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• Features & Benefits
• Preparation
• Application

Features & Benefits

• Uses:
  • Protecting concrete piles and decks on road and railway viaducts from carbon dioxide penetration
  • Protecting structures with insufficient concrete cover around reinforcing steel
  • Protecting concrete surfaces that come into contact with seawater, de-icing salts such as sodium chloride and calcium and sulphate salts
  • Protecting concrete with cracks caused by shrinkage to block the penetration of water and aggressive agents present in the atmosphere
  • Flexible skimming layers on concrete structures with thin sections, including those subjected to small deformations when under load (for example prefabricated elements)
• Two-component, flexible, light grey mortar made from cementitious binders, fine-grained selected aggregates, special additives and synthetic polymers in water dispersion according to a formula developed in the MAPEI Research & Development Laboratories
• Free-flowing mix which may be applied at thicknesses up to 2 mm, including on vertical surfaces
• Due to its high content of quality synthetic resins, the hardened layer maintains its flexibility under all environmental conditions, and is totally impermeable to water at pressures up to 1.5 atmospheres and the penetration of de-icing salts, sulphates, chlorides and carbon dioxide. Mapelastic Guard also has excellent adhesion on all concrete surfaces, providing they are sound and sufficiently clean
• These properties, together with its excellent resistance to U.V. rays, ensures that structures protected with Mapelastic Guard are durable, even when located in areas with particular climatic conditions, in coastal areas with a saline-rich atmosphere or in industrial areas where the air is highly polluted
• Complies with the principles defined in EN 1504-9 (“Products and systems for protecting and repairing concrete structures: definitions, requirements, quality control and conformity assessment. General principles for the use of products and systems”) and the minimum requirements of EN 1504-2 coating (C) according to principles PI, MC and IR (“Concrete surface protection systems”)

Preparation

• The surface to be treated must be sound and perfectly clean. Remove cement laitance, loose and crumbling parts and traces of dust, grease, oil and form release agents by hydro-sandblasting or with high pressure water jets
• If the structure to be protected with Mapelastic Guard is deteriorated, proceed as follows:
  • Remove all deteriorated and loose concrete to obtain a sound, strong, rough substrate. Any areas previously repaired and which are not bonded must be removed; the damaged parts must be removed by manual or mechanical abrading, or by hydro-demolition or hydro-scarifying. The last two techniques require the use of high pressure water. They are particularly recommended because they do not damage the reinforcing steel and structures are not subjected to vibrations that could provoke the formation of micro-cracking in the surrounding concrete
  • After preparation, the surface of the substrate must have an irregular finish with at least 5 mm roughness
  • Remove all dust, rust, cement laitance, grease, oil and old paint from the concrete and reinforcing steel by hydrosandblasting
  • Treat reinforcing steel with Mapefer or Mapefer 1K, according to the procedure illustrated in the relative technical data sheet for each produc
  • Wait until Mapefer or Mapefer 1K has dried
  • Saturate the substrate with water
  • Before carrying out repairs, wait until excess water has evaporated off. If necessary, use compressed air to help remove excess water
  • Repair the concrete using a shrinkage-compensating mortar from the Mapegrout or Planitop ranges
• Pour component B (liquid) into a suitable clean container and slowly add component A (powder) while stirring with a mixer.
• Carefully mix Mapelastic Guard for several minutes, making sure no powder remains attached to the sides or bottom of the container. Keep mixing until completely blended
• A mechanical mixer at low speed is recommended for this operation, to prevent entraining too much air into the mix. Avoid mixing the product manually
• Mapelastic Guard may also be prepared using a mortar mixer, generally supplied with rendering machine
• We recommend that it is well mixed and there are no lumps before it is discharged from the pump hopper
• Mapelastic Guard remains workable for approximately 1 hour at +20°C.

Application

Manual application of the mortar

• Skim the damp, prepared surface to a feather edge with a thin layer of Mapelastic Guard with a smooth trowel then, while still fresh, apply a second layer to form a total thickness of at least 2 mm
• For structures with micro-cracks or structures that are particularly stressed, we recommend embedding Mapenet 150 with a mesh size of 4.5 x 4 mm in the first layer of Mapelastic Guard to reinforce the mortar (refer to the technical data sheet for Mapenet 150)
• After embedding the mesh, finish off the surface with a flat trowel and apply the second layer of Mapelastic Guard when the first layer has hardened (after 4-5 hours)
• Take special care around expansion and structural joints and in irregular areas subject to high dynamic stress by applying Mapeband TPE tape made from thermo-plastic polymers and synthetic elastomers
• After applying Mapelastic Guard, the structure may be further protected by applying a coloured acrylic resin-based finishing product in water dispersion from the Elastocolor range. The products in the Elastocolor range are available in a wide choice of colours using the ColorMap automatic colouring system
• When completely dry, they form an elastic coating which is impermeable to water and aggressive agents present in the surrounding environment (CO₂ - SO₂), while remaining permeable to vapour
• Apply the elastic coating at least 7 days after application of Mapelastic Guard. In good weather and at the right temperature, this period may be reduced to 3 days

Applying the mortar by spray

• Apply Mapelastic Guard on a well-prepared, damp substrate by spray with a rendering machine with one of the following types of equipment:
  • Turbosol T6 or similar
  • Strobot 406S
  • Putzmeister MP12
  • Putzmeister S5 EV/TM/2
• Whatever type of equipment is employed, use a skimming lance with an 8-10 mm diameter nozzle and a pump or air compressor with a capacity of 800 l/min
• Apply a layer of Mapelastic Guard at least 2 mm thick
• To acheive a more even surface, we recommend applying Mapelastic Guard in 2 layers. Apply successive layers when the previous layer has dried (after 4-5 hours)
• In areas with micro-cracks or which are particularly stressed, we recommend embedding Mapenet 150 with a mesh size of 4.5 x 4 mm in the first layer of Mapelastic Guard while still fresh
• Smooth over the Mapelastic Guard with a flat trowel immediately after embedding the mesh. If the mesh needs to be covered even more, apply another layer of Mapelastic Guard by spray
• Take special care around expansion and structural joints and in irregular areas subject to high dynamic stress by applying Mapeband TPE tape made from thermo-plastic polymers and synthetic elastomers
• After applying Mapelastic Guard, the structure may be further protected by applying a coloured acrylic resin-based finishing product in water dispersion from the Elastocolor range. The products in the Elastocolor range are available in a wide choice of colours using the ColorMap automatic colouring system
• When completely dry, they form an elastic coating which is impermeable to water and aggressive agents present in the surrounding environment (CO₂ - SO₂), while remaining to vapour
• Apply the elastic coating at least 7 days after Mapelastic Guard. In good weather and at the right temperature, this period may be reduced to 3 days
• Because of the high adhesion of Mapelastic Guard, including on metals, we recommend cleaning tools with water before the mortar starts to set. Once hardened, cleaning must be carried out mechanically.
• Coverage rates:
  • Manual application: approximately 1.7 kg/m² per mm of thickness
  • Spray application using a rendering machine: approximately 2.2 kg/m² per mm of thickness
  • NB: the consumption figures indicated are for a seamless film on a flat surface, and could be higher if the substrate is uneven (e.g. ridges or pores).

Performance

Thanks to its crack-bridging capacity, Mapelastic Guard protects concrete structures against the formation of cracks generated by dynamic loads, shrinkage, temperature variations, etc., even in particularly rigid weather conditions. Also, according to tests carried out by external laboratories as described below, results show that Mapelastic Guard is highly resistant to chemical aggression and offers efficient protection for concrete against the penetration of CO₂ (carbonation) and chlorides.

Both types of aggression trigger off corrosion in reinforcing steel resulting in a loss in structural integrity. Carbon dioxide (CO₂) penetrates into the concrete at a parabolic rate: x = K · t where:

• X is the thickness of concrete penetrated by the CO₂
• K is the diffusion coefficient of CO₂
• t is the period of exposure to an atmosphere containing CO₂

The value of K depends mainly on the characteristics of the concrete (type of cement, additives where applicable, water/cement ratio, curing time, etc.) and environmental factors (humidity, temperature, concentration of CO₂, etc.), and must be determined experimentally, therefore, for each case.

Tests carried out by the Società Autostrade per l’Italia (Italian Motorways Society) research laboratories have measured the value of the diffusion coefficient K on concrete with water/cement ratios of 0.5 and 0.6.

Results gave an average K value of 7.6 for concrete with a water/cement of 0.5, and of 8.0 for concrete with a water/cement ration of 0.6. If we assume a thickness of concrete cover of x = 30 mm and these values are applied in the formula x = K · t , we get:

• t = 900 mm²/(57.76 mm² · year ) ~15.6 years for concrete with a water/cement ratio of 0.5
• t = 900 mm²/(64 mm² · year ) ~ 14 years for concrete with a water/cement ratio of 0.6
  where t represents the time required for carbonation to penetrate through all the concrete cover.

The same tests were carried out on concrete samples protected with Mapelastic Guard, and the results showed K values of 0.25 to 0.29. If we assume an average K value for Mapelastic Guard of 0.27 (mm · year ) and then use the formula: x = K · t where x is the thickness of Mapelastic Guard equal to 2 mm, we can calculate that, by applying Mapelastic Guard on the surface of concrete, it is possible to increase the durability of structures by providing an efficient barrier to the penetration of CO₂ to more than 50 years.

As far as aggression from chlorides is concerned, according to the Danish certification body COWI (Consultancy within Engineering, Environmental Science and Economics), a 2.5 mm thick layer of Mapelastic Guard corresponds to 30 mm of concrete cover made from concrete with a water/cement ratio of 0.45.

Limitations

• No particular precautions need to be taken if the temperature is around +20°C. In hot weather, we recommend avoiding exposure of the material to the sun before use (powder and liquid). In particularly dry, warm or windy weather, protect the surface with sheets after applying the product to prevent rapid evaporation
• Do not use Mapelastic Guard for thick coatings
• Do not apply Mapelastic Guard at temperatures below +8°C
• Do not add cement, aggregates or water to Mapelastic Guard
• Protect from rain and accidental spillages of water for the first 24 hours after application