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Concrete Technology
Published in P.K. Jayasree, K Balan, V Rani, Practical Civil Engineering, 2021
P.K. Jayasree, K Balan, V Rani
Air entrainment reduces the density of concrete and consequently reduces the strength. Air entrainment is used to produce a number of effects in both the plastic and the hardened concrete. These include: Resistance to freeze–thaw action in the hardened concrete.Increased cohesion, reducing the tendency to bleed and segregation in the plastic concrete.Compaction of low workability mixes including semidry concrete.Stability of extruded concrete.Cohesion and handling properties in bedding mortars.
Concrete Mix Design
Published in M. Rashad Islam, Civil Engineering Materials, 2020
Figure 4.2 shows how the compressive strength decreases with the increase in the W/C ratio for both the air-entrained and non-air-entrained concretes. In air-entrained concrete, air-admixtures are added to produce microscopic air bubbles inside the concrete, which are required when concrete is exposed to deicing, aggressive chemicals, moisture, or free water prior to freezing. For example, in Texas, air-entrained concrete is not practiced as there is no expansion issue for concrete, whereas in New York, air-entrained concrete is required to avoid cracking due to the expansion of ice during the freezing weather. Air entrainment also increases the workability of concrete. The details of air-entrainment requirements are discussed further in this chapter.
Materials and testing
Published in Malcolm Copson, Peter Kendrick, Steve Beresford, Roadwork, 2019
Malcolm Copson, Peter Kendrick, Steve Beresford
Air entrainment is important for all concrete members exposed to wetting and drying, freezing and thawing, or to the destructive action of chemicals. It is now a standard requirement for concrete roads, runways and, to some extent, for paved areas.
Rheology and printability of Portland cement based materials: a review
Published in Journal of Sustainable Cement-Based Materials, 2023
Uday Boddepalli, Biranchi Panda, Indu Siva Ranjani Gandhi
Air entrainment is the technique of inducing air bubbles in cementitious mortar by adding AEAs which can be natural or synthetic in nature. There are two types of AEAs, depending on the reaction. The first type combines with the cement paste’s calcium hydroxide solution to form an insoluble calcium salt. The surface tension of the water is not reduced in this type, but hydrophobic calcium salts precipitated at the water-air-cement grain contact regions are the primary cause of air entrainment and bubble stability [156]. Surfactants, on the other hand, are AEAs that reduce surface tension at the water-air interface, allowing stable air bubbles to form [157]. The later AEA is the most commonly used admixture among these AEAs. The addition of air bubbles to concrete improves pumpability and resistance to frost attack [156,158]. The mixed and pre-foaming techniques are the most widely used for air entrainment [159].
Comparison of the Impact of Protein Preparation and Modern Factory-Produced Admixture on the Air Entrainment Structure of Cement Paste: Modern and Historical Aspects
Published in International Journal of Architectural Heritage, 2020
Krzysztof Zielinski, Jozef Jasiczak, Przemysław Knast
In the 20th century in U.S., the addition of animal blood to concrete was also considered as an airing agent, ensuring frost resistance of the structure. The beneficial effect of animal organic additives as ox-blood and crusher oil or from works where beef tallow was used as a grinding aid which would have had the effect of entraining air on the properties of highway concretes was discovered quite accidentally in the 1930s. It was noted that certain sections of road that had better frost durability had been made with cement which had been contaminated by this additives. The improved durability was linked to the air-entraining effect of the blood, oil or tallow and this initiated experiments which led to the adoption of deliberate air entrainment to improve the resistance of roads and bridges to freezing and thawing and to the effects of de-icing salts. Whatever the reason, the use of air entrainment has become the accepted means of providing concrete with adequate resistance to freezing and thawing (US Bureau of Reclamation 1956).
Early Age Deflections in Newly Rehabilitated Steel Girder Bridges Made Composite with Concrete Slabs
Published in Structural Engineering International, 2019
Hema Jayaseelan, Bruce W. Russell, Alanna Corelle Webb
The concrete mix design conformed to the Class AA specifications contained in the construction specifications of ODOT. ODOT concrete mix design proportions are shown in Table 1. Cement conforming to ASTM C150,5 Type I/II was used for the concrete. Locally available aggregates were used. The coarse aggregate is a crushed limestone from a quarry near Drumright, Oklahoma that conforms to ASTM C33,6 #57 gradation. The fine aggregate also conforms to ASTM C33 and is known locally as “Guthrie sand” used in commercial concrete. The concrete was batched locally and delivered to the Cooper Lab for placement. The concrete mix targeted 5% air content and was achieved using an air entrainment agent. To ensure workability and ease of placement and finishing, a concrete slump of 178 to 203 mm was specified and achieved using both normal range and high range water reducing agents. The minimum 28-day specified compressive strength (f’c) for the ODOT Class AA concrete is 28 MPa.