Air entrainment

**Benefits of Air Entrainment:**
– Improves workability of fresh concrete
– Prevents bleeding and segregation
– Strengthens concrete for freeze-thaw cycles
– Enhances resistance to cracking and fire damage
– Increases overall durability and strength

**Process of Air Entrainment:**
– Concrete porosity due to excess water evaporation
– Importance of controlling air entrainment process
– Impact of materials like fly ash, silica fume, and slag cement
– Influence of natural pozzolans on air-entrained concrete
– Adjustments in admixture dosage based on material properties

**Characteristics of Air Entrainment:**
– Air bubbles diameter ranges from 10 to 500 micrometers
– Introduced in the 1930s for concrete subjected to freezing temperatures
– Act as lubricant for aggregates and sand particles
– Void compression reduces stresses from freezing
– Enhances workability of concrete mix

**Issues with Entrapped Air:**
– Presence of unintentionally entrapped air in hardened concrete
– Larger bubbles creating honeycombing and uneven distribution
– Vibration during concrete placement to minimize entrapped air
– Essential in minimizing deleterious entrapped air
– Particularly crucial in wall forms

**Challenges and Future Directions:**
– Maintaining consistent air content in concrete during mixing and placement
– Factors affecting entrained air like long hauling durations and high temperatures
– Over-entrainment or under-entrainment impacting concrete performance
– Balancing air content with other concrete properties crucial for desired outcomes
– Future direction with superabsorbent polymers (SAP) potentially replacing traditional air-entraining agents (AEAs) in concretehttps://en.wikipedia.org/wiki/Air_entrainment