Partial summary: "To assess the durability of concrete and other materials used in concrete construction when exposed to natural weathering, the Corps of Engineers maintains severe-, mild-, moderate-, and non-weathering exposure stations at various locations in the United States. Specimens from actual structures and experimental specimens in which the amounts or kinds of components are varied are exposed until they fail or until testing is completed, whichever occurs first. The specimens are inspected periodically, and tested to determine their dynamic modulus of elasticity and pulse velocity. [...] Volume 1 contains the active evaluations" (p. ix).