More forgiving roads with SAMIseal M500

The SAMIseal M500 is a bitumen used for sprayed sealing applications.

Conventional bitumen tends to become brittle at low ambient temperatures and soft at high road surface temperatures. SAMI Bitumen’s SAMIseal M500 binder solves this issue in sprayed sealing applications, helping retain the aggregate better. Bitumen Technical Manager Gerard Gnanaseelan explains.

Temperatures tend to vary greatly in parts of Australia, particularly in the sub-tropical regions of north Queensland and the Northern Territory and across the Australian Outback. As such, conventional, non-modified bitumen is not always the best option for sprayed sealing in these regions.

Bleeding or flushing seen with sprayed seals is a common symptom that shows the bitumen has become soft under the high temperature and is ‘pumped’ above the cover aggregate under the traffic load. The consequence is the formation of a slick membrane of bitumen on the road that can be picked up by tyres and constitutes a traffic hazard due to reduced skid resistance.

Sprayed seals becoming brittle and cracks in cold temperature is another hazardous outcome if the binder lacks flexibility. Here too, loss of aggregate may lead to the road becoming slippery and resulting in accidents.

The SAMIseal Multigrade M500 bitumen was developed by SAMI Bitumen Technologies specifically for such applications.

SAMIseal M500 is a grade of bitumen used for sprayed sealing applications and available on request for contractors looking for improved temperature susceptibility and superior performance compared to standard grade bitumen.

“This is a niche product in our portfolio,” says Gnanaseelan. “The SAMIseal M500 is characterised by low temperature susceptibility. It remains stable over a wide range of ambient temperatures, which means it’s flexible at low temperatures and stiffer at high temperatures.

According to Phil Stevens, SAMI Bitumen’s State Manager for Queensland, the SAMIseal M500 bitumen is manufactured from the same sources as conventional bitumen, but requires further processing to reduce its temperature susceptibility.

“We manufacture the SAMIseal M500 bitumen by compositionally adjusting the bitumen feed stock and processing it
in an oxidiser. This allows the product to impart lower temperature susceptibility and superior adhesion characteristics compared to conventional sealing grade binders,” says Stevens.

Both hot and arid climates and cold and moist climates can benefit from the use of the SAMIseal M500 binder, he adds.

“A bitumen like the SAMIseal M500 has the ability to remain stable under high road surface temperatures, where bitumen has a tendency to get soft, and also at night time and in cooler climates, it has the ability to remain resilient and not crack,” he says.

“That’s the beauty of this product: it is tough in hot temperature and flexible in cold temperature.”


Being a premium product in SAMI’s portfolio, the SAMIseal M500 has already received interest from major contarctors, according to Stevens.

“SAMIseal M500 is a premium product, so naturally it comes with a premium value compared to conventional bitumen. But the fact that major contractors still have a high demand for it and contact us to specifically ask for it, is testament to the superior quality and performance of the product, says Stevens.

As State Manager for SAMI Bitumen Technologies in Queensland, Stevens regularly organises deliveries to major contractors in the state, with orders for hundreds of tonnes, sometimes requiring overnight delivery to remote project sites.

Colas Queensland recently completed approximately 175,000 litres of 14/7 double/double seal as an initial treatment for Balonne Shire Council on Hebel Goodooga Road, located on the border of Queensland and New South Wales. Colas used the M500 binder for this project.

Colas Queensland recently completed approximately 175,000 litres of double/double seal for Balonne Shire Council using SAMIseal M500.

Matthew Johansen, Colas’ Operations Manager for South Queensland, says the SAMIseal M500 binder was adopted after considering the type of treatment required, the climatic conditions, and the traffic loadings at the site.

“The M500 has a reduced susceptibility to temperature changes, which was a key factor for the location of the site, given the very low overnight temperatures during winter, and high pavement temperatures experienced from spring onwards,”
says Johansen.

“The Balonne Shire Council had requested a surfacing treatment that did not require a prime on the newly constructed base due to site constraints, meaning a traditional PMB [polymer modified binder] bitumen could not be used in this application,” he adds.

According to Johansen, the choice of binder and treatment type allowed the seal to be undertaken in the middle of winter, meeting the program’s requirements and achieving a satisfactory outcome for all involved.


The Multigrade class of bitumen in SAMI’s portfolio extends beyond the M500 bitumen. While the SAMIseal M500 is best suited for sprayed sealing applications, SAMI also offers SAMIfalt M1000 (previously known as SAMIfalt Multigrade Plus), which is better suited for asphalt mixes.

“With the in-house manufacturing capabilities at SAMI, we have full control of the bitumen characteristics. The SAMIseal M500 and SAMIfalt M1000 are two special classes of multigrade bitumen, but we can also manufacture other products using a combination of standard grade bitumens on request,” says Stevens.

This flexibility in SAMI’s production system also extends to the delivery of bitumen in bulk at high temperatures.

Stevens says SAMI can provide flexible options depending on the conditions of the customer’s site and on how the customer prefers to use SAMI Bitumen delivery options.

“A product like the SAMIseal M500 ideally needs to be stored at temperature ranges between 120°C to 140°C for medium to
long term storage. The bitumen should be heated to around 180°C to 185°C at the time of application, but it should not be stored at this temperature for longer than two days,” says Stevens.

“So, as soon as the contractor takes the delivery from us, the clock is ticking. In an ideal situation, the contractor should be  able to use the bitumen immediately, but if site conditions such as excessive rain delays the process, maintaining the bitumen at the optimum temperature becomes a challenge.”

Apart from the SAMIseal M500 being a more forgiving product when it comes to temperature variations, Stevens says the SAMI team also do their bit to help out contractors.

“At our end, we try to keep the bitumen at our storage facility for as long as possible, because as long as we are retaining it,
there are many options by which we can ensure the product is maintained without any deterioration to the properties even at the high end of the temperature spectrum,” he says.

It’s not recommended for the SAMIseal M500 to be heated above 200°C. SAMIseal M500 can be sprayed without cutter
using conventional spray nozzles to a road surface temperature above 25°C and rising.


Having manufactured bitumen in Australia since 1978, SAMI Bitumen Technologies manufactures a range of speciality bituminous products at their modern manufacturing facilities located in Brisbane, Perth, Sydney and Melbourne.

As an independent operator with the global support from its French parent,the Colas global group, Stevens says the company keeps on investing in research and development for new products.

“Being part of a global group, we draw a wealth of information from our peers. Technology transfer is always at the forefront of our priorities,” he says.

“There are other companies around the globe as part of the group that are using bitumen technologies which are quite innovative for Australia. So, we always have the option for scientific and technical exchange with our peers within the global group, which feeds into our products and our services to the industry.”

This article was originally published in the November edition of our magazine. To read the magazine, click here.

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