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Specifications and Protocols for Acceptance Tests of Fly Ash Used in Highway Concrete

项目名称：	Specifications and Protocols for Acceptance Tests of Fly Ash Used in Highway Concrete
摘要：	Fly ash--a byproduct of coal combustion--is widely used as a cementitious and pozzolanic ingredient in hydraulic cement concrete. The use of fly ash in concrete is increasing because it improves some properties of concrete and often results in lower cost of concrete. However, the chemical and physical compositions of fly ash influence constructability, performance, and durability and may contribute to problems, such as cracking and alkali-silica reactivity in concrete pavements, bridge decks, and other highway structures. Regulatory requirements have also contributed to changes in fly ash properties that may adversely affect concrete performance. In addition, current specifications and test methods do not adequately characterize fly ash properties, address the effects of fly ash characteristics on fresh and hardened concrete properties, or consider the alkali content of the cement. For example, carbon content of fly ash is not usually determined directly, but is often assumed to be approximately equal to the loss on ignition (LOI). Such inadequate characterization may lead to unwarranted restrictions on the use of suitable materials. Although a great deal of research has been performed on the effects of fly ash characteristics on concrete properties, the research has not dealt with the applicability of current specifications to the fly ashes that currently are produced. In addition, existing test methods for sampling and testing fly ash used in concrete do not adequately address the characterization of fly ash or the performance aspects of highway concrete. Further research is needed to develop recommendations for improving fly ash specifications and test protocols and thus help highway agencies better evaluate and use fly ash that will provide acceptable structural performance and durability. The objective of this research is to recommend potential improvements to specifications and test protocols to determine the acceptability of fly ash for use in highway concrete.
状态：	Completed
资金：	749125.00
资助组织：	Federal Highway Administration<==>American Association of State Highway and Transportation Officials (AASHTO)<==>National Cooperative Highway Research Program
项目负责人：	Hanna, Amir N
执行机构：	Michigan Technological University, Houghton
开始时间：	20070716
实际结束时间：	20120914
主题领域：	Bridges and other structures；Highways；Pavements；I30: Materials