Thesis (MScEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: The UNFCCC (United Nations Framework Convention on Climate Change), enabled
by the Kyoto Protocol, set enforced responsibilities on industrialised countries to
reduce the amount of emissions (greenhouse gases) produced. This global call for
the reduction of greenhouse gas emissions ensured that the manufacturing sector
commit to emission reduction.
The asphalt industry has embarked on a quest to find alternative methods of
producing and constructing asphalt mixes which will release less greenhouse gasses
into the atmosphere. These new methods include the reduction in production and
construction temperatures which in turn will reduce the amount of greenhouse
emissions produced. These new methods introduced the concept of warm mix
asphalt (WMA) to the alternative hot mix asphalt (HMA).
To produce a WMA mix at lower temperatures the binder needs to be in a workable
state so to effectively coat the aggregate and produce a good quality mix. WMA
technologies have been developed to enable production of mixes at lower
temperatures (effectively reducing emissions) whilst retaining the required binder
viscosity and properties needed to produce a quality mix. The question which needs
to be answered is whether the performance of these WMA mixes can compare with
that of HMA mixes.
In this study several WMA mixes (with different WMA technologies) are evaluated
against their equivalent HMA mixes in terms of fatigue life and flexural stiffness.
Phase angle results were also considered. Flexural stiffness is a mix property which
is dependent on loading time and temperature. It is used to measure the load spread
ability of a mix and also influences fatigue behaviour. Fatigue cracking occurs in the
material as a result of repeated cyclic loading. The evaluation and analysis conducted in this study show that WMA mixes can
compare favourably and even exceed that of HMA mixes in certain cases, although
some WMA mixes resulted in lower fatigue life or flexural stiffness than its
corresponding HMA mixes, which could be attributed to differences in mix
components and variables.
In this study a literature study, methodology, laboratory test results, a comparison of
mix results and conclusions and recommendations are made. / AFRIKAANSE OPSOMMING: Die UNFCCC (United Nations Framework Convention on Climate Change) was in
staat gestel deur die Kyoto Protocol om verantwoordelikhede op geïndustrialiseerde
lande te forseer om die hoeveelheid van nadelige kweekhuisgasse wat geproduseer
word te verminder. Hierdie globale oproep tot die vermindering van kweekhuisgasse
verseker dat die vervaardigingsektor hulself verbind tot emissie vermindering.
Die asfalt industrie het begin met 'n soektog na alternatiewe metodes van
vervaardiging en die bou van asfaltmengsels wat minder kweekhuisgasse sal vrystel
in die atmosfeer. Hierdie nuwe metodes sluit die vermindering in produksie en
konstruksie temperature in wat op sy beurt die hoeveelheid kweekhuisgasse
geproduseer verminder. Hierdie nuwe metodes het die konsep van warm mengsel
asfalt (WMA) bekendgestel teenoor die alternatiewe ‘hot’ mengsel asfalt (HMA).
Om ‘n WMA mengsel te produseer by laer temperature, moet die bindmiddel in 'n
werkbare toestand wees om die aggregaat heeltemal te bedek en 'n goeie gehalte
mengsel te produseer. WMA tegnologie is ontwikkel om die produksie van mengsels
teen laer temperature te realiseer (vermindering die uitlaatgasse), terwyl die vereiste
bindmiddel viskositeit en eienskappe wat nodig is om 'n kwaliteit mengsel te
produseer behou word. Die vraag wat beantwoord moet word, is of die prestasie van
hierdie WMA mengsel kan vergelyk word met dié van HMA mengsel.
In hierdie studie is 'n paar WMA mengsels (met verskillende WMA tegnologie)
geëvalueer teen hul ekwivalent HMA mengsels in terme van vermoeiing en buig
styfheid. Fase hoek resultate is ook in ag geneem. Buig styfheid is 'n mengsel
eienskap wat afhanklik is van die laai tyd en temperatuur. Dit word gebruik om die las
verspreiding vermoë van 'n mengsel te meet en beïnvloed ook vermoeiing gedrag.
Vermoeidheid krake kom voor in die materiaal as gevolg van herhaalde sikliese laai. Die evaluering en ontleding in hierdie studie toon dat WMA mengsels goed vergelyk
en selfs in sekere gevalle meer as dié van HMA mengsels, hoewel sommige WMA
mengsels laer vermoeidheid lewe of buig styfheid as die ooreenstemmende HMA
mengsels gewys het, wat toegeskryf kan word tot verskille in mengsel komponente
en veranderlikes.
In hierdie studie word 'n literatuurstudie, metodiek, laboratorium toets resultate, 'n
vergelyking van die mengsel resultate en gevolgtrekkings en aanbevelings gemaak.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/86439 |
| Date | 04 1900 |
| Creators | Van den Heever, Johann |
| Contributors | Jenkins, K. J., 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 | English |
| Type | Thesis |
| Format | xix, 138 p. : ill. |
| Rights | Stellenbosch University |
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