webercem HB30

Preparation

Concrete substrates

Concrete substrates must be adequately prepared by use of scabbing, grit blasting, needle gunning or other means, as appropriate. Oil and grease must be removed by steam cleaning together with suitable detergent. Any contaminated concrete must be removed. All damaged concrete should be cut back to a sound surface and at least 15 mm behind any exposed reinforcement.

New concrete must be at least 14 days old.

Thoroughly saturate the concrete but remove excess water.

Steel substrates

These should be grit blasted to Swedish Standard SA 21/2 equivalent to BS 7079-A1 and degreased immediately prior to application. Where corrosion is absent, wire brushing to a clean, bright surface may be adequate. Care must be taken not to polish the rust. Apply a protective coating of webercem bondcoat as described in the next step to act as a holding primer.

Note: Preparation of both concrete and steel must achieve a clean, sound, roughened surface

Mixing

Mixing of bonding slurry

Mix 2.5 volumes of webercem bondcoat powder to 1 volume of clean water. Mix vigorously to a brushable, slurry consistency.

For detailed application instructions, see separate webercem bondcoat data sheet.

Mixing webercem HB30

A low-shear, forced-action mixer must be used e.g. Mixal Mixer or Creteangle. Hand mixing of the mortar is not recommended.

Mix for 2 minutes from adding the powder to the water.

Over mixing will entrain air and reduce compressive strength. Do not over mix.

Water addition is 2.4 to 2.6 litres of clean water per 20 kg bag. Start at 2.4 litres and adjust as required upwards to 2.6 litres.

Do not add more than 2.6 litres of water.

Note: in colder weather, below 12°C, use less water (2.2 litres) to achieve a damper mix for handballing the mortar.

Application

Priming of steel reinforcement

Apply one full, unbroken coat of webercem bondcoat , ensuring the back of the cleaned reinforcing bars are coated.

Priming of concrete substrate

Ensuring the prepared concrete substrate is saturated but surface damp, use a stiff brush to scrub the slurry well into the surface.

Apply the mortar to the substrate whilst the bonding slurry is still tacky and compact well into place, ensuring no air is trapped.

The minimum application thickness is 10 mm. Where very thick sections are required multiple applications may be necessary. Intermediate surfaces, should be scratched to give a good mechanical key.

Finishing

If subsequent materials or coatings are to be applied, finish with a wooden or plastic float or a sponge to present a lightly textured surface.

Curing

Unless a levelling mortar, coating, inhibitor, sealer or other system is to be applied to the surface, cure immediately after finishing with a suitable membrane.

Before application of a coating or a levelling mortar, cure the repairs by covering with closely-fitting polyethylene sheeting or use webertec latex as an intermediate curing membrane sprayed onto the repaired surfaces in a continuous film.

webertec HB30 can be overcoated by the levelling mortar webercem fairing coat or one of the anti-carbonation coatings in the webercote range. Overcoating times are dependent on weather conditions. When cured, webercem HB30 and webercem bondcoat are stable to freeze/thaw conditions but, following good concreting practice, they should not be applied in freezing weather or onto frozen surfaces or at temperatures below 5°C.