Specialist Techniques
Condition SurveyAPA Survey Ltd, a Group company, provides an independent surveying service that is staffed by both qualified engineers and chartered building surveyors. Structures surveyed can include buildings, bridges, tunnels, multi-storey car parks and industrial structures. These can be constructed from concrete, brick or steel.
Testing Techniques used include:- Visual Inspections Half-Cell Surveys Covermeter Surveys Hilti 'Ferroscan' Concrete Dust Sampling Leak Detection Abseil Surveys |
Concrete Repairs and CoatingsSpecialising in various forms of concrete repairs and coatings has formed the nucleus of the company's activities since its inception. The company can use either traditional mechanical breakers, suitable cushioned against vibration, to remove defective concrete or in circumstances where large volumes of concrete require removal, high and ultra high pressure water jetting is used. The latter techniques also have the added benefit of reducing noise in sensitive structures.
Once the exposed steel reinforcement has been cleaned, various methods of concrete reinstatement exist. The chosen method is usually dictated by the size and location of the repairs and can vary between small hand-placed mortars, through to larger shuttered and poured or sprayed concrete repairs. By directly employing its own operatives, APA Concrete Repairs Ltd can ensure that whichever reinstatement technique is chosen, the quality and longevity of the repair will not be in doubt. Finally, to ensure that future corrosion activity is slowed. Flexible anti-carbonation and anti-chloride coatings can be applied. |
Corrosion Monitoring and PreventionConcrete will, under most circumstances provide a highly alkaline environment in which steel reinforcement will be protected from corrosion by the formation of a passive oxide layer. This passive oxide layer can in time be compromised, primarily due to the effects of carbonation or chlorides, leading to corrosion of the steel reinforcement, thus putting the long term durability of the structure into question. Prior to deciding the relevance of corrosion monitoring or prevention, an assessment is made of a structures future vulnerability. APA Survey Ltd is able to establish through specialist testing what elements of a structure are at risk. Corrosion rate monitoring is used to assess the speed at which steel within the structure is likely to corrode.
If the established risk is low to moderate, corrosion monitoring can be installed to allow the structure to be checked regularly. If a higher degree of risk is identified, appropriate corrosion prevention techniques need to be employed. Corrosion inhibitors can be applied to a reinforced concrete structure, migrating to the steel upon which they form a barrier to inhibit future corrosion activity. Using technology dating back over 200 years, galvanic cathodic protection (GCP) can be achieved by using anodes that are inserted into the concrete alongside the steel reinforcement. These galvanic anodes contain zinc, which corrodes sacrificially over time instead of the structures reinforcement, giving upwards of 15 years corrosion protection. Based on similar principals to GCP but giving longer term protection is impressed current cathodic protection (ICCP). Here an anode is introduced either externally or internally to the reinforced concrete structure and a current is introduced so that the steel reinforcement becomes cathodic or protected against corrosion. These systems can give upwards of 30 years corrosion protection. |
Structural StrengtheningWhilst concrete structures are extremely capable of carrying the loads for which they were initially designed, change of use and physical deterioration can often lead to the requirement for some form of structural strengthening. In addition to the more traditional techniques of steel plate bonding, qualified engineers within APA Concrete Repairs Ltd are able to advise clients on the potential use of adevanced composite technology to solve their problems.
Materials such as carbon fibre, Kevlar and Aramid have transformed the repair and refurbishment market place, providing cost effective and fast solutions to structural strengthening problems, with the added bonus of low future maintenance costs. Composite technology is used on highway structures where the speed of application and low material weight minimise traffic disruption. On buildings and car parks, the systems attributes provide vital benefits to developers and building owners wishing to increase floor and roof loadings but with minimal disruption to existing tenants. |
Pressure Grouting and Vaccum InjectionCracks in structures and buildings occur for a variety of reasons but when these extend down to the steel reinforcement, remedial action is required to control corrosion. The correct selection of both injection pump and injection material is vital to ensure the successful sealing of potentially damaging cracks. Materials used can either be cemtitious grouts for the filling of relatively large cracks and voids, through to epoxy and other chemically cured advanced materials that are able to fill much finer cracks. In some cases the use of vacuum technology enables cracks as fine as 0.025mm or 25 microns to be sealed and overall fill levels of 98% to be achieved.
Vacuum technology is particularly effective in filling voids often found at the rear of mosaic-faced building facades. Presssure-only injection techniques would actually cause the facade to de-bond even further. The use of vacuum, however, effectively restrains the facade elements whilst the injection proceeds. Similarly, vacuum injection is very effective in filling the voids often formed around steel cantilever joists, in balcony construction. Often during the 1920's and 1930's, medium and high rise residential council dwellings were built with access balconies common to all the flats. The 'I' section cantilever beams were poorly encased in "clinker" concrete - a mixture of brick rubble and cement, leading ultimately to corrosion of the steel beam. Vacuum injection, with its ability to control resin flow, can successfully be used to encapsulate the steel beam, thus eliminating future corrosion. |
Roof MembranesRoof surfaces are subject to continual attack from the weather and from environmental pollution. During the lifespan of a roof the surface is subject to continual movement and degradation, which if left unchecked will lead to premature roof failure. Considerable savings can be made by repairing an existing roof and over-coating with a liquid applied roof membrane.
These systems are designed to give the client the life expectancy required without the need for excessive access costs, stripping of the existing roof coverings and even possible the excessive costs involved in providing a temporary weather-tight scaffold-roof. A number of proprietary systems exist in the market place and APA Concrete Repairs Ltd are able to provide a full specification selection service prior to the application of the chosen system with in-house operatives. |
Deck WaterproofingMulti-storey car parks (mscp's) are becoming an increasingly important infrastructure asset. Many shopping centres and office complexes would not be able to operate without them.
Whether new build or refurbishment, deck waterproofing is a vital element of any project, ensuring that harmful pollutants and chemicals do not enter the structure. APA Concrete Repairs Ltd in-house operatives and management have extensive experience in the specification and application of a variety of proprietary deck waterproofing systems including some that allow parking to take place within a few hours of application. |
Bearing ReplacementBridge bearings transfer loads and movements from the deck to the sub-structure and foundations. The majority of highway structures and bridges accommodate this movement through either elastomeric, sliding or rolling bearings.
The majority of highway structures and bridges accommodate this movement through either elastomeric, sliding or rolling bearings. Over time these bearings will degrade as the result of ever increasing traffic volumes and increased weights of vehicles. Accumulation of debris and atmospheric pollutants can also contribute to shorten lives. Without their replacement, the function and durability of the bridge structure will be compromised. APA Concrete Repairs Ltd operatives and management have considerable experience in this specialist repair and refurbishment activity |
Waterstop InjectionWaterstop is the term given to the technique where advanced resin technology is used to stop and prevent further water ingress within underground and water retaining structures. Water will follow the least path of resistance when faced with an obstacle. Thus defective joints and cracks in a structure will often be the point of entry but finding the source of the problem is notoriously difficult for the in-experienced individual.
APA Concrete Repairs Ltd has over 30 years combined expertise in waterstop in tunnels, sewerage systems, basements, shafts and reservoirs. Using a combination of this experience and advanced resin technology, along with progressive injection techniques, the company is able to resolve ingress problems. |
Bund LiningsEver increasing safety standards within most industries has resulted in the need for containment of potentially harmful substances, such as effluent, chemicals and fuel. Many industries have previously relied simply on brick or concrete bunds to contain any spillages or emergency failures/leakage.
However, new legislation demands that these bunds must not be structurally compromised by any spillage/leakage and this can only be achieved by careful selection and expert application of resistant lining systems. APA Concrete Repairs Ltd specify and apply chemically resistant bund lining systems throughout the UK from a variety of material suppliers. |
Insulated RenderA demand for work to take place to more exacting standards and to shorter timescales has led to advancements in building component technology. Within the repair and refurbishment market place, increases in heat retention requirements as part of the Governments "Decent Homes" initiative have also required advancements in facade refurbishment material technology.
Polymer modified, mineral and silicon renders are able to be utilised with or without insulation panels to provide durable and lightweight solutions that far exceed the capabilities of traditional sand/cement renders. A variety of finishes can be provided, ranging from smooth or textures, through to even replicating brick and stone, which in many instances is fifficult to differentiate from the original material. |
