SIG supply Webercem Spray to provide vital reparation to sea defence
The client for this project, Shepway District Council, have responsibility for a number of beaches along the coastline in their district in Kent, ranging from Dungeness in the west to Folkestone in the east. Coronation Parade, located in an exposed part of the Kent coast, is a concrete structure located on Sunny Sands beach, Folkestone, spanning 340m and originally built in the late 1930’s. The structure was designed as a sea defence and to prevent the cliff from eroding whilst also protecting a number of homes and businesses. At the eastern end is a National Grid interconnector that allows sharing of electricity between the UK and Europe.
Due to the continuous wave action from the tide, and the rocks which act as a barrier to reduce the wave forces, the concrete had suffered from both impact damage and chloride ingress. This in turn led to corrosion of the steel reinforcement and associated concrete spalling. The poor condition of the structure meant that hydro-demolition with high pressure water jetting was required to break out large areas of defective concrete, to clean the remaining substrate and to remove corrosion from the reinforcing steel.
After a conversation with Kevin Hodgson, Project Manager at Concrete Repairs Ltd, regarding the specifications, Tony Bartlett, SIG London Business Manager for SIG Distribution was made aware of the requirements for carrying out the repairs and also re-instating the concrete with sufficient cover to the reinforcement also had to include a method that would be suitable for working within the short low-tide time window. To meet this criteria Tony suggested a sprayed concrete method and Webercem Spray RS was selected as the repair material. Webercem Spray RS is a polymer-modified, rapid-setting (within 15 minutes), dry-sprayed concrete, ideal for concrete repairs where time constraints demand early strength gain. The formulation is designed for the dry spray process method of application and provides reduced rebound and excellent sprayability. Webercem Spray RS also conforms with BS EN 1504-3 as a Class R4 (>45MPa) repair product.
One of the challenges on the project was to achieve a good finish to the repairs of the arches on the concrete structure. Despite the rapid setting nature of the product, the specialist teams of applicators managed to float the repairs before the sprayed material had hardened to achieve an excellent finish to the Webercem Spray RS concrete.
Another challenge SIG were faced with were the logistics of delivering direct to site, Tony Bartlett explains, “The location of the site made delivery of the materials a challenge, the offload area was behind a very tight corner and there was a 12 ft 3 height limit for vehicles. The surrounding beach was also open to the public, and was naturally very busy during the warmer months, so extreme care was required by all parties involved in the delivery and works. Luckily our diverse fleet and experience delivery drivers enabled us to get the materials exactly where they needed to be safely, on time and within budget with the use a crane offload facility and hiabs”
Concrete Repairs Ltd, Infrastructure Manager Mike Balletta had the following to say about the project: ‘The project has been extremely complex logistically having to work around the tides and then into the winter months. This harsh environment has required ourselves and SIG to be innovative in both the use of plant and equipment used when delivering to site, and the materials specified, specifically when choosing a repair product with which to re-instate the repairs. After discussing various options, SIG suggested Webercem Spray RS as the natural choice. The decision proved to be the correct one with the Webercem Spray RS performing as promised. We are extremely pleased with the results, as is the Client.”
An impressed current cathodic protection (ICCP) system was also specified in order to further protect the steel reinforcement from corrosion and to ensure the structure withstands the harsh conditions it is subjected to for another 75 years!