INSIDE THE LAB AND OUT, CONCRETE IS MORE THAN IT'S CRACKED UP TO BE

摘要

The article notes the history of concrete, points out its importance in infrastructure construction, and describes recent developments in concrete technology including instruments and devices for monitoring its performance. It is noted that the current value of the nation's concrete-based structures exceeds $6 trillion, and that 10% of federal roads require immediate repair or replacement. The composition and structure of concrete is explained, and its history in the United States is traced. The process of concrete mixing and the occurrence of flaws, the effects of water, pollution, alkali-aggregate reaction, steel reinforcement, electric currents, and salt are described. The impact-echo device for detecting flaws in concrete is described, as well as equipment for simulating earthquake effects. Research in advanced concrete technology is described. Fiber reinforced (steel, glass, polypropylene, carbon) is described, as well as high performance concrete. Precast, prestressed concrete, and the use of robots in advanced concrete manufacturing factories are also described.