ASTM C231/C231M-24 PDF
Standard Test Method for Air Content of Freshly Mixed Concrete by the Pressure Method
Standard Test Method for Air Content of Freshly Mixed Concrete by the Pressure Method
- Статус документа:
- Действующий
- Формат:
- Электронный (PDF)
- Количество страниц:
- 10
- Дата публикации:
- 1 января 2024 г.
- Издание:
- C231/C231M
- ICS:
- 91.100.30
SIGNIFICANCE AND USE 3.1 This test method covers the determination of the air content of freshly mixed concrete. The test determines the air content of freshly mixed concrete exclusive of any air that may exist inside voids within aggregate particles. For this reason, it is applicable to concrete made with relatively dense aggregate particles and requires determination of the aggregate correction factor (see 6.1 and 9.1). 3.2 This test method and Test Method C138/C138M and C173/C173M provide pressure, gravimetric, and volumetric procedures, respectively, for determining the air content of freshly mixed concrete. The pressure procedure of this test method gives substantially the same air contents as the other two test methods for concretes made with dense aggregates. 3.3 The air content of hardened concrete may be either higher or lower than that determined by this test method. This depends upon the methods and amount of consolidation effort applied to the concrete from which the hardened concrete specimen is taken; uniformity and stability of the air bubbles in the fresh and hardened concrete; accuracy of the microscopic examination, if used; time of comparison; environmental exposure; stage in the delivery, placement and consolidation processes at which the air content of the unhardened concrete is determined, that is, before or after the concrete goes through a pump; and other factors. SCOPE 1.1 This test method covers determination of the air content of freshly mixed concrete from observation of the change in volume of concrete with a change in pressure. 1.2 This test method is intended for use with concretes and mortars made with relatively dense aggregates for which the aggregate correction factor can be satisfactorily determined by the technique described in Section 6. It is not applicable to concretes made with lightweight aggregates, air-cooled blast-furnace slag, or aggregates of high porosity. In these cases, Test Method C173/C173M should be used. This test method is also not applicable to nonplastic concrete such as is commonly used in the manufacture of pipe and concrete masonry units. 1.3 The text of this test method references notes and footnotes that provide explanatory information. These notes and footnotes (excluding those in tables and figures) shall not be considered as requirements of this standard. 1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. (Warning—Fresh hydraulic cementitious mixtures are caustic and may cause chemical burns to skin and tissue upon prolonged exposure.2) 1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Abstract
Overview
ASTM C231/C231M-24: Standard Test Method for Air Content of Freshly Mixed Concrete by the Pressure Method establishes a widely recognized procedure for determining the air content of freshly mixed concrete using pressure-based instrumentation. This test method is essential in quality control for concrete production and delivery, especially for concrete designed to be durable under freeze-thaw exposure and other environmental stresses. The standard is applicable primarily to concretes with relatively dense aggregates where the aggregate correction factor can be reliably determined.
Key Topics
- Pressure Method Principle: The test relies on observing the change in concrete volume under pressure to determine the air content. This volume change is directly related to the percentage of entrained and entrapped air in the mix.
- Applicability: The method is intended for concretes and mortars made with dense, non-porous aggregates. It is not suitable for lightweight aggregates, highly porous aggregates, air-cooled blast-furnace slag, or nonplastic concrete. For these materials, alternative test methods like ASTM C173/C173M should be used.
- Aggregate Correction Factor: A critical aspect of this method is the correction for any air that might be present within aggregate particles. Accurate determination requires calculation and periodic verification of this factor.
- Precision and Calibration: The method outlines strict requirements for calibration of the pressure meters and other apparatus to maintain accuracy and reliability of test results.
- Safety Considerations: Users must be aware of the caustic nature of fresh cementitious mixtures and are responsible for appropriate health, safety, and environmental practices.
Applications
- Quality Control for Concrete Production: Regular testing with ASTM C231/C231M is vital in ready-mix plants, precast facilities, and on construction sites to verify that air content meets the specified range for durability and workability.
- Durability Assurance: Adequate air content is essential for concrete exposed to freeze-thaw cycles or aggressive environments. The method ensures that air-entrained concrete has the necessary void system for enhanced durability.
- Comparative Validation: The pressure method provides results comparable to other accepted methods (such as gravimetric and volumetric) for concretes made with dense aggregates, supporting integrated quality programs and conformance to project specifications.
- Field and Laboratory Use: The test can be performed both in the field and laboratory settings, making it versatile for various points during the construction process, from batching to placement.
Related Standards
- ASTM C138/C138M - Standard Test Method for Density (Unit Weight), Yield, and Air Content (Gravimetric) of Concrete
- ASTM C143/C143M - Standard Test Method for Slump of Hydraulic-Cement Concrete
- ASTM C172/C172M - Standard Practice for Sampling Freshly Mixed Concrete
- ASTM C173/C173M - Standard Test Method for Air Content of Freshly Mixed Concrete by the Volumetric Method
- ASTM C31/C31M - Standard Practice for Making and Curing Concrete Test Specimens in the Field
- ASTM C192/C192M - Standard Practice for Making and Curing Concrete Test Specimens in the Laboratory
- ASTM C1758/C1758M - Practice for Fabricating Test Specimens with Self-Consolidating Concrete
Practical Value
Utilizing ASTM C231/C231M-24 ensures consistent, accurate measurement of air content in concrete, a key parameter in achieving optimal durability and service life for concrete structures. The standard supports material producers, contractors, and testing laboratories in maintaining compliance with project requirements and regulatory standards. By following established calibration, operation, and reporting procedures, users can trust test results to inform production decisions and quality assurance activities, ultimately contributing to the reliability and resilience of concrete infrastructure.
Primary keywords: ASTM C231/C231M-24, air content, freshly mixed concrete, pressure method, concrete testing, aggregate correction factor, calibration, concrete durability, quality control Secondary keywords: dense aggregate, air-entrained concrete, standard test method, pressure meter, concrete standards, field testing
Технические детали
- Технический комитет
- C09 - Concrete and Concrete Aggregates
- SKU
- ASTM C231/C231M-24
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