bitumen binder. Tegnieke om die sandtipe en
inhoud van die mengsel te optimiseer is ontwikkel en riglyne vir die verlangde
samevoegingstrukture (aggregate strukture) vir skuimbehandeling is opgestel.
Daar is bevind dat die temperatuur van die minerale aggregaat 'n duidelike invloed
op die gedrag en verrigting van 'n skuimbitumen mengsel het. Dit is gekies as In
fokuspunt vir verdere studie en die navorsingswerk daarop het gelei tot die
ontwikkeling van In nuwe proses wat "Die half-warm skuim bitumen behandelings
proses" genoem word. Hierdie proses produseer mengsels wat byna gelykstaande is
aan die gehalte van warm gemengde asfalt, maar met tot 40% minder energie
verbruik.
Ander prosesse wat met dié navorsing ontwikkel is, sluit koue gemengde asfaltiese
blokke in, wat gebruik word in die konstruksie van padplaveisel in ontwikkelende
gebiede. Hierdie tegnologie bevorder die ekonomiese gebruik van 'n hoë arbeidskomponent in padkonstruksie. Die studie stel besonderhede vir die
mengselontwerp en konstruksie vir koue gemengde blokke voor.
Laastens sluit die studie modelle in vir die werkverrigtingsvoorspelling van
skuimbitumen mengsels. Op basis van drie-assige proewe in die laboratorium en
versnelde belasting van paaie is modelle ontwikkel vir skuim bitumen mengsels wat
spanningsafhanklike gedrag vertoon (die sogenaamde "granulêre" groep) om die
permanente deformasie in die lae as gevolg van herhaalde verkeersbelasting te
voorspel.
'n Opsomming van al die praktiese toepassings van die ontwikkelings van die
navorsing word in Appendix F verskaf. Dit sluit in:
• optimesering van die eienskappe van skuimbitumen,
• riglyne vir gewenste samestelling van aggregaat in skuimbitumen mengsels,
• ontwerp metodes vir koue skuimbitumen mengsels in die laboratorium (meng,
verdigting en curing),
• produksie metodes vir half-warme mensels in die laboratorium,
• produksie metodes vir blokke wat met koue mengsels gemaak word, en
• plaveiselontwerp metodes van strukture wat skuimbitumen lae inkorporeer.
Appendix G gee 'n oorsig van statistiese tegnieke wat relevant is vir die ontwerp van
eksperimente, insluitend voorbeelde van toepassings van die prosedures in
plaveiselingenieurswese. Die tegnieke word selektief toegepas in die relevante
hoofstukke van die verhandeling.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/51831 |
| Date | 12 1900 |
| Creators | Jenkins, Kim Jonathan |
| Contributors | Van de Ven, Martinus F. C., Molenaar, Andre A. A., Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 368 p. : ill. |
| Rights | Stellenbosch University |
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