Fosroc Conplast AE380
Chloride-free synthetic air-entraining admixture that builds a stable microscopic bubble system into concrete for frost, freeze-thaw and de-icing-salt durability.
What is it?
A chloride-free, ready-to-use liquid air-entraining admixture based on synthetic surfactants. It deliberately introduces millions of tiny, stable, evenly spaced air bubbles into fresh concrete to protect the hardened concrete from freeze-thaw cycling and de-icing salts.
Where is it used?
Pavement-quality concrete, bridge decks, airport runways and taxiways, hill-station and high-altitude works, water-retaining structures and any cohesion-sensitive mix using poorly graded sands. In India it is specified mainly for projects in the Himalayan belt, J&K, Himachal, Uttarakhand and the North-East where frost is a genuine risk.
Why use it?
Entrained air is the single most effective way to make concrete frost-durable. The bubble system relieves the internal pressure of freezing water, cuts surface scaling, and as a bonus improves workability and cohesion while reducing bleeding and segregation.
How is it applied?
Dispensed as a liquid with the mixing water at a trial-established dosage (typically 0.05-0.12 litres per 100 kg cement). Air content is verified on site by the pressure method per ASTM C231 / BS 1881 and the dosage fine-tuned to hit the target air percentage.
About Fosroc Conplast AE380
Fosroc Conplast AE380 is an air-entraining admixture engineered to give concrete long-term resistance to frost, freeze-thaw cycling and de-icing salts. Unlike most older air-entrainers that rely on Vinsol (wood) resin, AE380 is built on synthetic surfactant chemistry. It arrives as a clear, colourless liquid that disperses instantly in the mixing water and is completely chloride-free, so it is safe for use in reinforced and prestressed concrete without any risk of contributing to steel corrosion.
The way it works is physical rather than chemical. When AE380 is introduced into the mix, its surfactant molecules act at the boundary between the water and the cement and aggregate particles, stabilising a network of microscopic air bubbles. These bubbles do not merge or escape during mixing, transport and compaction; instead they remain finely divided and evenly distributed through the paste. In hardened concrete this air-void system acts as a pressure-relief network: when water inside the concrete freezes and expands, the bubbles give it somewhere to go, preventing the internal tensile stresses that otherwise crack and scale a concrete surface.
For an Indian specifier this is a niche but important product. The large-volume admixture business in India is dominated by water-reducers and superplasticisers, because most of the country never sees a freeze. But for projects in the Himalayan and sub-Himalayan belt, hydro and tunnel works, high-altitude roads and airfields, and any structure subjected to repeated freezing, an air-entrainer is not optional, it is a code requirement. Conplast AE380 is Fosroc’s purpose-built answer for those conditions, and a deliberate alternative to resin-based entrainers where compatibility with other admixtures in the mix is a concern.
The technical insight
The headline number that matters is the target air content, not the dosage. Fosroc’s data sheet quotes a guide dosage of 0.05 to 0.12 litres per 100 kg of cement to achieve roughly 5.5% +/- 2% entrained air in a medium-workability concrete of 300-350 kg/m3 cement content, but it is emphatic that this is only a starting point. Air entrainment is famously sensitive: sand silt content, particle shape, cement fineness, mix temperature, the presence of fly ash or microsilica, and even mixer type and transit time all push the achieved air up or down for the same dosage. A temperature rise from 10C to 32C can roughly halve the air produced, and carbon or organic impurities (a real concern with some Indian fly ashes and lignite-bearing sands) can demand a markedly higher dose. This is why every serious specification, and Fosroc itself, insists the working dosage be fixed by site trials with the actual materials, and that air be checked continuously by the pressure method (ASTM C231 / BS 1881). Two practical cautions follow: overdosing by even double the intended amount sharply raises air and therefore drops compressive strength (very roughly, each extra 1% of air costs around 5% strength), and high air contents reduce pump efficiency over long lines. Treat air content as a quality-controlled parameter on par with slump, not a fire-and-forget admixture.
Where it is used
- Pavement-quality concrete (PQC) for roads and highways exposed to frost in the Himalayan and North-East belt
- Bridge decks and approach slabs subject to freeze-thaw and de-icing salt run-off
- Airport runways, taxiways and aprons at high-altitude airfields
- Hydroelectric, dam and tunnel-lining concrete in cold mountain regions
- Water-retaining structures where freeze-thaw durability and a cohesive, low-bleed mix are both needed
- Concrete using poorly graded or single-size sands, where the entrained air improves cohesion and finishability
- Mixes where a resin-based (Vinsol) air-entrainer creates compatibility problems with the chosen superplasticiser
Key advantages
- Chloride-free, so safe for reinforced and prestressed concrete with no corrosion risk
- Markedly improves frost and de-icing-salt resistance, cutting surface scaling and freeze-thaw failure
- Synthetic surfactant base avoids the compatibility problems common with Vinsol-resin entrainers when combined with other admixtures
- Excellent bubble stability across a wide range of aggregate qualities and mix conditions
- Improves workability and cohesion, reducing bleeding, segregation and sand runs
- Produces a dense, uniform, close-textured surface free from gravel nests
- Complies with internationally recognised standards (BS 5075 Part 2, ASTM C260)
- Liquid form disperses instantly in mixing water for easy, accurate dispenser-based batching
Limitations & considerations
- Achieved air content is highly variable and must be fixed by site trials, not read off a table
- Entrained air reduces compressive strength (roughly 5% per 1% air), so mix design must compensate
- Overdosing causes a steep, sometimes uncontrolled rise in air and a corresponding strength loss
- Air can be lost or altered by changes in temperature, sand source, fly ash, mixer type or transit time, demanding constant QC
- Of limited relevance across most of plains India, where frost is not a design condition
- Fosroc’s own data sheet cites BS and ASTM compliance rather than an Indian Standard, so IS-driven specifications should be confirmed with Fosroc India in writing
- Prolonged or over-vibration during compaction can drive entrained air out of the mix
- High air contents reduce pumpability over long pump runs
Selection & best practice
Always establish the working dosage by trial mixes using the actual cement, sand, aggregate and any fly ash or microsilica that the job will use, and target a specified air content (commonly 5-6% for severe exposure) rather than a fixed dosage. Add AE380 with the mixing water through a calibrated dispenser, never neat onto dry materials and never pre-mixed with other admixtures. Check air content on the fresh concrete continuously by the pressure method (ASTM C231 / BS 1881), and re-check whenever the sand source, ambient temperature or mix temperature shifts. Keep cube strengths under watch because the air costs strength. Store the drums sealed between 2C and 50C, protect from freezing (freezing point is about 0C), and use within the 12-month shelf life. For special or blended cements, confirm suitability with Fosroc’s technical team before the pour.
Specifications
| Product type | Chloride-free air-entraining admixture (synthetic surfactant based) |
| Appearance | Colourless liquid |
| Specific gravity | Typically 1.01 at 20 C |
| Chloride content | Nil (to BS 5075) |
| Alkali content | Typically less than 5.0 g Na2O equivalent per litre |
| Typical dosage | 0.05 to 0.12 litres per 100 kg of cement (trial-established) |
| Typical air content achieved | 5.5% +/- 2% in medium-workability concrete at 300-350 kg/m3 cement |
| Standards compliance | BS 5075 Part 2; ASTM C260; DoT Specification for Highway Works clause 1001 |
| Freezing point | Approximately 0 C |
| Flammability | Water-based, non-flammable |
| Packaging | 20 litre drums (bulk and storage-tank supply available) |
| Shelf life | Minimum 12 months stored between 2 C and 50 C |
Industry use cases
Highways & roads
Pavement-quality concrete for frost-prone mountain highways, where entrained air prevents surface scaling from freeze-thaw and de-icing salt.
Aviation infrastructure
Runways, taxiways and aprons at high-altitude airfields that must resist repeated freezing without spalling under aircraft loads.
Bridges
Bridge decks and approach slabs exposed to both freeze-thaw cycling and salt run-off, the classic durability use case for air entrainment.
Hydropower & tunnels
Dam, intake and tunnel-lining concrete in cold Himalayan catchments where frost durability is a code requirement.
Water-retaining structures
Tanks and reservoirs in cold regions where a cohesive, low-bleed, freeze-durable mix is needed simultaneously.
General concreting with difficult aggregates
Mixes using poorly graded sands where the entrained air is used as much for cohesion and finish as for frost resistance.
Frequently asked questions
Is Fosroc Conplast AE380 a real product?
What dosage of Conplast AE380 should I use?
Does it contain chloride, and is it safe for reinforced concrete?
How is AE380 different from a Vinsol-resin air-entrainer like Conplast AEA?
Will air entrainment reduce my concrete strength?
How is it packed and how long does it last?
How we position Fosroc Conplast AE380
Within the Fosroc Conplast admixture family, AE380 sits firmly in the durability-and-air-control niche rather than the volume water-reducer space. Its closest sibling is Conplast AEA, Fosroc’s Vinsol-resin air-entrainer; AE380 is the synthetic-based alternative chosen where admixture compatibility or bubble stability matters more. It is routinely paired in the same mix with Fosroc’s water-reducers and superplasticisers such as Conplast WL, Conplast SP430 and the Auramix high-range range, since frost-durable concrete almost always needs workability control as well, with each admixture dosed separately. Against the wider Indian market, the comparable air-entraining products are Sika AER (Sika), the Master Air / MasterAir line from Master Builders Solutions (formerly BASF, MBS), and air-entrainers from Dr. Fixit (Pidilite) and STP/Sika; specifiers typically choose on local technical support, trial performance and standards documentation rather than headline chemistry. Honestly assessed, AE380 is a specialist tool: across most of plains India it is rarely needed, but for frost-exposed work in the Himalayan and North-East belt it is a well-documented, internationally compliant choice. Space Arc Engineering, as an authorised Fosroc distributor and applicator covering Delhi NCR and Pan-India, can supply AE380, confirm current standards documentation for your specification, and support the trial-mix programme that this product genuinely requires.
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