Petrographic Examination of Aggregates for Concrete

Petrographic examinations are made for the following purposes: 1) To determine the physical and chemical characteristics of the material that may be observed by petrographic methods and that have a bearing on the performance of the material in its intended use, 2) To describe and classify the constituents of the sample, 3) To determine the relative amounts of the constituents of the sample that are essential for proper evaluation of the sample when the constituents differ significantly in properties that have a bearing on the performance of the material in its intended use, and 4) To compare samples of aggregate from new sources with samples of aggregate from one or more sources, for which test data or performance records are available. This guide may be used by a petrographer employed directly by those for whom the examination is made. The employer should tell the petrographer, in as much detail as necessary, the purposes and objectives of the examination, the kind of information needed, and the extent of examination desired. Pertinent background information, including results of prior testing, should be made available. The petrographer's advice and judgment should be sought regarding the extent of the examination.