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Founded in 1904 and headquartered in Farmington Hills, Michigan, USA, the American Concrete Institute is a leading authority and resource worldwide for the development, dissemination, and adoption of its consensus-based standards, technical resources, educational programs, and proven expertise for individuals and organizations involved in concrete design, construction, and materials, who share a commitment to pursuing the best use of concrete.
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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Title: Shrinkage-Cracking Characteristics of
Structural Lightweight Concrete
Author(s): Robert G. McKeen and W. B. Ledbetter
Publication: Journal Proceedings
Appears on pages(s): 769-777
Keywords: cement content; coarse aggregates;concretes; cracking (fracturing) ; curing; evaporation; gravel; lightweight aggregates; lightweight aggregate concretes;reseach;shrinkage;tensile strength;volume change.
Abstract:Tests were conducted to determine the effect of coarse aggregate type, cement content, and curing environment on unrestrained volume changes and restrained shrinkage cracking behavior. Measurements of restrained shrinkage stress and ultimate tensile strength were made for purposes of comparing these properties with the above characteristics. Two synthetic lightweight aggregates, commercially produced in Texas and having widely different saturation characteristics, were used along with a natural siliceous river gravel as coarse aggregates. After a 5 day initial moist curing period, the specimens were placed in four different curing environments. Unrestrained volume changes were measured on standard type specimens, 3 x 3 x 11.25 in. (7.5 x 7.5 x 28.1 cm). Cracking was evaluated as the number of cracks occurring on a specimen 4 x 4 x 48 in. ( IO x IO x 120 cm) with a #8 reinforcing bar through the center. Using concrete made with one of the lightweight coarse aggregates, specimens were cast for measurement of restrained shrinkage stress. After 60 days, these specimens were loaded to concrete’ failure in tension and ultimate tensile strength was determined. The effective or usable tensile strength was greatly affected by the curing environment. Results indicated that both unrestrained shrinkage and concrete water loss relate to restrained shrinkage stress. Unrestrained shrinkage did not indicate cracking tendency while water loss provided an indication of cracking tendency.
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