Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The increasing awareness of climate change causes a growing interest in pavement rehabilitation. Pavement rehabilitation by in-situ stabilisation with bitumen reduces the extraction of natural aggregate resources while enhancing flexibility and durability properties, which lowers maintenance costs over the design-life of the pavement structure. Incorporating Bitumen Stabilised Materials (BSMs) into a pavement structure can therefore have economic and environmental benefits, but more research is needed to fully understand the behaviour and potential of these materials. Stabilising materials with bitumen provides useful properties to pavement layers. The “TG2 2nd Edition, Bitumen Stabilised Materials” was published by the Academy of South Africa in May 2009, which provides a good understanding of the usage of Bitumen Stabilised Materials (BSMs). However, the shrinkage and flexible behaviour of these materials are still not fully understood and therefore more research on these materials is needed. The aim of this project is thus to determine the shrinkage and flexible behaviour of BSMs to incorporate these behavioural types in the revised design method for flexible pavements in the SAPDM. In addition, the influence of several additives on the shrinkage and flexible behaviour of BSMs have been evaluated to get an improved understanding of these properties. The additives included cement (1% and 2% content) and both bitumen emulsion (0.9% and 2.4% content) and foamed bitumen (only 2.4% content). Two linear shrinkage testing methods have been designed to test the shrinkage potential of BSMs, including a beam testing method and a cylindrical testing method. Based on the usage of the shrinkage measurements the applicable method can be used to determine the shrinkage potential of a BSM. The flexibility is a more complex property and was tested using a simple monotonic beam test. The strain-at-break parameter obtained from this test provided an indication of the material flexibility. Slight differences in the trends were observed between beam and cylindrical shrinkage due to specimen geometry, exposed surface area and shrinkage testing direction. Beam specimens initially show swelling when bitumen is added to the mixture and shrinks thereafter. Cylindrical specimens on the other hand show initial shrinkage followed by a slight length increase, where after shrinkage continues. The additives had the same influence on the shrinkage for both the beam and cylindrical specimens. Although all shrinkage measurements were small, an increase in bitumen reduced shrinkage and an increase in cement increased shrinkage. Stabilisation with foamed bitumen rather than bitumen emulsion proved to show less shrinkage, but only in
combination with 2% cement.
The strain-at-break, dissipated energy and material stiffness calculated from the monotonic
beam tests provided a good indication of the flexibility behaviour of BSMs. Higher bitumen
content increased the flexibility potential and an increase in cement decreased the flexibility
potential of BSMs.
This project has provided good insight on both the shrinkage and flexibility behaviour of BSMs,
which can be used in the revised copy of the SAPDM. Increased bitumen contents decreases
the shrinkage potential and increases the flexibility of a BSM. Increased cement contents on the
other hand, increases shrinkage and decreases flexibility of BSMs. The correct combination of
cement and bitumen in a BSM can thus provide a material with the wanted flexibility while
keeping the shrinkage to a minimum. / AFRIKAANSE OPSOMMING: Die toenemende bewustheid van klimaatsverandering veroorsaak toenemende belangstelling in
die rehabilitasie van plaveisels. Plaveisel rehabilitasie deur in-veld stabilisasie met bitumen
verminder die ontginning van natuurlike hulpbronne, terwyl die verbetering van buigsaamheid en
duursaamheid eienskappe die onderhoudskoste verlaag oor die ontwerp-lewe van die
plaveiselstruktuur. Die inkorporasie van Bitumen Gestabiliseerde Materiale (BGM) in 'n plaveisel
struktuur kan dus omgewings en ekonomiese voordele inhou. Meer navorsing word wel benodig
om die gedrag van hierdie materiale beter te verstaan.
Die stabilisering van materiale met bitumen verskaf nuttige eienskappe aan 'n plaveisellaag. Die
"TG2 2de Uitgawe, Bitumen Gestabiliseerde Materiale" is gepubliseer deur die Akademie van
Suid-Afrika in Mei 2009 en verskaf 'n goeie begrip van Bitumen Gestabiliseerde Materiale
(BGM). Die krimpings en buigsaamheid gedrag van die materiaal word wel nog nie ten volle
verstaan nie en daarom word meer navorsing oor hierdie materiaal benodig.
Die doel van hierdie projek is dus om die krimpings gedrag sowel as die buigsaamheid gedrag
van 'n BGM te bepaal en sodoende die kennis te gebruik in die hersiende ontwerp metode vir
buigsame plaveisels in die SAPDM. Die invloed van verskeie bymiddels op die krimpings en
buigsaamheid gedrag van 'n BGM is ook geëvalueer om 'n beter begrip van hierdie eienskappe
te verkry. Die bymiddels sluit sement in (1% en 2% inhoud) asook beide emulsie bitumen (0,9%
en 2,4% inhoud) en skuim bitumen (slegs 2.4% inhoud).
Twee lineêre krimpings toets metodes was ontwerp om die krimping potensiaal van BGM's te
bepaal, wat 'n balk toets metode en 'n silindriese toets metode insluit. Die metode wat gebruik
sal word om die krimping van 'n BGM te bepaal moet baseer word op die toepassing waarvoor
die krimpings resultate gebruik gaan word. Die buigsaamheid is 'n meer komplekse eienskap en
was getoets met behulp van 'n eenvoudige monotoniese balk toets. Die spanning-by-breekpunt
waardes wat verkry was vanuit die balktoetse, het 'n goeie aanduiding van die buigsaamheid
van die materiaal verskaf.
Klein verskille in krimpingstendense tussen balk en silindriese proefstukke is opgemerk tydens
die projek en is veroorsaak deur die geometrie van die proefstuk, die blotgestelde oppervlakte
asook die rigting van kimp toetsing. Balk proefstukke toon aanvanklike swelling wanneer
bitumen bygevoeg is, gevolg deur krimping. Silindriese proefstukke aan die ander kant toon
aanvanklike krimping gevolg deur 'n effense toename in lengte, waarna krimping weer
plaasvind. Die bymiddles het dieselfde invloed op die krimping van beide die balk en silindriese
proefstukke. Alhoewel al die krimpingswaardes baie klein was, het 'n toename in bitumen 'n vermindering in krimping voortgebring en 'n toename in sement het 'n toename in krimping
voortgebring. Stabilisasie met skuim bitumen in plaas van emulsie bitumen toon verlaagde
krimping, maar slegs in kombinasie met 2% sement.
Die spanning-by-breekpunt, verkose energie en materiaal styfheid wat bereken is vanaf die
monotoniese balk toets resultate, het 'n goeie aanduiding van die buigsaamheid gedrag van
BGM's verskaf. 'n Hoër bitumen inhoud verhoog die buigsaamheid potensiaal van BGM‟s terwyl
'n toename in sement die buigsaamheid potensiaal van BGM's verlaag.
Hierdie projek bied goeie insigte vir beide die krimpings en buigsaamheid gedrag van BGM's,
wat in die hersiende ontwerp metode van die SAPDM gebruik kan word. Verhoogde bitumen
inhoud verminder die krimping potensiaal en verhoog die buigsaamheid van 'n BGM. Verhoogde
sement inhoud aan die ander kant, verhoog krimping en verminder buigsaamheid van BGM's.
Die korrekte kombinasie van sement en bitumen in 'n BGM kan dus 'n materiaal produseer met
die gewenste buigsaamheidseienskappe en terselfde tyd die krimping tot 'n minimum beperk.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/96991 |
| Date | 03 1900 |
| Creators | Campher, Lizemari |
| Contributors | Jenkins, Kim Jonathan, 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 | 200 pages : illustrations |
| Rights | Stellenbosch University |
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