Petrography is the section of geology dealing with description and classification of rock. But Petrography technique can also be used to impact sample of concrete in the laboratory. A standard practice is describe in ASTM C 856 and description of microscopic method is given in concrete society technical report no 32.

Area in which microscopic method found to be useful include.

A) Identification of mixing ingredient including coarse and fine aggregate type, cement type, pulverized fuel ash and ground granulated blast furnace slag.

B) Assessment of mix proportion and air void content.

C) Investigation of various durability problem including carbonation, alkali aggregate reaction, fire damage and chemical attack.

Petrographic technique can be used in a quantitative way of asses the original mix proportion. Two method using either point counting or linear traversing of polish section are commonly employed. The basic principal of both method are describe in ASTM 457 in relation to the determination air void content and bubble size and spacing. In each of the method polished specimen is placed on hand or motor driver stage which can be move in two direction at right angles using either of these method the volume metric percentage of each of the component can be determine. With measurement of some parameter the cement content.