Reducing Samples of Aggregate to Testing Size

C702/C702M: Standard Practice for Reducing Samples of Aggregate to Testing Size

Ensuring the accuracy and representativeness of aggregate test results is paramount in construction and infrastructure projects. Even the most sophisticated laboratory analyses can yield misleading data if the initial sample is not properly prepared. ASTM C702/C702M, the "Standard Practice for Reducing Samples of Aggregate to Testing Size," provides the essential, industry-leading methodology to achieve this critical goal, offering engineers and technicians a proven pathway to reliable material characterization.

What is C702/C702M?

ASTM C702/C702M is an authoritative standard practice developed by ASTM International that outlines established procedures for reducing large aggregate samples to smaller, manageable sizes suitable for laboratory testing. Its primary purpose is to ensure that these reduced test samples accurately represent the properties of the original, larger aggregate lot, thereby minimizing variability and enhancing the reliability of subsequent material characterization.

Scope & Purpose

This standard governs the processes and techniques used to decrease the volume of aggregate samples, whether obtained from field sampling or laboratory production, to the appropriate size required for various material property tests. It specifically addresses methods for both fine and coarse aggregates, including procedures for reducing samples that are dry or contain surface moisture. The standard does not cover the initial sampling of aggregates nor the specific procedures for individual laboratory tests themselves, but rather the critical step of sample preparation prior to those tests.

Who Must Comply?

• • Primary audience: Laboratory Technicians, Materials Engineers, Civil Engineers, Geotechnical Engineers, and Construction Inspectors.
• • Industries affected: Construction, Infrastructure Development, Highway Engineering, Building Materials Manufacturing, and Mining.
• • Compliance nature: Recommended for best practice, often mandatory for projects adhering to specific contract specifications or quality control programs.
• • Enforcement: Compliance is typically monitored by project engineers, quality assurance personnel, and accredited testing laboratories.

Key Requirements Overview

• • The standard requires the selection of a method (mechanical splitting, quartering, or miniature stockpile) based on the aggregate type (fine, coarse, or mixed) and its moisture condition.
• • Professionals must ensure that their chosen reduction method minimizes segregation and bias, so the test sample reflects the characteristics of the original, larger sample.
• • Key provisions include detailed procedures for using mechanical splitters with specified chute widths and numbers, and for the meticulous quartering method to achieve a representative sample.
• • The standard emphasizes the importance of maintaining the sample's moisture condition as specified by the intended test method, or adjusting it appropriately before reduction.
• • It also advises caution when dealing with samples that have very few large particles or discrete contaminants, suggesting that in such cases, testing the entire original sample might be more appropriate.

Related Standards & References

ASTM C702/C702M works in conjunction with other essential standards. ASTM D75 ("Practice for Sampling Aggregates") provides the foundational guidance on how to obtain the initial large samples from which C702/C702M reduces. ASTM E11 ("Specification for Woven Wire Test Sieve Cloth and Test Sieves") is critical for defining the sieve sizes used in the characterization of aggregates and is referenced for determining appropriate splitter chute widths. Furthermore, standards like