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Issue 11 - April 2018

Strong demand for Alliance Practical Demonstration Days

Those interested in attending the next free Structural Concrete Alliance Practical Demonstration Day are encouraged to book early as the events are proving extremely popular. 

The next Demonstration Day is scheduled to take place on Tuesday 5 June at the Freyssinet Head Office in Telford. It follows a sell-out event at the Vinci Technology Centre, Leighton Buzzard on Tuesday 27 March 2018.

Running from 9-3.30pm, each Alliance Practical Demonstration Day offers delegates an opportunity to witness interactive demonstrations of key repair, protection, strengthening and sprayed concrete techniques.

Delegates visit a range of different demonstration stations. Each station will feature live displays highlighting the key preparation, skills and techniques involved in: concrete repairs; carbon fibre strengthening; concrete testing; sprayed concrete; and cathodic protection and monitoring systems.Demonstrations are subject to change at each event. 

They are also given an opportunity to discuss their queries with members of the Corrosion Prevention Association (CPA), Concrete Repair Association (CRA) and Sprayed Concrete Association (SCA) who will be exhibiting at the event.

Visit the Alliance YouTube channel to view the main activities that delegates can expect to see; or download a Booking form to reserve you place.

For those unable to make the Demonstration Days, the Alliance also offers CPD presentations which can be delivered on-site to interested parties.

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Flexcrete solution for power station chamber refurbishment

FlexcreteA protective coating manufactured by Flexcrete Technologies, part of the AkzoNobel group of companies, has been used to refurbish a surface water drain chamber at Dungeness B Power Station in Kent. Cemprotec E942, a waterborne cementitious coating, was chosen due to its rapid curing nature and ability to allow a speedy return to service.

Operated by EDF Energy, Dungeness B Nuclear Power Station was due to be decommissioned in 2018 but following £150 million extra investment, the station is expected to generate electricity until 2028. The chamber forms part of the surface water drainage system and is the authorised minor discharge route for waste condensate water being discharged. Although the chamber was intact, there were voids in the mortar and cracking around pipe penetrations. A protective lining was required that would tolerate the heat from the water being discharged.

CSC Services UK Ltd, a specialist repair and coatings contractor to the power and water industries, was appointed to carry out the application. The drain was first blocked and CSC Services installed an over-pumping system to isolate the chamber. The chamber was lined with Cemprotec E942 to provide a durable waterproofing solution with excellent resistance to abrasion and mechanical damage.

Cemprotec E942 can be applied to damp substrates with lower levels of preparation than conventional coatings. Its fast curing nature allowed a rapid return to service of the water drainage system. There are no concerns when Cemprotec E942 is applied in confined areas, as it has a water-based composition with no hazardous solvents or heavy odours.

Alan Smith, Project Engineer from Dungeness B Power Station said: “The work required confined space access and was subject to plant isolation. The refurbishment was completed to a very high standard and within programme.”

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Sika solution for Hoover Building

Sika supplied the long-term concrete repair and protection solution to the Hoover Building in Perivale, west London, a Grade II-listed Art Deco building built in the 1920s.

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.

Contractors Structural Renovations, on behalf of development company IDM Properties, conducted initial reparations involved cleaning and preparing the concrete surfaces and removing cracked and delaminated areas. In addition, exposed reinforcement was cleaned of all corrosion.

Once completed, Sika’s Monotop range was utilised to 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 previously-coated concrete – Sika® Margel VPI 580.

Sikagard®-545 W Elastofill was then applied. A crack-bridging intermediate coat, which closes pores, cavities and blowholes providing an ideal surface prior to the application of the concrete protection coating.

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. 

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StoCretec solution for Brandy Bridge

A package of StoCretec concrete repair products recently introduced into the UK market have provided the perfect solution for the refurbishment of a major road bridge in Wales.

The first of three piers of Brandy Bridge at Merthyr Tydfil was fully restored, using StoCrete TV 308 flowable mortar, TG 203 repair mortar, TF 204 fairing coat, StoCryl GQ Primer and StoCryl V700 protective coating.

The StoCrete TV 308 polymer-modified, flowable repair mortar was used to reinstate various parts of the cross-head beams and columns supporting the longitudinal bridge deck. Pumping the StoCrete TV 308 allowed the material to be applied at a rate of one and half tonnes per hour.

StoCrete TV 308 reaches a compressive strength in excess of 40N/mm2 within just 24 hours, yet also exhibits incredibly low shrinkage. Its low E-modulus means it’s flexible and very strong, making it ideal for fast repairs to civil engineering structures such as bridges and viaducts. Another advantage is that it is resistant to frost and de-icing salts.

Using the StoCrete TV 308 alongside other StoCretec products allowed all the concrete repair and protection products to be sourced directly from a single specialist manufacturer. After other works were completed using StoCrete TG 203 polymer-modified repair mortar and StoCrete TF 204 cementitious protective fairing coat, the concrete areas were treated with the quartz-filled StoCryl GQ Primer. This provided a reliable surface onto which the StoCryl V 700 protective coating was applied.

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Gunite repairs Ealing tower blocks

Following a competitive tender process, Gunite (Eastern) Ltd was appointed by Ealing Council to undertake concrete, render and brick façade repairs to three 11-storey blocks of flats at Gurnell Grove in Ealing.

Each block contains 66 residential flats of mixed tenure which were occupied throughout the 12-week duration of the works. The scope of works included: cradle access; cleaning discoloured and stained brickwork; brickwork repairs and repointing; concrete repairs and coatings; render repairs; cleaning windows and frames; and temporary removal and reinstatement of satellite dishes and pigeon netting.

Gunite provided Ealing Council with a 10-year Sika warranty for the concrete repairs and coatings.

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Weber defends Nothe Fort

Dry-sprayed repair concrete by Saint-Gobain Weber has been used to fortify the sea wall that acts as a coastal defence to Nothe Fort at Weymouth Harbour, Dorset.

Over decades of continuous exposure to tidal action, work to reinstate the concrete harbour wall became essential. Specialist contractor APA Concrete Repairs Limited took on this extensive project, completed in May 2017, using webercem spray DS and webercem spray RS.

While repair to the pier wall had taken place earlier for Portsmouth BC, the groyne wall foundations also had very serious tidal damage.

Access to the site was restricted and the project essentially ran in tandem with spring tides. The exposed surfaces above the water line were sealed with mesh and webercem spray DS which is designed for dry process spray application to give high early strength, reduced rebound and maximum application thickness. It complies with the Highways Agency Specification Class 29F for major structural repairs with an initial set in 2-3hrs and a compressive strength of 49.8Mpa in seven days.

The exposed half metre deep holes were filled with webercem spray RS. Taking advantage of its rapid setting qualities, it enabled build-up of the repair layers to maximum thickness in the two hour tidal windows. Altogether 16 tonnes of webercem spray DS was used on the upper surfaces and five tonnes of webercem spray RS on the foundation areas.

The groyne wall is expected to have a minimum extended life of 50 years following this renovation. 

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Duvine introduces new CP150

Duvine has introduced the new CP150 power module which is ideally suited for multi-zone systems.

Based on its many years of switch-mode power supply experience, the CP150 is a cost effective and robust solution which can cover up to 120 zones. The standard CP150 solution offers 0-25V and 0-10A on each output.

Duvine has been manufacturing Impressed Current Cathodic Protection power solutions for many years, in the form of the CP500 for single zones. Using our 30 years’ experience of switch-mode rectifier technology, our solutions are an ideal power source for ICCP applications.

Switch-mode rectifiers offer considerable advantages over traditional transformer rectifiers, such as versatility, control, ultra-low ripple, digital display interfaces, built-in interrupters, size and weight.

Duvine’s systems also offer a range of modular upgrade options to further enhance our solutions. These range from GPS synchronisation and parallel configuration to GPRS and 3G remote monitoring and control, including both email and text alerts.

Duvine’s cathodic protection systems have the option of being monitored and controlled remotely utilizing their unique software solution. Using the optional email communication software, our systems can also produce regular performance reports and automatic alarms and alerts.

Duvine’s switch mode-rectifiers are designed so that the users can select from a number of different controls: constant current, constant voltage, constant potential or a mix of all three, depending on the requirements.

We also custom-build integrated solutions to meet customers’ exact specifications and particular site requirements.

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CSC Services completes Hinkley Point B remediation

CSC Services successfully completed the 2017 Concrete Spalling Remediation Programme at Hinkley Point B Power Station for client EDF Energy

Over ten tonnes of specialist repair mortars and structural strengthening products were used to rectify the degradation of reinforced concrete at various areas across the station. A combination of environmental exposure, water ingress and the age of the station building had caused spalling in areas including the flask bay and turbine hall.

Maintaining ongoing nuclear safety and plant reliability were the key objectives driving the programme of work which began in April. The repair work will significantly expand the durability of structures, enabling their original design life to be achieved.

The scope of work included: provision of a suitable repair specification for each specified area; provision of suitably trained and experienced operatives to execute the repairs; and provision of all repair materials in accordance with the identified specifications

Repair areas included: the vent plant room, flask bay opening, and turbine hall. A range of protective coatings were used to protect the structures from moisture intrusion and further corrosion, reducing the need for ongoing maintenance work for the life of the station.

As part of the programme, carbon fibre wrapping was installed to the DW Plinths in the Turbine Hall. This will provide significant strength to the plinths and protect against further corrosion and erosion.

For more information about the services that CSC Services offer including case studies of recent work please visit www.csc-services.co.uk

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CAN Geotechnical completes rail project

CAN Geotechnical Ltd recently completed a soil nailing and sprayed concrete project on a rail widening scheme to increase the number of existing tracks from 2 to 4 on the approach to a busy station.

One of the key earthworks elements of the overall project was a steep 18.5m deep cutting, the base of which required widening to accommodate the new tracks. This was achieved by a steepening regrade of the cutting toe and removal of the existing toe-level retaining wall.

With the planned over steepened toe of the cutting decreasing the stability of the slope, a reinforced retaining wall along the toe of the cutting was required. Over 450 solid bar soil nails were installed to the newly cut slope, securing and tying back two layers of heavy duty steel reinforcement. A 200mm thick high strength sprayed concrete facing was then applied, with concrete specified to meet the 120 year design life and cope with the aggressive ground conditions on site.

With short term stability of the cutting being a concern during the construction period, the regrade was carried out by cutting 12 “hit and miss” bays. Each cut section was stabilised with soil nails and facing prior to cutting the adjacent bay, with daily monitoring of survey targets on the upper slope carried out to monitor any movement.

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Roncrete offers technical advice

Ronacrete is offering a range of technical articles to explain on various concrete repair techniques.

In Understanding Preparation of Concrete, Ronacrete’s Technical Manager, Mike Rhodes discusses the different methods of concrete preparation to ensure long lasting adhesion between concrete and new mortar / coating. He explains that adequate adhesion of screeds, renders, concrete repairs and floor coatings/membranes can only be achieved when correct substrate preparation has been carried out.

Finishing of concrete and screeds by trowelling, power-floating or tamping will leave a layer of laitance (a relatively weak layer of hydrated cement) on the surface which must be removed. Any adhesion to laitance will result in early failure of adhesion of floor screeds and coatings and early or eventual failure of adhesion of mortars to vertical and overhead surfaces.

The mode of failure is typically a breakdown of cohesion in the substrate at or close to the bond line and inspection of debonded mortars and coatings will reveal laitance and often parts of the concrete matrix adhered to the mortar or coating.

For further information visit https://www.ronacrete.co.uk/understanding-preparation-of-concrete/

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Freyssinet protects Lincolnshire bridge

Freyssinet was awarded a contract by Lincolnshire County Council Alliance at Clay Lake Bridge Spalding, Lincolnshire.

The works comprised of hydrodemolition by AquaForce Limited to remove the delaminated/spalled concrete, followed by sprayed concrete repairs. Additional concrete repairs to the parapet walls and to reinstate with spray concrete were instructed during the contract.

Works were undertaken to design, supply, install, commission and then monitor an Impressed Current Cathodic Protection system to a design developed by Freyssinet’s Subsidiary company Corrosion Control Services Limited. CCSL engaged the services of fellow CPA member Corrosion Prevention Limited to assist in the design.

All works beneath the deck were carried out from modular pontoons situated in the Coronation Channel. The concrete repairs were reinstated by Freyssinet’s Specialist Spray Concrete repair contractor Gunite Solutions Limited.

The impressed current cathodic protection (ICCP) system comprised of two anode types. Vector Ebonex discrete anodes were installed into drill holes and Chemical Newtech anode mesh was used to protect one metre either side of the joint.

The structures repaired and protected comprised of the four halving joints; which were split into eight independently controlled zones. The remote monitoring and control system was developed by fellow CPA member Omniflex Limited in conjunction with CCSL.

The works were installed by Freyssinet Limited and supervised throughout by Corrosion Control Services Limited. Once the electricity meter is installed CCSL will commission and monitor the system for 56 weeks.

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Cemplas re-energises EDF car parks

Cemplas has recently completed a full refurbishment of two car parks for power generation giant EDF Energy at their site in Bexley Heath, Kent.

The project – comprising works to the North & South Staff & Visitor Car Parks was delivered over a 9-week programme and comprised concrete repairs, anti-carbonation coatings to soffits, columns, beams and walls and full parking deck re-waterproofing.

Almost 1,300 repairs had to be carried out overall to both car parks following concrete damage caused by the long-term effects of both carbonation and chloride-induced corrosion, with water leaking through from the top decks via multiple cracks and split daywork joints across the existing asphalt waterproofing surfaces.

Sika’s Monotop repair system was utilised for the concrete repairs and subsequently all soffits, beams, columns and walls – including the newly repaired areas – were protected with Sikagard anti-carbonation coatings in brilliant white to maximise lux levels within the car parks.

The single deck of the South Car Park and multiple decks of the North Car Park were completely re-waterproofed with Sika’s RB58 car park deck waterproofing system. The rapid-curing system incorporates Sika Reemat Premium encapsulated within the resin layers to ensure full crack-bridging ability and durability when applied directly onto asphalt.

The waterproofing was applied in contrasting colours of mid-grey for both the traffic aisles & parking bays with red to highlight safe, pedestrian walkways. New line markings, directional arrows and instructions were also applied before handing back the car parks to the client following their full closure whilst works were carried out.

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Fosroc launches Patchroc 250

After working closely with contractors on major road projects, Fosroc recognised the requirement for a product which could provide rapid and permanent reinstatement of thick section patch repairs on concrete bridge decks and carriageways, and has now launched a new product, Patchroc 250.

Developed by Fosroc’s Technical Team, Patchroc 250’s unique cement chemistry means it can be used to reinstate concrete sections up to 250mm thickness without the excessive heat generation and thermal cracking associated with traditional rapid set materials.

With its rapid strength gain Patchroc 250 can generally accept traffic in just 2 hours at 20˚C, particularly useful when interruption of traffic must be minimised. Patchroc 250 can be left as a trafficable finish with its high strength, abrasion and weather resistance making it ideal for external works, alternatively it can be overlaid with compatible deck membranes and coatings once the surface moisture content reaches <6%, typically only 3-4 hours after cure.

Patchroc 250 is easy to use: it is supplied pre-bagged to overcome site batched variations and requires only the site addition of clean water to provide a consistent flow applied repair material. It can be used without a primer, yet still achieves an excellent bond to the concrete substrate.

Patchroc 250 is CE Marked to EN1504-3 (Class R4) and will sit alongside Fosroc’s Renderoc HB range (Hand Applied), Renderoc DS & DSR (Dry Spray) and Renderoc LA60 (Highly Fluid Micro Concrete) products, providing a comprehensive concrete repair offer to the highways and other infrastructure markets.

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Social Day invitation for Alliance members

The Concrete Repair Association is inviting all Alliance members to attend its social day and dinner on Thursday 5th July at Hawstone Park, Shrewsbury. The event offers a fantastic opportunity to socialise with members from all associations.

All members will have the chance to partake in either golf, shooting or archery before dinner. We will once again be welcoming a guest speaker for the after dinner entertainment which will be announced in due course.

The event will be taking place from 1.30pm on Thursday 5th July at Hawstone Park, Weston-under-Redcastle, Shrewsbury, Shropshire, SY4 5UY

For those wishing to attend please contact emma.simmonds@cra.org.uk

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Concrete Repair Association

Formed in 1989, the CRA is committed to promoting and developing the practice of concrete repair and allied disciplines, as well as advancing education, technical training and health & safety matters in this specialist construction sector.

www.cra.org.uk

CORROSION PREVENTION ASSOCIATION

The Corrosion Prevention Association represents consultants, contractors and manufacturers working in the field of corrosion prevention for reinforced concrete and masonry encased steel.

www.corrosionprevention.org.uk

SPRAYED CONCRETE ASSOCIATION (SCA)

Sprayed Concrete Association (SCA) represents leading contracting and manufacturing companies engaged in sprayed concrete.

www.sca.org.uk

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