CRL was appointed to undertake specialist repairs and external coatings to two preload effluent collection tanks forming part of a critical wastewater asset. The circular tanks are pre-load structures incorporating wire-wound stressing bands over their full height, a form of construction that relies on the integrity of both the concrete skin and the stressing system.
Although the tanks were generally in reasonable structural condition, widespread cracking was evident within the spray-applied concrete overlay to the stressing bands. If left untreated, this deterioration posed a risk to long-term durability and asset performance, making targeted concrete repairs and a comprehensive protective coating system essential to preserve the structures.
Services undertaken
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External concrete repairs to preload effluent collection tanks
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Repair of spray concrete overlay to wire-wound stressing bands
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Application of elastomeric anti-carbonation coating to full external surfaces
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Design and installation of purpose-built scaffold access
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Sequential repair and coating works to minimise disruption
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Specialist surface protection to enhance durability and reduce future maintenance
The scope of works was developed to address both localised defects and the overall condition of the external concrete surfaces, aligning with best practice in concrete repairs and long-term asset management. Initial inspections confirmed that cracking was predominantly confined to the spray concrete overlay rather than the primary structural elements. CRL therefore adopted a repair-led approach, focusing on targeted interventions where required, followed by full-surface protection to prevent further degradation.
Localised concrete repairs were carried out to the external skin of the tanks in areas where defects had developed. These repairs were carefully prepared to remove unsound material and reinstate the concrete profile, ensuring compatibility with the existing substrate and maintaining the integrity of the wire-wound stressing bands beneath. Particular care was taken to ensure that repair techniques did not compromise the stressing system, reflecting CRL’s specialist understanding of post-tensioned and pre-stressed concrete structures.
Following completion of repairs, an elastomeric anti-carbonation coating was applied to the entire external surface of both tanks. This system was selected for its ability to accommodate minor movement and cracking while providing a continuous, breathable barrier against carbon dioxide ingress. The coating application was undertaken in a controlled sequence, ensuring uniform coverage and a consistent finish across the full height and circumference of the tanks.
Access for the works was provided via a purpose-built scaffold that fully surrounded the structures. This arrangement allowed CRL’s directly employed operatives to work safely and efficiently, maintaining continuity of operations and avoiding disruption. The scaffold also enabled the works to be completed in a logical sequence, from repairs through to final coating, supporting quality control and programme certainty.
"Having carried out a concrete condition survey of the 2 No. pre-load, open-topped, effluent tanks at Airds Point on the Solway firth, we found the tendons which were housed in discrete bands to be in good condition. Local repairs and protective coatings were applied externally, whilst the tanks remained operational to extend the service life for a further 25 years."
Alasdair MacDonald | Senior Contracts Manager | CRL
The application of an elastomeric anti-carbonation coating provides long-term protection well beyond the immediate repair works. By limiting the ingress of carbon dioxide and moisture, the coating significantly reduces the risk of reinforcement corrosion and further cracking of the concrete overlay. Its flexible nature allows it to bridge hairline cracks, improving resilience under environmental and thermal movement.
In addition to enhancing durability, the new coating transformed the external appearance of the tanks, replacing a weathered concrete finish with a clean, uniform surface that is easier to inspect and maintain. This reduction in future maintenance requirements delivers tangible whole-life cost benefits. Through careful repair selection, robust surface preparation and the application of proven protective systems, CRL has extended the service life of these critical assets, demonstrating its expertise in structural repairs UK and sustainable asset management solutions.
