There is frequently the need to establish the identity of the mix constituents within hardened concrete and sometimes also the mix proportions. Petrographic examination is a direct and effective method of achieving these objectives. Typical causes of the need for such analyses include disputes during construction, materials assessments during the life of a structure for condition or for predicting performance in respect of a change of use and matching constituents for repair concretes. In one region of the United Kingdom, petrographic examination has been adopted as the method for classifying concrete materials during routine building surveys (Stimson 1997; Royal Institution of Chartered Surveyors 2015). A recent introductory guide to the usefulness of concrete petrography was published by the Concrete Society (2010) and Winter (2012a) gives a good summary of the allied technique of scanning electron microscopy (SEM) of cement and concrete.