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Stirling Lloyd Ouse Quality
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Stirling Lloyd, market leaders in structural protection technology, have recently provided the solution to the waterproofing and surfacing of a major structure where the available depth of surfacing could have been problematic to the projects success.
The M62 Ouse Bridge, near the small but busy working port of Goole, in the East Riding of Yorkshire spans almost one mile and is the largest of the many bridges in the area where flat land and countless river crossings are features of that part of the Country. Built to ease congestion on the nearby Boothferry Bridge and completed in the mid 1970’s the M62 Ouse Bridge dominates the local skyline, its height a consequence of the requirement to allow shipping to pass underneath.
One complication for the refurbishment was the need to restrict the surfacing depth to only 70mm to maintain the geometry of the bridge. In addition any saving in dead load had the advantage that it would significantly increase the dynamic load capacity.
A potential solution to this was to use a waterproofing system that could perform under the shear forces exerted under this unusually thin surface depth of only 70mm and without the need for the traditional 20mm thick sand asphalt carpet used on most UK bridges.
As a consequence Consulting Engineers, WSP Civils Ltd desired a system that had a record of success with thin surface specifications.
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Their investigations led them to the Eliminator® waterproofing membrane manufactured by Stirling Lloyd and their specially developed bond coat for bonding the membrane to thin surfacing systems, SA1030. The combination has an unsurpassed track record in this situation having been used hundreds of times in similar circumstances, with great success, in many countries around the world. The system has established itself as the ideal waterproofing system where the design criteria allows for only a thin layer of surfacing or where the bitumen content in the surfacing specification is low.
Client, the Highways Agency, also had confidence in and experience of, the Eliminator® / SA1030 combination beneath thin wearing courses following the success of the system on previous projects such as the M53 Bidston Moss Viaduct on Merseyside, where the failure of the surfacing on a previous applied polyurethane system had dictated a massive overhaul of the waterproofing and surfacing. Other examples of use in the UK include Rochester New Bridge, Kent, the Weaver Viaduct and Farndon Bridge, both in Cheshire.
In addition the Eliminator® / SA1030 combination has been tested both in the laboratory and on-site by the British Board of Agrément, and has been approved for use on Highways Agency projects where sand asphalt carpet is omitted (see BBA Road & Bridges Certificate R112/99 & R111/99).
Following competitive tendering Main Contractor, Balfour Beatty, awarded the contract for the application of the system to Stirling Lloyd Contracts Limited, one of a number of authorised contractors for the application of the Eliminator® system.
Following thorough preparation of the substrate by planning and grit blasting, Stirling Lloyd's methyl methacrylate (MMA) PAR1 primer was spray applied to the concrete deck. This helped to seal the surface of the deck and ensure adhesion of the subsequent waterproofing membrane was maximised. Once the primer had cured, typically in less than an hour, the Eliminator® membrane was then applied. Throughout the application thickness was monitored, using wet film gauge tests, to ensure the minimum required final thickness of 2mm was achieved. To further confirm the membranes integrity, after being applied it was subjected to high voltage, non-destructive spark testing. On completion of the integrity testing the Bond Coat SA1030 was then applied. SA1030 is a hot melt, solvent free adhesive based on a polymer modified bitumen.
The Bond Coat was heated to achieve the application temperature range of 175-200 °C. It was then applied to the deck to a minimum thickness of 1mm. After just thirty minutes, the system was ready to receive the surfacing. The temperature the hot rolled asphalt is laid at re-activates the bond coat, which then as it cools provides a strong long-lasting intimate bond between the membrane and the wearing course. Not only did the choice of the Eliminator® system solve the thin surfacing but it also provided a number of advantages to the Client, Consulting Engineer and Main Contractor. The use of a high rut resistant base which avoids the risk of poorly compacted sand carpet will provide a more durable surface and with the increased adhesion possible with the Eliminator® and Bond Coat SA1030 should allow the surface wearcourse to be removed at a later stage without removal of the waterproofing and base.
The importance of the structure, based on the volume of traffic it carries, meant that programming was tight and lane closures were limited. However the speed and ease with which the system can be applied, using simple to use, specially developed airless spray units meant that the waterproofing of the 47,500m² deck was carried out with the least amount of disruption possible, in four scheduled visits between July 2002 and March 2003. Furthermore, Eliminator® being based on MMA resins, means it is far more tolerant of difficult conditions including humidity, moisture and low temperatures than other membrane systems. This enables all year round application and the winter works on the River Ouse Bridge to remain on track.
In fact, after the successful conclusion of the contract Richard Green-Morgan of Balfour Beatty, commented, " The ease and speed of application make it (Eliminator®) an excellent product for covering large areas which require rapid protection."
This further example of the tried and tested partnership of Eliminator® and Bond Coat SA1030 enabling the successful completion of a major bridge refurbishment project with a restricted surfacing depth and no requirement for the much maligned and costly sand asphalt carpet layer demonstrates that a quicker, more cost effective and durable specification can be used provided the appropriate waterproofing and bond coat are used.
[ Stirling Lloyd Press Release PR03-12 : 12/2003 ] |
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