Advances in concrete technology over the past several years have led to the practical use of concrete with a low water/cement (w/c) ratio. The high strength and low permeability of these mixes make them a logical choice for structural members applied under conditions where durability is considered a key issue. Unfortunately, concretes at low w/c are prone to cracking at early age unless special precautions are taken. Because these mixes have relatively low water content and, therefore, less drying shrinkage, experts have had to look elsewhere for an explanation. During the last decade attention has focused on a well-established, but little-known phenomenon: autogenous shrinkage.