by Clayton DeKorne Concrete is a heavy material and any steps taken to make it easier to work with are understandable. Unfortunately, many finishers achieve greater workability by asking the driver to add more water to the mix. When the slab cracks, the blame passes from the contractor to the finisher and, ultimately, to the supplier, who usually winds up shouldering the responsibility. Suppliers go to great lengths to avoid this problem. Most routinely use air-entrainment agents, chemical admixtures that form air bubbles, to help decrease segregation (see "Glossary" at the end of this article for italicized terminology) of the mix. Many automatically add superplasticizers, another type of chemical admixture that retards setting times and produces concrete that flows better. In hot weather,