As part of a major £16 million upgrade of Eastbourne Wastewater Treatment Works being carried out on behalf of Southern Water, AkzoNobel’s range of Intercrete concrete repair materials have been chosen to refurbish an underground inlet chamber at the plant.

An Intercrete system was devised for the project comprising a dry spray application of Intercrete 4801 repair mortar followed by a final coat of Intercrete 4840 cementitious coating. Almost 140 tonnes of Intercrete 4801 was applied over a six month period by specialist asset maintenance contractor Concrete Repairs Limited.

The work was carried out on behalf of CMDP, a joint venture between Costain and MWH and one of Southern Water’s three business partners delivering AMP6 improvements until 2020. The Intercrete range has been expanded following AkzoNobel’s acquisition of Flexcrete Technologies Ltd in July 2017 with Flexcrete products becoming known as Intercrete, part of the International brand.

Dating back to 1997, Eastbourne Wastewater Treatment Works is located on a prime site on the seafront at Langney Point in East Sussex. Serving a population of circa 140,000 people across the Eastbourne area, the vast majority of the works is located underground, beneath a fortress-style building. Up to 74 million litres of wastewater is pumped in and treated every day almost entirely out of sight.

The concrete repair work was carried out by Concrete Repairs Limited (CRL) beneath ground level in extremely arduous conditions. The project involved the refurbishment of the underground inlet channel that receives wastewater flows, as the concrete had deteriorated due to attack from hydrogen sulphide (H2S) gas and sulphuric acid. The Intercrete application was carried out at night when flows were low.

Preparation and application

In order to remove the defective concrete first, CRL used hydro demolition methods before a dry spray application of Intercrete 4801 – a high strength, waterproof, shrinkage compensated, class R4 mortar which exhibits extremely low rebound when applied either by dry or wet spray techniques for the structural repair, rendering and profiling of vertical, overhead and horizontal surfaces. With excellent resistance to abrasion and the physical demands of general trafficking, Intercrete 4801 is a single component cementitious repair mortar, which incorporates the most advanced cement chemistry, microsilica, fibre and styrene acrylic copolymer technology. The product only requires the addition of clean water on-site.

Following the application of Intercrete 4801, Intercrete 4840 was applied. Intercrete 4840 is an innovative, two component, water based cementitious coating that benefits from modification with both a thermoplastic polymer as well as an epoxy resin to provide a hard wearing surface with greatly enhanced chemical and abrasion resistance.

This combined Intercrete 4801/4840 system was also specified for another Southern Water project carried out by CRL at Ford Wastewater Treatment Works in Arundel. For both projects it was chosen on the basis of the rapid curing properties and speed of reinstatement between application of the mortar and coating as there is no need for a skim coat due to the high quality finish of the mortar. The system also minimises environmental impact due to the fact that both products are water-based, ultra-low odour and solvent-free, making them safe to apply even whilst facilities are in operation.

The £16 million overhaul of Eastbourne Wastewater Treatment Works will bring many long-term benefits and ensure wastewater leaving the site is of the highest quality. As well as the concrete repair work, other upgrades include updating the biological filter, improving lighting, ventilation and odour controls and replacing pumps and other equipment. The refurbishment is due to be fully completed during early 2020.

Independent testing carried out at the VINCI Construction Technology Centre in Bedfordshire has officially confirmed that Intercrete 4841 (formerly Flexcrete’s Cementitious Coating 851) provides an effective barrier against chlorides lasting at least 30 years.

In 1988, a 2mm thick film of Intercrete 4841 was applied to a concrete slice and sealed in a chloride ion diffusion cell, and 30 years (10,950 days) later it is still providing full protection. Continuous tests carried out in the VINCI Construction Technology Centre laboratory show that the barrier properties of Intercrete 4841 have remained the same throughout the test period, a testament to product’s consistent and long-lasting performance.

“The performance demonstrated in this test by Intercrete 4841 is unparalleled,” said Chris Lloyd, cofounder of Flexcrete Technologies Ltd, acquired by AkzoNobel in 2017. “In VINCI’s experience, many coating systems degrade over time when on test in the cell, and even products that initially perform well can subsequently blister, resulting in more chloride ions passing through the product. Intercrete 4841 has not shown any signs of deterioration, despite being fully immersed in the chloride solution for 30 years. It would have taken 271 years for the product cell with the Intercrete 4841 to reach the same chloride concentration that the uncoated specimen reached in just 98 days.”

Advanced protection

Intercrete 4841 is a two-component, waterborne cementitious polymer coating, originally introduced in 1985. It remains a market-leading solution to chlorides and other forms of damage and corrosion by forming a hard, alkaline coating with outstanding pressure resistance.

Thanks to this advanced protection and proven performance, Intercrete 4841 is widely specified on both existing and new structures to waterproof concrete, reinstate concrete cover and provide an effective barrier against challenging conditions such as coastal environments, highways and water and wastewater industry.