Diagnosis and Control of Alkali-Aggregate Reactions in Concrete
Aggregates containing certain constituents can react with alkali hydroxides in concrete. The reactivity is potentially harmful only when it produces significant expansion.(1)** This alkali-aggregate reactivity (AAR) has two forms—alkali-silica reaction (ASR) and alkali-carbonate reaction (ACR, sometimes called alkali-carbonate rock reaction, or ACRR). ASR is of more concern than ACR because the occurrence of aggregates containing reactive silica minerals is more common. Alkali-reactive carbonate aggregates have a specific composition that is not very common. Alkali-silica reactivity has been recognized as a potential source of distress in concrete since the late 1930s.(2,3) Even though potentially reactive aggregates exist throughout North America, ASR distress in structural concrete is not common. There are a number of reasons for this:
Test Methods for Identifying the Susceptibility of Aggregate to Alkali Silica Reaction ( ASR ) – An Overview
Concrete is a mixture of cementitious material, aggregate, and water. Aggregate is commonly considered structural filler (Inert), which occupies 60 to 80 percent of the volume and 70 to 85 percent of the weight of concrete, but its role is more important than what that simple statement implies. Aggregate is a necessary component that defines the concrete’s thermal, elastic properties and dimensional stability. The aggregate mineralogical compositioninfluences durability of the concrete. Hence, this paper discuses about various standards for identifying the deleteriously reactive aggregates, selecting appropriate aggregate for using it in making concrete in new construction and appropriate preventive measures to be taken to minimize the risk of expansion, when such aggregates are used in concrete. Several tests methods have been developed to identify aggregates subject to ASR and mitigation but each has its limitations. Keywords-Alkali Aggregate Reaction (ASR), Alkalis, Reactive silica, Moisture
Philosophy of Education
LIST OF FIGURES PREFACE ACKNOWLEDGEMENTS 1 Philosophy of Education Before the Twentieth Century Socrates and Plato Aristotle Rousseau Pestalozzi, Herbart, and Froebel Summary Questions Introduction to the Literature 2 The Philosophical and Educational Thought of John Dewey Dewey's Philosophical Orientation The Meaning and Aims of Education Dewey's Psychology Dewey's Theory of Knowledge Democracy and Education The Place of Subject Matter Dewey Today: An Assessment Summary Questions Introduction to the Literature 3 Analytic Philosophy Philosophical Analysis in Education The Analysis of Teaching Current Analyses of Teaching Summary Questions Introduction to the Literature 4 Continental Philosophy Existentialism Phenomenology Critical Theory Hermeneutics Postmodernism Summary Questions Introduction to the Literature 5 Logic and Critical Thinking Formal Logic Informal Logic McPeck's View of Critical Thinking An Alternative Approach Summary Questions Introduction to the Literature 6 Epistemology and Education Justified True Belief Foundationalism Truth Nonfoundational Theories of Knowledge Epistemology and Education Constructivism Summary Questions Introduction to the Literature 7 Philosophy of Social Science and Educational Research How Does Science Grow? A Debate in Educational Research Some Examples Summary Questions Introduction to the Literature 8 Ethics and Moral Education Pre-Enlightenment Ethics Enlightenment Ethics Utilitarianism Deweyan Ethics Moral Education Cognitive Developmentalism Summary Questions Introduction to the Literature 9 Social and Political Philosophy The Current Debate Justice and Equality in Education Summary Questions Introduction to the Literature 10 Problems of School Reform Equality Accountability Standards Testing Summary Questions Introduction to the Literature 11 Multiculturalism and Cosmopolitanism Multiculturalism Cosmopolitanism The Educator's Dilemma Summary Questions Introduction to the Literature 12 Feminism, Philosophy, and Education Feminist Critiques of Philosophy Epistemology Philosophy of Social Science Ethics Care and Education Summary Questions Introduction to the Literature NOTES BIBLIOGRAPHY INDEX