Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Concrete Growth Problems and Remedial Measures at TVA Projects
Most concrete structures are designed and detailed to provide for a volume decrease without excessive cracking. Occasionally, however, a concrete structure exhibits a long-term increase in volume termed concrete growth. Concrete growth may result from a variety of reactions, such as the hydration of unstable oxides included in the concrete mix, or the oxidation of minerals or from an outside attack of sulfates. The most important reaction creating concrete growth is that between minor alkali hydroxides from cement and the concrete aggregates. Two distinctly different harmful reactions have been recognized: the alkali-silicate and alkali-carbonate reactions. Concrete deteriorating from an alkali-aggregate reaction, regardless of the type, develops an obvious network of cracks called pattern or map cracking. These alkali-aggregate reactions and their accompanying concrete growth have presented numerous problems at TVA's Fontana Dam, Chickamauga Dam and lock, and Hiwassee Dam. Much has been learned about alkali-aggregate reaction since 1940. Most harmful reactions can now be prevented in proposed structures by interpreting the results of standard test methods. It is not possible, however, in existing structures to determine how far the growth phenomenon has progressed, how long the effects will have to be dealt with, or what the future effects will be. A program of close surveillance and monitoring is maintained at these projects, and problems are dealt with as they arise. (ERA citation 10:013744)
Concrete Growth Problems and Remedial Measures at TVA Projects
Most concrete structures are designed and detailed to provide for a volume decrease without excessive cracking. Occasionally, however, a concrete structure exhibits a long-term increase in volume termed concrete growth. Concrete growth may result from a variety of reactions, such as the hydration of unstable oxides included in the concrete mix, or the oxidation of minerals or from an outside attack of sulfates. The most important reaction creating concrete growth is that between minor alkali hydroxides from cement and the concrete aggregates. Two distinctly different harmful reactions have been recognized: the alkali-silicate and alkali-carbonate reactions. Concrete deteriorating from an alkali-aggregate reaction, regardless of the type, develops an obvious network of cracks called pattern or map cracking. These alkali-aggregate reactions and their accompanying concrete growth have presented numerous problems at TVA's Fontana Dam, Chickamauga Dam and lock, and Hiwassee Dam. Much has been learned about alkali-aggregate reaction since 1940. Most harmful reactions can now be prevented in proposed structures by interpreting the results of standard test methods. It is not possible, however, in existing structures to determine how far the growth phenomenon has progressed, how long the effects will have to be dealt with, or what the future effects will be. A program of close surveillance and monitoring is maintained at these projects, and problems are dealt with as they arise. (ERA citation 10:013744)
Concrete Growth Problems and Remedial Measures at TVA Projects
J. J. Hammer (Autor:in)
1984
6 pages
Report
Keine Angabe
Englisch
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