Issue 2 - December 2014
The Structural Concrete Alliance has announced Mott Macdonald’s refurbishment of Ryde Pier in the Isle of Wight as the winner of the 2014 Structural Concrete award, presented at the Concrete Society Awards Dinner held at the Grosvenor Hotel, Park Lane, London on 29th October.
The judging panel felt that the innovative approach implemented by Mott Macdonald in this refurbishment project best represented the expertise of the asset protection and repair industry.
The contractors overcame access challenges related to working in a tidal environment and within a site of special scientific interest, while keeping the pier and its railway line open to the public throughout the works. By introducing the use of marine anodes fixed to the sea bed to protect both the steel structure of the pier and the concrete, Mott Macdonald demonstrated an innovative use of technology, resulting in substantial savings in time, materials, disruption and costs.
BAM Ritchies was awarded second place for its work on the Hooley Cutting, Surrey. This project involved the innovative use of sprayed concrete technology to create an intricate concrete grillage stabilisation structure.
Third place went to Balvac for the Silver Jubilee Bridge project in Widnes, Cheshire. A lightweight pre-fabricated bolt-on ‘cassette’ cathodic protection (CP) system was used to extend the life of the main suspended deck of the bridge.
The winners were chosen from entries received from members of the three trade associations which make up the Structural Concrete Alliance: the Concrete Repair Association (CRA); Corrosion Prevention Association (CPA); and the Sprayed Concrete Association (SCA). Ken Dykes, spokesman for the Structural Concrete Alliance declared:
“The judging panel was impressed by the high standards of the entries, which served to highlight the professionalism of CRA, CPA and SCA members. Each entry demonstrated the depth of knowledge and skills our members possess and their ability to provide innovative solutions to even the most demanding of engineering challenges."
For further information and to download a booking form visit www.structuralconcretealliance.org or call 01420 471619.
Having refurbished the main car park decks at Luton’s shopping centre several years ago, Cemplas Waterproofing and Concrete Repairs upgraded the protection and appearance of various concrete elements after being engaged by consultants Tuffin Ferraby and Taylor. Cemplas was asked to provide a specification and costs for repairs to the external roof car park and two main concrete spiral entry and exit ramps totalling over 3,000sqm.
All concrete surfaces were cleaned using a DOFF system, which cleans stonework and masonry using high temperature steam. Diamond planing and shot blasting was carried out to remove all existing heavily tamped concrete surfaces from the walls, soffits, and roadways.
Having completed all the concrete preparation, Cemplas operatives carried out repairs to the structure using Fosroc repair mortars and anti-carbonation coatings. Resurfacing of ramps and roadways were carried out using Vulchem’s quick methacrylate coating system with a fully blinded finish with a colour coat, together with the replacement of expansion joints.
Work was phased over an eight-week period to allow the car park to remain open with one access ramp always in use, and was largely carried out using mobile elevating work platforms together with some fixed scaffold.
Capital & Regional, the management company and owner of The Mall Luton, gave very positive feedback. The Mall Luton’s operations manager noted that the works were completed on time and on budget, declaring that the Cemplas on-site team were “a credit”, working very well with the Mall’s own staff.
Alfred Bagnall & Sons (Restoration) Ltd was appointed by the Royal Borough of Greenwich Council to undertake restoration of four 10-storey tower blocks on the Armstrong Estate, situated next to Woolwich Arsenal Station in South East London.
The work was to various external elements and for the decoration of concrete beams and columns. Repairs were undertaken using a Sika system of Monotop 610 bonding bridge, Monotop 615 repair mortar and Monotop 620 fairing coat.
The external concrete was painted in a Sika Elastocolor 550W and 675W, designed to reduce cracking and improve the durability of the finish. Floor coatings to the private balconies required localised repairs to the asphalt followed by a Watco 2-part anti-slip coating.
A Crown paints undercoat and gloss specification was used to decorate timber handrails and cladding panels and also on the metal frames of the balcony glazing.
Bagnalls began works for just two of the towers initially, and then as one block was completed scaffold was erected on the remainder, one block at a time. This lowered the overall costs and minimised disturbance to the residents.
Roger Marriott, Greenwich Council’s Project Manager for the works praised various elements of Bagnall’s service, particularly its good standard of workmanship and its willingness to help and advise the client when needed.
Bagnalls have since been awarded a Bronze Award in the Considerate Constructors Scheme, partly down to the audit of the Armstrong Estate site, which reflects our exemplary consideration of Appearance, Community, Environment, Safety and our Workforce.
Concrete Repairs Ltd (CRL) has completed a major repair scheme for Transport for London at the Woolwich Ferry – a vital link across the Thames in East London connecting the North and South Circular roads.
Constructed in 1966, the ferry’s jetties each consist of a reinforced concrete deck supported on precast concrete piles, with a tower at the end containing the lifting gear for the steel link spans. There are four traffic lanes over each jetty leading to the ferry docking station.
Initial inspections by Royal HaskoningDHV identified cracking of the support columns due to reinforcement corrosion initiated by high chloride levels from the marine environment.
CRL was awarded the contract to repair the South jetty in 2013. CRL Surveys carried out a detailed investigation of the concrete with a half-cell potential survey, core sampling chloride testing and cover meter survey which identified chloride levels of up to 3% by weight of cement and significant cracking of the concrete pile rises.
The tidal range at Woolwich is up to 7 metres, so CRL opted to use hydro demolition to remove the defective areas of concrete and reinstate them using Natural Cement’s Shotcrete 530 dry spray mortar, which is fast-setting and has rapid strength gain.
After completion of the South jetty CRL was instructed to continue with similar repairs to the North jetty. The £2 million, 11-month contract was completed in September 2014 without disrupting ferry operations. CRL has been repairing marine installations on the Thames since 1955 and operates worldwide.
Fosroc has completed a contract for a refurbished taxi-way at a military airbase.
An initial survey found that the cambered surface on the taxi-way was insufficiently accurate to safely support fast moving, multi-million pound fighter jets. In addition, security fences and electronic gates had to be installed which crossed the taxi-way, and can only operate on a level surface (2mm tolerance). Levelling the taxiway was therefore a major priority.
Fosroc, with the help and expertise of Anderson Specialist Contracting, prepared a specification for planing the taxi-way, applying Nitobond EP to the surface and laying varying depths of Paveroc (12mm-100mm). This was accepted by the MoD with the proviso that the Paveroc be laid to a minimum depth of 30mm.
In the areas where the taxi-way needed to be raised by more than 100mm, the Paveroc would be laid in 2 passes, re-priming the first layer with Nitobond EP before applying the final 30mm of Paveroc. The rails for the high-tech security gates were also to be incorporated into the taxi-way, and this meant laying them in place using threaded rods, and grouting them in place using Conbextra HF. To complete the package, all the joints in the taxi-way were sealed with Nitoseal PU878.
By providing a fit-for-purpose specification, and recommending a specialist contractor, highly experienced in the application of Fosroc products, the company says it was able to give confidence to main contractor, as well as decision makers at the MoD and NATO..
Freyssinet brought skilled engineers, unique products and experience plus a willingness to dedicate significant resources in the latest phase of repairs to the Hammersmith Flyover, having been brought in at an early stage by the TFL/Costain/RPB Early Contractor Involvement team.
Freyssinet used Ultra-High Performance Fibre Reinforced Concrete (UHPFRC) as part of the Post Tensioning (PT) strengthening system.
UHPFRC cannot be pumped using conventional plant due to the presence of the steel fibres. Freyssinet used a hydraulically activated specially designed device to ‘inject’ the pre-mixed concrete through cored holes in the deck directly into the backing slabs and internal in-situ blisters. Almost 100m3 of UHPFRC was placed using this method. The device is able to ‘push’ the concrete up to 8 metres high and, when in reverse mode, removes the spare concrete from the pipes, thus reducing waste.
Other key innovations that Freyssinet says it brought to the project included adaptation of standard post-tensioning (PT) systems, which helped minimise the requirement to install over live roads and during night-time closures. The PT system was designed to be a ‘Plug & Play’ system with high durability which allowed the system to be installed quickly.
Freyssinet also designed, fabricated and won CE and LOLER certification for bespoke lifting devices.
Water Energy, the owners of the Aberpergwm mine in South Wales, tasked Natural Cement Distribution with the problem of stopping water dripping from the roof of the drift onto a new man rider belt.
The drift is supported using steel TH ribs with corrugated metal sheets placed behind. The water ingress occurred between the metal sheets and around the steel ribs, in many cases this was quite substantial, whereas in other areas it was only continuous annoying drips.
Following a thorough inspection of the problem by Dale Whittaker of SES and Phil Richardson of Natural Cement Distribution, it was decided that the best course of action would be the application of Natural Cement’s fast setting spray applied product, Shotcrete 530.
To deal with the problem where there was an excessive amount of water ingress it was decided that Shotcrete AS 90, a product that sets in 90 seconds would be needed.
Shotcrete AS 90 is a newly developed Shotcrete. Like all the Natural Cement Distribution products, it is based on natural cement and, due to its formulation, has exceedingly fast setting capabilities, starting to set in 60 seconds and becoming totally set in 80 seconds.
According to a colliery representative, sprayed shotcrete was applied from 410m to 425m down the drift. The first 5m was applied 20mm thick as to plan. In this area there were not a lot of drippers and they were stopped by the shotcrete. Further application was made at this thickness with good results.
Skyform (Scotland) Ltd was appointed by Aberdeen City Council to undertake refurbishment of Ashgrove Court, a 10-storey block forming council supervised sheltered accommodation.
The £240,000 contract covered works to the external elevations and included render repairs, crack stitching, balcony waterproofing and replacement balcony screens. On one elevation of the block, a substantial area of render was removed and replaced.
Upon completion of the repair works all rendered faces were coated with a mineral paint manufactured by Keim Coatings.
Due to the unusual plan footprint of the block, there were a total of 14 vertical elevations to which the specialist contractors had to gain access. The chosen means of access was suspended cradles. Due to the modular construction of the cradles the lengths of each were tailored to the individual drop.
As the block offered sheltered accommodation, it was essential that access was maintained to the main entrances for residents, those with mobility difficulties and day clinic ambulances. This was achieved through the construction of temporary enclosed walkways, boarded scaffold fans and protective crash decks.
South West Concrete Repairs has completed a move to larger premises to allow room for future expansion.
The company says that its larger storage area and accompanying office suite will give it the opportunity to expand its workforce, provide a comfortable environment for visitors and enable clients and customers to be served more effectively. A dedicated meeting room will also be used for in-house training, CPD seminars and for contract meetings.
The office move is the latest step in the company’s business development programme, which has included rebranding, overhauling Health & Safety systems, and gaining CHAS, SAFE Contractor, and OHSAS 18001 Occupational Health & Safety Management Accreditations.
The company is also now a Bronze level Investors in People organisation, and has set up a Quality Management System (ISO 9001) and Environmental Management
System (ISO 14001).
For more information or to arrange a visit call 01752 561300.
Over 100 tonnes of structural concrete repair products from Weber were used at the Hunterston B Nuclear Power Station at West Kilbride in Scotland, in a £1.3 million jetty refurbishment contract carried out for EDF Energy.
Completed by Balfour Beatty Regional (BBR), this project was nominated for the Concrete Specialist of the Year Awards 2014, in which BBR was the overall winner.
A high-pressure water jetting system was used to break out the spalled and cracked concrete and to wash out the surface chlorides. The installation of a cathodic protection (CP) system, which uses an electro-chemical process for arresting corrosion, will ensure long-term performance. weber.cem spray CP, a low-resistivity, ready-to-use, structural repair concrete was used to embed the sacrificial anodes but for small patch repairs a less conductive concrete was required. After installation of the CP system, weber.cem spray DS concrete was used as an overlay, making the substantial structural repairs to the required profiles, while forming a new protective cover for the whole structure.
weber.cem spray DS is a ready-to-use, polymer modified, dry-spray cement-based concrete mix containing inert limestone aggregates and dust suppressants. The formulation has been designed especially for dry process spray application to give early strength, reduced rebound and maximum application thickness. Its core applications include repairs to marine structures such as jetties, seawalls, dry-docks and concrete offshore platforms. The product also complies with Highways Agency specifications for repairs to highway structures.
Chris Atkins, former chairman of the Corrosion Prevention Association (CPA) and current member of the technical committee, recently ‘enjoyed’ an abseil to raise money for The Legacy Rainbow House. His daughter Jessica had a troubled start to life and Rainbow House is helping the family get through and do the best they can.
Rainbow House help 200 kids and their families with a range of different abilities. They’re a small charity and money is tight. It costs around £2 million a year just to keep going, so Chris now spends his free time being dropped off things, tramping through the countryside and trying to organise golf days / raffles / auctions.
Chris says: “I appreciate you probably give money to charities that matter to you, I appreciate you may not have any spare money, and that there are so many organisations that need it, but if you can spare anything there’s 200 kids and families who say thank you.”
If you have any spare money, you can help here: www.justgiving.com/c-atkins
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