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Evaluation of the curing time and other characteristics of prime coats applied to a granular baseMohan, Gouri 08 July 2011 (has links)
Prime coats have been in use for many decades to help protect the base before the subsequent application of bituminous surface treatments. Prime coat is an application of a low viscosity binder onto the base to help protect the base from moisture, to provide an adequate bond between the bituminous surface coating and the base, to strengthen the base near the surface by binding the fines, and to protect the base from detrimental effects of weather and light traffic until the surface can be constructed. For a prime coat to function efficiently it should penetrate sufficiently into the base and should be cured before the application of subsequent layers. Evaluation of the time required for curing of prime coats and how the curing time depends on various weather parameters has received a lack of attention.
In view of this, the time taken for curing of different prime coats and the dependence of curing time on weather parameters was studied. The prime coats most commonly used in Texas were selected for this study, namely; MC-30, EC-30, CSS-1H, SS-1H and AEP. All testing was done in real conditions, that is, samples were prepared and exposed to actual weather conditions. Since each prime coat is chemically very different, they were analyzed separately to determine the minimum curing time. Curing time was calculated in three different weather conditions to understand how the weather affects curing time. Further, two different application methods were used to determine the effect of application method on the curing time.
In addition to determining curing times, other important engineering properties of prime coats that determine the performance of prime coats such as strength, permeability and penetration were also studied. Strength and permeability tests were done on cured specimens and the effect of application method on these values was also determined. Strength values were measured using a pocket penetrometer and penetration was determined by using sand penetration tests. A unique ranking system list was developed using curing time, strength, penetration and permeability as the key factors to determine the prime coat which would serve all the intended functions effectively and efficiently. / text
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Behaviour of cementitious subbase layers in bitumen base structuresDe Beer, M. January 2009 (has links)
Thesis (M.Eng.(Civil and Biosystems Engineering))--University of Pretoria, 1985. / Summaries in Afrikaans and English. Includes bibliographical references.
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Flexibility and performance properties of bitumen stabilised materialsNwando, Tiyon Achille 04 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: This research investigates the flexibility and the performance properties of bitumen stabilised
materials under the influence of mix variables. The laboratory testing consisted of two main phases.
During the first phase (mix design), the strength and the flexibility of the mixes were assessed
through ITS (Indirect Tensile Strength), UCS (Unconfined Compressive Strength), displacement at
break, strain at break and fracture energy. The second phase consisted of a series of triaxial tests
done to assess the performance properties (shear strength: cohesion and angle of internal friction; and
stiffness: resilient modulus) of the mixes.
The mineral aggregates used in this study were milled from different locations of the R35, near
Bethal. This was a blend of granular material (dolerite, from various locations of the existing base
and subbase layer of the R35) and Reclaimed Asphalt (RA) milled from the existing surfacing.
During the mix design phase, two types of bituminous binders were used (bitumen emulsion and
foamed bitumen) at bitumen content ranges of 2%, 2.4% and 2.8% each. Two types of active filler
were used separately and in combination at a proportion of 1% and 2%. Finally, specimens were
tested in wet and dry conditions for each mix combination. During the triaxial testing phase, only the
optimum bitumen content of 2.4% was used, both for bitumen emulsion and foamed bitumen, with
only cement as active filler in a proportion 1% and 2%. The specimens were tested at different
ranges of densities and saturation levels. The flexibility of the mix was assessed through the fracture energy, the strain and the displacement at
break parameters. An analysis of variance (ANOVA) was conducted on the data to assess the
significance of experimental variables on this property. This property was found to be very sensitive
to bitumen and cement content added to the mix. When assessing the combined effect and the
significance of the variables on the flexibility of the mixes, it was found that fracture energy is
mostly influenced by the cement content, followed by the bitumen content, then the type of treatment
and finally the testing condition. However, the level of significance was not in the same order for the
other two parameters (displacement and strain at break). It was also found that the combined effect
of some independent variables (cement content + testing condition, type of treatment + cement
content + bitumen content) had a significant effect on the fracture energy and the strain at break
respectively.
From the ITS and UCS tests, an increase in strength was noticed with the increase of cement content.
On the other hand, the increase in bitumen content led to a decrease in strength of the material. The
statistical analysis on the ITS and UCS values show that the independent variable with the most significant effect on the ITS is the cement content, followed by the testing conditions, then the
bitumen content and finally the type of treatment. The combined effect of cement content + bitumen
content was found to be significant both for ITS and UCS.
In the second phase triaxial tests were performed in order to evaluate the performance properties of
the mixes. It was found that the increase of the active filler content significantly improves the shear
strength of the material. It was also found that at a fixed cement content, specimens tested at low
density and/or high level of saturation show low shear strength. The Mr-θ model was used to model
the resilient modulus of the mixes and the model coefficients used to evaluate the effect of
experimental variables on the resilient modulus. It was found that the resilient modulus of the mixes
increases as the bulk stress increases. This confirms the stress dependent behaviour of bitumen
stabilised materials. The analysis show that increasing the percentage of active fillers content results
in a significant increase in the resilient modulus values. An increase in relative density also resulted
in an increase in the resilient modulus of the mixes, while the opposite effect was observed with the
increased of the saturation level.
Besides the engineering properties and the mechanical test parameters, other parameters such as the
Tensile Strength Ratio (TSR) was calculated in order to evaluate the moisture sensitivity of the
mixes. Weakening due to moisture was found to be more predominant in the mixes with less active
filler. In addition, bitumen emulsion mixes were found to have a better resistance to moisture
weakening effects compared to foamed bitumen. In addition, a comparison between the rapid curing
and the accelerated curing was done. Higher ITS and UCS results were obtained for specimens cured
using long term curing compared to specimens cured using the accelerated curing method. In conclusion, flexibility is an important property of bitumen road construction material (bitumen
stabilised material include) however, it is not an easy property to measure. Although,
displacement/strain at break and fracture energy from ITS and UCS were able to give us some
indications on the main factors governing the flexibility of bitumen stabilised materials (the bitumen
and active filler content), more accurate and adequate tests are required to evaluate the parameter. / AFRIKAANSE OPSOMMING: Die buigsaamheid en gedragseienskappe van bitumen gestabiliseerde materiale was getoets om
sodoende die invloed van verskeie mengselveranderlikes te evalueer. Die ondersoek het uit twee
fases bestaan. Tydens die eerste fase (mengfase) is die sterkte en buigsaamheid deur middel van
indirekte treksterkte toetse (ITS), onbegrensde druksterkte toetse (UCS), verplasing – en vervorming
by breekpunt sowel as breek-energie toetse gedoen en ondersoek. Die tweede fase het bestaan uit ʼn
reeks drie-assige triaksiaal toetse. Triaksiaaltoetse is uitgevoer om die gedragseienskappe soos die
skuifsterkte, kohesie, hoek van interne wrywing, styfheid en weerstand modulus te ondersoek.
Die gemaalde mineraal-aggregaat wat in hierdie ondersoek gebruik is, was verkry op verskeie areas
van die R35, geleë naby Bethal. Die materiaal is ʼn mengsel van granulêre materiaal (van die
bestaande kroonlaag en stutlaag van die pad) en herwonne asfalt (RA). Tydens die mengontwerp fase
is twee tipes bitumen gebruik naamlik bitumenemulsie en skuimbitumen in hoeveelhede van 2%,
2.4% en 2.8%. Twee tipes aktiewe vulstof (hoeveelhede van onderskeidelik 1% en 2%) was saam
met elk van die verskeie bitumen-hoeveelhede gebruik. Proefstukke van elk van hierdie mengsel
kombinasies is onder beide nat en droë kondisies getoets. Tydens die tweede fase, is slegs die
optimum binder inhoud (2.4%) gebruik vir beide emulsie- en skuimbitumen, gekombineer met 1%
en 2% aktiewe vulstof. Proefstukke was getoets by ʼn reeks van verskillende digthede en
versadigingvlakke. Die buigsaamheid was ondersoek deur middel van breek-energie, vervorming en die verplasing by
breekpunt. ʼn Analise van variasie (ANOVA) is uitgevoer op die toetsdata om sodoende die te
evalueer of die veranderlikes beduidend is ten opsigte van buigsaamheid. Daar is gevind dat die
buigsaamheideienskap sensitief is vir beide bitumen en sement inhoud. Met assessering van die
gekombineerde effek en betekenis van die veranderlikes op die buigsaamheid van die mengsels, is
daar gevind dat die hoogste beduidende veranderlike t.o.v breek-energie die sement inhoud is, gevolg
deur die bitumeninhoud, tipe behandeling en laastens die toetskondisie. Die orde van belangrikheid
verskil vir die ander twee parameters (verplasing en vervorming by breekpunt). Daar is ook gevind
dat die gekombineerde effek van sommige veranderlikes (sement inhoud en toets kondisie, tipe
behandeling en sement inhoud tesame met bitumen inhoud) ook beduidend was t.o.v breek-energie
en vervorming by breekpunt.
Vanuit die ITS en UCS toetse was daar ʼn toename in sterkte waargeneem soos die sementinhoud
toeneem. Aan die anderkant, het ʼn toename in bitumeninhoud ‘n afname in sterkte veroorsaak. Die
statistiese analise van ITS en UCS resultate, toon dat die grootste beduidende onafhanklike t.o.v ITS waardes ook die sement inhoud was, gevolg deur toets kondisies die grootste effek, bitumen inhoud
en die tipe behandeling. Die gekombineerde effek van sementinhoud en bitumeninhoud, was
betekenisvol vir beide ITS en UCS.
Drie-assige triaksiaaltoetse was uitgevoer om die gedragseienskappe van die mengsels te evalueer.
Daar is gevind dat die toename in sement inhoud, die skuif sterkte van die materiaal grootliks
verbeter. By ʼn konstante sementinhoud, wys toetsresultate van proefstukke wat getoets is by lae
digthede en hoë vlakke van versadiging, lae skuif sterkte.
Die Mr – θ model was gebruik om die veerkragsmodulus van die mengsels te moduleer en die
modelkoëffisiënte is gebruik om die effek van eksperimentele veranderlikes op die weerstand
modulus te evalueer. Met toename in die omhullende spanning is ‘n toename in die
veerkragsmodulus waargeneem, wat bevestig dat die gedrag van bitumen gestabiliseerde materiale
spannings afhanklik is. ʼn Toename in die sement en relatiewe digtheid het ʼn merkwaardige toename
in die veerkragsmodulus tot gevolg gehad, terwyl die teenoorgestelde waargeneem is met toename in
versadigingsvlakke.
Buiten die ingenieurseienskap en meganiese toetsfaktore, is ander faktore (soos die trekspanning
verhouding) bereken om die vogsensitiwiteit van die mengsels te evalueer. Mengsels met laer sement
inhoud het groter verswakking ervaar met blootstelling aan water. Bitumenemulsie proefstukke toon
beter weerstand teen water as skuimbitumen. Vergelyking tussen versnelde en korttermyn
nabehandelingsprosedure van proefstukke, toon hoër ITS en UCS waardes vir die versnelde
nabehandelingsprosedure prosedure. Buigsaamheid is ‘n belangrike eienskap van bitumen in padkonstruksie materiale (insluitend bitumen
gestabiliseerde materiale), maar word moeilik gemeet. Alhoewel verplasing/vervorming by
breekpunt en breek energie, bepaal vanaf ITS en UCS, ‘n indikasie toon van die hooffaktore (binder
en sement) wat buigsaamheid van bitumen gestabiliseerde materiaal beïnvloed, word meer akkurate
toetse benodig om die eienskap te ondersoek.
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Mix design considerations for cold and half-warm bituminous mixes with emphasis of foamed bitumenJenkins, Kim Jonathan 12 1900 (has links)
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.
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Vibratory hammer compaction of bitumin stabilized materialsKelfkens, Rex Willem Constantyn 12 1900 (has links)
Thesis (MScEng (Civil Engineering))--Stellenbosch University, 2008. / There are currently well established compaction methods being used in laboratories globally
to prepare specimens for material testing. None of these methods provides the repeatability
and reproducibility, ease of execution or simulation and correlation to field compaction desired
by engineers. The research presented in this report was aimed at the development of a new
or adapted compaction method for bituminous stabilized materials (BSM) that would address
the aforementioned factors, by making use of a vibratory hammer. Along with this, a new
protocol was to be established.
The initial vibratory hammer that was tested was the Kango 637®. This specific vibratory
hammer suffered irreparable damage to the gearbox during the research. A replacement
Kango hammer could not be purchased, therefore a substitute hammer was purchased i.e. a
Bosch GSH 11E®, for which back-up service and replacement parts are readily available
throughout South Africa.
Significant progress had been made with the development of a laboratory compaction
protocol for BSM using the Kango Hammer. The specifications of the Bosch® hammer showed
it was superior in terms of power, weight and other technical features. Comparative testing
was therefore carried out. This allowed for the adaptation of the results achieved to that
point.
Extensive experimentation was then carried out using two types of BSM i.e. foamed bitumen
(80/100 bitumen) and bitumen emulsion (60/40 Anionic Stable Grade) stabilized material. The
initial material used for the experimentation was a G2 quality graded crushed stone.
Additional material was also obtained from a recycling project taking place along the N7 near
Cape Town. The N7 material was used to perform correlation experiments so as to determine
how representative the laboratory compacted specimens were to field compacted material.
Results showed that the vibratory hammer is capable of producing specimens for testing in
the laboratory as well as providing a possible benchmark method for accurately controlling the
quality of work on site i.e. field density control. This was done by identifying the time to and
level of refusal density compaction. The level of refusal density compaction was expressed as
a percentage of Mod AASHTO compaction and using current specifications, a potentially new
site compaction level specification was determined.
In order to asses the material applicability of the vibratory hammer compaction method, tests
regarding moisture sensitivity analysis were carried out on a G5 material. The vibratory
compaction protocol includes a specification for the type of hammer, guide-frame, surcharge
weight, compaction moisture and number of layers. Vibratory compaction can be used to
prepare two types of specimens:
• Specimens for triaxial testing with a diameter of 150mm and a height of 300mm
• Specimens for laboratory testing with a diameter of 150mm and a height of 125mm. Tests showed that the material properties prove to have an influence on the compactability
of the material. Material from the N7 recycling project had been milled out thus altering the
grading and including some RAP. This in turn influenced compaction. The vibratory hammer
moisture curve was found to shift slightly to the left when compared to the Mod AASHTO
moisture curve. The variability of the vibratory hammer was found to be well below the
specified variability of 15%. Repeatability experiments on G5 material indicate that vibratory
hammer compaction may be used on lesser quality granular materials.
A recommended procedure for the compaction of BSM was developed following the
experimentation results.
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Development of a simple trixial test for characterising bitumen stabilised materialsMulusa, William Kapya 03 1900 (has links)
Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2009. / The need for a more reliable testing procedure for the characterisation and Quality Assurance/
Control of Bitumen Stabilised Materials (BSMs), besides UCS and ITS testing, has long been
recognised by the roads industry. In fact, at CAPSA 2004 and CAPSA 2007, discussions of improved
test methods for granular materials, i.e. possible replacement tests for CBR procedures, were
conducted in workshops. Triaxial testing for the evaluation of shear parameters is widely recognised
as a reliable method of measuring these critical performance properties of granular and Bitumen
Stabilised Materials (BSMs). However, the triaxial test in its current state as a research test has little
chance of extensive use by practitioners and commercial laboratories, because of complexity, cost
and time issues. Major adaptations to the research triaxial test are necessary, before this useful test
can have a chance of being accepted by road practitioners.
The main aim of this study is to investigate possibilities of developing a simple, affordable, reliable
and robust test for characterizing granular and bitumen stabilized materials thus linking test outcome
with in-situ performance. This is achieved through the innovative design and manufacture of a
prototype triaxial cell capable of accommodating 150 mm diameter by 300 mm deep specimens. The
cell is simpler than the research (geotechnical) triaxial cell and the operational protocols have been
streamlined, thereby reducing the time and steps required in assembling specimens and testing them.
In order to ensure the development of an appropriate triaxial cell for industry, a survey was
conducted aimed at investigating currently available facilities, testing capacity and resources within
civil engineering laboratories in South Africa. Findings of the survey (Appendix 4) have provided
guidance with regard to the nature and sophistication of any new tests to be developed. The survey
highlighted some of the limitations and lack of sophistication of the current loading frames used for
CBR and UCS testing such as lack of electronic LVDTs, limited overhead space, limited loading
capacity and others. Most laboratories would need to invest in new loading facilities to carry out
triaxial tests.
A review of the test procedure for monotonic triaxial test showed that two main factors contribute to
the complexity of the research (geotechnical) triaxial cell namely, time taken to assemble the
specimen accurately in the cell and secondly the inherent design of the cell which makes it water
and/or air tight at relatively high pressures.
The design of the Simple Triaxial Test, therefore, was aimed at overcoming the drawbacks of
research triaxial test e.g. fitting a membrane to each specimen to be tested, through considerable
simplification by means of a new structure design and procedure of assembly of specimen into the
cell. The advantage of addressing these issues would be reduction in the number of steps required in the test procedure and therefore reduction in testing time. The design of the cell particularly was
preceded by a conceptualization process that involved investigation of numerous options. Concepts
such as the bottle, encapsulated-tube, bottle and sandwich concepts were considered and given
reality checks. In addition, available triaxial procedures of a similar nature e.g. Texas Triaxial, were
evaluated and analyzed.
Ultimately, with some trials and innovation, a design was developed for a simple triaxial cell
comprising a steel casing with a latex tube which is then introduced around the specimen sitting on a
base plate. It is based on the ‘tube concept’ in which the specimen acts like a ‘rim’ and the cell acts
like a ‘tyre’ providing confinement to the triaxial specimens for testing, within the tube. This approach
eliminates the use of O-rings and membranes for the specimen and tie-rods for the triaxial cell, thus
reducing testing time considerably. The overall dimensions of the cell are 244 mm diameter by 372
mm height (Appendix 5).
The cell was manufactured at Stellenbosch University Civil Engineering workshop and preliminary
tests were conducted under this study. Parallel tests were also conducted with the Research Triaxial
Test setup at Stellenbosch University in order to determine if preliminary results obtained with the
Simple Triaxial Test setup were comparable therefore providing a means of validating the data.
Results of analysis of variance (ANOVA) show that variability between Simple Triaxial Test (STT) and
Research Triaxial Test (RTT) results is less significant whilst that within samples of STT and RTT
results is quite significant. Comparisons also show that good correlation were obtained from
Reclaimed Asphalt Pavement (RAP) Hornfels + 3.3 % Emulsion + 0 % Cement mix and mixes with
the G2 base course aggregate whilst completely different correlation was obtained from RAP + 3.3 %
Emulsion + 1% Cement. It is evident however that the differences observed stem from material
variability i.e. random variability to one degree or the other and not to the STT apparatus. It is
recommended for future research that more STT versus RTT testing be done especially on a mix with
known mechanical properties when compacted to a specified dry density, e.g. graded crushed stone
(G1) compacted to 100% mod. AASHTO.
In summary, a locally made, low cost, relatively durable triaxial cell with relatively easy and quick
specimen assembly procedures has been developed. It is now possible to perform triaxial tests on
150 mm diameter by 300 mm high specimen relatively easily and quickly. However, the challenge of
validating results obtained, as well as improving the manufacture process of its main component, the
tube, still remains.
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Rheology of polymer modified binders : a comparative study of three binders and three binder/filler systemsBurger, A. F. January 2001 (has links)
Thesis (MEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: The use of polymer modified binders have increased drastically over the past twenty
years. It is generally accepted that current empirical specification tests do not adequately
characterise the improvement in binder properties when bitumen is modified with
polymers.
At the University of Stellenbosch, a programme was initiated to relate binder properties
to asphalt mix performance. This study forms part of that programme.
This study focuses on three binders and is an attempt to characterise binder properties
fundamentally. The binders that were tested are:
• 60/70 penetration grade bitumen
• SBS modified 60/70 bitumen
• Bitumen-Rubber
Two rheometers were used to characterise the binder properties:
• Sliding Plate Rheometer (SPR)
• Dynamic Shear Rheometer (DSR)
The Sliding Plate Rheometer was modified to allow testing at elevated temperatures. The
modification is described in this thesis.
Three types of testing were used to test the binders:
• Creep tests (SPR and DSR)
• Dynamic tests (Strain and Frequency Sweeps - DSR)
• Flow tests (high temperature viscosity tests - DSR) The results of the tests were used to characterise differences between the binders. Shear
susceptibility lines were plotted and viscosities calculated from the creep test results;
Master Curves and Black Diagrams were plotted from frequency sweep results; flow test
results were used to characterise high temperature behaviour.
A further development in the asphalt industry is the move towards the development of
performance based specifications. A programme has been initiated in this regard and this
study forms part of the programme.
As a step towards the development of performance based specifications filler was
included in this study. BinderlFiller systems were subjected to the same test programme
the binders were, to characterise the influence on binder properties of filler addition.
Some of the conclusions that were drawn at the end of the study are:
• Polymer modification improves binder properties related to rutting.
• Filler addition does not affect binder properties negatively.
• Shear rate is very important during production of asphalt mixes and construction
of asphalt layers containing polymer modified binders. / AFRIKAANSE OPSOMMING: Die gebruik van polimeer gemodifiseerde bitumen het drasties toegeneem oor die
afgelope twintig jaar. Dit word algemeen aanvaar dat die huidige empiriese spesifikasie
toetse nie die verbetering in bindmiddeleienskappe van polimeer modifisering
aanvaarbaar karakteriseer nie.
'n Program is geïnisieer by die Universiteit van Stellenbosch om 'n verband te vind
tussen bindmiddeleienskappe en asfaltmengseleienskappe. Hierdie studie vorm deel van
die program.
Hierdie werk fokus op drie bindmiddels en is 'n poging om die bindmiddeleienskappe
fundamenteel te karakteriseer. Die bindmiddels wat gebruik is in hierdie werk, is:
• 60/70 penetrasiegraad bitumen
• SBS gemodifiseerde 60/70 bittimen
• Bitumen-Rubber
Twee reometers is gebruik om bindmiddeleienskappe te karakteriseer:
• Glyplaat Reometer (SPR)
• Dinamiese SkuifReometer (DSR)
Die glyplaat reometer is aangepas om toetse by hoër temperature te doen en die
aanpassing wat gemaak is word in die tesis beskryf.
Drie tipes toetse is uitgevoer om die bindmiddels mee te toets:
• Kruiptoetse (SPR en DSR)
• Dinamiese toetse (DSR)
• Vloei toetse (DSR) Die resultate van die toetse is gebruik om die verksille tussen die bindmiddels te
kwalifiseer. Verskillende grafieke en figure is getrek van die resultate om die onderskeie
bindmiddels te karakteriseer.
Die beweging weg van empmese spesifikasies na werkverrigting gebaseerde
spesifikasies in die asfalt industrie is 'n verder nuwe ontwikkeling. 'n Program is
geïnisïeer ten opsigte hiervan en hierdie werk vorm deel van die program.
As 'n stap in die ontwikkeling van die werkverrigting gebaseerde spesifikasies is 'n
vuIler ingesluit in die toetsprogram. Bindmiddel/vuIler stelsels is onderwerp aan dieselfde
toetse waaraan die bindmiddels onderwerp is om die invloed van die vuIler op die
bindmiddels te karakteriseer.
Sommige van die gevolgtrekkings waartoe gekom is aan die einde van die tesis, is:
• Polimeer modifisering verbeter bindmiddeleienskappe met betrekking tot
wielsporing.
• Die toevoeging van vuIler affekteer nie die bindmiddeleienskappe negatiefnie.
• Die vervormingstempo is van groot belang wanneer asfaltmengsels gemeng en lae
gebou word van mengsels wat polimeer gemodifiseerde bitumen bevat.
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Adhesion of bituminous and cementitious materials using Particle-Probe Scanning Force MicroscopyLi, Yujie 01 January 2019 (has links)
As the most important materials in civil engineering, bituminous and cementitious materials have been used widely in pavements and constructions for many years. Accurate determination of adhesion is important to the bonding properties of bituminous and cementitious materials. In this work, we presented a novel approach to measure the adhesion between binders and aggregate mineral particles at microscopic scale.
Particle probe scanning force microscopes (SFM) were used to study the adhesion between mineral microspheres representing the primary aggregate constituents (Al2O3, SiO2 and CaCO3) and various control (PG 64-22 and PG 58-22) and modified binders. Results showed that these modified SFM probes could effectively measure the adhesion between binders and aggregate minerals. Consistent adhesion measurements were obtained between different asphalt binders and aggregate mineral particles. Statistical analyses were performed to evaluate effects of different factors on the aggregate-modified binder adhesion, including aggregate constituents, binder types, modifier types and cantilever properties. Due to the stronger polarity of alumina particles, stronger interactions occur within alumina-binder pairs than within silica- and calcium carbonate-binder pairs. Meanwhile, morphologies of different modified binders clearly demonstrated microstructural variations in these binders.
The adhesion between steel and different cement hydrated products was measured using particle probe SFM. Adhesive forces are collected between steel microspheres and new (four-week old) and old (six-month old) cement in air and saturated lime water. Mixed Gaussian models were applied to predict phase distributions in the cement paste, i.e., low density C-S-H, high density C-S-H, CH, other hydrated products and the unreacted components. For new cement in saturated lime water, adhesive forces between steel and low density C-S-H, high density C-S-H and other hydrated products are intermediate among all groups selected. The adhesive forces between steel and calcium hydroxide are smallest, whereas the adhesive forces between steel and the unreacted phases are largest. For the six-month old cement, the interweaving of calcium carbonate crystals and C-S-H during the carbonation produces greater adhesive forces to steel, consistent with the adhesive forces between steel and the control calcium carbonate specimen. CH turned into calcium carbonate by reacting with carbon dioxide in air. An increase in adhesive forces was found between steel and calcium carbonate in the old cement than those between steel and CH in the new cement.
Particle probe SFM is able to measure the adhesion in bimaterials. For bituminous materials, this methodology provides opportunities to evaluate the effects of different processing methods and to generate quantitative information for the development of multi- scale asphalt mixture cracking models. For cementitious materials, these studies opened new avenues to study the interactions between steel and cement at microscale under a variety of environmental conditions and can be formulated as crack initiation and propagation criteria incorporated in multiscale models for reinforced concrete structures.
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Investigations on moisture damage-related behaviour of bituminous materialsBagampadde, Umaru January 2005 (has links)
This doctoral thesis presents results of literature review on classical and contemporary aspects of stripping, as well as experimental investigations on moisture damage as influenced by bituminous materials. Previous research in the area of moisture damage was reviewed and synthesized into a state-of-the-art. Important parameters linked to moisture sensitivity, like bituminous material characteristics, dynamic loads from heavy vehicles, environmental factors, construction practice and nature of anti-stripping additives, are presented. The state-of-the-art in current test methods is summarized and given. The experimental work involved investigations of the influence of bitumen and aggregate composition on water susceptibility. The influence of aggregate mineralogy and chemistry was evaluated using eleven aggregates and one bitumen, followed by studying the interactive effect of four bitumens and four aggregates. Moisture sensitivity was evaluated in accordance with (EN 12697-12:2003) for conditioning, ASTM D 4123 for resilient modulus determination, and (EN 12697-23:2003) for indirect tensile strength testing. Furthermore, thermal stability of two liquid amine anti-stripping additives mixed with two bitumens of varied acidity was investigated using potentiometric titration and Fourier Transform Infrared (FTIR) Spectroscopy. Lastly, a technique based on Fourier Transform Infrared Spectroscopy-Attenuated Total Reflectance (FTIR-ATR) was developed and used for studying transport of water across thin bitumen films, as well as stripping at bitumen/substrate interfaces. Bitumens from different sources and three substrates (silicon, germanium and zinc selenide crystals) were used. Based on the results obtained, it was concluded that aggregates containing sodium and potassium in alkali feldspars generally showed high moisture sensitivity. In contrast, presence of calcium, magnesium and iron was associated with aggregates with low moisture sensitivity. Contrary to several previous findings, one aggregate with practically 100% quartz exhibited low moisture sensitivity. No linear relationship between moisture sensitivity and the contents of SiO2 and Al2O3 in the aggregates studied was established. Results of the interactive influence of bitumen and aggregate composition showed that high acid and low penetration bitumens exhibited high dry strength for all the aggregates studied. On the other hand, for a given bitumen, the wet strengths were found to be aggregate specific. The results of tests on thermal stability of amine additives showed that usefulness of these additives reduces considerably, when the more alkaline additive was mixed with the high acid bitumen, followed by storing the blends under pronounced conditions of time and temperature (24 hours and 140ºC, or more, in this study). Much less interaction occurred when the less alkaline additive was blended with the low acid bitumen. Even if a correlation was found between the results of potentiometric titration and Fourier Transform Infrared spectroscopy, the latter was not considered good enough at detecting amine additives, especially at low dosages. The technique based on FTIR-ATR developed in this study distinguished between good and bad bitumens with regard to stripping. The effectiveness of amine-based additives in reducing stripping was also shown by the method. Three likely processes occurred during the test, namely water diffusion, film break, and displacement (stripping) of bitumen from the substrate surface. The results also indicated that the diffusion process of water into the bitumen/substrate interface does not obey Fick’s law. / QC 20100831
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Viscoelastic{Viscoplastic Damage Model for Asphalt ConcreteGraham, Michael A. 2009 August 1900 (has links)
This thesis presents a continuum model for asphalt concrete incorporating non-
linear viscoelasticity, viscoplasticity, mechanically-induced damage and moisture-
induced damage. The Schapery single-integral viscoelastic model describes the
nonlinear viscoelastic response. The viscoplastic model of Perzyna models the time-
dependent permanent deformations, using a Drucker-Prager yield surface which is
modified to depend on the third deviatoric stress invariant to include more complex
dependence on state of stress. Mechanically-induced damage is modeled using continuum damage mechanics, using the same modified Drucker-Prager law to determine
damage onset and growth. A novel moisture damage model is proposed, modeling
moisture-induced damage using continuum damage mechanics; adhesive moisture-
induced damage to the asphalt mastic-aggregate bond and moisture-induced cohesive
damage to the asphalt mastic itself are treated separately.
The analytical model is implemented numerically for three-dimensional and plane
strain finite element analyses, and a series of simulations is presented to show the
performance of the model and its implementation. Sensitivity studies are conducted
for all model parameters and results due to various simulations corresponding to
laboratory tests are presented.
In addition to the continuum model, results are presented for a micromechanical
model using the nonlinear-viscoelastic-viscoplastic-damage model for asphalt mastic and a linear elastic model for aggregates. Initial results are encouraging, showing the
strength and stiffness of the mix as well as the failure mode varying with moisture
loading. These initial results are provided as a an example of the model's robustness
and suitability for modeling asphalt concrete at the mix scale.
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