Issue 4 - October 2015
The Concrete Repair Association (CRA), one of the Associations that comprise the Structural Concrete Alliance, has released a new edition of its Standard Method of Measurement for Concrete Repair. The document, now in its third edition, has been fully revised to reflect new and current methods, practices and standards.
The Standard Method of Measurement for Concrete Repair aims to assist the origination of clearer Bills of Quantities for concrete repair work by providing a uniform basis for measuring concrete repair and for fully itemising all aspects of the work involved.
It provides notes on repair measurement and a specimen Bill of Quantities. The method of measurement includes detailed instructions for : General, Trials and Routine Testing; Surface Cleaning; Survey; Repairs; Crack Repairs; Pore/Blow Hole Fillers; Levelling Mortars/Fairing Coats; Surface Coatings and Treatments; and Resin Injection. It also itemises time-related elements such as provision of access and site facilities.
The Standard Method of Measurement has proved of enormous benefit to construction professionals since the first edition was published in 1990. Being one of the CRA’s most popular technical documents, thousands of copies have been downloaded from the CRA website or provided in hard copy format.
The new third edition of the document is available for free download from the CRA website, www.cra.org.uk.
Bersche-Rolt Ltd has completed concrete repair and coating works to the Grade II listed Barry Island Eastern Shelter, as part of the regeneration of the Eastern promenade for Vale of Glamorgan Council.
The reinforced concrete structure, constructed in the 1930s, has a concrete roof slab supported by columns on the seaward side, a retaining wall on the landward side and a series of primary and secondary concrete beams.
All structural elements showed signs of concrete defects, with cracking and delamination within the beams and columns, reinforcement corrosion and peeling and discoloured paintwork.
Working closely with consultant engineers, Bingham Hall Partnership, Bersche-Rolt first carried out a survey of the structure, which included hammer testing, a cover meter survey, carbonation depth testing and the analysis of samples for chlorides, sulphate and cement content.
The Bersche-Rolt engineer prepared a specification for the repairs using products from Sika. Works included cleaning and priming the reinforcement, the application of a bonding bridge, erecting shuttering and repairing the concrete. The complete structure was then coated with a three-part protective anti-carbonation system in a decorative coloured finish.
The survey and remedial work was completed ahead of schedule and coordinated with the other regeneration works. Cherry pickers, scissor lifts and a suspended cradle were used for access to each part of the structure.
The Eastern Shelter reopened to the public in September 2014, having been restored to its former glory. It sits proudly alongside a typographic traversing wall and colourful new beach huts.
Repairs to six blocks of flats on the St Saviours Estate in London were carried out using products from the Ronacrete RonaBond Concrete Repair & Coatings range.
Main contractor Lengard was awarded the internal and external refurbishment project for six blocks of five-, six- and seven-storey residential flats by the London Borough of Southwark and appointed Ronacrete approved contractor Gunite (Eastern) Ltd to carry out concrete repair and protective coatings, mastic joint sealing and brickwork repair.
Gunite cut out and prepared areas of damaged concrete, primed the exposed reinforcement with Ronacrete Standard Primer and then re-primed the reinforcement, before applying RonaBond HB40 high build polymer modified mortar.
The repaired areas were then made ready for decorative and protective coatings by the application of RonaBond Easy Skim FC, a levelling mortar that provides a smooth “harder than plaster” finish to walls.
The final stage involved the application of decorative and protective coatings to the repaired surfaces. RonaBond Crack Bridging Anti-Carbonation Coating WB was used to protect the façades against water ingress, providing excellent protection against corrosion of the steel reinforcement.
RonaBond Anti-Carbonation Coating WB was used on vertical surfaces, soffits and at DPC level, it allows the passage of moisture vapour and is particularly suited for application to substrates which may contain entrapped moisture.
The RonaBond products used provided a complete four stage concrete repair system, greatly improving the integrity of the concrete and appearance of the St Saviour’s Estate, as well as providing protection from further corrosive damage for years to come.
Inspection of the Bidston Bypass Road Bridge, which spans Merseyrail’s Wirral line, revealed concrete cracking, delamination and spalling due to reinforcement corrosion.
Concrete Preservation Technologies (CPT) designed a bespoke repair and refurbishment solution which included the installation of both DuoGuard Hybrid and PatchGuard Galvanic anodes to control corrosion and extend the life of the structure.
The product systems were chosen due to their rapid and straightforward installation (crucial due to the track possessions required to work on railway land) and the ease with which the anodes can be installed overhead. The Hybrid system stops corrosion during a short impressed current phase followed by long term galvanic protection. Its low ongoing maintenance requirement was ideal for this site due to access difficulties and the likelihood of vandalism to permanent power supplies.
CPT offers a complete and independent corrosion testing and evaluation service, including bespoke corrosion protection solutions and long-term monitoring of your structure. The company also provides free accredited CPD seminars to inform staff about the mechanisms of corrosion and the options available to protect and preserve reinforced concrete structures.
Structural Renovations Ltd was employed to carry out both cosmetic and structural repairs to various parts of the Salters Hall, home of the Worshipful Company of Salters, which is ninth in precedence within the Livery Companies of the City of London located at the Barbican.
Their original home was bombed during a German air raid in 1941 and the Company moved to its current location in 1976, following the completion of a new building to the designs of the renowned architect Sir Basil Spence. This unusual structure, built in the Brutalist style, was listed in 2010 and carries Grade II status. It is currently closed for its first major refurbishment since construction and due to reopen in 2016.
Using high strength mortars, Structural Renovations has been able to maintain the structural integrity where required. The design of the exterior of the building includes extensive knapped rib and texturing, which have been replicated by hand using lightweight mortars.
Structural Renovations will return later in the year to apply a pigmented anti-carbonation coating to both repaired and unrepaired areas of concrete.
This is the second Sir Basil Spence commission that Structural Renovations has repaired and coated, following the successful completion at the ‘The Meeting House’ at the University of Sussex.
10-72 Sussex Square, a large private residential block in the heart of Bayswater, is a 1960s building constructed using a reinforced concrete frame clad with brickwork and strip windows, with projecting mosaic covered balconies.
In 2013, it was noted that frost damage to the brickwork and failure of the mosaics to the balconies had reached a critical point where repairs needed to be carried out as a matter of urgency. A complete survey of the building was carried out to determine the extent and nature of the defects and, based on this survey, a tender was drawn up for the works required.
Concrete Repairs Ltd was successful in securing the contract for the external cladding and general refurbishment of the building and work commenced on site in September 2014, with a duration of 20 weeks.
Works included the design and installation of 2,000m² of the Rockwool Redart Insulated Render System, including all powder coated pressed metal cills and cappings. Significant concrete repairs and brick reinforcement (HELIFIX) were also carried out.
CRL Restoration, a new division of Concrete Repairs Ltd, was called in to carry out extensive cleaning to the travatine and granite cladding to the main entrances using the DOFF steam cleaning system.
The works were completed on budget and to the client’s, and residents’ satisfaction, with numerous residents praising the high quality of the finished product and the polite and courteous manner in which the works were carried out.
The contract was undertaken for the Church Commissioners of England and administered by Knight Frank LLP.
Fosroc products had a starring role in the repair of a giant water tank at a film studio. After the destruction of a ship on a previous movie, it was discovered that the giant water tank was allowing water to escape. As the tank was no longer able to hold water, the production of the next film was at stake.
Water was escaping from two expansion joints running through the concrete deck and up the adjacent walls (80 linear metres in total and 35mm wide). Fosroc provided a solution using its new product Nitofill UR63 to waterproof the expansion joints.
Nitofill UR63 is designed for injection into cracks in concrete in wet conditions to form a slightly elastic seal. It has low viscosity allowing it to penetrate fine cracks and reacts with water to form flexible closed cells that can withstand differential movement.
Oversized lengths of glass fibre wool insulation impregnated with Fosroc Nitofill UR63 were inserted deep into the joints for the full length, ensuring a 20mm recess was left from the surface. Water was then added to the wool insulation in-situ to initiate the reaction of the Nitofill UR63.
When the foam had set Fosroc Primer MS2 was applied to the exposed joint faces and finally, Fosroc Nitoseal MS600 was installed into the joints to seal the outer joint edge.
Creating a water tight seal in the joints enabled the tank to be refilled with water and the film production to carry on with minimum delay.
Walkden Street multi-storey car park is a reinforced concrete ‘waffle-pot’ structure built in 1964. It comprises six parking decks split over three levels above a retail space that had lain vacant for a number of years having been vacated by a major retailer.
The waterproof membrane applied to the reinforced concrete top deck had degraded and failed in many areas allowing the ingress of de-icing salts through the original daywork and failed movement joints in the concrete deck, resulting in a significant volume of spalling and corrosion damage to the concrete soffits below.
Following a competitive tender process, Makers Construction was awarded the contract to carry out the repairs and re-waterproofing works. Prior to commencement, a detailed hammer survey was carried out which identified a significant volume of delaminated concrete as a result of reinforcement corrosion.
Following removal of the defective concrete and thorough preparation of the exposed reinforcing bars, a full programme of concrete repairs were carried out using the Sika Monotop system with some 5m² of repair having to be reinstated. A migratory corrosion inhibitor was also applied along the daywork joint lines for added protection.
The top deck was completely re-waterproofed with the Sika Pronto deck waterproofing system to ensure that the previously leaking daywork joints could not fail again. The system was applied to some 4,600m² of deck area including the up and down access ramps between the upper decks.
USL Group’s Special Projects team recently completed a challenging concrete repair project at The Crofts in Smethwick, a complex comprising of three 14-storey high rise tower blocks.
The works, which were completed via mast climbers, involved high pressure water jetting, concrete repairs, asphalt repairs and the installation of a high performance waterproofing system to all residential balconies and roofs.
Although the work was conducted in unusually cold and wet weather conditions, the Special Projects team was able to ensure works were completed on time by using products that were rapid setting or where the curing process could be accelerated. This enabled areas to be handed back on schedule as quickly as possible.
USL Group’s in-house specialist manufacturing department Nufins was consulted on the most appropriate and functional repair products. Nufins Epicon Fast Set Mortar was specified due to its excellent adhesion to a range of substrates.
A waterproof coating that would be compatible with the various products used in the repair of the balconies and roofs also had to be sourced. Britdex CPM Treadseal, another USL Group in-house manufactured system, was used since its fast curing nature enabled the experienced operatives to complete the waterproofing within tight weather windows.
Since completion, the client (a leading community regeneration specialist), has expressed its gratitude to for the speedy response and proactive manner in which the Special Projects team dealt with the project, from initial enquiry, recommending solutions, mobilisation on site, and finally delivering the project within a tight and challenging programme.
In January 2015, VolkerLaser commenced works on a £630,000 contract to deliver specialist Cathodic Protection works to the EcoPark for LondonWaste in Edmonton.
Beginning operations in 1971, the structure is Britain's largest recycling facility, handling waste from seven London boroughs. The waste is sorted and combustible materials burnt to generate sufficient electricity to meet the needs of 72,000 local households, along with creating “recycled” garden compost and other building materials.
A comprehensive investigation of the entrance and exit ramps into the Tipping Hall Building showed that the support structures had begun to decay due to the ingress of chloride ions and the subsequent corrosion of the reinforcement.
VolkerLaser were employed to remove areas of delaminated concrete by means of hydro-demolition, reinstating it using Flowable high strength concrete, and subsequently installing an Impressed Current Cathodic Protection System to protect the existing reinforcement and thus substantially increasing the design life of the structures.
Working alongside heavy plant and vehicles, clear signage and strict traffic and pedestrian management were put into place to ensure the safety of the public and workforce. Under continuous scrutiny with regards to Health and Safety, VolkerLaser erected independent tied scaffolding to all 13 structures, fully encapsulated with Monoflex and debris netting in order to contain any falling debris from the works.
VolkerLaser Director, Dave Williams, commented: “A professionally run project with exemplary client feedback in regard to our approach and execution in this challenging environment. The recent award of the Considerate Contractors certification further reinforces evidence of the entire project team’s drive and commitment.”
Vector Corrosion Technologies (VCT) has developed the Post-Tech© PTI Impregnation system, an innovative treatment process that mitigates corrosion of bonded post-tensioned structures, such as bridges, tanks and stadia.
Such structures are at risk of corrosion, with common causes including grout voids, segregated grout, soft grout with high sulfate content, and chloride-contaminated grout.
To begin the treatment using the Post-Tech© PTI Impregnation system, access is gained to the post-tensioned strands by removal of the grout injection caps or by installing ports at intermediate tendon locations.
A formulated anti-corrosion impregnation fluid is then applied to the post-tensioned tendon under pressure. This flows along the tendon using the interstitial spaces of the seven wire strands and cracks and voids in the existing post-tension grout. Field experience has shown that the impregnation material can saturate post-tension tendons to a distance of 75m (250ft) from the entry point.
The function of the Post-tech PTI Impregnation treatment is two-fold. Firstly, the impregnation material displaces moisture and leaves an anti-corrosion barrier on the steel surface. Secondly, the material penetrates into the surrounding post-tension grout to significantly improve its moisture and corrosion resistance properties.
The corrosion resistance properties of the Post-Tech PTI Impregnation treatment have been demonstrated in laboratory studies conducted by Vector and the Florida Department of Transportation.
Places are still available on the last two Structural Concrete Alliance CPD seminars scheduled in 2015.
These half-day events are designed to provide delegates with an introduction to Structural Asset Protection and Repair, to corrosion and to the various techniques for repair, protection and strengthening.
Presentations are varied to reflect the region in which the seminar takes place but include: An introduction to corrosion; An overview of electrochemical systems; Concrete repairs and coatings; Carbon fibre strengthening; Introduction to sprayed concrete; and Inspection of reinforced buildings & structures.
The next seminar will be held at the Crowne Plaza Hotel in Liverpool on Tuesday 20 October 2015. To view the programme and to book a place for this event please click here.
The final event in 2015 will be held in Swansea on Tuesday 24 November.
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