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Lightly cemented rubber tire chips as highway pavement sub-base and the use of fiber Bragg's grating (FBG) as instrumentation sensors /Fung, Wing Wah. January 2004 (has links)
Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004. / Includes bibliographical references. Also available in electronic version. Access restricted to campus users.
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Evaluation of laboratory durability tests for stabilized aggregate base materials /Roper, Matthew Brent, January 2007 (has links) (PDF)
Thesis (M.S.)--Brigham Young University. Dept. of Civil and Environmental Engineering, 2007. / Includes bibliographical references (p. 65-69).
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Evaluation of laboratory durability tests for stabilized subgrade soils /Parker, John Wesley. January 2008 (has links) (PDF)
Thesis (M.S.)--Brigham Young University. Dept. of Civil and Environmental Engineering, 2008. / Includes bibliographical references (p. 67-71).
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Influence of surface seal variables on bitumen bond strength propertiesLombard, Le Riche 12 1900 (has links)
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.
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Characterization of road materials and environmental conditions for the analysis and design of flexible pavements in Hong KongTeague, Frederick Thomas. January 1999 (has links)
published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy
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Accelerated curing of concrete with high volume pozzolans - resistivity, diffusivity and compressive strengthUnknown Date (has links)
This investigation presents results of the temperature effect on durability properties (resistivity and diffusivity) and compressive strength of concrete with pozzolans, and the effect of pozzolanic admixtures on microstructure and chemical compositions of concrete pore solution. ... Temperature dependence of electrical resistivity and chloride diffusivity was studied by dynamic temperature tests. Accelerated curing regimes involving curing concrete specimens in 35À C lime water with different durations were tested. Compressive strength test, resisivity measurement and rapid chloride migration (RCM) tests were performed. A leaching method was used to measure pH and conductivity of concrete pore solution. ... The accelerated curing regimes were found to increase the compressive strength and resistance to chloride ion penetration at short-term and long-term. With the developed correlation between resistivity and migration coefficients, it is possible to employ the resistivity measurement as an alternative or replacement of the RCM test to evaluate resistance of chloride ion penetration of concrete. Pozzolanic admixtures were found to decrease both pH and conductivity of concrete pore solution as the replacement ratio increased. Moreover, the migration coefficients were found to be greatly correlated to the microstructure properties of concrete, such as porosity, formation factor and tortuosity. / by Yanbo Liu. / Thesis (Ph.D.)--Florida Atlantic University, 2012. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.
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Modification of black cotton soil using a mixture of fly ash and slagment for road construction.Maneli, Andile. January 2014 (has links)
M. Tech. Civil Engineering / Black cotton soils are fertile and very good for agriculture, horticulture, sericulture and aquaculture. However, they are not good as road construction material because of their undesirable engineering properties and, therefore, need to be removed from site or modified to meet the minimum design standards required for roads subgrade material. This type of clay is very expansive and causes significant damages and problems on South African roads. Roads that are built on expansive clays are adversely affected by the behaviour of the expansive clay. Conventional methods of road design and construction over such material has proved to be very costly. It has been a practice in road construction to remove black cotton soil and replace with better quality soil. This results in high construction costs. The use of by-product and waste materials for modification and stabilization of engineering properties of expansive clays has environmental and economic benefits. On the other hand, problematic material may be treated in its natural state "in situ", thereby leading to reduction in cost. Thus, the modification of Black cotton soils using a mix proportion of fly ash and slagment may improve the engineering properties of the material. The overall objective of the study was to investigate and determine the appropriate mix proportion of fly ash and ground granulated blast furnace slag in the modification of engineering properties of black cotton soil for use in road construction.
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Laboratory characterization of Ohio-strategic highway research program test road pavement materialsMargowati, Margaretha January 2001 (has links)
No description available.
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Influence of durability properties on performance of bitumen stabilised materialsTwagira, Elias Mathaniya 03 1900 (has links)
Thesis (PhD (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: In both developing and developed countries, to ensure sustained economic growth the quest for
optimal roads performance is an extremely high priority. A global increase in the use of foamed
bitumen and bitumen emulsion materials (BSMs) as a solution to roads maintenance,
rehabilitation, and upgrading has become evident. This is driven by environmental policies
aimed at conserving energy and limiting the exploitation of new borrows pits. It has therefore
become imperative that BSMs are used optimally, and, in order to achieve this, practitioners
need to understand the mechanisms that influence durability and long-term performance.
The changes in the behaviour of materials and the failure mechanisms of BSM mixes
are long-term phenomena. This implies that the study of the physicochemical and mechanical
properties of the mixes is vital. Therefore, a fundamental understanding of the moisture damage
and age-hardening characteristics, which are related to materials’ properties, is required. The
main objective of this study is to advance BSM technology by assessing the influence of the
selected materials on durability behaviour 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 of binder and mineral aggregates. The properties of bitumen (foamed bitumen or
bitumen emulsion) and mineral aggregates were reviewed. This was followed by review into the
colloidal behaviour of foam and emulsion and physicochemical and mechanical interaction with
mineral aggregates. Factors influencing the interaction of BSMs were then identified. Finally, the
fundamental theories on thermodynamics, hydrodynamics, and electrokinetics were used to
describe the step-by-step process by which adhesive bonding and cohesion occur in BSMs.
The mixture durability in terms of moisture damage was investigated. To achieve this
aim, the physical and mechanical moisture-induced damage process was analysed. The test
control parameters were established and a laboratory device to quantify these parameters
designed. New moisture conditioning procedures were developed and demonstrated in this
study. From the moisture induction simulation test (MIST) procedure, it became evident that
pulsing water pressures into compacted and cured BSM mixes simulates the hydrodynamic
effect that occurs in the field due to dynamic traffic loading. The different mix matrices typically
applicable to the recycling processes – such as Hornfels-RAP and Quartzite crushed stone,
stabilised with either foamed bitumen or bitumen emulsion and the addition of active filler
(cement or lime) – were investigated. It was found that a new moisture-conditioning procedure
using the MIST device and monotonic triaxial testing can distinguish those BSM mixes that are
resistant to moisture damage from those that are less resistant. The validation of the MIST and
monotonic test results was done using the APT device, which is the MMLS3 wet trafficking test.
The results on both tests showed good correlations in evaluating and screening BSMs in terms
of moisture susceptibility.
Field temperature data was collected and a model to accurately simulate the curing of
BSMs was identified and proposed for further investigation and validation. It was found from the
field temperature data collected in this study that the temperature gradient on the study site
varied according to the depth of the BSMs (that is, 10oC-17oC during winter and 17oC– 47oC
during summer). Understanding the influence of the temperature conductivity and rate of
evaporation is important for inferring moisture damage and age-hardening behaviour and proper
selection of BSMs.
The age-hardening behaviour of BSMs is linked to the durability properties and longterm
performance of these materials. The fundamental characteristics associated with shortand
long-term age hardening were investigated in this study. The short-term dimension involved
assessing the age-hardening characteristics of the binder (foamed bitumen colloids and bitumen emulsion droplets) prior to the production of BSMs. The long-term study involved extracting and
recovering the binder from the briquettes (made from different mixes) compacted in the
laboratory and cores extracted from different field pavement sections which were in service for
8-10 years. The study found that the length of time bitumen is kept in circulation in the
laboratory plant at elevated temperature (170oC–180oC) before making BSM-foam contributes
to the ageing of the binder, especially after eight hours. The foaming process in itself was found
not to alter the bitumen properties. It is recommended that a temperature range between 160oC-
165oC be used for the production of foamed bitumen with softer bitumen. This will not
compromise its quality. In addition, the time of circulation of bitumen in laboratory plant should
not be longer than three (3) hours.
The rheological properties of the bitumen recovered from laboratory briquettes and cores
from field pavement show that age hardening on foamed bitumen and bitumen emulsion during
in-service life occurred. The ageing also seemed to be dependent on the effect of traffic, with
trafficked areas (i.e. on-wheel path and inner-wheel path) experiencing more ageing than untrafficked
areas (i.e. between-wheel path). However, the extraction and recovery process was
found to be complex, and produce uncertain results. Although the results show that binders in
BSMs undergo age hardening, its distinct behaviour in BSM performance was not obvious from
the extensive tests carried out in this study.
The last part of the study contains its conclusions and recommendations. The study
provides an insight into fundamental material durability properties, and 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
apply a mix that is durable and long-lasting. The specific durability-related issues addressed in
this study are substance for future research. This novel solution to the application of BSMs will
benefit all parties involved in the development of pavement recycling technology. / AFRIKAANSE OPSOMMING: Om volgehoue ekonomiese groei te verseker in beide ontwikkelende en ontwikkelde lande,
geniet die soeke na die optimale werkverrigting van paaie ’n baie hoë prioriteit. ‘n Wêreldwye
toename in die gebruik van skuimbitumen en bitumen-emulsiemateriale (BSMs) as ’n oplossing
vir padonderhoud, rehabilitasie en opgradering is merkbaar. Dit word meegebring deur die
omgewingsbeleide wat die ontginning van nuwe leengroewe beperk en besparing van energie
bevorder. Die korrekte gebruik van hierdie materiale vereis dat die meganismes wat die
duursaamheid en langtermyn-werkverrigting daarvan beïnvloed, deeglik verstaan word.
Die verandering in materiaalgedrag en falingsmeganismes van BSM materiale is
langtermynverskynsels. Dit impliseer dat bestudering van die fisiochemiese en meganiese
eienskappe van die mengsels uiters belangrik is. Dis dus voor die hand liggend hoe belangrik
vogbeskadiging en verharding met tyd, wat verwant is aan materiaaleienskappe, is. Die
hoofdoelwit met hierdie studie is om die vooruitgang van BSM tegnologie te versnel deur dit
moontlik te maak om gekose materiale te evalueer op grond van hulle invloed op duursaamheid
en langtermyn-werkverrigting in alle toepassingsfases (naamlik mengontwerp, konstruksie en
dienstoestand).
Hierdie studie begin met ’n uitgebreide literatuuroorsig oor fundamentele begrippe van
die karakterisering van interaksie van die bindstof en die minerale-aggregate. Inligting oor
bitumen (skuimbitumen en bitumen emulsies) en eienskappe van minerale aggregate is
bestudeer. Dit is gevolg deur ’n studie van die fundamentele begrip van die kolloïdale gedrag
van skuim en emulsie, asook fisiochemiese en meganiese interaksie met minerale aggregate.
Faktore wat die interaksie van BSM-materiale beïnvloed is geïdentifiseer. Die basiese teorie
van termodinamika, hidrodinamika en elektrokinetika is daarna gebruik om stap vir stap die
proses en formulering van adhesie-binding en kohesie in die BSMs, wat in hierdie studie
aangebied word, te beskryf.
Die kwantifisering van mengsel-duursaamheid in terme van vogbeskadiging is ontwikkel.
Om hierdie doel te bereik, is die fisiese en meganiese proses van beskadiging deur
vogindringing geïdentifiseer. Die gekontroleerde parameters is bepaal en ’n
laboratoriumapparaat is ontwerp om hierdie parameters te kwantifiseer. Nuwe
vogkondisioneringsprosedures is ontwikkel en in hierdie studie gedemonstreer. Van prosedures
van voggeïnduseerde sensitiwiteitstoetsing (Engels: moisture induction simulation test (MIST))
was dit duidelik dat pulsering van waterdruk in BSM materiale die hidrodinamiese effek naboots
wat in die veld bestaan as gevolg van dinamiese verkeerslaste. Verskillende mengselmatrikse
wat tipies is van hergebruik, soos byvoorbeeld hoornfels-hersikleerde asfalt produk (Engels:
recycled asphalt product (RAP)) en vergruisde granietklip, met skuimbitumen of bitumenemulsie
gestabiliseer en met byvoeging van aktiewe vulmateriaal (sement of kalksteen), is
ondersoek. Daar is bevind dat nuwe vogkondisioneringsprosedures (soos bepaal deur MIST
apparaat en drie-assige toets) kan onderskei tussen BSM materiale wat weerstandig is teen
vogbeskadiging en dié wat minder weerstandig (vatbaar) is. Die geldigheid van die MIST en
monotone toetsresultate is bepaal deur gebruik van die APT apparaat wat ’n MMLS3 nat
verkeerstoets is. Die resultate van beide toetse toon goeie korrelasie in die keuring van BM
materiale in terme van vogvatbaarheid.
In hierdie ondersoek is veldtemperatuurdata versamel en die toepaslike model om
verouderende BM lae akkuraat te simuleer is geïdentifiseer en voorgelê vir verdere ondersoek
en verifikasie. Daar is uit veldtemperatuurdata bevind dat temperatuurgradiënt op die betrokke
terrein gewissel het met die dikte van die BSM, naamlik 10oC-17oC gedurende die winter en
17oC-47oC gedurende die somer. Begrip vir die invloed van temperatuuroordragkoëffisiënt en
verdampingstempo is belangrik by die afleiding van vogbeskadiging en verharding met
ouderdom en die korrekte keuse van BSM materiale.Verouderingsverhardinggedrag van BSMs is verwant aan die duursaamheidseienskappe en
langtermynwerkverrigting van hierdie materiale. Die basiese karakteristieke wat met kort- en
langtermyn verouderingsverharding geassosieer word, is in hierdie studie ondersoek. Die klem
op die kort termyn is geplaas op die verouderingsverhardingsgedrag van die bindstof
(skuimbitumen kolloïdes en bitumen-emulsiedruppels) voordat BSMs vervaardig word. In die
lang termyn evaluasie het die studie ekstraksie en herwinning van bindstof uit brikette wat in die
laboratorium gekompakteer is (van verskillende mengsels) en uit kerns verkry vanaf verskeie
plaveiselgedeeltes na 8-10 jaar diens ingesluit. Die ondersoek het bevind dat die tydsverloop
waarin bitumen in sirkulasie gehou is by verhoogde temperatuur (170oC-180oC) in die
laboratorium-aanleg voordat BSMs vervaardig is, veral indien na 8 uur, bydra tot die
veroudering van die bindstof. Die skuimproses op sigself verander nie die bitumeneienskappe
nie. Daar word aanbeveel dat temperature tussen die grense 160oC-165oC gehandhaaf word
vir produksie van skuimbitumen met sagter bitumen sonder dat die kwaliteit benadeel word en
dat die sirkulasietyd nie 2 tot 3 ure behoort te oorskry nie.
Die reologiese eienskappe van die herwinde bitumen vanuit laboratoriumbrikette en
kerns van plaveisels toon dat ouderdomsverharding van skuimbitumen en bitumen-emulsie
tydens die diensleeftyd plaasvind. Die veroudering is skynbaar ook afhanklik van
verkeerseffekte, met belaste areas (in wielspoor of binne wielspoor) wat ’n hoër mate van
veroudering toon as onbelaste areas (tussen wielspore). Die ekstraksie- en herwinningsproses
op sigself was egter bevind as baie kompleks met uiters onseker resultate. Dit het gelei tot
onsekere gedrag in terme van ouderdomsverharding van die BSM bindmiddel (skuim of
emulsie). Alhoewel resultate toon dat die bindmiddels ouderdomsverharding ondergaan het, is
die BSM werkverrigting nie duidelik uit die uitgebreide toetse wat in hierdie studie uitgevoer is
nie.
Die laaste deel van die studie bevat gevolgtrekkings en aanbevelings. Die studie lewer
insig in die fundamentele duursaamheidseienskappe van die materiaal, wat bydra tot
verbetering van die huidige prosedure van seleksie, saamstelling en formulering van die
mengmatriks vir BSMs. Verder voorsien dit ’n metode wat in die praktyk gebruik kan word om
met vertroue duursame mengsels met lang diensbaarheidsleeftye te vervaardig. ’n Nuwe
oplossing en vooruitgang in die toepassing van BSMs is daargestel tot voordeel van alle partye
betrokke by die ontwikkeling van herwinningstegnologie.
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Towards a performance related seal design method for Bitumen and modified road seal bindersMilne, Terence Ian 12 1900 (has links)
Thesis(PhD (Civil Engineering))-- University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Bitumen based road surfacing seals and asphalt wearing courses have been used by society's Engineers "to counter the damage to the existing unsurfaced roadways by the newly developed automobile with its rubber driving wheels" since the early 1900's. Early experiments were conducted with both tar and bitumen to find a suitable material to alleviate the situation, and ongoing research has been carried out through the past century and into the new millennium, throughout the world, examining improvements, from materials used, to design and construction methods. However, there is still much to be understood, improved and refined, when considering road surfacing seal design.
Pavement designers have the choice of utilizing either an asphalt (graded aggregate remanufactured
with a bitumen binder and applied as a complete product) or a surfacing seal (including variations of bitumen binder sprayed onto the road surface, with the addition of single size
stones, either in one or two layers of binder and aggregate, i.e. single or double seals) as a
pavement wearing course.
Current road surfacing seal design practice depends on empirical analysis and experience, being primarily a volumetric based assessment of bitumen application. This research project assesses
South African seal design philosophy, investigates design areas where review or updating is
required to accommodate changing bitumen sources and types, and traffic loading. Seal
performance criteria are examined, with the development of a matrix of influences on seal
performance. Using this, the need for a seal design method based on mechanistic material
properties is proposed, and the prototype example of such a numerical model using finite element
method is presented.
To contribute further towards a performance related seal design method, the feasibility of modelling
of road surfacing seals using mechanistic principles was examined. The potential of developing
failure and fatigue criteria or relationships to enable assessment of the expected seal performance, with inclusion of different component material characteristics and variations, varying traffic and
environmental conditions, was also examined.
From assessment of literature, and understanding of the components of the seal, pavement, and influencing factors, a choice of numerical model of seal performance was made. The Finite Element
Method (FEM) Analysis was selected for the purpose of modelling seal performance. The model was developed to enable examination of the interaction of individual seal components (i.e. stone and bitumen), at micro-mechanic scale.
The prototype 3-dimensional numerical seal model was undertaken in 2002 and 2003 at Technical
University Delft, using the CAPA research program. On the basis of the linear calculations the
developed numerical prototype model is able to provide insight into seal behaviour and distinction
between mechanical (seal geometry) and chemical (components) seal aspects, and insight into
stress and strain development in the different seal types. Simulations of different seal,
environmental and traffic scenarios are provided to demonstrate the potential of the model
(excluding seal aggregate interlock and embedment effects at prototype stage).
In order to provide data for the verification of the prototype numerical model, and to further
contribute to the development of a performance related seal design method, performance tests were
developed, with a new tool for assessment of comparative seal performance using the Model Mobile
Load Simulator Accelerated Pavement Testing apparatus. The performance of each different seal
binder type - Penetration grade Mumen, SBS, SBR, EVA and Bitumen Rubber - was undertaken. A
methodology for the assessment of in-service seal performance was developed, and the
performance of the respective seals reported. The results of this examination showed that each
binder type has its unique contribution to seal performance.
These new performance tests will be able to assist designers in the added determination of the
fundamental binder properties on seal performance, and the seals' ability to contribute to the overall
performance of the pavement.
An additional comparative performance test method was developed to enable assessment of the
effect of ageing and moisture, to complement the MMLS results.
In summary, the performance testing has assisted in identifying the critical parameters a seal
designer should consider during the design process.
From this research, it is evident that the current seal design method requires further development to
able designers to predict the effect of:
Varying axle loads, tyre pressures and design speed;
Varying characteristics of the different binders, (i.e. temperature - viscosity relationships,
adhesion and visco-elastic behaviour);
on the performance of seals.
The major areas for suggested improvement in current seal design methods towards a performance
based design method are:
inclusion of variable traffic load and environmental characteristics, including temperature and
moisture influences, and
inclusion of mechanistic material characteristics into the design methodology. / AFRIKAANSE OPSOMMING: Bitumengebaseerde padoppervlakseellae en asfaltslytlae is sedert die 1900's deur ingenieurs
gebruik as teenwig teen die skade wat die pas ontwikkelde voertuig met sy rubberwiele aan
bestaande ryvlakke sonder oppervlakbehandeling aangerig het. In vroeëre eksperimente wat
daarop gemik was om 'n geskikte materiaal te vind om die probleem teen te werk, is 'n kombinasie
van teer en bitumen gebruik. Sedertdien word voortgesette navorsing steeds wêreldwyd gedoen om
verbeterings te ondersoek, nie net ten opsigte van materiale nie maar ook ontwerp- en
konstruksiemetodes. Wat die ontwerp van padoppervlakseëling betref is daar egter heelwat wat
reg begryp, verbeter en verfyn moet word.
Plaveiselontwerpers het die keuse om of 'n asfalt te gebruik (gegradeerde aggregaat
voorafvervaardig met 'n bitumen bindmiddel en aangewend as 'n klaarproduk), of 'n oppervlakseël
(een laag of twee lae [m.a.w. enkel- of dubbelseël] bitumen bindmiddel met aggregaat [enkelgrootte
klippies] bygevoeg, gespuit op die padoppervlak).
In die praktyk berus die ontwerp van padoppervlakseëling tans op empiriese analise en ervaring
(wat hoofsaaklik 'n volumetriesgebaseerde assessering van die aanwending van bitumen is).
Hierdie navorsingsprojek doen 'n waardebepaling van die Suid-Afrikaanse filosofie van seëlontwerp,
en ondersoek ontwerpterreine wat hersiening of bywerking benodig om vir veranderende
bitumenbronne en -tipes, asook verkeerslading, voorsiening te maak. Met die ontwikkeling van 'n
matriks van die invloede op seëlprestasie is die kriteria vir seëlprestasie ondersoek. Op grond
daarvan word aangevoer dat daar 'n behoefte is aan 'n seëlontwerpmetode gebaseer op die
meganistiese eienskappe van materiaal, en word 'n voorbeeld van 'n numeriese modelprototipe wat
die eindige-element-metode gebruik, voorgelê.
Ten einde 'n verdere bydrae te lewer tot die ontwikkeling van 'n prestasiegerigte seëlontwerpmetode,
is die uitvoerbaarheid van die modellering van padoppervlakseëllae gebaseer op meganistiese
beginsels, ondersoek. Daar is ook ondersoek ingestel na die potensiaal vir die ontwikkeling van
kriteria vir die vasstel van mislukking en vermoeidheid of verhoudinge wat die assessering van die
verwagte seëlprestasie (ingesluit die verskillende kenmerke en variasies van
seëlkomponentmateriaal en wisselende verkeers- en omgewingsomstandighede) moontlik kan
maak.
Met oorweging van die bestudeerde literatuur en 'n begrip van die komponente van seël, plaveisel en inwerkende faktore, is 'n keuse van 'n numeriese model vir seëlprestasie gemaak. Die eindige-element-metode (Finite Element Method [FEM]) is gekies as die analitiese metode vir die
modellering van seëlprestasie. Die model is ontwikkel om die ondersoek van die interaksie tussen
individuele seëlkomponente (klip en bitumen) op mikromeganiese skaal moontlik te maak.
Die ontwikkeling van die driedimensionele, numeriese, model-seëlprototipe is tussen 2002 en 2003 by die Delft Tegniese Universiteit gedoen, met gebruikmaking van die CAPA-navorsingsprogram.
Wat lineêre berekenings betref, kan die ontwikkelde numeriese modelprototipe 'n insig gee in seëlgedrag en in die onderskeid tussen aspekte van seëlgeometrie (meganies) en seëlkomponente
(chemies), asook in die spanning- en vervormingsontwikkeling van die verskillende tipes seël.
Simulasies van verskillende seël-, omgewings- en verkeerscenario's word voorgestel om die
potensiaal van die modelprototipe te demonstreer.
Met die oog daarop om data vir die verifikasie van die numeriese modelprototipe te voorsien, en om verder tot die ontwikkeling van 'n prestasiegerigte seëlontwerpmetode by te dra, is prestasietoetse, met 'n nuwe instrument vir die assessering van vergelykende seëlprestasie met behulp van die
Model Mobile Load Simulator Accelerated Pavement Testing apparaat, ontwikkel. Die prestasie van
elke verskillende tipe seëlbindmiddel- penetrasiegraad bitumen, SBS, SBR, EVA en bitumenrubber - is getoets. 'n Metodologie vir die assessering van die ingebruiksprestasie van seëllae is ontwikkel,
en daar is verslag gedoen oor die prestasie van die verskillende seëllae. Die resultate van die
ondersoek het getoon dat elke tipe bindmiddel 'n eie unieke bydrae tot die prestasie van die seël
lewer.
Die nuwe prestasietoets sal ontwerpers help met die bepaling van die grondliggende bindmiddeleienskappe
wat by seëlprestasie ter sprake is, asook van die seël se vermoë om tot die algehele
prestasie van die plaveisel by te dra.
'n Bykomende prestasievergelykingstoetsmetode vir die assessering van die effek van veroudering
en vogtigheid is ontwikkel om die MMLS-resultate aan te vul.
Ter opsomming, die prestasietoetsing het bygedra tot die identifisering van die kritiese parameters
wat die seëlontwerper tydens die ontwerpproses in gedagte behoort te hou.
Die navorsing wat gedoen is, dui daarop dat die huidige seëlontwerpmetode verder ontwikkel moet
word om ontwerpers in staat te stel om die effek van die volgende te kan voorspel:
Wisselende aslas, banddruk en ontwerpspoed; Verskillende kenmerke van die verskillende bindmiddels (bv. temperatuur
viskositeitsverhoudinge, vashegting en viskoëlastiese gedrag).
Wat huidige seëlontwerpmetodes betref, is die hoofterreine waarop 'n verbetering voorgestel word, die insluiting van veranderlike verkeerslas- en omgewingskenmerke, ingesluit die invloed van
temperatuur en vogtigheid, en
insluiting van meganistiese kenmerke van materiaal in die ontwerpmetodologie.
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