Issue 10 - November 2017
The Structural Concrete Alliance has announced Concrete Repairs Limited (CRL) as the winner of the 2017 Structural Concrete Alliance Award for Repair and Refurbishment, for its refurbishment of the Coronation Parade promenade/breakwater in Folkestone.
CRL worked in challenging conditions to provide extensive sympathetic structural repairs and to install an impressed current cathodic protection system to the Coronation Parade promenade/breakwater in Folkestone.
CRL recommended the installation of a cathodic protection (CP) design, which allowed the anodes to be installed from the top of the structure along the promenade roadway, thus allowing work to continue during high tide.
Freyssinet achieved third place for its work on the M6 J16-19 Smart Motorway upgrade project. Its concrete repair solution offered an innovative encasement and encapsulation approach utilising a flowing concrete and installed an Impressed Current Cathodic Protection (ICCP) system to overcome remaining chloride contamination.
The winners were announced by former BBC Breakfast Host, Bill Turnbull, at the Concrete Society Awards Dinner held at the Grosvenor Hotel, Park Lane, London on 16th November.
CPT’s innovative DuoGuard hybrid anode system was chosen to control corrosion and extend the life of the Aust Jetty on the Severn Estuary, which provides vital access to a National Grid pylon.
The deck, beams and trestles of the structure are constructed from reinforced concrete and are heavily contaminated with marine chlorides. This has led to corrosion of the embedded steel and cracking of the cover concrete.
The anodes were grouted into small drilled holes within areas of identified corrosion risk and then connected to an external power source for a period of seven days. A relatively high current density was applied, stopping active corrosion. The power source was then removed and the same DuoGuard anodes were left in place to operate self-sufficiently, generating galvanic current and controlling corrosion.
The DuoGuard system, which has a 10-year track record in the UK, has the benefit of providing long term protection coupled with low maintenance, critical for remote structures such as Aust Jetty.
High performance technical mortars by Saint-Gobain Weber have been specified for the repair of concrete balconies with metal railings to apartment buildings in Northwood.
Metal railings to attractive balconies on the first and second storey apartments had rusted at the base over time and this in turn lead to spalling of the surrounding concrete.
‘This was both visually unattractive and a potential safety risk for the residents,’ says Karl Roberts, contracts manager of main contractor Alfred Bagnall & Sons Limited.
With technical advice from Weber, the team from Alfred Bagnall cut away the spalled concrete and repaired the metal barrier before re-instating the concrete. webercem concrete repair system was specified, a multi-component system compliant with BS EN 1504 for concrete patch repairs.
The system contains webercem HB40 for high-build repair and levelling, the associated bonding slurry webercem bondcoat and finally a high performance finishing coat of webercote smooth.
webercem bondcoat, a cementitious bonding aid, provides high initial grab to improve the build of the repair mortar and promote the bond to the concrete. It contains fibres for improved thixotropy, is solvent-free and simply requires mixing with clean water onsite.
Once repaired the balconies were coated with webercote smooth which provides excellent anti-carbonation protection. It has a minimum 15 years’ life expectancy and is protective, durable and decorative. webercote smooth can be applied by brush, roller and spray and is resistant to chloride ingress.
Click to view the full case study.
During the 2017 summer holidays Currall Lewis & Martin worked for Kier who manage and maintain motorways and trunk roads in the West Midlands on behalf of Highways England.
CLM’s role was to complete essential concrete repairs to the deck of the A38M viaduct. This viaduct forms part of the Midland Links and is the main arterial route connecting the City of Birmingham to the M6.
These sensitive repairs required a series of seven complete weekend closures of the eight lane carriageway. The requirement for structurally sequenced repairs using conventional repair products was not viable as the repair strength gain time would cause unacceptably long road closures.
The challenge for during CLM each weekend of full carriageway closure was to, remove the carriageway surfacing and deck waterproofing system; remove the defective concrete using hydro demolition; to undertake welding repairs to reinforcement; and finally to place the rapid set repair CSA concrete.
Using the rapid set material, CLM placed in excess of 9m3 per repair sequence by volumetric delivery and Rapidset bagged products. The rapid set concrete reached strength within the critical programme period of 18 hours.
Once the repairs reached the prescribed strength the viaduct was re- surfaced in time for Monday morning’s rush hour traffic.
The exposed aggregate panels at Gravesham Borough Council’s Civic Centre in Kent have been protected with a transparent anti-carbonation coating manufactured by Flexcrete Technologies, part of the AkzoNobel group of companies. The building’s external walls were protected with Monodex Clear applied by specialist contractor Concrete Repairs Ltd.
The Civic Centre is an iconic 1960s building originally designed by Henry Thomas Cadbury-Brown, architect of the Royal College of Art and pioneer of British modernism. The £6 million project comprised refurbishment and repair of the exterior and interior of the building. Gravesham Borough Council required an anti-carbonation protection which would not significantly alter the building’s original appearance.
A solvent-based coating was originally specified but, due to odour release of the solvent borne product during application, it was replaced by Monodex Clear. Monodex Clear is water-based making it being low hazard, low VOC and virtually odourless resulting in no disruption during installation. Monodex Clear is transparent and allows the original appearance of the substrate to be retained, whilst providing an excellent defence against carbon dioxide ingress and the effects of general weathering.
Monodex Clear significantly prolongs the maintenance free life of buildings and other structures. It cures to form an attractive satin finish which sheds dirt and retains clarity throughout its long life. It offers complete protection from carbonation and provides an effective barrier to water penetration, preventing acid rain attack and the ingress of airborne chlorides, whilst also allowing the release of moisture from the substrate.
CCL recently carried out the replacement of pot bearings on a bridge structure in the south of England. The company also undertook remedial work to part of the bridge abutment which had sustained damage because of the failure of the existing bearings.
Replacement of the bearings involved jacking the bridge using four hydraulic cylinder jacks on each abutment. A jacking beam which could not be accessed from the abutment, was lifted using an additional jack mounted on a specially-constructed tower.
Hydrodemolition work was carried out on the concrete beams to release the bridge and was also used to remove the damaged abutment section and three bearing plinths.
The failed bearings were removed and replaced with free-sliding pot bearings to allow the correct degree of movement to take place. The new bearings supplied by CCL were designed to accommodate up to 4500kN in vertical load. To ensure installation could not be delayed because of climatic conditions, and could be carried out at any time of year, the bearings were specifically designed to allow fixing to take place when the bridge deck was at its most extreme ends of movement, at its highest and lowest temperatures.
Finally, CCL supervised the installation of new expansion joints which replaced those which had been damaged by the initial bearing failure.
Vector Corrosion Technologies Limited (VCTL), is pleased to announce the launch of a second-generation hybrid system, Galvashield Fusion.
Traditionally, Impressed Current Cathodic Protection (ICCP) has worked by utilising a small electrical current to control corrosion. Due to the nature of the technology, external power, monitoring and maintenance are all continuously required over its design life. This often leads to systems being overlooked with time. One independent report indicates that after 15 years, there was a 50% probability that the system would not be working, which increased to 75% at 20 years.
Galvanic Corrosion Control (CC) systems have increased in popularity over the past 20 years due to their simplicity. No external power or monitoring are required for their function. This makes them an attractive option, even though they have a finite life and their performance cannot be altered once installed.
Galvashield Fusion T2 is a second-generation hybrid anode system that combines designable performance of an ICCP system with simple maintenance-free performance and installation of a galvanic system. Through extensive innovation Vector has developed a unit capable of offering short term ICCP to re-passivate steel (phase 1) and long-term cathodic prevention to maintain that state (phase 2). This all being achieved in a single unit without the need for any external power or complicated wiring. This two-phase treatment is designed to the performance requirements of ISO BS EN12696:2016.
StoCretec has introduced a new product into the UK which provides a proven method of keeping concrete structures dry and protected against the threat of corrosion.
‘All buildings and civil engineering structures made from concrete are subject to the effects of environmental factors such as water, frost, pollutants, and CO2,’explains StoCretec’s UK Market and Product Manager, Greg Astill.
‘If a concrete surface remains damp for long periods, it allows micro-organisms to become established. Initially this can impair the appearance of the structure, but it can also start to damage both the concrete itself and the reinforcing steel it contains.’
StoCryl V700’s innovative formulation creates a surface coating which is covered by microscopic peaks and bumps. These repel water very efficiently, while the channels between them funnel the water away quickly and easily. This enables the surface to dry far more rapidly than with traditional finishes. By controlling the moisture present on the concrete surface, StoCryl V700 restricts the establishment of microorganisms, meaning the surface looks better for longer.
StoCryl V700 incorporates an acrylic binding agent which gives the coating excellent mechanical strength, great CO2 resistance and a high degree of structural consistency. It forms a rugged and reliable bond with the concrete surface, and also makes an important contribution to environmental protection as it not only protects against the ingress of CO2 but is a CO2 neutral product in its manufacture. It is available in a wide range of colour shades.
Fosroc has added to its extensive range of concrete repair and protection systems with Protectosil CIT, an advanced surface-applied corrosion inhibitor for steel reinforced concrete based on organo-functional silanes.
The use of a surface applied corrosion inhibitor is a cost effective method of managing issues caused by reinforcement corrosion. Corrosion inhibitors can reduce the amount of repairs that are undertaken, by managing contaminated, but undamaged concrete.
Fosroc Protectosil CIT is a unique product offering multi-functional steel protection and resistance against ingress. The product is based on silane technology providing very deep concrete penetration, and binding to steel and concrete. This means that the steel is protected by the formation of a bonded chemical barrier on its surface and the concrete is protected by the reduction of moisture uptake and chloride ingress.
Due to the strength of its chemical bond Protectosil CIT can be used on wet substrates and is even effective in tidal zones. It can be used on any uncoated concrete surface and is highly effective at managing incipient anode formation and corrosion induced by chlorides and/or carbonation. The product can be monitored for effectiveness using Linear Polarisation methods.
Fast and easy to apply, Protectosil CIT is normally spray applied to the concrete surface and quickly penetrates to the reinforcement. It has negligible visual effect on the concrete because it is a clear liquid, however if the project requires a coloured finish, it is possible to over-paint with Fosroc Dekguard coatings.
The structure was subject to an independent 10-year survey to detect linear polarisation within the reinforced concrete. Tests revealed high levels of chloride which, if left untreated, would have resulted in corrosion sites on the steel rebar.
For the Almond Valley Bridge project, a total of 2,800 anodes were installed. The bridge’s height, approximately 40m from the ground, presented on-site teams with a potentially challenging repairs programme.
The affected carriageway remained closed whilst installation of the corrosion management was carried out, hence the need for a rapid, easy-to-install solution. Sika Galvashield sacrificial anodes are quickly and easily installed into concrete to control corrosion activity and prevent the new formation of corrosion sites on reinforced concrete structures.
With CC anodes there is no requirement to break- out the chloride contaminated concrete, which would result in dust and debris being released into the atmosphere. Their use also reduces the workers’ time being exposed to percussive tools which can cause hand transmitted vibration health issues.
The easy-to-install Sika Galvashield anodes system not only ensured the preventative works programme was completed eight days ahead of the agreed two-month timeframe, it will provide long-term protection against potential damage caused by corrosion, ensuring this fine structure will continue to provide daily access for thousands of vehicles for many years to come.
CRL Surveys has opened its sixth office in the UK as the business continues to expand to meet a growing demand for its services. The new office is in Kenilworth, Warwickshire, serving the Midlands Region.
The business, which has been established for over 20 years, has five other offices in London, Bristol, Chesterfield, Runcorn and Falkirk. It employs 20 engineers and technicians, providing building and structure inspections and using the latest techniques to determine the nature and extent of any deterioration.
CRL Surveys provides a comprehensive service using NDT equipment, intrusive sampling and testing, and visual inspections. Material samples are tested off-site for chemical analysis and compressive strength. The inspection reports include suitable repair options and can also include budget costs for the repair work to be undertaken.
The company works in all market sectors both in the UK and overseas for owners, contractors, surveyors and engineers. The staff are qualified in confined space working and working at height to ensure all work is executed in a safe and controlled manner.
The business is UKAS-accredited for on-site inspection services, which provides assurance to clients that the work is undertaken to a recognised standard. The company is also proceeding with applications for the Bridge Inspection Certificate Scheme to ensure its staff meet the national requirements for bridge inspectors.
The Corrosion Prevention Association, one of the associations that comprise the Structural Concrete Alliance, has awarded a £1,000 prize to a student team that submitted the best project in its University Engagement Programme piloted at Coventry University.
The winners, Dominic Nursey and Diana Ciurte, submitted their proposal on how they would investigate a real-life corrosion problem found in a civil engineering structure. In conjunction with Coventry City Council, data from a site on the Coventry Ring Road, adjacent to the University was provided to the students for the project. The students detailed options available to rectify the damage and arrest the issue, and a thorough evaluation of each option (based on health and safety, cost, effectiveness, carbon footprint, material selection, programme etc).
Making the award, CPA Chairman Jim Preston said:
'We were impressed with the team’s submission as it demonstrated an excellent understanding of the full range of issues involved. Dominic and Diana clearly took on board the instruction they received and applied their knowledge to create a well-researched and professionally assembled report.
'The scheme aims to raise awareness and understanding of corrosion issues in infrastructure and to encourage learning in the subject. As a result of this successful pilot programme we will be continuing to run the programme at Coventry University in 2018 and extending the scheme to an additional university in the coming year.'
The course aims to provide a solid foundation of knowledge about corrosion, repair and protection of reinforced concrete together with some basic knowledge on the prevention of steel corrosion using paint coatings.
The students were invited to a Structural Concrete Alliance CPD seminar in Birmingham on 7 November to receive their prize. As well as attending the seminar, which provided an introduction to Structural Asset Protection and Repair, they were given an opportunity to speak with exhibitors at the event to learn about working within the industry.
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