Page 5 - Hub 4 Magazine issue 53
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Total Bitumen
Plastomers tend to impart stiffness which can be useful if and when this is required but are less valuable in fatigue resistance. Elastomer PMB’s impart elastic recovery characteristics where plastics resist deformation with stiffness but deformation is permanent or in engineering terms “plastic deformation” once load tolerance is exceeded.
When selecting a PMB it is important to understand which characteristic is required in the end product. Selection should be based on a holistic three dimensional design considering fatigue characteristics, stiffness, material handling and compaction capabilities. Using the softest binder that can withstand the forces to be applied is generally the best way to avoid cracking.
The production of PMB involves the dispersion of polymer units in bitumen. Performance is dependent on bitumen type and grade, polymer type, polymer size and quality of dispersion. In the case of cross linked PMB such as Total Styrelf® an additional manufacturing step which “cross-links” the polymer units is employed. Using these chemical bonds the polymers become networked and act as a single unit or “polymer matrix” within the PMB.
Sustainability through durability!
As understanding of PMB performance spreads it is certain that asphalt products will benefit in terms of durability. This in turn implies the whole life performance and asset management of a structure can become more predictable.
A recent scheme benefiting from Styrelf technology is The Mersey Gateway toll bridge connecting Widnes and Runcorn in Cheshire. A strategic route for South Liverpool as such requiring minimal future maintenance interventions. Total Styrelf eXtreme 100 PMB was chosen in the asphalt layers for over ten kilometers of network here by contractors Tarmac. This highly modified cross linked PMB is a premium product with high elasticity and fatigue resistance. Used on the bridge decks for these reasons it will give years of enhanced service extending the design life of this critical pavement. This PMB grade can be used in a multitude of asphalt designs including CL943 HRA, CL942 TSC and Scottish TS2010 SMA.
The Total Styrelf® range also incorporates lower temperature technology with Total Styrelf EC02®. The addition of warm mix additives to Total Styrelf®
allows a temperature reduction of up to 40°C during the mixing stage of asphalt production. This has many benefits.
Warm mix asphalt is becoming seen as beneficial not just in terms of environmental gains from energy reduction but for the benefits it brings to the material, contractor and client. Lower temperature imparts less premature ageing of the product. Improved compaction is often cited, greater tolerance to travelling and speed of opening the newly surfaced road to traffic are all tangible benefits of these systems.
A recent example of this was collaboration between Highways England, Tarmac and Total Bitumen on the refurbishment of the A66, Penrith to Kirkby Stephen. Productivity gains allowed 1000 tonnes of asphalt per shift to be installed. Total ECO2® technology was used in the binder course and surface course. Despite Storm Callum hitting during the scheme works were completed on schedule.
Pre blended warm mix PMB removes the manual addition of additives at the asphalt plant while reducing energy consumption and emissions moving the industry in a responsible sustainable direction.
It is possible now to engineer PMB’s to specific applications.TheTotalStyrelf® portfolioincludes tailored PMB’s such as Styrelf Intakt® for resistance to fuel and chemical corrosion such as encountered in airfield applications. Motorsport specific Total Styrelf GP® is designed to withstand the stresses, strains and shear forces encountered on Formula 1 tracks being applied to areas such as the Monaco GP.
Sustainability through durability is the responsible direction of the modern supply chain which is driven by the current drive for improved highways asset management.
If you would like to learn more about bitumen technology why not try the “MOOC” the Massive Open Online Course. MOOC is free to access and can be completed in your own time.
For more information visit products/bitumen Nov 2018 - Issue 53
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