Australian Concrete Exposure Classes
Concrete exposure classes in Australia account for the severity and conditions that a concrete element is expected to withstand during its design life. The required concrete exposure classes, along with the concrete strength grade, the required rebar size, and other related factors, are all considered by structural engineers when designing a concrete-based structural member. All these requirements are listed in Australian Standards, specifically under AS 3600, and are used by engineers and manufacturers in conjunction with concrete mix design and,reinforcement standards in Australian engineering practice.
Choosing the concrete exposure class is essential for ensuring the long-term durability, corrosion resistance, and performance of a structure. Concrete designed with the correct exposure class will prevent premature deterioration caused by moisture ingress, chlorides, sulfates, and chemical attack. Higher exposure classes often require higher-strength or special-class concrete, influencing cost, constructability, and curing requirements. Incorrect exposure classification can lead to reduced service life, increased maintenance costs, and early structural repairs.
Australian Concrete Exposure Class Designation Table
| Exposure Class | Use | Example Environment |
|---|---|---|
| A1 | Mild Environments (Limited Exposure) | Interior environments with minimal to no moisture exposure |
| A2 | Mild Exterior Environments | Above ground exterior environments with only occasional moisture exposure |
| B1 | Moderate Exposure Environments | Interior or exterior environments with regular moisture but not exposed to marine salts |
| B2 | Severe (Salt Influenced) Exposure Environments | Coastal and marine environments, exposed to salt-laden air but not directly exposed to marine spray or splash |
| C1 | Severe Marine Exposure Environments | Locations with direct and continuous exposure to seawater spray or where chloride attack is significant |
| C2 | Severe Tidal/Splash Zone Exposure Environments | Tidal and splash zones of marine structures or places with the potential for continous and high chloride exposure |
| U | Unspecified | Environment not covered by A1–C2; durability requirements must be specifically engineered in accordance with AS 3600 |