ASTM D5821
Full Name
ASTM D5821 – Standard Test Method for Determining the Percentage of Fractured Particles in Coarse Aggregate
Scope
ASTM D5821 helps determine the percentage of fractured particles, either by mass or count, within a coarse aggregate sample. This information is valuable for several reasons:
- Shear strength: a higher percentage of fractured particles can enhance shear strength in both bound (e.g., asphalt) and unbound (e.g., gravel roads) aggregate mixtures due to increased interparticle friction.
- Surface treatment stability: fractured particles contribute to the stability of surface treatments.
- Pavement surface properties: the angularity of fractured particles improves friction and texture in pavement surface courses.
Understanding key terms is essential for proper application of the standard:
- Fractured face: an angular, rough, or broken surface on an aggregate particle resulting from crushing, other artificial processes, or natural forces. To be considered a fractured face, the surface area must be at least one-quarter of the particle’s maximum cross-sectional area, with sharp or slightly blunted edges (excluding small nicks).
- Fractured particle: an aggregate particle with at least the specified minimum number of fractured faces (typically one or two).
Test procedure summary:
- Sample preparation: the aggregate sample is first sampled and reduced according to ASTM D75 and C702, respectively. It’s then dried and sieved using the 4.75 mm (No. 4) sieve or another specified sieve, as per ASTM C136. For larger aggregates (19.0 mm or greater), a 9.5 mm (3/8 in.) sieve can be used for initial separation. The retained portion is then reduced to a suitable test size.
- Fractured particle assessment: the sample is washed and dried to a constant mass. It’s then spread on a flat surface for individual particle inspection. Each particle is examined to determine if it meets the fractured face criteria (at least 1/4 of the maximum cross-sectional area). The particles are categorized as fractured or non-fractured.
- Calculation: the percentage of fractured particles is calculated by mass or count, as specified, based on the number of fractured particles identified. If the sample was separated using the 9.5 mm sieve, a weighted average percentage is calculated considering the mass of each portion.
- Specification considerations: different specifications may require a specific number of fractured faces per particle and may specify whether the percentage should be calculated by mass or count. If not specified, the criterion is typically at least one fractured face, and the percentage is calculated by mass.
ASTM D5821 plays an important role in:
- Material selection: ensuring the selected aggregate meets project requirements for strength, stability, and surface characteristics.
- Quality control: monitoring aggregate production and ensuring consistent quality.
- Performance prediction: estimating the performance of pavements and other aggregate-based constructions.
ASTM D5821 Accredited Laboratory
Applied Testing & Geosciences, LLC is accredited for performing tests using the ASTM D5821 standard. We provide accurate and reliable results, helping you make informed decisions about your construction materials.
Contact us today to learn more about our testing capabilities and how we can assist with your aggregate testing needs.
Resources
Keywords
fractured particles; fractured faces; crushed particles; crushed aggregate; crushed gravel; aggregate; percentage; mass; count; coarse aggregate; sample; specification; requirements; shear strength; friction