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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: Early Loading Effects on Bond Strength
Author(s): Craig R. Clark and David W. Johnston
Publication: Journal Proceedings
Appears on pages(s): 532-539
Keywords: anchorage (structural); bond (concrete to reinforcement); bond
stress; concrete construction; cracking (fracturing); creep properties; embed-ment;loads (forces); reinforced concrete; reinforcing steels; slippage.
Abstract:An investigation was conducted to determine the effects of early loading on concrete bond with deformed steel reinforcement. Bond tests were conducted on identical beam end specimens with a 4000 psi concrete mix using 60 ksi reinforcement. The 28 day ultimate bond strength and the concrete bond load-slip characteristics were compared for specimens loaded at one day and maintained for 27 days to specimens only loaded at 28 days and to specimens loaded to ultimate at one day. Three different embedment lengths were tested. The results indicated no detrimental effects on the day ultimate bond strength as a result of the early working stress level of load that was applied at one day. The tests also indicate that such early loading will result in larger permanent deformations due to the increase in slip that takes place during early loading. But the total slip and thus probable deflections that took place at the ultimate loading were very similar to the 28 day loading results without early loading.
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