Flexcrete - UniCem Rapid Repair Mortar has unique hydraulic properties. Mixing with water produces a rapid curing mortar is produced that has reliable strength development and which is not significantly affected by low temperatures. Can be used as supplied up to 100mm deep, or can be bulked out with sharp sand or aggregate to a flowing consistency for floor, deck or concrete repairs up to maximum depth of 300mm.

Advantages

• Incorporates the latest proven cement chemistry, fibre and styrene acrylic copolymer technology.
• Reliable strength development, even at sub-zero temperatures which therefore gives rapid return to service.
• Pre-packaged material requiring mixing with clean water. Sand or aggregate can be used for bulking it out.
• High bond strength exceeds tensile strength of concrete.
• Sets in 10 minutes at 20°C yielding a durable, high strength mortar.
• Dense matrix resists 10 bar water pressure and moreover, very high diffusion resistance to acid gases and chloride ions.
• Sulphate resistance to class DS-5/5m of BRE Special Digest 1 and ideally suited for sewage and wastewater applications.
• Portland cement base with physical properties of cured material similar to base concrete.
• Non-toxic when cured and is listed as authorised under Regulation 31 for use in the supply of drinking water.
• Economic mortar requiring no substrate or inter-layer priming.

Application

Preparation

Mechanically remove all damaged concrete or failed repairs back to a sound core. Except in new construction, expose the full circumference of the steel reinforcement 25mm behind the bars and 50mm beyond visible corrosion. On cutting back, feather edges must be avoided. Step the perimeter of the repair to a depth of 10mm preferably using a power chisel or by saw or disc cutting.

The areas to be repaired must be free from all unsound material including laitance dust, oil, grease, corrosion byproducts and organic growth. Smooth surfaces should be roughened and reinforcement cleaned to bright steel using wet grit blasting techniques or equivalent approved methods. Power tools such as a needle gun, angle grinder or wire brush may be used on concrete which is not chloride contaminated.

➢ The compressive strength of the parent concrete should be minimum 20 MPa.

The prepared substrate should be thoroughly soaked with clean water until uniformly saturated without any standing water. In winter, use warm water or a heat source to ensure the substrate temperature is ≥ 5ºC before application.

Treatment of Steel Reinforcement

Treat exposed steel reinforcement with 2 x 1mm coats of STEEL REINFORCEMENT PROTECTOR 841 applied by brush.

Priming of Concrete

Unicem Rapid does not generally require a primer. Highly porous substrates may be primed with a POLYMER ADMIXTURE 850 slurry coat. The slurry coat should also be used when treating larger areas of waterproof concrete.

Mixing 

Unicem Rapid should be mechanically mixed using a forced action pan mixer or in a clean drum using a slow speed drill and paddle. A normal concrete mixer is NOT suitable. For normal applications, use 3.5 litres of clean water per 25kg bag. For part bags, this equates to 5.5 volumes of powder to 1 volume of water. In cold temperatures, tepid water may be used to adjust working life. Mix for 2-3 minutes entraining as little air as possible. Use without delay.

For screeding applications or larger pockets in decks up to a maximum depth of 100mm a clean, washed, medium grade concreting sand can be added (up to 50% by weight). For deeper repairs, clean sharp 5-10mm aggregate can be added to a maximum of 100% by weight to a produce a semi-pourable consistency ➢ Note - These instructions must be adhered to as Flexcrete will not be responsible for failure due to incorrect mixing.

Placing

For normal applications, FASTFILL should be compacted, using a placing technique to ensure full contact with the substrate. When bulking out with aggregate, temporary support with shuttering may be required. Tamp to remove any entrapped air. For multi-layer applications, it is important to ensure that the previous layers are well keyed and stable but not fully set (typically 15-30 minutes) prior to the application of subsequent layers. No inter-layer priming is required. Final profiling is achieved with a steel float.

On larger floor repairs, the area should be divided into individual bays of approximately 1m2 to allow for completion of work within the open time. Do not polish the surface with a steel float, use a stiff brush on the wet surface to provide a slip-resistant finish. In tidal works, allow a minimum cure time of 30 minutes prior to immersion.