CINTEC International News
1992

The CINTEC system has been used to save 16 system-built blocks of flats suspected of being vulnerable to progressive collapse if subjected to a gas explosion.

The 1 million pound repair project involved strengthening the buildings using specially designed CINTEC stitching anchors. To limit damage to the building interior and disruption to the lives of tenants, the new technology of dry diamond drilling was used in this project.

Owned by the Watford Borough Council, the flats were structurally assessed by Curtins Consulting Engineers. Consultant Scott Wilson Kirkpatrick designed the scheme for the Watford project using CINTEC ties, meeting the loading requirements specified by Curtins.

To tie the external walls at the front and back of the building together required some of the longest CINTEC anchors used so far in building repair. Running across the full width of the building, these were 8.8m long. Three of these anchors were installed into each flat. CINTEC anchors are also installed at the floor joint with the external wall. Here they are placed at an angle of 45 degrees. The ties were installed in the floor voids at roof level and all floors above ground level.

Hans Ramsauer of WT Specialist Contracts, the installer of anchors at Watford explains why dry diamond drilling was used: "In tests we found that wet drilling results in water finding its way along the hollow panels and pouring out through any available opening into the interior of the flats. This was unaccceptable in terms of both reinstatement costs and tenant reaction.

"The results of the new dry core drilling technique that we developed in collaboration with Golz of Germany were highly satisfactory. We were able to drill the required 8.8m with great accuracy."

As the structural stability of an increasing number of system-built blocks of flats throughout Europe is being questioned, this technique provides an effective repair solution - in some cases it may be the only means of prolonging the life of these buildings.

The historic adjoining cottages that comprise the birthplace of the Bronte sisters have recently been saved from decline using the CINTEC system.

The four cottages have stone walls with rubble infill, which due to age and exposure to weather were in danger of disintegrating. Voids had begun to appear in the rubble infill and the external stone leaves were beginning to bow outwards.

English Heritage investigated the site and laid down strict repair guidelines. Having seen the CINTEC system used on a number of previous projects, the organisation was keen to see CINTEC anchors used here.

The objective was to tie the internal and external stone leaves together, stabilising the walls and halting any further decline. This had to be achieved causing an absolute minimum of disruption. The local listed buildings officer was adamant that no signs of repair should show externally.

Inserted from the building interior, the anchors were used to tie together the internal and external stone leaves. As the grout was injected the polyester sleeve expanded and provided a positive bond, filling voids in the rubble infill. Anchor lengths were selected according to the extent of the bow. All 10mm in diameter, these ranged from 375mm to 425mm in length. To tie the external walls back to the internal dividing walls 750mm 20 x 20 SHS stainless steel anchors were used.

David Anderson, project manager of structural repair specialists MPI (Airedale) Limited, commented: "The CINTEC system provided the only means of acheiving an 'invilible' repair. Now that the project is completed, there is no sign that remedial work has been carried out. English Heritage are delighted."

Recently launched into Canada, the CINTEC system has already received a great deal of interest in this important new market. One project recently completed was the repair of St. Anne's Church in Ottawa.

Designated an historic building by the city, a major defect was that over time the mortar in the joints and interior core had deteriorated due to weathering, moisture penetration and frost so that the stability of the walls could no longer be relied upon.

The CINTEC system was used to repair the damage caused by rubble and loose stone which had formed a wedge driving the two outer wythes apart. The aim was to cause minimum disruption, stabilise the walls and halt any further decline.

The two limestone wythes were anchored together using 22" (500mm) CINTEC wall ties. The inner wall core was then pressure grouted to fill any voids and the existing mortar in their exterior wythe were removed to a depth of 2" (50mm) and replaced.

In addition, the exterior wythe of masonry was stitched using CINTEC stitching anchors. These were installed in holes drilled parallel to the exterior wall face in two directions and spaced at 12" (300mm) centres. Long anchors were used. In one direction these were 10ft (3m) long and in the other 4ft (1.2m).

Anrep project engineer, John Cooke said: "We are delighted with the anchors performance. The system provided the only means of acheiving an 'invisible' repair, leaving no sign that work has been carried out."

Cardiff City Council are using specially designed CINTEC anchors to save thousands of homes in the area threatened by wall tie failure, caused by black ash mortar corrosion.

Black ash mortar combined with moisture ingress through the exterior brickwork leaf creates chemical agents that corrode the ties. Particularly at risk are the zinc-coated wall ties which have been traditionally used in UK housing.

The solution involves totally removing existing wall ties. It is feared that if they are simply bent back, further corrosion would damage the internal brickwork skin.

The existing ties are located using a metal detector. They are over-drilled using a 60mm diameter over-coring drill and totally removed. A 60mm CINTEC replacement wall tie is then installed with fabric sleeves at either end, locating the internal and external walls.

Said Ian Jones, a spokesman for Cardiff City Council: "We are pleased with the new CINTEC wall tie. It is an excellent solution to this large scale problem with which we are faced. It allows us to remove the existing wall ties without removing whole bricks. This saves time and expense.

The new system provides a very neat way of carrying out the remedial work. Disruption to tenants is minimised and there is very little apparent damage to the external skin of the houses. Once we have finished a home the repair is virtually invisible. This new system has made our huge task much easier."

The Fordham John Partnership has used the CINTEC system to repair a number of 17 storey tower blocks in Barking. Here, Robert Davies, a partner with the practice outlines the project.

Built in 1967 the tower blocks at the Beacontree Heath Estate in Barking each contains 93 flats. The basic form of construction is a fair face brickwork external skin, a cavity of varying width and a 150mm thick reinforced insitu concrete inner skin. The brick cladding is supported at each floor by a projecting nib from the inner reinforced concrete floor.

We discovered some potentially dangerous defects. There was a serious lack of wall ties throughout the structures. In the worst sections there were no effective wall ties at all. As a result there was evidence on a large number of panels of movement.

The survey team also found that the brickwork considerably overhung the concrete nib in most locations, with the brickwork standing proud on the slab face at the top of each panel. This overhang had been disguised by a render "make-up", which in some areas is so thick that it transferred the vertical loading from the brick panel above to that below, without taking bearing from the concrete slab as was intended.

Conventional mechanical fixings, relying on mechanical expansion, crush the mortar, causing cracking. We have serious concerns about the efficiency of using mechanical fixings to support brick cladding. These ties are inserted into the centre of the brick, which means that they are often fixed into the underside of the brick frog, where there can be voids. As a result it is not always possible to rely on their efficiency.

With the CINTEC system, if the anchor is installed into a brick frog, the grout will fill the void, creating a highly satisfactory key.

We were concerned about the performance of resin fixings in the event of a fire. They tend to be progressively weakened by temperatures rising above 100 degrees Celcius. The BRE recommends that they are not used above fourth storey height.

Before deciding on the CINTEC ties, a careful evaluation of various products was carried out by the London Borough of Barking & Dagenham's engineers. The BRE was commissioned to undertake independent tension tests on trial ties. The result was a strong endorsement of the system.

Following the results of these tests, we proceeded to design in detail a repair using the CINTEC anchors. Our solution was to supplement existing wall ties with CINTEC fixings, tied back to the inner wall.

Our remedial programme was designed to cause a minimum of inconvenience to residents. Disruption was minimised by the use of dry diamond coring through the clay bricks.

Before beginning the repair programme on the tower blocks in Barking, Fordham Johns recommended to the Barking engineers department that the Building Research Establishment (BRE) be approached to undertake extensive testing of the CINTEC system.

The BRE undertook independent tension tests on trial ties where the cement had cured for two days. As a result of these tests the BRE concluded that the CINTEC ties: "Were capable of giving a very satisfactory performance in a range of masonry and backing materials."

The BRE engineer recommended that further tests be conducted to simulate the effect of alternative wetting and drying together with temperature fluctuations in the outer leaf of a cavity wall, examining the long term durability of the system.

The BRE undertook a programme of accelerated moisture/temperature cycling simulating 40 years weathering. The system performed extremely well and the BRE concluded that: "The experiments show that the pull-out performance of the test anchor/clay brick combination tested would not be affected adversely in any significant way in the conditions of exposure to rain."

Geoffrey Harris House, an 18th-century Grade II listed building has been saved using Cavity Lock stitching anchors.

Owned by Croydon Health Authority, the building was to be turned into a day centre for use by the Mental Handicap Unit. Unfortunately the structural report for the conversion revealed that the walls were unstable and their general condition would require careful attention.

Geoffrey Harris House, before the remedial work using CINTEC anchors.

It was found that in some places the brickwork lacked vertical support and that the internal faces of external walls were crumbling and needed to be strengthened.

Recommended by English Heritage, who had seen the CINTEC fixing system used to save other buildings, Cavity Lock Systems were asked to design a solution using the CINTEC system.

The repair solution involved inserting anchors into the external and internal walls at approximately 450mm centres. Stitching anchors were then used to fix the facing skin to the main wall, which was tied back to a solid internal wall.

The repair resulted in virtually invisible mending leaving the facade of the building completely unaltered.

British Rail has used the CINTEC system to repair the Worcester viaduct. Comprising 65 brickwork arches, the viaduct has suffered from water penetrating its structure, saturating the clay fill material.

A lack of sufficient drainage has led to the spandrel walls being forced away from the intrados arch, creating longitudinal cracks close to the edge of the viaduct. This problem has been exacerbated by freezing and thawing.

Water penetration has also contributed to cracking at the springing of some spans and delamination of external parts of some columns.

Following the failure of previous attempts to restore the integrity of the structure using conventional steel plates, British Rail approached Cavity Lock Systems to discuss using CINTEC anchors to provide an effective repair for the structure.

British Rail are carefully monitoring the performance of the CINTEC system. To date 10 arches of the viaduct have been repaired and there are plans to extend the programme, reinstating further arches. British Rail are also now using the CINTEC System for further projects.

A reliable, straightforward system has been found for testing the grout used in CINTEC anchors on site at an early age. This involves point load testing specimens, a method that has been effectively used in the examination of rock cores.

The Hydrajaws test rig

The tests are carried out on site using simple, robust equipment manufactured by Hydrajaws Limited. Test specimens are formed by filling a length of CINTEC "sock" under the same conditions as the production anchor. These are then placed into the Hydrajaws apparatus.

Tests reveal that after 24 hours, provided that the ambient curing temperature is not too low, the strength of the grout will be about 90% of its maximum in situ strength.

The following guidelines are proposed for a practical site test regime:

• Produce 15 test specimens from any batch
• Place each specimen in a small plastic bag
• Test five specimens each at 10 hours, 24 hours and 36 hours to confirm the quailty of the batch.

Before the ancestral home of Chester Arthur, the 21st President of the United States could be opened to the public, the building had to be made safe. This meant stabilising the external walls which had shown signs of movement.
The challenge facing the restoration team was to find an effective means of repairing the building without detracting from its appearance – for example it would have been impossible to use an external pattress plate without affecting the character of this historic building.

The CINTEC system has been used on the Ancestral home of Chester Alan Arthur, 21st President of the United States.

Ace Fixings was approached and suggested the CINTEC WSA stitching anchor. The resulting repair has been highly satisfactory. After painting there are no external signs of the repair. The grout sock has meant that a good fix has been obtained in the rubble-filled wall. The stress-free nature of the anchor means that no stresses are exerted on the structure. A further advantage is the fact that the anchor is unaffected by any dampness or moisture within the stone wall, Ace Fixings were appointed earlier this year to promote the CINTEC system in Northern Ireland. Supported by spokesmen from Cavity Lock Systems and Ove Arup a very successful seminar was held in April to launch the system into the Province.

The CINTEC anchor system was introduced to local engineers in a series of seminars conducted by Ace Fixings. Pictured left to right are: John Dimmick, sales manager Cavity Lock Systems, Robert McAleese, sales manager Ace Fixings, Austin McGillian, managing director Ace Fixings and Rory Gibbons, Ove Arup & Partners.

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