The microstructure of dry concrete products

In North America, the use of dry concrete products has significantly expanded over the past decades. Despite the growing interest in these materials, little is known of their microstructure. In order to obtain more information on the subject, the microstructure of various dry concretes was investigated by means of optical microscopy, scanning electron microscopy, and mercury intrusion porosimetry, and compared to that of ordinary concretes. The results indicate that the cement paste fraction of most dry concretes is generally much more heterogeneous than that of ordinary concretes. High-energy mixing and the use of mineral additives, such as silica fume and fly ash, were found to significantly enhance the homogeneity of the cement paste. Considerable improvements of the engineering properties of dry concretes can be achieved by using these additives.