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Structural Concrete Alliance E-Bulletin

Issue 13 - November 2018

Structural Concrete Alliance announces 2018 award shortlist

The Structural Concrete Alliance has shortlisted three projects for the 2018 Structural Concrete Alliance Award for Repair and Refurbishment, with the winner to be announced by broadcaster, Huw Edwards, at the Concrete Society Awards Dinner to be held at The Royal Lancaster Hotel, London on Wednesday 21st November 2018.

The shortlisted projects include Kier Design Services - Highways for its repairs to the A38(M) Gravelly Hill Viaduct; Volkerlaser Ltd for its repair and strengthening of a marine quayside at King George Docks, Hull; and Currall Lewis & Martin Construction for repairs and re-waterproofing to the M6 North East Spur & Rushall Canal bridge deck.

Kier Design Services - Highways introduced an innovative delivery solution to complete extensive concrete repairs, re-waterproofing and resurfacing of the A38M – the main link between the M6 ‘Spaghetti Junction’ and the centre of Birmingham. To minimise travel disruption Kier developed a ground-breaking weekend closure scheme, with the entire junction shut for 58 hours at a time over each weekend. This unprecedented change to traditional delivery models offered considerable travel benefits, with weekday access maintained throughout.

The repair and strengthening works to 12 Quay at King George Docks in Hull presented an extremely challenging project for Volkerlaser. It involved the use of concrete repair, sprayed concrete, cathodic protection and Carbon Fibre Reinforced Polymer (CFRP) strengthening, to provide a unique solution. Access to the quay was restricted by various factors, including; weather conditions, port activity, tide times and most importantly water levels. A bespoke access craft was designed and built and trials of the proposed CFRP application undertaken on timber mock ups of the quay structure.

Currall Lewis and Martin worked collaboratively with Kier Highways to identify new fast-curing materials and implement a weekend closure delivery model to complete concrete repairs and re-waterproofing to the North East Spur & Rushall Canal bridge deck in minimal time. The CLM and Kier teams reviewed available repair products on the market both in terms of practical and technical compatibility and conducted material trials based on a departure from standard, which was approved by Highways England Safety Engineering Standards (SES).The results were reviewed from both a strength gain and functionality perspective and the Korodur Rapid Set product was selected.

Announcing the shortlisted projects, the Alliance judging panel declared:

“While choosing the winners was extremely difficult, each shortlisted project impressed the judges by demonstrating innovation and technical ability while showcasing advances in technology and understanding.

“Kier’s multidisciplinary approach resulted in a collaborative solution within extremely tight constraints; while by widening the range of available materials, CLM was able to provide an innovative rapid repair process; and Volkerlaser’s detailed planning and collaboration provided a highly inventive solution to a very logistically complex problem.”

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Gunite repairs Shackleton Hall

FlexcreteGunite (Eastern) Ltd was contracted by the University of Birmingham to carry out the concrete testing and the subsequent concrete repairs and application of protective coatings at Shackleton Hall over three phases.

Shackleton Hall is used for student accommodation, student meeting rooms, cafe, restaurant, bar and offices and was occupied throughout the works.

The scope of the concrete repair works included jet washing; concrete testing – including hammer tests, carbonation tests and chloride tests;  and concrete repairs to window cills, columns and panels.

Internal and external concrete repair to stairwells and staircases were also undertaken as well as localised brickwork repairs and re-pointing and repairs to flat roofs and to projecting bay roofs including enlarging rainwater outlets.

MCI corrosion protection was also provided and clear anti-carbonation coatings applied to concrete aggregate. Liquid coatings were applied to stairwell roofs.

All works were carried out by Gunite’s highly trained, skilled and experienced operatives and a 15-year Sika warranty provided for the concrete repairs and coatings.

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Renderoc DSR succeeds in Resolven Weir

Renderoc DSR from Fosroc is the ideal solution for projects where repairs have to be carried out quickly in challenging environments, such as the refurbishment works to the Resolven Weir on the river Neath in Mid-Glamorgan.

A flat V weir had been installed in 1978 on the natural river section with a 28m channel width and 1:20 cross slope. However, over the years the face of the weir had become degraded and required repair. The location of the weir in a large fast flowing river required extensive measures to divert the flow, with the original project abandoned in 2016 due to high flows and the temporary works being washed away several times.

Fosroc suggested the application of Renderoc DSR rapid setting dry spray repair mortar which is designed for large area repairs such as bridges, marine structures and tunnels and may be used for large scale repairs and for overlay system. The dry spray application would enable the works to be undertaken quickly and the rapid cure would eliminate the risk of freshly placed material being washed away in case of flash flooding.

Contractor Sealability carried out the refurbishment works on behalf of Natural Resources Wales over a period of 4 months with approximately 3,000 bags being placed in three phases.

The introduction of Renderoc DSR, as an alternative option to the hand placed material previously specified by the engineers, ensured that this time the project was completed successfully.

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Surgical repairs from Ronacrete

Ronacrete products were used to repair the nurses’ accommodation at Grantchester House, a high rise block of flats situated at Addenbrooke’s Hospital, Cambridge. The windows needed replacing, and the facades required restoration.

Three components of Ronacrete’s concrete repair and protection system were used to carry out the repair.

Firstly, damaged concrete was removed and following preparation of the concrete and reinforcement, Ronacrete Standard Primer was applied to the steel and concrete. Once the primer was ready, RonaBond HB40, lightweight repair mortar, was hand applied to the required areas at depths between 30 and 75mm. The mortar was then trowelled to leave a nice smooth finish.

Once the repair was complete and the mortar had set and cured sufficiently, the concrete façades were coated with RonaBond Anti-Carbonation Coating WB. While the client opted to coat the facade in white, RonaBond Anti-Carbonation Coating WB can be pigmented to over 300 colours.

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CSC Services completes NHS remediation

Over the summer, CSC Services completed a scheme of refurbishment work at University Hospital North Tees. This was completed within budget and to strict timescales. Work was planned to ensure public safety and minimise disruption to patient services.

The age of the buildings, combined with environmental factors had resulted in spalling of concrete at various areas across the hospital. Defective concrete was removed and concrete repairs undertaken using cementitious repair materials.

To prolong future use of the building, a cementitious coating was used to protect steel rebar from further corrosion. The highly alkaline coating passivates the steel surface chemically to prevent further rust formation. It protects the steel from moisture, gasses and chlorides.

With patient and public safety core drivers of the project, repair materials were hand-applied. On sensitive sites such as hospitals, CSC Services can use a range of concrete protection products and application methods to minimise disruption.

Speaking about the work, the Design and Development Manager at North Tees and Hartlepool Solutions LLP said:

“CSC Services site team played a vital role in fulfilling this programme, providing an excellent quality of workmanship and have given the Trust the confidence that the building is safe until more funds can be raised to cover further work.”

All work undertaken was in accordance with the BS EN 1504 standard, in which all CSC Services’ operatives are fully trained.

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APA defends marine structures

APA Concrete Repairs Limited has recently completed repair works on the Exmouth Royal National Lifeboat Institution slipway. Various defects were located on the structural beams which form the launch slipway ramp.

Upon completion of inspections, high pressure water jetting techniques were undertaken in order to effectively prepare the surfaces, in readiness for the repair process. Isolated concrete repairs were then carried out on the structural beams, before the application of protective coatings. Repair materials used for the successful completion of this project were provided by Sika Ltd.

A full case study detailing the works completed is now available to view on the Concrete Repair Association’s new website.

APA has also begun the project of undertaking seawall repairs at Porthcawl Town Beach, Wales. Concrete repairs will be carried out on the surrounding sea wall, complete with the installation of sacrificial galvanic anodes on the existing steel reinforcement, before the application of a sprayed concrete overlay.

The second phase of repair and refurbishment at Northfleet Deep Water Jetty, Kent, on behalf of Kimberly-Clark Ltd, is due to commence later this month, with the first phase of works comprising of extensive concrete repairs to the jetty and supporting columns.

APA is launching a new website soon.

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Cemplas re-constructs joints at Elmsleigh

Cemplas have recently completed a full re-construction of the main mechanical movement joints to the Primary Service Deck above the Elmsleigh Shopping Centre in Staines, Middlesex.

With a market dating back to 1218, links to the stagecoach trade and connections such as Charles Dickens, Staines is a thriving town filled with historical importance with the Elmsleigh Centre itself an important and popular retail destination.

In order to finally banish long-term water ingress problems into the centre’s retail space directly below the main service deck, Cemplas were appointed to remove and replace some 85 linear metres of troublesome longitudinal and transverse movement joints.

The Service Deck areas are subject to continuous loading from a range of delivery vehicles from small vans to articulated HGVs. Emseal’s SJS Coverplate jointing system had been chosen by the project’s designers as meeting the client’s stringent performance criteria that would withstand such heavy and frequent loads being imposed on the service deck. The movement joint system is such that the cover plate is not attached to the concrete deck and doesn’t loosen during load transfer and vertical deflection movement.

With access to the elevated Primary Service Deck via a single reinforced concrete service ramp, Cemplas also implemented a traffic management system that allowed the service areas to be continually accessed whilst the works were carried out and keeping disruption to retail tenants to an absolute minimum where possible.

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Weber repairs Kent sea defence

webercem spray RS repair concrete from St Gobain Weber has been specified for the protection of a 75 year old sea wall in Kent which suffered damage over decades of continuous tidal erosion. Coronation Parade, built in the 1930s as a sea defence, is a concrete structure located in Folkestone spanning 340m.

Tidal action and the impact of chloride ingress had led to corrosion of the steel reinforcement with associated spalling. Birmingham City Laboratories, carried out the analytical service and designed the repair for main contractor Concrete Repairs Limited, Surrey.

The repairs required a method that would work within the short low tide cycle. A sprayed concrete repair method using webercem spray RS was specified. This is a rapid setting, dry-sprayed concrete is ideal for permanent repairs where time constraints demand early strength gain. It prevents wash out from the tidal water flow and minimises the penetration of chlorides.

Designed for dry-spray processes, webercem spray RS contains inert limestone aggregates, dust suppressants and accelerators. It has passed the durability test and the bonding adhesive standards of BS EN1504 and provides initial set in 15 minutes. In six hours it has a compressive strength of 10-15 N/sqmm.

It is primarily used in marine applications, river bridge abutments and structural repairs to concrete beams, columns and soffits and meets the standards contained in Exposure Class XF4 for long term durability being exposed in flood plain environment.

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CCL strengthens Liverpool One unit

An existing retail unit in Liverpool One required structural modifications to accommodate the needs of the future tenant, Apple. The company wanted to double the height of the space to create an impressive open entrance area.

This required removing part of the first floor which involved cutting post-tensioned concrete beams and precast slabs. CCL was appointed to perform the modification work required to the post-tensioned beams to accommodate the needs of the client.

CCL analysed the new loadings associated with a new steel mezzanine and steel post support and located the existing post-tensioning tendons which needed to be cut. Concrete was removed at the tendon locations to provide access, and then the duct was opened and removed from around the local strands.

Resin grout anchors were then installed around the exposed strand prior to cutting them. This ensured that the PT tendons remained anchored at both ends and the structural integrity of the beam was intact. The removal of part of the post-tensioned concrete beams could then take place.

Carbon fibre reinforced polymer (CFRP) was then wrapped around the beams to accommodate increased shear loads with additional CFRP laminate strips to enhance the longitudinal bending strength.

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CRL refurbishes Royal Derby car park

Concrete Repairs Ltd has completed the refurbishment of car park 2 at the Royal Derby Hospital working for the main contractor, Skanska. The scope of works included the removal of the existing deck coating, concrete repairs to the exposed deck and the application of 1800 sqm of Triflex Propark HD deck waterproofing.

At the same time, the deck joints were resealed using WF250 and S100 Radflex expansion joints. To ensure the integrity of the deck membrane, the vehicle barriers and cycle shelters were removed and re-fixed after the application of the new membrane.

This was a challenging contract during the height of the summer, which required flexible working hours to lay the new deck membrane early in the morning when the temperatures were lower. The car park is situated immediately adjacent to one of the main entrances with limited access, so deliveries were undertaken out of normal hours.

Working in close collaboration with Skanska and the Estates Department this major project was successfully completed in 6 weeks and the car park returned to service.

CRL specialise in the inspection and refurbishment of multi storey and underground car parks across the UK using the latest repair techniques and high quality materials. Its 60 years’ experience in the industry and six regional offices allows it to provide a professional local service.

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Flexcrete choice for wastewater project

London BuildConcrete repair materials manufactured by Flexcrete Technologies, part of AkzoNobel, have been chosen to restore the structural integrity of a wet well in the Colchester area, enabling it to be rapidly returned to normal service.

The refurbishment project was carried out by specialist contractor CSC Services on behalf of Anglian Water. CSC Services was commissioned to remove all vegetation and reline the wet well. A Flexcrete repair and protection system was chosen due to its outstanding track record of use in wastewater applications.

All joints, grout holes, cracks and voids were sealed using Monomix HD - a waterproof, class R4 structural repair mortar which has outstanding abrasion resistance and can be applied up to thicknesses of 80mm in a single application. The high bond strength of Monomix HD exceeds the tensile strength of concrete and it offers low permeability to water, even at 10 bar pressure.

Monolevel 844SP - a waterproof, engineering quality fairing coat - was then applied to bring the concrete back to profile prior to the application of two 1mm coats of Cemprotec E942, an innovative, two component, water-based cementitious coating that provides a hard-wearing surface with greatly enhanced chemical and abrasion resistance. The product exhibits excellent resistance to sulphuric acid attack.

Just 24 hours after application, a physical check was made to ensure that the coating was fully cured and bungs were removed before the wet well was returned to normal service.

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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.

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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.

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SPRAYED CONCRETE ASSOCIATION (SCA)

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

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