Reviews in Engineering Geology
This is the second in a series of volumes prepared by the Geological Society of America Division on Engineering Geology designed to summarize the states of knowledge on various aspects of the application of geology to engineering problems. Through an unfortunate series of delays, publication of the book was delayed several years beyond the completion of the contained papers. The geologic principles are still sound, however, and are certain to be useful to the practicing engineering geologist. Nine papers review the following subjects: foundations for heavy structures; geology and pedology in highway soil engineering; clay as a canal sealant; Portland cement and concrete; pozzolan; geocryology and engineering; land subsidence due to withdrawal of fluids; land subsidence due to the application of water; and geologic settings of subsidence.
Pozzolans are finely divided siliceous or siliceous and aluminous materials that are by themselves of little or no cementitious value but that react with calcium hydroxide in the presence of water at ordinary temperatures to form cementitious compounds. They include natural materials such as some types of volcanic tuff, opaline chert, shale, or calcined clay and artificial materials such as precipitated silica and some types of fly ash. Pozzolans are used mainly as admixtures in portland-cement concrete, particularly in massive structures, in proportions ranging from 5 per cent to more than the amount of portland cement. Their use may effect reduction in cost of construction, improve workability, decrease permeability, reduce heat of hydration, increase resistance to sulfate waters, and reduce expansion caused by alkali-aggregate reaction. Concrete made with portland-pozzolan cement generally has lower early strength and takes longer to cure than that made only with portland cement, but under favorable conditions it often has higher ultimate strength.