ASTM C295/C295M-19 PDF Download

ASTM C295/C295M-19 is a standard guide that outlines the procedures for conducting petrographic examinations on aggregates proposed for use in cementitious mixtures or as raw materials for the production of such aggregates. The guide serves several purposes, including determining the physical and chemical characteristics of the materials that may impact their performance, describing and classifying the constituents of the sample, and comparing samples from different sources for evaluation purposes.

The guide provides instructions for employers who are commissioning petrographic examinations, emphasizing the importance of communicating the purposes, objectives, and desired extent of the examination to the petrographer. It also suggests that a written agreement be established between the purchaser and the consultant, detailing the kind, extent, and objectives of the examination.

Petrographic examination plays a vital role in evaluating aggregates for concrete. It helps identify chemically unstable minerals, such as soluble sulfates, and volumetrically unstable materials, such as smectites, which can affect the performance of concrete. The examination also focuses on identifying iron sulfide minerals that may oxidize within the concrete, potentially causing popouts, rust staining, or cracking. It assesses the weathering or alteration of aggregates and determines the proportions of various particle shapes, as well as identifies potentially alkali-silica or alkali-carbonate reactive constituents. Additionally, petrographic examination can be used to identify potential contaminants in aggregates that may have undesirable effects on concrete.