Air Content
Air Content - Related Videos
01:23
Measurement of Air Content in Concrete
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2024
Air content measurement in concrete is critical for ensuring structural integrity and durability of concrete structures, especially in environments prone to severe weather conditions. Accurate air content analysis optimizes concrete's resistance to freeze-thaw cycles and enhances its workability and strength. Several methods are standardized under ASTM guidelines to measure the air content in fresh concrete, each suitable for different concrete types and conditions. The pressure method,...
09:16
Air-sampled Filter Analysis for Endotoxins and DNA Content
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2016
Two complementary analyses of atmospheric biological particles from air sampled filters are described herein: the extraction and detection of endotoxin, and of DNA.
07:04
Determination of the Glycogen Content in Cyanobacteria
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Cited by 25 •
2017
Here, we present a reliable and easy assay to measure the glycogen content in cyanobacterial cells. The procedure entails precipitation, selectable depolymerization, and the detection of glucose residues. This method is suitable for both wildtype and genetically engineered strains and can facilitate the metabolic engineering of cyanobacteria.
06:16
Determination of Moisture Content in Soil
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2023
Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - The University of Arizona Demonstrating Author: Bradley Schmitz Soils normally contain a finite amount of water, which can be expressed as the “soil moisture content.” This moisture exists within the pore spaces in between soil aggregates (inter-aggregate pore space) and within soil aggregates (intra-aggregate pore space) (Figure 1). Normally this pore space is occupied by air and/or water. If all the pores are occupied by air, the...
02:16
Stereotype Content Model
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2020
The Stereotype Content Model (SCM) was first proposed by Susan Fiske and her colleagues (Fiske, Cuddy, Glick & Xu, 2002; see also Fiske, 2012 and Fiske, 2017). The SCM specifies that when someone encounters a new group, they will stereotype them based on two metrics: warmth—or that group’s perceived intent, and how likely they are to provide help or inflict harm—and competence—or their ability to carry out that objective. Depending on the warmth-competence categorization, a person will feel...
FAQs
Entrained air consists of small, stable bubbles deliberately introduced into concrete, whereas entrapped air remains unintentionally from mixing. This distinction matters because the two forms represent different degrees of mixture control. Identifying whether air is intentional or accidental helps engineers interpret measured air content, adjust mixture design, and evaluate whether the concrete is likely to meet performance requirements.
Air content creates a performance tradeoff in concrete. Increasing the proportion of suitable air can improve workability and help the material resist freeze-thaw cycling, but excessive air reduces compressive strength. Engineers therefore target controlled rather than simply maximum air content, balancing placement behavior and durability against the strength required for a structural or infrastructure application.
The stability of entrained bubbles is important because air content is not judged only by the presence of air. Small, stable bubbles provide the intended concrete behavior, while uncontrolled or excessive air can change density and lower compressive strength. Consequently, engineers monitor the measured proportion as a mixture-design variable rather than treating all air within fresh concrete as equivalent.
Pressure, volumetric, and gravimetric methods provide alternative ways to measure air content in fresh concrete. Each offers a route to quantify the air proportion for engineering control. Applying a measurement approach consistently allows results to support mixture design, quality control, and performance assessment, without treating one named method as universally superior for every engineering situation.
An air-content assessment begins with fresh concrete, because the stated methods are used before the material hardens. The measurement determines the proportion of air present, and that result can then be compared with the mixture-design or quality-control target. Consistent testing is important because inaccurate values could lead engineers to misjudge density, strength, durability, or workability.
Engineers use air-content measurements during mixture design and quality control for concrete in structural and infrastructure applications. The result helps connect a fresh mixture's measured condition with expected properties such as density, compressive strength, workability, and durability. This makes air content relevant both when developing a mixture and when checking whether production remains aligned with intended performance.
Within engineering, air content is especially relevant when concrete must withstand freeze-thaw cycling. Controlled entrained air can improve resistance to that environmental demand, while excessive air can compromise compressive strength. Measuring fresh concrete provides an early control point: engineers can identify whether the mixture's air proportion supports the intended durability-strength balance before relying on the hardened material.