Three important landmark buildings get the renovation treatment from Sika
The key to success for any new-build or renovation project is preparation, as according to the well-worn saying, ‘fail
to prepare; prepare to fail’. It’s a motto that is particularly pertinent to concrete refurbishment – good quality surface preparation goes hand-inhand
with a safe, effective and long-term repair.
By getting the basics right, the first step to successful concrete repair has been taken. Before any work is carried out, it’s essential to check the right tools and products are available
to do the job. This means ensuring said tools are in excellent condition – clean and wellmaintained.
In terms of concrete removal, only defective areas highlighted by a supervising officer or qualified engineer should be removed, and as with any repair project, only use clean,
potable water when required. It’s essential to avoid contaminating the mixture with other chemicals, or mixing powders from different products. It’s also
not advisable to add more water than recommended. In addition, mixing and applying product in direct sunlight should be avoided.
For the all-important substrate preparation, defective concrete should be marked and removed accordingly. For small patch repairs, a hammer and chisel will likely suffice. A hammer
drill should be used on larger areas, whilst even larger sites might best be treated with a highpressure water jetting.
Concrete should be removed to a minimum of 15mm behind the reinforcing bars. Cut the sides to a minimum of 90° to avoid undercutting and a maximum of 135° to reduce de-bonding around edges. The substrate should
be sound and devoid of loose material before repairs continue. If the substrate appears cracked, immediately inform a supervisor.
For the reinforcement preparation, remove all tie wires, mortar/concrete, rust/scale and any other loose material using one of the following techniques:
• Steel wire brush or hand/power tools – this technique is applicable only in carbonated concrete and under environmental constraints where techniques two and three cannot be used
• Abrasive blast cleaning – if chlorides are present, reinforcement should be cleaned with water afterwards
• High pressure water jetting – 1,100 bar minimum
Sika recently showcased the scope of its construction sector specialities during the refurbishment and conversion of three historic buildings, two of which are Grade II-listed, with its industry-leading products
selected for both roof and basement works. The Cunard is described as one of Liverpool’s most iconic buildings. Built in 1917, the six-storey construction not only provided sanctuary as a Second World War air-raid shelter, its dockside
location also made it an ideal site for ship building blueprints and luggage storage.
Following its conversion into high-end office blocks, a survey of the building revealed issues with the roof and basement. At the top of the building, aged asphalt patches with varying level changes and multiple cases of
cracking, slumping and blistering were identified.
Meanwhile, in the basement soffits, beams and columns located in its sub-basement began to show signs of deterioration. Carbonation and chloride levels in the concrete led to the reinforcement bars becoming exposed in areas,
leading to surface cracking and spalling.
Sika had the ideal solutions for both problems. Designed Roof Systems Ltd was given the task of solving the roofing issues. They specified a 20-year Decothane system in light grey with red walkways. Michael Devlin, Managing Director at Designed Roof Systems
Ltd, said; “The Decothane system was chosen as the client didn’t want to replace the asphalt and wanted to avoid the need for hot works to be carried out, but at the same time was looking for a roofing solution that was aesthetically suitable and effective over varying details and angles as well as the more basic flat areas. Decothane more than delivered on this brief.” Clan Contracting were instructed to carry out the basement’s concrete repair and began by removing the cracked and delaminated concrete
and cleaning the areas in preparation for the application of Sika’s reinforcement system.
Firstly, the steel reinforcement was applied with Sika MonoTop®-610, a high-performance, one-component, cementitious polymer-modified protection coating. This was followed by Sika MonoTop®-612, a high-strength repair and re-profiling system suitable for overhead and vertical concrete substrates. Spray or hand-applied, Sika MonoTop®-612 provides superb resistance to water and chloride penetration. For the onecomponent, polymer-modified cementitious smoothing coat, Sika MonoTop®-620 was applied.
CARBON FIBRE STRENGTHENING
As well as crack repairs, Sika provided carbon fibre strengthening in the form of Sika CarboDur®, carbon fibre-reinforced polymer (CFRP) laminates which are bonded onto the structure as externally-bonded reinforcement using Sikadur®-30 structural adhesive. Sika
Ferrogard®-903+, a surface-applied, multi-functional liquid corrosion inhibitor, and Sikagard®-550W Elastic, a plasto-elastic, anti-carbonation coating supplied the system’s final protective layers.
“The Sika concrete repair system was specified on the strength of its proven properties as a dependable, long-term refurbishment and strengthening system,” explains Damian Meyers, Commercial Director at Clan Contracting. “It performed as promised, delivering a superb solution to the debilitating soffits, beams and columns without issue.” Thanks to the superb properties of Sika’s concrete repair, strengthening and roofing systems, the top and bottom of the landmark Cunard building has been improved, leaving a well- protected, structurally-sound belowground floor and water-tight, visually-pleasing roof.
In another project, Sika supplied the longterm concrete repair and protection solution to facilitate a landmark listed building’s transformation into a luxury residential complex. The Hoover Building in Perivale, west London remains one of the most stunning examples of Art Deco architecture in the UK. Built in the 1920s for the Hoover Company, the original building was Grade II-listed in 1980.
In 1991, the rear of the building was refurbished to accommodate a Tesco supermarket – a project on which Sika was also involved. Now the building is once again undergoing a transformation with work on the front elevation, to convert the building into 66 luxury studio, one, two and three-bedroom apartments.
Due to its age and city location, the building’s exterior had begun to show signs of deterioration, with carbonation-induced cracks, spalls and exposed concrete reinforcement appearing in several areas. Sealants around the structure were also showing signs of deterioration.
The implementation of a concrete repair and protection system, with effective corrosion control measures, was required to make good the damage and extend the life of the building. Sika had the solution for all requirements.
Contractors Structural Renovations, on behalf of development company IDM Properties, initial reparations involved cleaning and preparing the concrete surfaces and removing areas that were cracked or delaminated. In addition, exposed
reinforcement was cleaned of all corrosion.
Once completed, Sika® MonoTop-610, a high-performance, one-component, cementitious polymer-modified primer was applied to the exposed reinforcement. Brush applied, Sika®MonoTop-610 simply required mixing with water to provide a superb, anti-corrosive protection to any exposed reinforcement and bonding. This in preparation for concrete repairs using Sika® MonoTop-615, a high-build, hand-placed concrete repair mortar.
These products provide the perfect repair mortar system for delaminated, weak, damaged and deteriorated concrete.
To manage the steel corrosion within the structures, products from Sika’s Total Corrosion Management (TCM) portfolio were utilised. These included Sika® Ferrogard®-903+, a surface-applied, multi-functional liquid corrosion inhibitor, and for areas of previouslycoated concrete – Sika® Margel VPI 580, which is inserted inside concrete structural elements close to the reinforcing steel to inhibit corrosion.
Sikagard®-545 W Elastofill was then applied, which is a crack-bridging intermediate coat that closes pores, cavities and blowholes, providing an ideal surface prior to the application of the concrete protection coating. Sikagard®-550 W Elastic, a high-performance elastic protective coating, offering protection from the elements which cause corrosion was then applied in the colour scheme required by the client.
“Sika’s concrete repair and protection system performed superbly as expected,” reports Tom Haynes, Director at Structural Renovations. “It came with a guarantee, which offered great peace of mind to the clients and future residents of this fantastic building that the concrete repairs are of the highest quality. The potential for future maintenance has been minimised thanks to Sika’s effective corrosion management programme.”
With the building’s concrete repair programme completed to the client’s deadline, the striking building’s transformation to a desirable and stylish and city residence can continue, safe in the knowledge the façade will soon be returned to its original splendour and stand protected for many years to come.
THIRD OF THREE
In the final project of the trio, Sika supplied the concrete repair, protection and anti-carbonation system to replenish the facade of a celebrated town landmark.
Chatterton Water Tower in Spalding in the UK has been a long-standing feature of the area’s landscape. At 30 metres-high, it dominates the town centre’s local bus station which it overlooks, whilst its distinctive tulip fascia has
made it a stand-out feature throughout its 62-year existence.
However, time and the elements had taken their toll on the tower’s surface, leading to its refurbishment for minor repairs involving the removal of flaking and algae growth.
Requiring a proven, durable concrete repair, protection and anti-carbonation system, contractors, Concrete Repair Ltd, in conjunction with clients, Anglican Water, turned to Sika for
the necessary solution.
In preparation for the protective coatings, the tower’s 4,000m2 surface was prepared to remove dirt and other impurities. After breaking out defective concrete and cleaning the exposed reinforcement, Sika Monotop®-610, a highperformance, one-component, cementitious, polymer-modified slurry was then applied.
Sika Monotop®-610 simply required mixing with water to provide a superb, reinforcement corrosion protection coating and bonding primer in preparation for concrete repairs using Sika Monotop®-615. This concrete repair mortar – which also requires nothing more than simple water mixture for preparation – is the perfect reinforcement mortar for delaminated, weak, damaged and deteriorated concrete.
Sikagard®-675 W GB ElastoColor was then installed. Easy to apply, the system prevents water ingress and is suitable for a range of concrete structures as an anti-weathering, two-way vapour permeable solution to stop pollutants and water penetrating into the concrete matrix, whilst protecting the internal reinforcement.
“The Sika products were superb in repairing and protecting the tower’s surface,” explains Olu Ogunwale, Senior Contracts Manager at Concrete Repair Ltd. “They were very easy to use, and provided the perfect base with which to restore the tower’s aesthetic qualities. We were very pleased.”
The tower’s restoration was completed in October 2017 to the client’s full satisfaction. This outstanding town landmark is now looking as smart as it did when it was first built in 1955. Thanks to the robust properties of Sika’s dual concrete protection system, it will remain a much-admired fixture on Spalding’s town centre horizon for many years to come