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- Air_entrainment abstract "Air entrainment is the intentional creation of tiny air bubbles in concrete. The bubbles are introduced into the concrete by the addition to the mix of an air entraining agent, a surfactant (surface-active substance, a type of chemical that includes detergents). The air bubbles are created during mixing of the plastic (flowable, not hardened) concrete, and most of them survive to be part of the hardened concrete. The primary purpose of air entrainment is to increase the durability of the hardened concrete, especially in climates subject to freeze-thaw; the secondary purpose is to increase workability of the concrete while in a plastic state. While hardened concrete appears solid, it is porous, having small capillaries resulting from the evaporation of water beyond that required for the hydration reaction. A water:cement ratio (w/c) of approximately 0.25 (this means 25 parts water for every 100 parts cement) is required for all the cement particles to hydrate. Water beyond that is surplus and is used to make the plastic concrete more workable or flowable. Most concrete has a w/c of 0.45 to 0.60, which means there is substantial excess water that will not react with cement. Eventually the excess water evaporates, leaving little pores in its place. Environmental water can later fill these voids. During freeze-thaw cycles, the water occupying those pores expands and creates stresses which lead to tiny cracks. These cracks allow more water into the concrete and the cracks enlarge. Eventually the concrete spalls - chunks break off. The failure of reinforced concrete is most often due to this cycle, which is accelerated by moisture reaching the reinforcing steel. Steel expands when it rusts, and these forces create even more cracks, letting in more water. The air bubbles are typically 10 to 500 micrometres in diameter (0.0004 to 0.02 in) and are closely spaced. The air bubble can be compressed a little, and so the bubbles act to reduce or absorb stresses from freezing. Air entraining was introduced in the 1930s and most modern concrete, especially if subjected to freezing temperatures, is air-entrained. The bubbles contribute to workability by acting as a sort of lubricant for all the aggregates and large particles in a concrete mix. In addition to entrained air, hardened concrete also contains entrapped air. These are larger bubbles, and are typically less evenly distributed than entrained air. Entrapped air is considered to not make a positive contribution to durability and is undesirable though not entirely avoidable.".
- Air_entrainment wikiPageID "3051078".
- Air_entrainment wikiPageRevisionID "590865131".
- Air_entrainment hasPhotoCollection Air_entrainment.
- Air_entrainment intromissing "May 2009".
- Air_entrainment refimprove "May 2009".
- Air_entrainment subject Category:Concrete.
- Air_entrainment subject Category:Hydraulic_structures.
- Air_entrainment subject Category:Spillways.
- Air_entrainment type Artifact100021939.
- Air_entrainment type Conduit103089014.
- Air_entrainment type HydraulicStructures.
- Air_entrainment type Object100002684.
- Air_entrainment type Passage103895293.
- Air_entrainment type PhysicalEntity100001930.
- Air_entrainment type Spillway104277034.
- Air_entrainment type Spillways.
- Air_entrainment type Structure104341686.
- Air_entrainment type Way104564698.
- Air_entrainment type Whole100003553.
- Air_entrainment type YagoGeoEntity.
- Air_entrainment type YagoPermanentlyLocatedEntity.
- Air_entrainment comment "Air entrainment is the intentional creation of tiny air bubbles in concrete. The bubbles are introduced into the concrete by the addition to the mix of an air entraining agent, a surfactant (surface-active substance, a type of chemical that includes detergents). The air bubbles are created during mixing of the plastic (flowable, not hardened) concrete, and most of them survive to be part of the hardened concrete.".
- Air_entrainment label "AE剤".
- Air_entrainment label "Air entrainment".
- Air_entrainment label "Luftporenbildner".
- Air_entrainment sameAs Luftporenbildner.
- Air_entrainment sameAs AE剤.
- Air_entrainment sameAs m.08n6gl.
- Air_entrainment sameAs Q3523286.
- Air_entrainment sameAs Q3523286.
- Air_entrainment sameAs Air_entrainment.
- Air_entrainment wasDerivedFrom Air_entrainment?oldid=590865131.
- Air_entrainment isPrimaryTopicOf Air_entrainment.