Concrete Tank Repair Contractors

A tank that had failed a programmed inspection was repaired by a team of concrete tank repair contractors from CSC. Following a site visit to agree scope and budgets the onsite work began the following week to repair the asset for the client. All site inductions, method statements, permits and site briefings from site agent and framework delivery manager were conducted before work commenced.

Areas for Repair Identified

• Ingress into tank from six no. upstands and access hatches
• Loss of concrete cover to internal tank walls
• Concrete repairs required to various internal areas
• Tank in need of cleaning

Site Set-up

Due to the off-road nature of the project site, conventional welfare provision was not possible. We were therefore able to use our mobile welfare unit and off-road vehicles to ensure efficient transport of concrete tank repair contractors, materials, plant and equipment to and from the site, as well as ensure the welfare of the project team.

Repair Process: External Work

Step 1: Trench dug around all upstands

A 500-600mm trench was dug around the upstands, with turf and soil stored to one side to enable the repairs to take place. Fencing was erected around all upstand trenches to secure and protect any falls.

Step 2: Failed coatings removed

Old, failed coatings were removed back to sound concrete using a mixture high-pressure water and mechanical power tools.

Step 3: All hatches lifted and re-bedded

All Techno cover access hatches were unbolted and lifted from their concrete upstands, cleaned and re-bedded using a Fosroc sealant. Bolts were tightened correctly and the internal and external joint interface between concrete and steel sealed.

Step 4: All upstand joints sealed

Leaking joint interfaces due to incorrectly cast roof upstands or those that had been capped off were sealed using a Hypalon Bandage System (BASF Masterseal 930 and 933).

Step 5: All upstands received a new protective coating and cover

All upstand concrete was sealed and protected using Sika roofing product Decothane Ultra, which incorporates a low odour, moisture-tolerant polyurethane liquid membrane and a fiberglass matting, which binds and adds strength to the liquid coating. After the Decothane coating had cured a hard plastic cover was wrapped around each upstand to protect from any future damage caused by lawn mowers etc.

Step 6: All upstands re-instated

All upstands were re-instated with the previously removed sub soil and turf and any tyre marks from 4×4 vehicles were repaired with new soil/turf and all fencing removed.

Repair Process: Internal Remedial Works

Step 1: HPW Jetting to all tank internal surfaces

All concrete surfaces were cleaned and prepared using high-pressure water between 4000psi to 7500psi to prepare the concrete walls to receive the new coating.

Step 2: Concrete repairs to various areas

Areas of spalling concrete or rust from embedded steel were broken out, steel cleaned and protected, followed by a DWI-approved concrete repair material (Natchem 35) placed into the repair area to finish back to profile.

Step3: Thin coat render to walls

The prepared walls received a 5mm DWI-approved cementitious thin coat render (BASF Masterseal 586) to bring the walls back to profile and waterproof long into the future. The coating was tested for thickness during application, photographic evidence taken and compiled for QA documentation.

Step 4: Tank cured, tested, cleaned and then returned to client

A small heating unit was installed to provide an ambient temperature range suitable for curing the internal coating work, this was 3 days above 3o. The coating was then tested for adhesion and full cure. Finally depth gauge marker boards were refixed before a full and final clean to back out and return to the client.

concrete tank repair contractors at work

All concrete repairs and coatings were completed in accordance with BS EN 1504 standards for products and systems for the protection and repair of concrete structures and all current manufacturers safety and technical data sheets.

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