A Sika admixtures solution has been specified in a Hanson concrete mix as part of the new £20 million Leeds Station Southern Entrance scheme across the River Aire.
The solution has ensured that the platform’s underwater concrete foundations will offer high resistance to washout and will last for years to come.
Built by Carillion Rail for clients West Yorkshire Combined Authority and Network Rail, the Leeds Station Southern Entrance (LSSE) will allow for greater access to one of the UK’s busiest stations.
The entrance will comprise a concourse deck over the River Aire within an aesthetically pleasing enclosed building; with open link span bridges providing direct stepped access from the concourse deck to the east and west banks of the river.
To form the structure’s concrete foundations, Martello Piling sunk steel tubes into the river bed in front of the bridge bases using 360m3 of Hanson concrete, with Sika PilePak admixtures placed into the tubes.
Ideal for difficult piling conditions, the Sika PilePak was specified to ensure consistency and workability of the concrete over a prolonged period of time and to avoid any concrete problems at any one pile position.
Stephen Armfield, Product Development Manager, Sika commented: “The environmental extremes of having to place concrete into a river were a particular challenge on this project. Requiring high quality concrete and specialist kit including special pumps as well as commercial divers ensured the critical path of these foundations was a success.”
Pre-cast sections of concrete were used to form the sides and ‘nose’ of the structure protecting the brick bases.
Sika UCS Pak, a specialist underwater admixture, was used in 152m3 of Hanson concrete that was placed in the middle of the structure. This was free from the flow of water but still placed underwater.
The structure was filled up with fresh concrete between the pre-cast segments to force out any remaining water.
Meeting the requirements of BS 8443, Sika UCS Pak prevents the wash out of the cement paste and increased the cohesion of concrete. It is packaged in water soluble bags to enable ease of addition on site.
The use of Sika admixtures within the underwater concrete foundations ensured the success of one of the most critical elements of the infrastructure project and enabled the LSSE to open on schedule in January 2016.
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