Strengthening its
position as the go-to supplier for complex renovations, Aggregate Industries’
unique Lytacrete solution has played a pivotal role in the £5 million
structural refurbishment of Nene Bridge in Peterborough.
Constructed over the
River Nene in the 1970s, Nene Bridge is an award-winning structure, iconic for
its ‘v’ shaped pier.
As a major traffic
route, it provides access to vehicles travelling from the A1 to A47, as well as
pedestrians and cyclists going between the north and south of the city. The bridge is currently undergoing extensive
refurbishment, including reinforcing the bridge piers and replacing
bearings, as part of a repair programme being
carried out by Skanska.
Recent inspections of
the bridge revealed signs of structural distress to the bearings and cracking
to the saddles of the piers. Traditional methods of replacing the bearings were
not possible because the ornate architectural design of the original piers did
not allow space on top of the piers for jacks to be positioned beneath the
superstructure replacing the bearings. In addition, jacking points were not
provided within the box girders.
As such, the designers
at Skanska considered various options for replacing the bearings and
strengthening the piers, whilst remaining sympathetic to the appearance of the
original piers. This led them to develop the solution of encasing the piers in
reinforced concrete jackets, to strengthen the piers and also to provide
jacking platforms for the superstructure lifted to enable the bearings to be
replaced. For this solution to work, the concrete used in the jackets needed to
be strong enough to strengthen the piers and to carry the jacking loads,
self-compacting, to flow around the dense reinforcement, and lightweight, to
minimise the additional load on the foundations.
As the first bridge
repair of its kind in the UK to deploy this method, Aggregate Industries
suggested the use of Lytacrete, a concrete mix using the innovative lightweight
secondary aggregate, Lytag, which can effectively reduce the dead load by
approximately 25% over normal weight control, while offering the same level of
structural performance.
Throughout the
project, Lytacrete was placed around the piers, and owing to its high strength
and self-compacting nature, this meant the mixture needed to be free flowing to
ensure it could be placed around the complex and congested steel reinforcement.
As a result, the solution proved ideal for strengthening the pier as well as
maintaining its unique ‘v’ shaped design. The concrete can also withstand the
jacking of the deck of the bridge to replace the bearings - a core process of
the refurbishment.
Over the next 12
months, Aggregate Industries’ robust delivery framework will also ensure all
concrete arrives on time and to the exact specification to ensure the concrete
is available to surround, rebar and form the required shape.
Simon Wycherley, General Manager at Aggregate
Industries, comments: “We’re incredibly proud to be involved in the repair
works of Nene Bridge, the first project of its kind to use our Lytacrete
solution in this way. Coupled with our on-site technical expertise, we hope our
innovative concrete solution ensures this iconic structure lasts the test of
time.”
Dan Wood, Site Manager
for Skanska Infrastructure Services, said: “Lytacrete has performed well on the
Nene Bridge bearings project, successfully flowing around the complex steel
reinforcement to form the unique geometry required. I would like to thank Aggregate
Industries for taking on board feedback and working with Skanska to refine the
mix design to suit the bridge’s unique requirements.”
