AASHTO T196
Full Name
AASHTO T196 – Standard Method of Test for Air Content of Freshly Mixed Concrete by the Volumetric Method
Scope
AASHTO T196 is a standard test method used to determine the air content of freshly mixed concrete. This test is essential for quality control in concrete production and construction, as the air content significantly influences the concrete’s workability, durability, and resistance to freeze-thaw cycles.
Key aspects of AASHTO T196:
- Purpose: the volumetric method is a reliable and straightforward way to measure the total air content in freshly mixed concrete, including both entrained and entrapped air. Entrained air, intentionally introduced through admixtures, forms microscopic bubbles that improve freeze-thaw resistance. Entrapped air is unintentionally incorporated during mixing and can vary depending on the aggregate type and mixing process.
- Principle: the method involves filling a container of known volume with a representative sample of fresh concrete. The container is then sealed, and the concrete is agitated to consolidate it. The change in volume due to the release of entrained and entrapped air is measured, and the air content is calculated as a percentage of the total concrete volume.
- Apparatus: the standard specifies the equipment required for the test, including an air meter, a measuring bowl, a strike-off bar, a tamping rod, and other accessories. The air meter is a calibrated device that directly measures the volume change and displays the air content.
- Procedure: AASHTO T196 outlines the step-by-step procedure for conducting the volumetric method, including sample preparation, consolidation, meter operation, and calculations. It also addresses potential sources of error and provides guidance on how to minimize them.
Significance of AASHTO T196:
- Quality control: by measuring the air content of freshly mixed concrete, contractors and producers can ensure that it falls within the specified limits, ensuring the concrete’s durability and resistance to freeze-thaw damage.
- Mix design: the test results can be used to adjust the mix design, primarily by modifying the amount of air-entraining admixture, to achieve the desired air content for specific applications and environmental conditions.
- Acceptance criteria: the air content determined by AASHTO T196 is often used as an acceptance criterion for concrete deliveries to ensure compliance with project specifications.
AASHTO T196 Accredited Laboratory
Applied Testing & Geosciences, LLC is accredited for performing tests using the AASHTO T196 standard.
Our laboratory offers comprehensive concrete testing services, including the determination of air content by the volumetric method according to AASHTO T196. Our experienced technicians utilize calibrated equipment and adhere to strict quality control procedures to provide accurate and reliable results.
Contact us for more information.
Resources
Keywords
air content; volumetric method; freshly mixed concrete; air meter; measuring bowl; tamping rod; strike-off bar; calibration vessel; entrained air; entrapped air; consolidation