Fosroc Conplast AE300
A chloride-free, vinsol-resin air-entraining admixture that builds a stable microscopic air-bubble system into concrete for lasting freeze-thaw and de-icing-salt durability.
What is it?
Conplast AE300 is a ready-to-use, chloride-free air-entraining admixture based on a neutralised vinsol resin. Added to the mixing water, it generates a controlled system of fine, evenly spaced air bubbles inside fresh concrete.
Where is it used?
Concrete roads, bridge decks, airport runways, hardstandings, pavements and any large concrete area exposed to frost, freeze-thaw cycling or de-icing salts, plus mixes made with poorly graded or marginal aggregates.
Why use it?
The entrained air gives the hardened concrete proven resistance to frost damage, surface scaling and spalling, while in the fresh state it improves workability, cohesion and finish without adding water.
How is it applied?
Dispensed into the mix as a liquid at the mixing-water stage, typically 0.05 to 0.15 litres per 100 kg of cementitious material, with the exact rate set by a site trial to hit the target air content.
About Fosroc Conplast AE300
Conplast AE300 is Fosroc’s vinsol-resin air-entraining admixture, engineered to deliberately introduce a measured volume of microscopic air into concrete. Unlike the random voids that come from poor compaction, this air is present as millions of tiny, discrete, well-distributed bubbles. That distinction is the whole point: a stable, finely divided bubble system relieves the internal pressure generated when pore water freezes and expands, which is what protects the concrete from the cracking, scaling and spalling that plague pavements and decks in cold climates.
The product is supplied as a brown liquid that disperses instantly in water. Chemically it is a neutralised vinsol resin, chloride-free, so it carries no risk of contributing chlorides that could promote reinforcement corrosion. It works at the interface between the mixing water and the cement and aggregate particles, stabilising the air it draws in during mixing. Fosroc highlights that the bubble system stays stable across a wide range of aggregate qualities and mix conditions, which matters on Indian sites where aggregate gradings and sources vary considerably from one batch plant to the next.
For contractors, consultants and ready-mix producers, AE300 is the admixture you reach for when durability against freeze-thaw or de-icing salts is specified, or when you need to improve the cohesion and finish of a harsh, poorly graded mix. It is most relevant to projects in India’s Himalayan belt, the North-East, Ladakh, Kashmir and other high-altitude regions where winter freeze-thaw is a genuine design case, and to any structure where a specification calls for a defined air content. Air entrainment is a powerful but precise tool, and AE300 is formulated to deliver it predictably.
The technical insight
The durability mechanism is purely physical. Water in concrete’s capillary pores expands by roughly 9 percent on freezing; without relief, that expansion generates hydraulic pressure that fractures the cement paste. The entrained bubbles act as empty expansion chambers, giving the freezing water somewhere to go and dissipating the pressure before it can crack the matrix. Effectiveness depends not just on the total air volume but on the bubble spacing factor: many small, closely spaced bubbles protect far better than a few large ones, which is why bubble fineness and stability, not just the headline air percentage, are the real engineering targets. A practical rule worth respecting on site is that each additional 1 percent of entrained air typically costs around 5 percent of compressive strength, so the air content must be controlled to the specified band, not maximised. Conplast AE300 is dosed to land air content within a tight window, and because air yield is sensitive to cement content, fines, mix temperature, mixing time and the use of supplementary cementitious materials such as fly ash, slag or microsilica, the dosage is always confirmed by trial mix and verified with an air meter rather than assumed.
Where it is used
- Concrete roads, highways and rigid pavements exposed to winter freeze-thaw cycling
- Bridge decks, approach slabs and parapets subject to de-icing salt application
- Airport runways, taxiways and aprons in cold-climate regions
- Hardstandings, car parks and external paving in high-altitude and hill-station projects
- Concrete in Himalayan, Ladakh, Kashmir and North-East India sites where frost durability is a design requirement
- Improving cohesion, workability and finish in mixes made with poorly graded or marginal aggregates
- Reducing bleeding and segregation in lean and harsh concrete mixes
- Mass and pavement-quality concrete where a defined air content is specified for durability
Key advantages
- Produces frost- and de-icing-salt-resistant concrete with markedly reduced surface scaling and spalling
- Chloride-free formulation, so it adds no risk of chloride-induced reinforcement corrosion
- Excellent air-bubble stability across a wide range of aggregate qualities and mix conditions
- Improves workability and cohesion without adding extra water to the mix
- Gives a denser, more uniform, close-textured finish free from gravel nests and sand runs
- Reduces bleeding and segregation, especially in harsh or poorly graded mixes
- Disperses instantly in water for easy, uniform dosing at the mixer
- Ready-to-use liquid requiring no on-site mixing or dilution
Limitations & considerations
- Air entrainment reduces compressive strength, roughly 5 percent loss per 1 percent of entrained air, so mix designs must account for it
- Dosage must be established by trial mix and verified with an air meter; it cannot be reliably fixed from the datasheet alone
- Air yield is sensitive to cement content, fines, fly ash or slag, mix temperature, mixing time and even sand grading, so consistency control is essential
- Over-dosing causes excessive air and serious strength loss; under-dosing leaves the concrete unprotected against frost
- Extended or over-mixing, and pumping or excessive vibration, can knock out entrained air and lower the in-place air content
- Primarily a durability admixture, it is not a water reducer or superplasticiser and does not by itself deliver high strength or high slump
- Best results need competent batching control; it is less forgiving of careless QA than a simple plasticiser
Selection & best practice
Always establish the dosage with a site trial mix using your actual cement, aggregates and any fly ash, slag or microsilica, then verify the fresh air content with a pressure air meter to confirm you are inside the specified band (commonly around 4 to 6 percent for frost durability). Start near 0.08 litres per 100 kg of cement and adjust. Add AE300 to the mixing water or the wet mix, never to the dry cement, and keep mixing time, mix temperature and aggregate grading as consistent as possible from batch to batch, because all of these shift the air yield. Re-check air content if you change the mix, the aggregate source or the season. Avoid over-vibration and prolonged pumping, which expel entrained air, and design the mix for the strength you need after accounting for the strength reduction that the air content brings.
Specifications
| Product type | Air-entraining admixture for concrete |
| Chemical base | Neutralised vinsol resin, chloride-free |
| Appearance | Brown liquid that disperses instantly in water |
| Chloride content | Chloride-free (nil chloride contribution) |
| Typical dosage | 0.05 to 0.15 litres per 100 kg of cementitious material |
| Example dosage | 0.08 L/100 kg cement gives approx. 5% +/- 1.5% air in medium-workability concrete (cement 250-300 kg/m3) |
| Primary function | Frost and de-icing salt resistance via stable microscopic air-bubble system |
| Standards (EU) | Complies with EN 934-2 (Table 5, air-entraining admixtures); UNE-EN 934-2:2010 Table 5 |
| Compatibility | Compatible with most Conplast admixtures; verify combinations by trial |
| Verification | Air content to be confirmed on site with a pressure air meter |
Industry use cases
Highways & rigid pavements
Pavement-quality concrete for roads in frost-prone hill regions, where a controlled 4 to 6 percent air content resists scaling from freeze-thaw and de-icing salts and extends pavement life.
Bridges & infrastructure
Bridge decks and approach slabs that face winter salting; entrained air limits surface spalling and protects the deck without adding chlorides near the reinforcement.
Aviation
Runway, taxiway and apron concrete at high-altitude airfields needing durable, scaling-resistant surfaces under repeated freeze-thaw exposure.
High-altitude building works
External slabs, hardstandings and paving on projects in Ladakh, Kashmir, Himachal and the North-East where frost durability is specified by the consultant.
Ready-mix production
RMC plants supplying cold-region projects use AE300 to meet specified air contents and to improve the cohesion and finish of harsh or poorly graded mixes.
Frequently asked questions
What exactly is Fosroc Conplast AE300?
How much Conplast AE300 should I add?
Will air entrainment reduce my concrete’s strength?
Does Conplast AE300 contain chlorides?
When do I actually need an air-entraining admixture in India?
Can I use Conplast AE300 together with other Fosroc admixtures?
How we position Fosroc Conplast AE300
Within the Fosroc Conplast range, AE300 sits in the air-entraining family alongside Conplast AEA and the AE316 and AE383 variants, all aimed at frost and de-icing-salt durability rather than strength or slump; the AE variants differ mainly in vinsol-resin concentration and dosing, with AE300 a widely used general-purpose option. It is distinct from the water-reducing and superplasticising Conplast grades such as Conplast SP430 (high-range water reduction) and the plasticiser grades, which target workability and strength, and on many durability mixes an air-entrainer like AE300 is run together with one of those superplasticisers. Against the wider market, credible alternatives sold in India include Sika’s air-entraining admixtures (the Sika AER range), BASF/Master Builders Solutions MasterAir, and the air-entraining grades from STP and other domestic admixture houses; integral-waterproofing brands such as Dr. Fixit address a different problem (water ingress) rather than freeze-thaw durability, so they are not direct substitutes. As an authorised Fosroc distributor and applicator serving Delhi NCR and pan-India, Space Arc Engineering supplies Conplast AE300 with the trial-mix support, air-content verification guidance and specification advice that make air entrainment reliable on site; contact our technical team to confirm the right grade, dosage and pack size, and to cross-check current TDS values such as specific gravity, pack sizes and shelf life against your project specification.
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