ASTM C138/C138M-24a PDF

Full title and description

ASTM C138/C138M-24a — Standard Test Method for Density (Unit Weight), Yield, and Air Content (Gravimetric) of Concrete. This standard specifies a gravimetric procedure for determining the density (unit weight) of freshly mixed concrete and provides formulas and procedures for calculating yield (volume produced from a known batch), relative yield, cement content, and air content. It includes required apparatus, test measure capacities, and notes on units (SI and inch‑pound treated separately).

Abstract

This test method covers the determination of freshly mixed concrete density and the calculation of yield, cement content, and gravimetric air content. It defines yield as the volume of concrete produced from a mixture of known material quantities and specifies apparatus (balance/scale, tamping rod, internal vibrator, cylindrical measure, strike‑off plate, mallet, scoop) and test procedures. The standard treats SI and inch‑pound units independently and includes safety and explanatory notes.

General information

• Status: Active / Current standard.
• Publication date: 1 July 2024 (designated 24a; incorporates amendment dated 6 August 2024).
• Publisher: ASTM International.
• ICS / categories: 91.100.30 — Concrete and concrete products.
• Edition / version: C138/C138M-24a (current edition).
• Number of pages: 6 pages.

Scope

The standard covers measurement of the density (mass per unit volume) of freshly mixed concrete and provides formulas to compute yield (volume produced from a specified batch), relative yield, cement content, and air content on a gravimetric basis. It specifies test equipment and measure capacities, procedures for filling and consolidating the measure (tamping or vibration), mass measurements, and unit conversions when using either SI or inch‑pound units (each system used independently). The document also notes safety and handling considerations for fresh cementitious materials.

Key topics and requirements

• Definitions: density (unit weight), yield, relative yield, cement content, gravimetric air content.
• Required apparatus: calibrated balance/scale, standard cylindrical measures of specified capacities, tamping rod, internal vibrator (where used), strike‑off plate, mallet, and scoop.
• Procedures for sampling freshly mixed concrete, placing and consolidating concrete in the measure (tamping or vibration), striking off, and determining mass of filled measure and empty measure to compute density and yield.
• Formulas to calculate unit weight, yield (absolute and relative), theoretical cement content, and percent air (gravimetric method).
• Separate treatment of SI and inch‑pound units (values in one system are not exact equivalents and must be used independently).
• Notes on measure capacities, correction factors, and basic safety precautions for handling fresh cementitious mixtures.

Typical use and users

Used by concrete testing laboratories, ready‑mix producers, quality control/quality assurance personnel, field technicians, contractors, materials engineers, and inspectors to verify batch yield, check conformity of mixture proportioning, estimate cement content per unit volume, and determine gravimetric air content for fresh concrete. It is commonly applied during production checks, field acceptance testing, and research or development of mix designs.

Related standards

Frequently referenced or complementary ASTM standards include other fresh‑concrete test methods such as ASTM C231 (Air Content of Freshly Mixed Concrete by the Pressure Method), ASTM C173 (Air Content by Volumetric Method), ASTM C31 (Making and Curing Concrete Test Specimens in the Field), ASTM C29 (Bulk Density of Aggregate), and standards on sampling and concrete test procedures. Users should consult the referenced standards section of C138/C138M‑24a for specific cross‑references.

Keywords

concrete; density; unit weight; yield; relative yield; cement content; air content; gravimetric; fresh concrete; test method; ASTM C138/C138M-24a.

FAQ

Q: What is this standard?

A: ASTM C138/C138M‑24a is the ASTM test method that defines a gravimetric procedure for measuring the density (unit weight) of freshly mixed concrete and for calculating yield, relative yield, cement content, and air content.

Q: What does it cover?

A: It covers sampling and measurement procedures, required apparatus and measure capacities, consolidation by tamping or vibration, mass measurements, and the calculation formulas needed to determine unit weight, batch yield, cement content, and gravimetric air content; SI and inch‑pound units are provided but treated independently.

Q: Who typically uses it?

A: Concrete testing laboratories, ready‑mix producers, field QC/QA technicians, contractors, materials engineers, and inspectors use it for production checks, acceptance testing, mix verification, and research.

Q: Is it current or superseded?

A: It is current — published as the 24a edition (effective 1 July 2024) with an update/amendment on 6 August 2024. Users should reference the 24a edition for the latest technical requirements.

Q: Is it part of a series?

A: Yes — C138/C138M is part of ASTM Committee C09’s suite of standards on concrete and concrete aggregates and is commonly used alongside other fresh‑concrete test methods (for air content, sampling, slump, strength, aggregate testing, etc.).

Q: What are the key keywords?

A: density, unit weight, yield, air content, cement content, gravimetric, fresh concrete, ASTM C138/C138M‑24a.