Sealoflex Combination – 9 Years and Counting – 2005 Debut in UK Car Parks Revisited
July 2005 saw the start of a contract to lay approximately 50,000m² of GridSeal® at London’s Heathrow airport on the Pink Elephant Car Park, reputedly the largest car park in Europe.
This is the first use in the UK of GridSeal®, a combination of GlasGrid® and Sealoflex SC-33, a system that has been successfully used to reduce reflective cracking in asphalt overlays throughout Europe, the Middle East, Far East and Australia since 1990.
Consultants Project Techniques were faced with a common difficulty of providing a thin flexible overlay system over a concrete base with the client’s requirement to minimise reflective cracking. The system chosen after in depth technical consultations and fierce competition was GridSeal® which is a combination of GlasGrid® 8550 with tensile strength 50kN/m in each direction and Sealoflex SC-33 a hot sprayed polymer modified binder at 1.7kg/m² rate of spread. This combination is finally overlaid with 10mm chippings to keep paving traffic aware from the highly adhesive binder layer.
Asphalt Reinforcement Services Ltd, Ringway and Material Edge Ltd. UK representative of Ooms Avenhorn Holding, the manufacturer of Sealoflex SC-33 (now SC-4). The registered owners of the GridSeal® are responsible for the spraying of Sealoflex SC-33 (now SC-4). This specialist binder requires a specialised surface dressing spray tanker that can spray highly polymerised binders at up to 200°C.
For this project Ooms Avenhorn Holding contractor arm Ooms Producten provided sub-contracted supply and laying of the Sealoflex SC-33 to Asphalt Reinforcement Services.
On the first visit approximately 11,000m² of GlasGrid® was laid with a special laying machine by ARS Ltd in about five hours the day before the Sealoflex SC-33 was laid. Overnight rain did not affect the grid which remained adhered to the surfacing through its contact adhesive. The surface was dry by the morning and spraying of the hot PMB took about three hours with chipping a further two hours.
The chippings keep the paving traffic away from the highly adhesive binder layer and provide an excellent key into the overlay which in this case was a 10mm SMA specification design to provide good skid resistance and low scuffing under power assisted steering from parking cars.
The asphalt overlay design provides a smooth well drained surface for car parking over an area of concrete including some spalled joints and fractured PCC slabs that was previously Heathrow Airport taxiway. Commencing with a layer of approximately 20mm of regulating onto which the GridSeal® system is applied the whole area is being overlaid with 40mm minimum thickness of SMA surfacing by the main contractor Ringway.
On our most recent visit to the Pink Elephant Car Park in 2013 a thorough examination of the surfacing showed some areas of fretting on corners where traffic was turning. There were isolated cracks showing in one area at the top of the project where it is believed GridSeal was missing from the pavement, however the total amount of cracking on the project reflects a very small % of the concrete bay joints underneath the 40mm overlay, a considerable achievement after 9 years performance of such a thin overlay. Next time you fly from Heathrow take a look yourself at the Pink Elephant Car Park.
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