Issue 12 - August 2018
The Structural Concrete Alliance has announced its final Practical Demonstration Day in 2018 will take place on Wednesday 12 September at Glasgow Caledonian University.
Those wishing to attend are encouraged to book early as the events are extremely popular.Earlier sell-out events during 2018 were in Telford and Leighton Buzzard.
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.
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.
For those unable to make the Demonstration Days, the Alliance also offers CPD presentations which can be delivered on-site to interested parties.
Meticulous planning and a scheme of 24-hour working meant power station refurbishment work that historically took over one hundred days was completed within three weeks by CSC Services.
Working for EDF Energy‘s contract partner Cape, CSC Services installed a cathodic protection system to one of the drumscreen chambers at Hartlepool Power Station during the planned shut-down of one of the reactors, earlier this year. Two twelve-hour shifts were worked each day/night.
Carbonation and chloride ingress of the reinforced concrete structure had been caused by sea salt passing through the drumscreen as part of the Power Station’s cooling process.
A cathodic protection system was specified to address corrosion across the entire area treated. This could not be achieved with conventional repair methods without removing all the concrete where salt or carbon dioxide had penetrated.
Hammer testing of concrete surfaces was undertaken prior to hydro-demolition to give an estimated square meterage of the repair site. Following the hydro-demolition of spalled concrete, a site inspection quantified the structural reinforcement replacement bar and anode requirements.
580 sacrificial anodes were installed and several hundred metres of structural reinforcement replacement bar fitted, in a range of dimensions. Over 22,000kg of concrete was then spray applied to return the structure’s surface to profile. Access ladders, platforms and framework were then replaced.
For more information about this scheme of work or the other services CSC Services can provide, please contact, email@example.com or visit www.csc-services.co.uk
CLM Construction was commissioned by Kier Highways to complete Repair Contract R185, a concrete repairs and ICCP scheme in Bescot Walsall for crucial elements of the supporting structure for the M6 mainline elevated motorway section.
Once access was gained, it became evident that water contaminated with chlorides was continuously leaking through the half joint structure orientation onto the half joint face, supporting crossbeams and columns. The identified corrosion, delamination and spalling of the structure was worse than anticipated at design stage, which caused the CLM site team to raise a technical query and recommend a further condition survey to be carried out.
Working together closely with scheme designers, the survey was carried out. The results revealed that the design required enhancement of additional repair areas and the introduction of additional CP discreet anodes and zoning to afford both suitable and long term protection for these difficult elements.
The location of the additional anode zone presented a number of installation challenges which required careful consideration from both design and construction teams alike. A solution was identified and an innovative method was trialled and successfully tested.
This involved casting the discreet anode location into the concrete repair using foam surrounding a steel bar. Once cured the cast in foam and steel was easily manually removed, leaving a pre formed cavity in the correct location ready to receive the anode installation. This method made clear and quantifiable savings in health and safety, quality and cost, making an overall welcomed benefit to the project.
When Inovyn Chemicals needed to extend the life of corroding reinforced concrete plinths supporting a saline liquid tank they turned to CPT. The CPT DuoGuard corrosion protection system was chosen due to a long track record in protecting structures in aggressive environments, a low maintenance requirement and performance measuring capability.
DuoGuard is a two stage treatment whereby galvanic anodes are temporarily wired up to an external power source for an impressed current phase. After this typically 7 day phase, the power source is disconnected and the same anodes are left in place to provide long term sacrificial anode protection to the steel reinforcement. Phase 1 brings great benefit in terms of halting aggressive corrosion. Phase 2 maintains steel passivity.
Following installation at the Inovyn site, checks were made to ensure that no anodic sites, indicative of corrosion, were identifiable on the reinforcement within the treatment area (see image). The only anodic sites should be at DuoGuard locations.
This procedure demonstrates both the efficacy of the system and acts as a QA check on the installation. DuoGuard is the perfect solution for controlling corrosion in all manner of reinforced concrete structures, including bridges, car parks, jetties and commercial buildings.
Anti-carbonation coatings manufactured by Flexcrete Technologies, part of AkzoNobel, are used all around the world, with one of the company’s latest projects in Taiwan.
Monodex coatings were chosen to coat the external walls totalling 1,000sqm at a new build clinic in Tai-Nan City, Taiwan.
The architect was seeking the use of anti-carbonation coatings to increase the aesthetics of the structure and provide the external walls with effective weatherproof protection from humid conditions and heavy rain.
Flexcrete’s Monodex coatings are waterborne, cure without releasing hazardous solvents or heavy odour and are non-toxic, non-leaching and non-tainting, meaning they could be safely and rapidly applied to this medical facility.
The clinic’s external walls were initially coated with one coat of Monodex Textured, a waterborne, single component, acrylic-based decorative wall coating with an attractive textured finish. It waterproofs surfaces for at least 10 years, yet allows high levels of entrapped substrate moisture to escape without causing blistering or delamination.
To achieve the desired finish for this project, Monodex Textured was overcoated with Monodex Ultra, a rapid drying, minimal VOC, elastomeric water-based coating with a smooth, matt finish. Able to extend the service life of both newly constructed and existing buildings, it is ideal for the external decorative protection of facades, soffits and elevations of structures.
The impressive project has been nominated for the Taiwan Residential Architecture Award - an annual awards scheme run by the Taiwan Architecture publishing company, which is regarded as the pioneer in promoting building design in Taiwan.
Fosroc has supplied a repair solution to three large residential blocks in Herbrand Street, in the London Borough of Camden.
The Dickens, Thackery and Coram buildings were showing signs of decay with visible spalling of concrete and joint failure around the windows which allowed water into the structure. The client wanted to refurbish the building with limited disturbance to the residents.
Fosroc provided a detailed specification, approved by the client, including the design of a protection system to protect encased steel H sections. This was achieved using Fosroc’s Protectosil CIT Corrosion Inhibitor, which not only to provides additional protection to the corroded sections, but also reduces future detrition of the steel.
Main contractor Mullaley and Co Ltd removed the loose and defective concrete, then cleaned the exposed steel “H” sections and treated them with Protectosil CIT, which was also applied to the surrounding area. The steel was primed with Nitoprime Zincrich Plus prior to carrying out the repairs using Renderoc HB30 repair mortar and injecting cracks in lintels with Nitokit LV and TH. Renderoc ST 05 was then applied as a fairing coat, in some areas over existing coatings, before finally applying Dekguard W protective coating to the overall concrete elements to extend the life of the structure.
Fosroc were able to provide a total solution package, allowing the client to specify all the concrete repair and protection materials from one manufacturer, in addition to on-site technical support, ensuring the project was successfully completed with minimum disruption to residents.
Concrete Repairs Ltd (CRL) have strengthened three access underpasses on the M5 in the West Midlands using near surface mounted carbon fibre reinforced polymer (CFRP) composite rods.
The unreinforced mass concrete walls of the structures had been strengthened using steel plates bonded and bolted to the concrete surfaces during the 1980s. These were in a state of partial de-bond at several locations and at risk of physical damage from farm machinery using the subways.
Under Early Contractor Involvement (ECI), the Principal Contractor - Kier Highways - consulted with CRL who recommended using near surface mounted (NSM) CFRP rods to replace the failed steel plate bonding system.
To remove the existing plates, the floors of the underpasses had to be excavated to a depth of 1m either side to access the ends of the plates. The slots in the parent concrete substrate for the new NSM strengthening scheme were cut using high frequency track saws and hand break out at each end, to provide a 25mm wide x 50mm deep rebate.
The slots were pressure washed prior to Sikadur 30 epoxy resin mortar being used to embed 12mm diameter CFRP rods. Further resin was applied over the rods and a Sikadur 32 primer applied over the top to act as a bonding bridge for an R4 cementitious repair mortar, used to level off the cut out.
The wall heights varied between 2.5m and 7.0m. Over 2,200 linear metres of 12mm CFRP rod were installed during a 22-week contract period.
Freyssinet provided an innovative solution using Ultra High Strength Fibre Reinforced Concrete used in precast form and manufactured offsite to strengthen a carpark extension in Eastbourne.
The £85 million redevelopment of the Arndale Shopping Centre included an additional 22 retail units, seven restaurant units, a multiscreen cinema and a two-storey extension to the existing multi-storey car park. The existing concrete columns of the car park had to be strengthened in order to carry the additional loads.
Freyssinet was instructed to carry out the full design, supply and installation of column strengthening to 84 columns. Traditional methods of reinforcement were considered in the initial stages of the project, which included traditional jacketing, propping, partial demolition and installation of new in-situ concrete.
By utilising its innovative ExoLeaf system - an Ultra-High Performance Concrete (UHPC) in pre-cast form - Freyssinet was able to reduce the 47 week programme down to just 15 weeks, including work on a number of special columns. As a result, the car park stayed open to the public for the majority of the works, which was crucial in the lead up to the Christmas period.
The ExoLeaf system can be developed as pre-cast, cast in-situ or even sprayed, suiting a wide range of applications and site conditions.
The expertise of Freyssinet in design and installation, combined with knowledge of Precast led to an excellent result serving all of the client’s needs: safety, speed, aesthetics and quality.
High performance webercem spray DSF by Saint-Gobain Weber was specified by BAM Ritchies for the repair of a concrete retaining wall on the approach to Blair’s Bridge in Falkirk.
BAM Ritchies was commissioned by Falkirk Council to repair the retaining wall which had suffered progressive concrete spalling over its full length. Exposed reinforcement covered an area of up to 200 sqm.
Following a survey of the structure, the weak and delaminated concrete was removed by hydro-demolition. The surface was made ready for the installation of 69mm stainless steel formers which were fixed into position to match the movement joints in the wall capping beam. Around 40 tonnes of webercem spray DSF was applied to the structure incorporating A252 steel reinforcing mesh to the full 69mm thickness and hand trowelled to provide a flat profile. A final flash coat was applied to give a uniform texture to the wall.
webercem spray DSF is designed especially for dry process spray application to give high early strength, reduced rebound and waste, and maximise application thickness. It contains alkali glass fibres that offer better strain relief and stress distribution and help to reduce shrinkage cracking.
Conformity testing to BS EN 1504-3 meets the requirement of a Class R4 repair product and complies with Highway Agency specifications for repairs to highway structures. It offers high-build – up to 150mm thickness can be applied in one pass on vertical and overhead faces – and has low permeability to water and chlorides.
CCSL was awarded a contract by BEAR Scotland at the A9 Cromarty Bridge Invernesshire to undertake the impressed current cathodic protection (ICCP) design for Phase II.
Prior to the site works commencing, investigations were undertaken to assess the effects ICCP would have on the existing Macalloy bars. Once this was determined not to be an issue, an ICCP and galvanic anode system was designed and accepted. CCSL engaged the services of CPA member Corrosion Prevention Limited to assist in the design.
The ICCP system comprised of two anode types: NMT discretes anodes 1,300mm long were drilled and installed into the stem wall from above the deck; and 350mm long discrete anodes were installed to the bearing shelf. CNT anode mesh was used to protect the diaphragm walls, atmospherically exposed capping beam, sides, column tops to MHWS and to the columns at mid-tide level. Impalloy galvanic anodes were used to protect the pile cap and columns up to mid-tide.
The works package comprised of hydrodemolition by CCSL’s sister company AquaForce Limited to remove the delaminated/spalled concrete, followed by sprayed concrete repairs undertaken by Gunite Solutions Limited. CCSL’s parent company Freyssinet installed the system under CCSL supervision.
Three piers were repaired and protected. The remote monitoring and control system was developed by CPA member Cathodic Protection Company Limited. CCSL has the contract to monitor the systems for 56 weeks and to incorporate the Phase I piers into the monitoring programme.
The Structural Concrete Alliance will be exhibiting at London Build, the leading building and construction show for London and you are invited to attend.
The show taking over Olympia London on 23rd & 24th October, will feature construction leaders and experts giving you a live update on the industry trends, developments and investment opportunities.
London Build features:
Secure your free ticket for the show and submit your registration details which will only take you 2-3 minutes to complete.
Interested in getting involved as an exhibitor?
As a member of the Structural Concrete Alliance, you are entitled to 10% discount off any exhibitor package. If you have any further questions, please do not hesitate to get in touch with the London Build Team on either firstname.lastname@example.org or 020 3058 2350.
The Structural Concrete Alliance publishes a quarterly E-Bulletin providing the latest industry updates and news from members of the CRA, CPA and SCA, as they occur.
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.
The Corrosion Prevention Association represents consultants, contractors and manufacturers working in the field of corrosion prevention for reinforced concrete and masonry encased steel.
Sprayed Concrete Association (SCA) represents leading contracting and manufacturing companies engaged in sprayed concrete.Tweets by @SCAlliance3