Fosroc Renderoc HB45

Fosroc Renderoc HB45 is a high performance, hand / wet-spray applied, fibre reinforced high build, high strength, concrete reinstatement mortar conforming to the requirements of BS EN 1504-3 Class R4.

Best Uses

Fosroc Renderoc HB45 is best used for the reinstatement of reinforced concrete where low permeability characteristics are required and where higher compressive strength is a consideration. Renderoc HB45 has been specifically developed for the repair of columns and beams, but because of its medium fresh wet density, is also suitable for soffit repairs. Renderoc HB45 is suitable for repair methods 3.1, 3.3, 4.4, 7.1, 7.2 as defined by BS EN 1504-3.

Renderoc HB45 is supplied as a ready to use blend of dry powders which requires only the site addition of clean water to produce a highly consistent, medium-weight repair mortar. It is based on Portland cements, graded aggregates, lightweight fillers, fibres and chemical additives which provide the mortar with good handling and finishing characteristics while minimising water demand. The low water requirement ensures good strength gain and long-term durability. Renderoc HB45 has been specifically engineered for vertical and overhead repair work. It can be applied in sections up to 80 mm thickness in vertical locations and up to 70 mm thickness in overhead locations in a single application without formwork. Thicker sections can be achieved by the use of formwork or can be built up in layers. Deep pockets can sometimes be filled in a single application, dependent on the configuration of the pocket and the volume of exposed reinforcing steel. Renderoc HB45 can be quickly and efficiently applied by the wet spray technique.

The material should not be applied at less than 10 mm thickness.

• Exceptional handling characteristics - easy to finish
• High-build applications possible while maintaining higher compressive strengths — fewer layers
• Frequently obviates the need for formwork
• Polymer-modification provides extremely low permeability to water, carbon dioxide and chlorides
• Exceptional system of shrinkage compensation provides long-term dimensional stability
• Can be applied quickly and efficiently by wet spraying
• One component, pre-bagged to overcome site-batched variations
• Contains no chloride admixtures
• Suitable for use with cathodic protection systems
• Shade can be varied with Fosroc Renderoc Lightener / Darkener on request

Application

Preparation
Form a square edge perimeter to the repair area using appropriate methods (feather edging must be avoided), break out the complete repair area up to a minimum depth of 10mm up to the square edge. Clean the surface and remove any dust, unsound or contaminated material, plaster, oil, paint, grease, corrosion deposits or algae. Where breaking out is not required, roughen the surface and remove any laitance by light scabbling or abrasive-blasting. Oil and grease deposits should be removed by steam cleaning, detergent scrubbing or the use of a proprietary degreaser. The effectiveness of decontamination should then be assessed by a pull-off test. Expose fully any corroded steel in the repair area and remove all loose scale and corrosion deposits. Steel should be cleaned to a bright condition, paying particular attention to the back of exposed steel bars. Abrasive blasting, hydrodem equipment, powered mechanical scraping or other suitable means is recommended for this process. Where corrosion has occurred due to the presence of chlorides, the steel should be high-pressure washed with clean water immediately after abrasive-blasting to remove corrosion products from pits and imperfections within its surface.

Reinforcing steel priming
Apply one full coat of Fosroc Nitoprime Zincrich Plus and allow to dry before continuing. If any doubt exists about having achieved an unbroken coating, a second application should be made and, again, allowed to dry before continuing.

Concrete Priming
The concrete substrate should be saturated surface dry immediately before the application of the primer, i.e. it should be thoroughly saturated with clean water and any residual surface water removed prior to applying Fosroc Renderoc Primer. Under severe drying conditions, repeated soaking may be necessary to ensure the substrate is still saturated at the time of application of the primer. Add 3 parts by volume of Fosroc Renderoc PrimerPart A to 1 part by volume Fosroc Renderoc Primer Part B (4 to 1 by weight) in a clean mixing vessel and mix with a spatula or slow speed drill until a homogeneous smooth slurry is produced. Scrub Fosroc Renderoc Primer slurry into the surface.

Renderoc HB45 can be applied immediately to the primed surface. If the primer dries, apply another coat of primer before continuing. In exceptional circumstances, e.g. where a substrate/repair barrier is required or where the substrate is wet or likely to remain permanently damp, Nitobond EP bonding aid should be used.

Mixing
Care should be taken to ensure that Renderoc HB45 is thoroughly mixed. A forced-action mixer is essential. Mixing in a suitably sized drum using an approved Renderoc Mixing Paddle (MR4) in a slow speed (400/500 rpm) heavy-duty drill is acceptable for the occasional one-bag mix. Free-fall mixers must not be used. Mixing of part bags should never be attempted. For normal applications, depending on the consistency required, place 3.0 to 3.5 litres of drinking quality water into the mixer (typically 3.25 litres). With the machine in operation, add one full bag of Renderoc HB45 and mix for a minimum of 3 minutes and a maximum of 5 minutes, until fully homogeneous. The consistency may be adjusted (if required) by the addition of small amounts of water up to the maximum total water content of 3.5 litres. Note that the powder must always be added to the water.

Mixing warning: As with other one pack repair mortars, Renderoc HB45 may exhibit satisfactory handling characteristics even though inadequately mixed. This will result in a significantly lower level of performance or possible failure. It is therefore essential that mixing instructions are strictly adhered to with particular emphasis on the quantity of water used and the time of the mixing operation.

Application
Exposed steel reinforcing bars should be firmly secured to prevent movement during application. Apply the mixed Renderoc HB45 by gloved hand or trowel, thoroughly compacting onto the primed substrate and around exposed reinforcement. If sagging or slumping occurs Renderoc HB45 should be completely removed and reapplied at a reduced thickness to a correctly primed substrate.

Build-up
Additional build-up can be achieved by application of multiple layers. The surface of the intermediate layers should be comb scratch-keyed and cured with Fosroc Nitobond AR. Repriming with Fosroc Renderoc Primer and a further application of Renderoc HB45 may proceed as soon as this layer has set.

Spray application
Renderoc HB45 can be quickly and efficiently applied by the wet spray technique. In circumstances where large areas of repair are required, the rapid placement and higher build attainable by this method offer economic advantages over hand-trowelling. The resultant repair also offers a generally more dense compound with enhanced mortar/substrate bond characteristics.

Finishing
Renderoc HB45 is finished by striking off with a straight edge and closing with a steel float. Wooden or plastic floats, or damp sponges, may be used to achieve the desired surface texture. The completed surface should not be overworked. After spray application, the mortar may need to be cut back to the required profile using a steel float and then finished with damp sponges as described above.