FiveStar Repair Concrete 

Five Star repair concrete is a preblended cementitious repair concrete which fully complies with the Highways Agency Specification for Highway Works and Department of Transport specification BD 27/86 for a high strength flowing concrete. Contains nonreactive aggregates and a low soluble alkali cement content. The repair concrete can be applied to a range of thicknesses, minimum15mm. Contains RHPC & PFA to clause 1702, 5mm non-reactive carboniferous limestone to clause 1704, microsilica and shrinkage compensating agents.

• Permanent structural repair concrete.
• Rapid strength development thus reducing repair possession times.
• Dimensionally stable, forms an integral bond to existing concrete and restores structural integrity with proven durability.
• Economical repair.
• Variable application thickness providing flexibility of use.
• Free-flowing repair concrete allowing formation of intricate falsework.
• Ideally suited in structural elements where reinforcement is congested.
• Shrinkage-compensated to avoid shrinkage cracks and enhance durability.

The concrete substrate shall be adequately prepared by suitable methods to remove all defective concrete or suspect concrete by high pressure water cutting or by mechanical means, i.e breakers, scabbling, grit blasting, etc. The perimeter of the prepared area shall be well defined by a saw cut, avoid feather edging of the repair concrete. All concrete shall be removed to give a minimum clear dimension of 20 mm to all exposed rebar reinforcement. The extent of the concrete removal shall be agreed with the contract supervisor or engineer.

Rust scale corrosion products and other deposits shall be removed from the exposed steel reinforcement by grit blasting or high pressure water cutting. Finish shall be to achieve second quality to BS7079:1989 which is equivalent to Swedish Standard SA 21/2 quality. Degrease with weber.tec solvent 3 where appropriate immediately prior to pouring. No priming of the reinforcement is required, Five Star repair concrete forms a good cementitious bond to the clean exposed reinforcement.

Old concrete surfaces contaminated with oil or grease will require cleaning, care must be taken to ensure all contamination and any coating is removed prior to application of concrete.

Grout-tight formwork is essential. Use a light uniform application of release agent and good quality sealed ply formwork. The formwork shall be adequately supported and fixed to resist fluid concrete pressures. The parent concrete shall be thoroughly saturated with potable water prior to the application of the repair concrete. This may be achieved by filling the formwork with water, usually for 2 hours, then draining off the water and removal of all surplus water.

Use only freshly opened bags of Five Star repair concrete and a clean forced action mixer of suitable volume, i.e Daines Mixal mixer, Cretangle pan mixer or a Putzmeister P13 mixer and pump.

Charge the mixer with 3·1 - 3·3 litres of water per 25 kg bag, followed by a gradual addition of repair concrete. For optimum flow use 3·3 litres of water. Mix for 3 minutes. Mix only full bags, do not mix part bags.

nb: do not exceed maximum water addition of 3·3 litres water per 25kg bag.

The mixed concrete shall be used within 30 minutes of mixing and kept agitated prior to use.

The mixed concrete can be placed either by gravity pouring or by pumping through hoses at least 50 mm diameter. Care shall be exercised to avoid air entrapment during placing. No vibration is needed to compact the repair concrete but the formwork should be tapped with a mallet to release minor air bubbles on the surface of the formwork.

Setting time
Setting time at 20°C is approximately 225 minutes.

Winter working
Five Star repair concrete can be used down to 5°C provided cold weather working precautions are carried out. At low temperatures the strength development gain of repair concrete is greatly reduced with strengths similar to that expressed by the Sadgrove method. Striking times of formwork will be effected.

For further information please contact weber Technical Services.