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생성 날짜 08.11
Air Bubbles in Concrete: Friend or Foe?
Air bubbles are common in concrete, but their impact depends on size and distribution.
- Small bubbles
- (≤20μm): Improve frost resistance, durability, and workability with little impact on strength.
- Large bubbles
- (≥50μm): For every 1% increase in air content, compressive strength can drop by about 5%, and issues like higher porosity, segregation, and surface defects may occur.
Why Control Matters
Excessive or oversized bubbles weaken the density and durability of concrete, shortening its service life. In severe cases, they cause delamination, voids, and poor finishes. The goal is not to remove all bubbles, but to control their size and quantity to maximize benefits and minimize harm.
How to Control Air Bubbles
- Start with quality materials: low-alkali cement, well-graded aggregates, and proper mineral admixtures.
- Design the mix with the right water–binder ratio, slump, and air content.
- During construction, use proper vibration techniques, prepare formwork correctly, and apply water-based release agents.
- Modern polycarboxylate-based water reducers with defoaming properties or suitable defoamers can further optimize results.
Bottom Line
Air bubbles may be tiny, but their impact is huge. Controlling materials, proportions, and construction practices can significantly improve the strength, durability, and longevity of concrete structures.
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