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Parex LA Repair Concrete
LA Repair Concrete complies with the requirements of BS EN 1504-3 Class R4.
Parex LA Repair Concrete is a blend of special Portland cements, ground granulated blast furnace slag plus high quality continuously graded non ASR reactive aggregates. The product, when mixed with water, produces a homogenous concrete which will not segregate or bleed and has a dual shrinkage compensating system giving volume stability in both the plastic and hardened states. The mix has high flow characteristics and will not rapidly stiffen.
Parex LA Repair Concrete may be used for all concrete repairs wherever a flowing concrete is required. The product is easily mixed and placed under gravity or by pumping. The placed material is self compacting and will displace air from the repair area ensuring a strong bond between the placed material and the repair substrate.
The use of the Portland blast furnace type of cement gives a mix design with less than 3kg of equivalent sodium oxide per m3 thus minimising the risk of alkali aggregate reaction even in the parent concrete. In addition, the midrange resistivity enables cathodic protection to be undertaken in conjunction with Parex LA Repair Concrete.
Parex LA Concrete is suitable for the following repair methods as defined in BS EN 1504.
3.2 – Concrete restoration – Recasting with concrete or mortar
4.4 – Structural strengthening – Adding mortar or concrete.
5.3 – Increasing physical resistance – Adding mortar or concrete.
6.3 – Resistance to chemicals – Adding mortar or concrete.
7.1 – Preserving or restoring passivity – Increasing cover with additional mortar or concrete.
7.2 – Preserving or restoring passivity – Replacing contaminated or carbonated concrete.
Uses include:
- Motorway bridge repairs.
- Repairs to large structural concrete elements.
- Protection of corroded and damaged reinforced concrete.
- Refurbishment of soffits to bridge beams and crossheads.
- Grouting under baseplates.
Specification Outline
Concrete repairs and replacement shall be carried out using LA Repair Concrete as manufactured by Parex Ltd. The product must be stored, handled and used strictly in accordance with the manufacturer’s instructions.
Quality Assurance
Parex Limited has an integrated business management system. This is externally accredited by UK CARES to BS EN ISO 9001:2015, BS EN ISO 14001:2015, BS ISO 45001:2018 and BES 6001.
Standards
LA Repair Concrete conforms to the requirements of the Department of Transport Standard BD27/86, clause 4, “Materials for the Repair of Concrete Highway Structures”.
LA Repair Concrete conforms to the requirements of “the Department of Transport Specification for Highway Works, clause 1704.6 Control of Alkali Silica Reaction.”
LA Repair Concrete complies with the classification R4 according to BS EN 1504-3 and is a concrete repair product for structural repair CC mortar (based on hydraulic cement).
Instructions For Use
Preparation
Repair surfaces should be roughened to produce a good mechanical key. Ensure all contact surfaces are clean and free of contamination. Concrete surfaces should be soaked then blown free of standing water prior to concreting. Enclosed formwork sections should have drain holes to remove any standing water.
Formwork must give sufficient hydrostatic head for the concrete to flow across the work area and be strong enough to resist the force of concreting. When placing concrete upwards from the bottom of a section, air release and tell-tale outlets may be required.
Mixing
The recommended water addition is 3.25 litres (13% by mass) per 25 kg bag. Place the required quantity of water in a suitable forced action mixer such as a Creteangle. Slowly add the powder to the water whilst continuously mixing. After all the powder is added mix for a further minute to ensure a smooth lump free consistency is achieved.
Placing
Ensure sufficient Parex LA Repair Concrete has been mixed and available so the placing operation can be carried out in one continuous pour. Place from one side of the form until the area is full. When placing through a flexible tube to the bottom of the section, pour slowly and continuously to displace air upwards within the work piece.
Curing
At temperatures between 5°C and 35°C, formwork should be left in place until the compressive strength of the Parex LA Repair Concrete has reached at least 10N/mm2. Once the formwork has been struck any exposed concrete should be cured immediately with Polycure sprayed at a rate of 10m2 per litre. In adverse ambient conditions of rapid drying such as high temperatures and drying winds apply a second coat after the first coat has dried. In cold ambient conditions protect recently placed concrete from freezing.
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