Assessing Physical Characteristics of Concrete Using Digital Image Analysis of Polarized Light Micrographs

Abstract

Image analysis algorithms are often used to identify features of interest in an image and then to count or categorize them. These algorithms can also be used to determine the geometric properties and distribution of features in the image. When concrete is observed in the form of a polished cross-section, several physical characteristics of the material can be determined that have the potential to be quantified using image analysis. These characteristics include the relative quantities of its constituent materials, the air void content, and the freeze-thaw durability of the material. A microscope operator generally estimates these characteristics by making statistical measurements. The air content of the cement paste, for example, is normally measured using the ASTM C-457 test [1], where air voids in the paste are counted by the operator as the specimen traverses linearly beneath the microscope. This procedure is very time consuming and is prone to human error because of the extended viewing periods, (up to four hours), required to complete the test. It is therefore desirable to develop an image analysis procedure that will decrease the amount of time required to complete the test and reduce the inconsistencies that human error can produce. As this paper will detail, a preliminary program for making these types of evaluations has been developed which calculates a durability parameter based on the analyzed physical characteristics.