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Contractors World UK & Ireland Vol 6 No 1

32

Admixtures Key

To Underwater

Foundations

At New Station

Entrance

Built by Carillion Rail for clients

West Yorkshire Combined Authority and Network

Rail, the new, design-award winning, Leeds Station

Southern Entrance (LSSE) will enable greater access

to one of the busiest stations in the UK . It comprises

a concourse deck over the River Aire within a visually

eye catching enclosed building.

The addition of open link span bridges provide

direct stepped access from this concourse to the east

and west banks of the river. This was the challenge for

the contractors. Installing underwater foundation to

support to new steel and glass entrance.

Because of the situation, special attention had to be

made to the concrete mix which was supplied by Hanson

Concrete. The specification of Sika admixtures solutions

in the concrete mix ensured that the underwater con-

crete foundations offered very high resistance to wash-

out and will stand the test of time.

To form the concrete foundations of the structure,

specialist contractor Martello Piling sunk steel tubes into

the river bed in front of the bridge bases with 360m

3

of

Hanson concrete containing Sika PilePak placed into

these tubes. This ensured consistency and workability

of the concrete over a prolonged period of time, 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 then used to form

the sides and ‘nose’ of the structure protecting the brick

bases. Some 152 m

3

of Hanson concrete containing Sika

UCS Pak, a specialist underwater admixture, was then

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 con-

crete between the pre-cast segments, which forced any

remaining water out.

The station was opened on schedule in January 2016.

[cw]

Contractors World UK & Ireland