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Asphalt Review - Volume 29 Number 2 (June / July 2010)

Asphalt Review - Volume 29 Number 2 (June / July 2010)

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ASPHALT REVIEW NEWS<br />

Replacing load-bearing ballast with asphalt was used for the<br />

first time in Germany around 25 years ago, with an asphalt<br />

base course. Since then, seven different systems of the asphalt<br />

construction method have been developed and constructed in<br />

Germany.<br />

Requirements for the asphalt layers<br />

In general, the requirements for the asphalt are determined<br />

by the load type. In the case of the solid railway trackbed,<br />

loading frequency is at a lower level than with asphalt roads.<br />

In contrast, the axle loads, and consequently the wheel loads,<br />

are far higher. On roads, the actual distributed load results<br />

in a wheel load of 5.75 tons for a truck with an 11.5-ton axle,<br />

which works out to around 0.8 MPa for a surface area of<br />

around 710 cm². For railways, however, there is a considerable<br />

load distribution over the rail and the sleeper. The wheel load<br />

of 11.25 tons results in stress on the bottom of the sleeper of<br />

around 0.25 MPa, and thus only around one-third of the load<br />

experienced on roads.<br />

The asphalt needs to be designed to be permanent, flexible<br />

and dense in order to avoid the need for maintenance work<br />

and subsequent improvements. The lifetime of the solid<br />

railway trackbed has been estimated to be around 60 years.<br />

Experience in Germany has shown that asphalt types with a<br />

high binder content and a low void content have proven to be<br />

reliable.<br />

Advantages<br />

The solid railway trackbed laid in Germany to date has been<br />

shown to be very successful due to the reliability of the paving<br />

and by the material-specific characteristics of the asphalt:<br />

• <strong>Asphalt</strong> can be paved without joints due to its visco-elastic<br />

characteristics; stresses arising from the effects of load and<br />

temperature are reduced.<br />

• <strong>Asphalt</strong> can also be used with extreme super-elevation<br />

because no separation arises from the high internal friction<br />

in the paved state.<br />

• <strong>Asphalt</strong> can be paved at a precise tolerance (± 2 mm) due to<br />

its material characteristics.<br />

• Load can be put on the asphalt immediately after it cools<br />

down; shorter construction times are achieved because of<br />

this.<br />

• Corrections in the position that may be needed (e.g. due<br />

to settlement of the embankment) can be quickly and easily<br />

made either by milling off or by putting on another layer.<br />

The preceding article highlights some of the Europe<br />

experience in using asphalt in rail track construction. In<br />

Australia asphalt has not been used, but with the increasing<br />

demands on our rail network and with the construction of<br />

new railways, the Australian Transport industry should look<br />

at the advantages of asphalt.<br />

The use of asphalt in the construction of tram lines also<br />

offers many potential advantages including smoother rides,<br />

lower noise, quick track rehabilitation and maintenance times<br />

and potentially less maintenance of wheels and suspensions.<br />

If there is interest in using asphalt in railways or tramways,<br />

AAPA will consider inviting experts from both Europe and the<br />

US to participate in workshops to discuss the technical and<br />

commercial advantages of this material.<br />

For further information about EAPA and contact details<br />

refer to www.eapa.org<br />

SAMI expands its boundaries<br />

May 5, <strong>2010</strong>, saw the opening of SAMI Bitumen Technologies’<br />

new bitumen import terminal facility at the Port of Brisbane.<br />

The terminal complements the company’s high standard of<br />

product and service delivery, and significantly expands its<br />

reach.<br />

Bulk bitumen is usually imported into Brisbane from Asia<br />

via purpose built ships and the new bitumen storage and<br />

processing terminal facility has a pipeline that connects the<br />

bulk storage tanks to the new general purpose wharf. But it’s<br />

not simply about making the process of unloading and storage<br />

easier.<br />

SAMI’s new import terminal incorporates some of the most<br />

advanced technology of its kind in the world. The facility is<br />

capable of producing a variety of high performance bitumen<br />

grades used in road construction and maintenance, as well as<br />

bitumen product for various industrial applications.<br />

This one-stop import and production approach makes the<br />

terminal one of the most efficient in Australia. It is in addition<br />

to the company’s terminals at Geelong in Victoria and at North<br />

Fremantle in Western Australia.<br />

Pioneering new technologies has been part and parcel of the<br />

SAMI approach to business since the company’s inception 32<br />

years ago. In 1978, it was formed because there was a need to<br />

develop new technology; a way by which a polymer modified<br />

bitumen could be used as a stress absorbing membrane interlayer<br />

under asphalt overlays in road pavements.<br />

SAMI not only succeeded in developing a polymer modified<br />

bitumen for use as a sprayed seal and as an asphalt overlay<br />

binder, but also created a new market in Australia. This was<br />

just the beginning for SAMI and from that starting point<br />

the company focused its resources on developing innovative<br />

road technologies, products and securing other contracting<br />

services.<br />

In 2008, SAMI significantly expanded its global reach beyond<br />

Australia by establishing a formal collaborative relationship<br />

with Colas SA. It was a natural development as SAMI had<br />

been exchanging technical information over the previous 16<br />

years with the French company in what was described at the<br />

time as a ‘long term mutual courtship’.<br />

Interestingly, there were other similarities between the<br />

two companies. Both Colas and SAMI are company names<br />

that have their origin in the innovative products created by<br />

each entity and both companies began life in the pursuit of<br />

a bitumen related solution which led to the creation of those<br />

particular products.<br />

Bulk Bitumen Cargo being off loaded at the General Purpose wharf,<br />

Port of Brisbane<br />

42 ROADS JUNE <strong>2010</strong>/JULY <strong>2010</strong>

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