Flexcrete Fastfill is a rapid setting, Portland cement-based structural mortar for the durable repair of concrete which cannot be taken out of service for long periods, or in areas subjected to heavy wear such as roads, runways, bridges, decks, floors and footpaths. Fastfill can be used as supplied or bulked out with sharp sand or aggregate.

FASTFILL is a single component, polymer modified, fibre reinforced Portland cement-based repair mortar. It is rapid curing with enhanced polymeric properties and reliable strength development. Used for the durable repair of concrete subject to heavy wear such as roads, runways, bridges, decks, floors and footpaths. Also suitable for marine repairs and approved for potable water applications.

Features

• Incorporates the latest cement chemistry, microsilica, fibre and styrene acrylic copolymer technology.
• Simply mixed with clean water, part bags can be mixed.
• Generally requires no substrate or inter-layer priming.
• Sets in 10 minutes at 20°C, yielding a durable, high strength mortar.
• Rapid strength development at sub-zero temperatures.
• Repairs can be walked on after one hour and opened
• vehicular traffic in two hours.
• Ideal for tidal repairs due to rapid setting properties.
• Bond strength exceeds tensile strength of concrete, ensuring monolithic performance.
• Dense matrix with low permeability to water.
• High diffusion resistance to acid gases & chloride ions.
• Resistant to sulphates to class DS-5M of BRE Special Digest 1.

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 by products 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

FASTFILL 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

FASTFILL 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.

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.