Glass Reinforced Concrete Maintenance

[edit] Introduction

Glass reinforced concrete (GRC), also known as glass-fibre reinforced concrete (GFRC), is a cementitious composite containing alkali-resistant glass fibres. It is commonly used for architectural cladding panels and other relatively thin, lightweight components. GRC is generally durable and resistant to weathering, but its appearance and performance can be affected by atmospheric pollution, biological growth, staining, impact damage, movement, water penetration and deterioration of associated joints and fixings.

Maintenance requirements depend on the design, surface finish, exposure conditions and detailing of the GRC system. Regular inspection and appropriate cleaning can help maintain appearance and identify defects at an early stage. Cleaning should be carried out using methods and products that are compatible with the particular GRC panel and its surface treatment.

[edit] Why GRC panels need cleaning and inspection

GRC panels can accumulate dirt and staining over time. Common sources include airborne dust, traffic pollution, rainwater deposits, bird droppings, organic matter and biological growth. The severity of soiling depends on the location of the building, exposure, panel geometry, surface texture and the effectiveness of rainwater run-off.

GRC is not inherently impermeable or completely resistant to staining. Its cementitious matrix has pores, and surface characteristics vary according to the mix, manufacturing process and any applied finish or coating. Water absorption and soiling behaviour should therefore be considered when selecting cleaning methods.

Cleaning is primarily undertaken to maintain appearance and remove contaminants that could contribute to staining or biological growth. Inspection during cleaning can also identify cracking, impact damage, exposed reinforcement or fixings, failed sealants, open joints, localised surface deterioration and other defects. Cleaning should not be regarded as a substitute for periodic inspection of the complete cladding system.

The frequency of cleaning depends on the exposure conditions and appearance requirements of the building. More frequent cleaning may be appropriate in heavily polluted environments, areas subject to significant bird fouling or locations where biological growth is prevalent. Cleaning should generally be undertaken before deposits become difficult to remove.

[edit] Cleaning methods

Routine cleaning should normally begin with the least aggressive method that is capable of removing the contamination. Loose dirt can usually be removed with clean water, followed where necessary by a mild detergent compatible with the panel finish. A soft brush, sponge or cloth can be used to loosen deposits without unnecessarily abrading the surface.

The panel should first be rinsed to remove loose particles. Rubbing dry deposits against the surface can cause scratching or abrasion, particularly where the panel has a relatively smooth or treated finish. After applying a suitable cleaning solution, the surface should be rinsed thoroughly so that loosened contamination and cleaning residues are removed.

Soft brushes can be useful for textured or profiled surfaces and for areas that are difficult to access. Wire brushes, abrasive pads and other aggressive mechanical cleaning methods should generally be avoided because they can damage the surface and alter its appearance.

Pressure washing can sometimes be used for external GRC, but it should not be treated as a universally suitable cleaning method. Excessive water pressure or an inappropriate nozzle can damage the surface, coatings, sealants or adjacent materials and can drive water into joints and interfaces. If pressure washing is considered necessary, the pressure, nozzle, spray distance and technique should be established using the manufacturer's recommendations and tested on an inconspicuous area before general application.

Stubborn stains may require a cleaning product specifically selected for the type of contamination. Biological growth such as algae, moss or mould may require an appropriate biocidal or specialist cleaning treatment. Oil, grease, rust and other persistent contaminants may require different treatments. Strong acids, alkalis, solvents or abrasive cleaners should not be used unless their compatibility with the particular GRC product and surface finish has been established.

Any cleaning agent should first be tested on a small, inconspicuous area. The test should assess both immediate effects and any visible change in colour, texture or surface finish. Adjacent materials, including glass, metal, sealants, coatings and painted surfaces, should be protected from cleaning chemicals and contaminated wash water.

[edit] Recommended cleaning products

For routine cleaning, clean water and a mild, compatible detergent are generally preferable to aggressive chemical treatments. A pH-neutral cleaner may be appropriate where ordinary water washing is insufficient, provided that it is compatible with the GRC and any applied surface treatment.

There is no universal detergent concentration that is suitable for every GRC product. The concentration, contact time and application method should follow the cleaning product and GRC manufacturer's instructions. Excessive concentrations can leave residues or affect the surface finish.

Specialist cleaning products may be required for persistent deposits, but their use should be based on the nature of the contamination and the characteristics of the panel. Acidic cleaners, highly alkaline products, solvents and abrasive compounds can cause discolouration, surface damage or deterioration of protective treatments. They should therefore not be selected solely because they are effective on conventional concrete.

Where a GRC panel has been painted, coated, sealed or otherwise surface-treated, the compatibility of the cleaning method with that treatment is particularly important. Cleaning can affect gloss, colour and surface texture even where the underlying GRC is not significantly damaged.

[edit] Maintenance and repair considerations

Cleaning should form part of a wider maintenance regime for the GRC cladding system. Periodic inspections should consider the condition of panels, joints, sealants, fixings, support systems and interfaces with adjacent construction. Particular attention should be given to cracks, chips, impact damage, staining associated with water run-off and deterioration around fixings or panel connections.

Minor surface damage may sometimes be repaired using proprietary repair systems compatible with the original GRC. More significant cracking, loss of material, distortion or damage affecting fixings and support arrangements may require assessment by a suitably competent specialist. Repairs should address the underlying cause where possible rather than simply treating the visible defect.

Sealants and movement joints may have a different service life from the GRC panels themselves and may require periodic replacement. Defective joints can allow water to enter areas behind the cladding and may contribute to deterioration of associated components.

Maintenance should also take account of safe access requirements. Cleaning and inspection of external GRC panels may involve work at height, lifting equipment or specialist access systems. The method of access should be planned as part of the maintenance operation, with appropriate risk assessment and control measures.

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