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Conplast PA21 - Air-entraining and plasticising additive for concrete

Air-entraining (air-entraining) additive based on lignosulphonates. The air-entrainment increases durability and resistance to sudden temperature changes that occur in freeze-thaw conditions.

Consumption: 0.25 - 0.6% of the weight of cement.

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Conplast PA21 is an air-entraining admixture based on selected lignosulphonates and air-entraining agents. It is supplied as a brown liquid that disperses instantly in water. The active agents in Conplast PA21 act at the interface between the mixing water and the cement/aggregate particles to produce microscopic air bubbles, which are evenly distributed throughout the mass.

The occluded air increases durability, providing protection against sudden temperature changes that occur in freeze-thaw conditions.

Uses

  • To produce air-entrained concrete that increases durability and resistance to damage from freezing and de-icing salts. Suitable for concrete roads, bridges, runways and other concrete areas exposed to frost damage.
  • To improve the cohesion and workability of concrete where poor particle sizes have to be used and exudation or segregation may occur.
  • To reduce the permeability of concrete with sandy or aggregate-poor granulometries.
  • To improve the stability, cohesion and appearance of concrete joists and slabs in the precast industry.

Advantages

  • Air occlusion increases the resistance of concrete to frost attack, reducing concrete defects.
  • The occluded air bubbles assist in the formation of a stable cohesive mix, which reduces segregation and exudation.
  • Air occlusion improves workability and helps produce a dense, uniform, closed-textured mass free of gravel concentrations and segregation, increasing its durability.
  • A reduction of water allows the production of a concrete with low permeability and higher strength, compared to that obtained with air occlusion alone.

Standards

Conplast PA21 complies with UNE-EN 934-2:2010 Table 5 as an air inclusor.

Typical dosage

The optimum dosage of Conplast PA21 to achieve specific requirements should be determined by testing, using the materials and conditions that will be tested in practice. This allows optimisation of the admixture dosage and mixture as well as a complete evaluation of the concrete.

As a starting point for such tests, a dosage of between 0.25 and 0.60 litres/100 kg of binder, either cement alone or cement with additions such as ash, slag or microsilica, is usually used.

Use in other dosages

Dosages outside the above range may be used under appropriate supervision. Test samples should be used to check compliance with the regulations and their specifications.

Properties

  • The following results were obtained at a temperature of 20ºC:
  • Appearance: Light brown liquid
  • Density: 1,215 ± 0,005 kg/l
  • pH: 3,0 ± 1,0
  • Water soluble chloride content (CI-): ≤ 0,10%.
  • Alkali content (Na2O equivalent): max. 5 % by mass
  • Primary function: Air occlusion in concrete
  • Secondary function: Water reducer

Mode of application

Analysis and control

Once the appropriate dosage has been selected, care must be taken to ensure the consistency of the materials used and the mixing and distribution processes. Variability in the cleanliness and grade of the aggregates can have differing effects on the plasticising and aerating properties of the additive. The air content should be analysed regularly.

Factors affecting air entrapment

There are several factors that can affect the air-lock obtained for a particular dosage of aerating admixture, such as the type of sand used, the fineness of the cement, the presence of carbon or organic impurities, the temperature of the concrete, the type of mixer, the transit time or the compaction.

Compatibility

Conplast PA21 is only compatible with the superplasticisers of the Fosroc Euco range if the lowest possible w/c ratio is to be maintained. If more than one admixture is used, they must be added to the concrete separately and not mixed together before being added. The resulting properties of concrete containing more than one admixture should be checked by prior testing.

Conplast PA21 is suitable for use with all cements complying with RC-08.

Dosing system

The correct amount of Conplast PA21 should be measured out using a suitable dosing system. The additive is added to the concrete with the mixing water to obtain the best results. Contact the Fosroc Euco Technical Department for advice and to request a suitable equipment and its installation.

Effects of overdosage

An overdosage of twice the normal amount of Conplast PA21 results in a significant increase in air entrapment, which reduces the strength as well as increasing the setting time.

Curing

The final characteristics of any structural concrete will depend on good curing practice. It is therefore very important to use a Fosroc Euco Concure curing membrane, water spray or wet burlap.

Clean-up and disposal

Spills of Conplast PA21 should be absorbed with sand or earth and transferred to suitable containers. Product residues should be flushed away with a large amount of water. Disposal of the product and packaging is the responsibility of the end user.

Limitations

Conplast PA21 is designed to provide water reducing and aerating properties. A change in dosage will change both at the same time.

In situations where highly variable aggregates are used, and independent control of water reduction and air entrainment is required, the use of a combination of additives such as Conplast P520 and Conplast AE300 (water reducing and air entraining respectively) is recommended.

Storage

Conplast PA21 has a storage period of 12 months if kept in a dry place and in its original, closed containers at a temperature between 2°C and 40°C.

Freezing point: -2 ºC approx.

Precautions

Safety and Hygiene

Conplast PA21 is alkaline and irritant and should not be ingested or put in contact with skin and eyes. Wear protective gloves and goggles. Splashes on the skin should be washed off with water. In case of contact with eyes, flush with plenty of water and seek medical advice. If swallowed, seek immediate medical attention. Do not induce vomiting.

For further information, please refer to the Material Safety Data Sheet.

Fire

Conplast PA21 is water based and non-flammable.

Fosroc

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