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A description is given of a series of tests and test results from an investigation of the mechanical properties of structural-grade lightweight and normal-weight concretes. The major part of the work was planned to obtain comparative values of compressive creep, drying shrinkage, strengths, and moduli of elasticity for concretes made with 24 lightweight and 5 natural, normal-weight aggregates and having the same nominal strength at the time the specimens were placed under load. Data are presented from a total of 76 different concretes which show that there is a wide range in values of the mechanical properties of concretes of the same nominal compressive strength. It is shown that relatively high values of creep and drying shrinkage are not always associated with lightweight concretes and that, in fact, some lightweight concretes have practically the same mechanical properties as some normal-weight concretes. In addition to environmental conditions, the two major factors affecting the creep of concrete appear to be the ratio of the applied stress to the strength at the time of loading, and the aggregate used. Curing conditions, type of cement, mix proportions, and several other variables appear to affect the creep chiefly insofar as they affect the stress-strength ratio. It was observed that the creep at the age of two years can be estimated from the 90-day results with reasonable accuracy. (Author).
CREEP, SHRINKAGE AND DURABILITY MECHANICS OF CONCRETE AND CONCRETE STRUCTURES contains the keynote lectures, technical reports and contributed papers presented at the Eighth International Conference on Creep, Shrinkage and Durability of Concrete and Concrete Structures (CONCREEP8, Ise-shima, Japan, 30 September - 2 October 2008). The topics covered
Lightweight aggregate concrete is undergoing something of a renaissance. Although this material has been available for many years, only now is it being used more widely. This book provides a comprehensive review of this growing field from an international perspective.
Graphs of the change in input impedance of electrically short dipole antennas in the presence of an isotropic and homogeneous ground are presented, considering four types of antennas: horizontal and vertical, electric and magnetic dipoles.Curves of the change in both the input resistance and reactance are shown for a wide range of values of the frequency, antenna height above the ground, and electromagnetic ground constants.(Author).