Frequently asked questions.
Below, you'll find answers to the most frequently asked questions on our erosion protection technologies.
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About Open Stone Asphalt Technology
What is Open Stone Asphalt (OSA) and why is it used in hydraulic engineering?
OSA is a robust, flexible and porous asphalt comprising 20/32mm limestone bound together with a bituminous mastic. Its thermoplastic properties (resisting short impacts (waves) and accommodating long-term loads (settlement)) make it an ideal choice for the hydraulic environment.
What is Open Stone Asphalt (OSA) and why is it used in hydraulic engineering?
OSA is a robust, flexible and porous asphalt comprising 20/32mm limestone bound together with a bituminous mastic. Its thermoplastic properties (resisting short impacts (waves) and accommodating long-term loads (settlement)) make it an ideal choice for the hydraulic environment.
What is Open Stone Asphalt (OSA) and why is it used in hydraulic engineering?
OSA is a robust, flexible and porous asphalt comprising 20/32mm limestone bound together with a bituminous mastic. Its thermoplastic properties (resisting short impacts (waves) and accommodating long-term loads (settlement)) make it an ideal choice for the hydraulic environment.
What applications is OSA best suited for?
What applications is OSA best suited for?
What applications is OSA best suited for?
How does OSA differ from traditional asphalt?
How does OSA differ from traditional asphalt?
How does OSA differ from traditional asphalt?
Is OSA suitable for underwater applications?
Is OSA suitable for underwater applications?
Is OSA suitable for underwater applications?
What are the environmental benefits of using OSA?
What are the environmental benefits of using OSA?
What are the environmental benefits of using OSA?
Can vegetation grow through Open Stone Asphalt surfaces?
Can vegetation grow through Open Stone Asphalt surfaces?
Can vegetation grow through Open Stone Asphalt surfaces?
What is Lean Sand Asphalt (LSA), and how does it differ from OSA?
What is Lean Sand Asphalt (LSA), and how does it differ from OSA?
What is Lean Sand Asphalt (LSA), and how does it differ from OSA?
What is “grouted rock” and when is it used?
What is “grouted rock” and when is it used?
What is “grouted rock” and when is it used?
Applications and Use Cases
Where can Open Stone Asphalt be used?
• River estuary flood defences where wave impacts are <3m. • Zones where there is enough room for a revetment but insufficient room for a extensive gravel/sand foreshore wave impact zone. • Upstream faces of dams for wave impact protection. • Downstream faces of dams for overtopping protection & auxiliary spillways.
Where can Open Stone Asphalt be used?
• River estuary flood defences where wave impacts are <3m. • Zones where there is enough room for a revetment but insufficient room for a extensive gravel/sand foreshore wave impact zone. • Upstream faces of dams for wave impact protection. • Downstream faces of dams for overtopping protection & auxiliary spillways.
Where can Open Stone Asphalt be used?
• River estuary flood defences where wave impacts are <3m. • Zones where there is enough room for a revetment but insufficient room for a extensive gravel/sand foreshore wave impact zone. • Upstream faces of dams for wave impact protection. • Downstream faces of dams for overtopping protection & auxiliary spillways.
Is OSA effective for coastal and flood protection?
Is OSA effective for coastal and flood protection?
Is OSA effective for coastal and flood protection?
Can OSA be used on steep slopes or irregular terrain?
Can OSA be used on steep slopes or irregular terrain?
Can OSA be used on steep slopes or irregular terrain?
What types of infrastructure projects benefit most from OSA?
What types of infrastructure projects benefit most from OSA?
What types of infrastructure projects benefit most from OSA?
What are the main benefits of using asphalt-based solutions over concrete or block systems?
What are the main benefits of using asphalt-based solutions over concrete or block systems?
What are the main benefits of using asphalt-based solutions over concrete or block systems?
How does OSA perform in high-velocity water environments or over-topping conditions?
How does OSA perform in high-velocity water environments or over-topping conditions?
How does OSA perform in high-velocity water environments or over-topping conditions?
How long does OSA take to set?
How long does OSA take to set?
How long does OSA take to set?
How is OSA installed—on slopes, underwater, as prefabricated mattresses?
How is OSA installed—on slopes, underwater, as prefabricated mattresses?
How is OSA installed—on slopes, underwater, as prefabricated mattresses?
Design and Installation
What is the process for designing an OSA solution?
· Specify the design loads (significant wave height or water velocity) · Know the formation material beneath the new erosion protection · For wave impacts refer to ‘Revetment systems against wave attack – A design manual’ published by HR Wallingford or ‘Communications – the use of asphalt in hydraulic engineering’ published by Rijkwaterstaat for the design formulae. · For high water flows the weight of the OSA plus its short-term flexural strength must be able to resist the uplift forces from the water flow. For permeable materials this force is 0.2V2/2g (McLelllan, G. 1976 - Chute spillway sub-drainage and anchorage. In: Proceedings 12th ICOLD Congress, Mexico, Vol. IV, C.16. pp. 1029-1037. International Commission on Large Dams, Paris.) · For port scour protection refer to PIANC Report No. 180 – 2015.
What is the process for designing an OSA solution?
· Specify the design loads (significant wave height or water velocity) · Know the formation material beneath the new erosion protection · For wave impacts refer to ‘Revetment systems against wave attack – A design manual’ published by HR Wallingford or ‘Communications – the use of asphalt in hydraulic engineering’ published by Rijkwaterstaat for the design formulae. · For high water flows the weight of the OSA plus its short-term flexural strength must be able to resist the uplift forces from the water flow. For permeable materials this force is 0.2V2/2g (McLelllan, G. 1976 - Chute spillway sub-drainage and anchorage. In: Proceedings 12th ICOLD Congress, Mexico, Vol. IV, C.16. pp. 1029-1037. International Commission on Large Dams, Paris.) · For port scour protection refer to PIANC Report No. 180 – 2015.
What is the process for designing an OSA solution?
· Specify the design loads (significant wave height or water velocity) · Know the formation material beneath the new erosion protection · For wave impacts refer to ‘Revetment systems against wave attack – A design manual’ published by HR Wallingford or ‘Communications – the use of asphalt in hydraulic engineering’ published by Rijkwaterstaat for the design formulae. · For high water flows the weight of the OSA plus its short-term flexural strength must be able to resist the uplift forces from the water flow. For permeable materials this force is 0.2V2/2g (McLelllan, G. 1976 - Chute spillway sub-drainage and anchorage. In: Proceedings 12th ICOLD Congress, Mexico, Vol. IV, C.16. pp. 1029-1037. International Commission on Large Dams, Paris.) · For port scour protection refer to PIANC Report No. 180 – 2015.
Can OSA be installed as prefabricated mattresses?
Can OSA be installed as prefabricated mattresses?
Can OSA be installed as prefabricated mattresses?
What are the key considerations for installing OSA in rivers or dams?
What are the key considerations for installing OSA in rivers or dams?
What are the key considerations for installing OSA in rivers or dams?
How long does an OSA installation typically last?
How long does an OSA installation typically last?
How long does an OSA installation typically last?
What maintenance is required for OSA structures?
What maintenance is required for OSA structures?
What maintenance is required for OSA structures?
Sustainability, Health and Permeability
Is OSA compatible with drinking water reservoirs?
The concentration of harmful compounds leaching from OSA has been shown to be well below the limits for potable water and so is considered safe for use in drinking water reservoirs. The Drinking Water Inspectorate (DWI) recommend each water company carries out its own risk assessment when considering its use. (See DWI Regulation 31 - Advice Sheet 7 (Construction products for water company assets)
Is OSA compatible with drinking water reservoirs?
The concentration of harmful compounds leaching from OSA has been shown to be well below the limits for potable water and so is considered safe for use in drinking water reservoirs. The Drinking Water Inspectorate (DWI) recommend each water company carries out its own risk assessment when considering its use. (See DWI Regulation 31 - Advice Sheet 7 (Construction products for water company assets)
Is OSA compatible with drinking water reservoirs?
The concentration of harmful compounds leaching from OSA has been shown to be well below the limits for potable water and so is considered safe for use in drinking water reservoirs. The Drinking Water Inspectorate (DWI) recommend each water company carries out its own risk assessment when considering its use. (See DWI Regulation 31 - Advice Sheet 7 (Construction products for water company assets)
Can wildlife housing and thoroughfares be built into OSA, such as eel passes and crab housing?
Can wildlife housing and thoroughfares be built into OSA, such as eel passes and crab housing?
Can wildlife housing and thoroughfares be built into OSA, such as eel passes and crab housing?
Does OSA or Grouted Rock leach any toxic matter into the water or environment it is placed in?
Does OSA or Grouted Rock leach any toxic matter into the water or environment it is placed in?
Does OSA or Grouted Rock leach any toxic matter into the water or environment it is placed in?
Is OSA carbon-intensive? How does it compare to concrete alternatives?
Is OSA carbon-intensive? How does it compare to concrete alternatives?
Is OSA carbon-intensive? How does it compare to concrete alternatives?
Can asphalt be recycled?
Can asphalt be recycled?
Can asphalt be recycled?