ASTM C128-22 PDF

Overview

ASTM C128-22: Standard Test Method for Relative Density (Specific Gravity) and Absorption of Fine Aggregate provides a unified procedure for determining two critical physical properties of fine aggregates: their relative density (also called specific gravity) and their absorption. Developed by ASTM International, this standard supports the consistent assessment of aggregates used in construction materials, particularly in concrete and bituminous mixes, contributing to quality control and accurate mix design.

This test method measures three types of relative density: oven-dry (OD), saturated-surface-dry (SSD), and apparent. The absorption is determined as the percentage of water absorbed by the aggregate relative to its dry mass. The method is not applicable to lightweight aggregates complying with ASTM C332 Group I.

Key Topics

• Relative Density (Specific Gravity): The ratio of the mass of aggregate particles to the mass of water occupying the same volume as those particles. Commonly reported as oven-dry, saturated-surface-dry, and apparent values.
• Absorption: The increase in mass of aggregate due to water entering the pores, important for determining moisture corrections in concrete and other construction materials.
• Test Procedures: Involves soaking, surface-drying, and oven-drying aggregate samples, followed by accurate measurements of mass and volume using either gravimetric (pycnometer) or volumetric (Le Chatelier flask) methods.
• Sample Preparation: Samples are prepared and conditioned according to defined durations and temperatures to ensure consistent SSD or OD states.
• Use of SI Units: All values are determined using the International System of Units.

Applications

• Concrete Mix Design: Accurately measuring the specific gravity and absorption of fine aggregate is essential for calculating mix proportions by absolute volume, ensuring correct water-to-cement ratio, and predicting concrete strength and durability.
• Bituminous Mixtures: Used in asphalt mix design to determine aggregate volume and void content, affecting material performance.
• Moisture Corrections: Helps establish the correct amount of water to add to a concrete mix by accounting for absorbed and surface moisture in the aggregate, reducing risks of workability or strength problems.
• Quality Control: Enables comparison of aggregate properties from different sources and batches, ensuring compliance with engineering specifications.

Related Standards

• ASTM C29/C29M: Test Method for Bulk Density ("Unit Weight") and Voids in Aggregate - important for distinguishing between aggregate particle density and bulk density inclusive of void spaces.
• ASTM C70: Test Method for Surface Moisture in Fine Aggregate - uses specific gravity data for moisture corrections.
• ASTM C117: Test Method for Materials Finer than 75-μm Sieve in Aggregates by Washing - impacts measured absorption and specific gravity.
• ASTM C1252: Test Methods for Uncompacted Void Content of Fine Aggregate - influenced by relative density measurement.
• ASTM C127: Test Method for Specific Gravity and Absorption of Coarse Aggregate - companion test covering coarse aggregates.
• AASHTO T 84: Specific Gravity and Absorption of Fine Aggregates - closely related procedure from AASHTO.

Practical Value

Using ASTM C128-22 ensures that fine aggregate properties are consistently and accurately measured across the construction industry. This supports reliable mix design, reduces the risk of construction defects, and permits meaningful comparisons between aggregate sources. Standardizing the method for determining relative density (specific gravity) and absorption of fine aggregates underpins the production of high-quality concrete and bituminous mixes for durable infrastructure.

Keywords: ASTM C128-22, relative density, specific gravity, absorption, fine aggregate, concrete mix design, construction materials, aggregate testing, ASTM standards.