Turning the tide for Newhaven sea wall
Following a trio of severe storms, the 140-year-old Newhaven sea wall required repairs to ensure the structure continued to protect the port.
In the port town of Newhaven in East Sussex stands a 730 metre-long concrete breakwater that has shielded the harbour from the elements since the late 1800s.
Like any concrete structure exposed to water, the sea wall requires regular maintenance work, but following damage to the breakwater caused by three consecutive storms that swept across the UK in February 2022 – Storm Dudley, Storm Eunice and Storm Franklin – more urgent repairs were needed.
The construction of the sea wall itself is an interesting example of Victorian engineering. Proposals to transform Newhaven into an official harbour were drawn up in the 1870s when the Earl of Sheffield, the owner of the land, commissioned the levelling of the chalk cliffs to form a promenade. In 1879, work began to build the breakwater that still stands today.
To form the foundations, concrete was poured into 100-tonne tarpaulin bags and dropped into the water through an opening in the bottom of a steamboat at medium-tide. These bags eventually reached the surface, at which point mass concrete was added, allowing the workers to finish the top half. It is the weight of the concrete on top of the base that keeps the structure in place.
Without the help of heavy machinery, it took the best part of a decade to create the breakwater and promenade in Newhaven – the former becoming only the second construction of its kind at the time.
The wall itself is eight metres wide, including a 200-300mm outside skin, and is infilled with a combination of chalk and cement. Building the structure in this way means that it has the flexibility to move, helping it to better withstand the impact from severe weather and waves. However, it does mean that if water breaches the outside skin, it can take out any loose material and form cavities that the water can sit in. If left, these cavities will grow over time and erode the structure from the inside which is why routine maintenance is so critical in this case.
Newhaven Port and Properties – which owns the port – assesses major repairs and defects and is responsible for prioritising works. For the last 12 years, Newhaven Port and Properties has enlisted the help of specialist concrete repair and civil engineering contractors AJC Contractors to carry out works that keep the port operational.
To address the damage caused to the sea wall by the storms in February, AJC Contractors began by removing any concrete around the steel reinforcements that had been damaged or was likely to break. They did this as a preventative measure to stop the damage getting worse rather than as part of the emergency repair.
The team then added starter bars around the area followed by reinforcement mesh and L bars. This initial work was done to prepare for the spray operations, which were then delayed due to adverse weather conditions.
“We were checking weather reports daily to assess when we could start the spray works, while knowing that even if the forecast looked ok, it could still be called off at a moment’s notice if the conditions weren’t suitable,” explained Sean Cummins, managing director of AJC Contractors.
“Weather can be one of the biggest obstacles when carrying out this type of work: it has to be just right. We can’t use certain pieces of equipment if winds are over 20mph because it wouldn’t be safe.”
It wasn’t until early October 2022 when the weather finally settled enough for Sean and his team to progress the final stages of the project. The remaining works involved spraying the repair concrete on the damaged areas, to remove the risk of breaches.
Sean Cummins, Managing Director of AJC Contractors
“Even when we’ve had as little as 20 minutes before we’ll be impacted by the tide or weather conditions, we’ve never had any issues or failures when using Weber’s products. The other benefit for us is that webercem spray RSF can be sprayed on with a thickness of up to 400mm in just one application. This means that we don’t have to wait around to re-layer the material; we can build it up thicker first time, which saves us valuable time and money.”
The fibres within the product bind it together allowing for a thicker build up and increasing the tensile adhesion strength. Another key feature of webercem spray RSF is that it’s fast setting; within just one to two minutes the initial set is complete and after 15 minutes the tide can come in, wash against the product and not scour it at all.
Tony Bartlett, technical sales manager at Weber, has worked with AJC Contractors on previous repairs at the Newhaven sea wall and is familiar with the challenges they face working in these environments.
“Remedial work such as this is not uncommon in coastal environments. Where structures like the Newhaven breakwater are built to withstand constant exposure to the sea, there is only so much damage that can be done over time before repairs need to be made,” explains Tony.
“When it comes to concrete repairs, the main considerations that should be made when choosing products are set time, build thickness and early strength gain. Due to the tight timeframes usually associated with these types of repairs, all of these factors can help applicators to save valuable time and make their projects run as efficiently as possible. Even a few minutes can make a huge difference.
“It’s crucial to review the time the product will take to set. It would not only be frustrating but also potentially very costly if you were to invest in a product that didn’t set in time and was then washed away. Also note the maximum build thickness as this will dictate how much can be done in one pass. Early strength gain is particularly critical in marine projects as there simply isn’t the time to wait. The repair works must be effective as soon as possible.”
webercem spray RSF is a ready-to-use, polymer-modified, dry sprayed concrete which contains inert limestone aggregates, dust suppressants and accelerators. The formulation is designed for the dry spray process method of application with reduced rebound and excellent sprayability. Its fibres help to improve resistance to cracking and adhesion to concrete substrates, it offers early strength gain, and it has good resistance to chloride absorption which is essential in a marine environment.
These works were completed in October 2022, but ongoing maintenance of the seawall continues.
AJC Contractors specified Saint-Gobain Weber’s webercem spray RSF for the repairs, a product they’ve used numerous times before, including on past works on the Newhaven sea wall.
The webercem spray RSF is a ready-to-use, polymer-modified, dry sprayed concrete which contains inert limestone aggregates, dust suppressants and accelerators. The formulation is designed for the dry spray process method of application with reduced rebound and excellent sprayability. Its fibres help to improve resistance to cracking and adhesion to concrete substrates, it offers early strength gain, and it has good resistance to chloride absorption which is essential in a marine environment