Solution: Concrete Repair & Protection,Waterproofing
Architect: South Lanarkshire Council
Contractor: Clark Contracts / UK Gunite
An incredible 3,500 individual concrete repairs and two miles of treatment to concrete surfaces have given a much loved building in East Kilbride a new lease of life.
The £7 million pound refurbishment of Scotlands stunning Dollan Aqua Centre proved to be one of the most complex and essential restoration projects for South Lanarkshire Council who had to not only strike the right balance between vital repairs but also the rigorous rules applied to ensure the Historic Scotland grade A listed status is protected.
Designed by Alexander Buchanan Campbell and built in 1968, a distinctive feature of this visually striking building is the pool tank which is elevated with reinforced concrete support walls running perpendicular to the tank at five metre intervals along its length. Following a structural inspection, the main pre-stressed structure was generally in good condition, however the tanks supporting concrete beams and peripheral supports and columns were suffering from cracking and spalling due to reinforcement corrosion.
A further issue was the internal and external areas of the pool tank which had serious chloride contamination due to the poor quality of the concrete and joint detailing.
With all key decisions regarding repair and strengthening taken by South Lanarkshire Councils in-house project engineer Vincent Connolly, this demanding project necessitated an extensive design and specification process with respect to steel reinforcement and concrete repairs, floor slab strengthening, pool tank joint repairs and waterproofing render repairs.
The agreed methodology of stripping back of all tiling and rendering on the internal walls, floors and pool tank being agreed prior to the application of a range of Sika products by specialist subcontractor UK Gunite, working for main contractor Clark Contracts.
The floor slabs directly surrounding the pool tank were deemed to be beyond economic repair and these were replaced with new steel and concrete composite floors. Following the removal of the tiles to the pool, the waterproofing render to the tank walls was found to be extensively cracked with large areas of delaminated render behind which was damp concrete substrate with small areas of chlorine crystals. The joints to the pool tank were also found to be severely deteriorated which along with the other findings suggested the tank waterproofing system had failed.
To ensure maximum durability and performance, the substrate of the pool tank was first lined using fibre reinforced dry spray concrete SikaCem 133F which enabled the effective application of the Sika 1 waterproofing system. Once applied to the pool tank, walls and floors, the systems admixture reacts to any water ingress by turning into a jelly-like substance, blocking all gaps and capillaries, and providing an impregnable and invisible seal. Bonding monolithically with the substrate, it essentially becomes one with the structure and forms an invisible seal.
Further repair work to all movement joints and cracks in the pool tank were sealed with Sikas Sikadur Combiflex Jointing System, a highly flexible and elastic waterproof sealing system.
External concrete repairs as well as patch repairs to the concrete floors in the grandstand, pool tank support walls and edge support beams at the centre were repaired using Sika Monotop, a cementitious two-component system which provides future protection againstwater and chloride penetration, helping to prevent future damage to the buildings concrete structure. For structural crack repairs to the floor slabs and to the pool tank support walls, a Sikadur crack injection was used.
Lightweight and non-corrosive Sika Carbodur S Type strengthening plates were used to strengthen the identified weak floors in the reception area from the underside and then sealed with SikaTop Seal 107, a waterproofing coating.
The application of corrosion inhibiter Sika FerroGard 903 was essential following all concrete repairs to prevent the development of incipient anodes and also to slow down future reinforcement corrosion. This surface applied system penetrates the concrete to provide a protective layer around steel reinforcement without changing the visual appearance of the structure.
As with all repair and strengthening systems and materials, failures can sometimes occur but this is often down to a number of factors including the poor preparation of the substrate surface, how they have been mixed and how they have been applied. To minimise the risk of any failure, the careful planning of the works, provision of adequate supervision and the use of well trained and experienced personnel are all vital components. Recognition of these components by all parties including South Lanarkshire Council, Clark Contracts, UK Gunite and Sika was paramount in the successful completion of the work at the Dollan Aqua Centre.
The Dollan Aqua Centre reopened in May 2011 following this complex and demanding restoration which has secured the long term future of this Grade A listed swimming pool.
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