ASTM C 856 : 1995 : EDT 1

1.1 This practice outlines procedures for the petrographic examination of samples of hardened concrete. The samples examined may be taken from concrete constructions, they may be concrete products or portions thereof, or they may be concrete or mortar specimens that have been exposed in natural environments, or to simulated service conditions, or subjected to laboratory tests. The phrase "concrete constructions" is intended to include all sorts of objects, units, or structures that have been built of hydraulic cement concrete.

Note-A photographic chart of materials, phenomena, and reaction products discussed in Sections 7 through 12 and Tables 1 through 6 are available as Adjunct C856.

1.2 The petrographic procedures outlined herein are applicable to the examination of samples of all types of hardened hydraulic-cement mixtures, including concrete, mortar, grout, plaster, stucco, terrazzo, and the like. In this practice, the material for examination is designated as "concrete," even though the commentary may be applicable to the other mixtures, unless the reference is specifically to media other than concrete.

1.3 Annex A1 outlines an uranyl acetate method for identifying locations where alkali-silica gel may be present. It is a requirement that the substances in those locations must be identified using any other more definitive techniques, such as petrographic microscopy.

1.4 The purposes of and procedures for petrographic examination of hardened concrete are given in the following sections:

Section Qualifications of Petrographers 3 Purposes of Examination 4 Apparatus 5 Selection and Use of Apparatus 6 Samples 7 Examination of Samples 8 Specimen Preparation 9 Visual and Stereomicroscope Examination 10 Polarizing Microscope Examination 11 Metallographic Microscope Examination 12 Report 13

1.5 The values stated in inch-pound units are to be regarded as the standard. The SI units in parentheses are provided for information purposes only.

1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. A specific hazard statement is given in 5.2.10.1.