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alkalisilica reaction in concrete understanding cement

PDF Advisory U.S. Department of Transportation Federal

Alkali-silica reactivity (ASR) occurs either in mortar or concrete. A deleterious chemical reaction between hydroxyl (OH-) ions associated with alkalis (sodium and potassium) present in cement or other sources and certain reactive siliceous components that may be present in coarse or fine aggregates, produces a gel.

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Chemical Attack on Concrete - Structural Guide

This nature chemical attack on concrete occur in certain situations as discussed herein. Most of the time aggregates are chemically inert. However, some times, they react with the alkali hydroxides in the concrete. It causes expansion and cracking of the concrete. Na 2 O and K 2 O alkali are present in the cement react with active silica in the

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INFLUENCE OF SIMULTANEOUS CYCLIC LOADING ... - ICAAR

Nov 15,  · Keywords: alkali-silica reaction, ASR, pavement concretes, mechanical pre-damage, external alkali supply 1 INTRODUCTION In recent years the German motorway network has seen an increase in the occurrence of damage to concrete road surfaces which can be attributed to the alkali-silica reaction (ASR). Often this

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Alkali-Silica Reaction and High Performance Concrete

Damage due to alkali-silica reaction (ASR) in concrete is a phenomenon that was first recognized in the U. S. since 1940 and has since been observed in many countries. Despite numerous studies published, the mechanism is not yet clearly understood. Nevertheless, the three major factors in concrete have been identified, i.e., the alkalies

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ALKALI AGGREGATE REACTION IN NZ CONCRETE

to concrete structures needs to be managed during construction by selecting appropriate concrete materials and mix designs. The most common type of AAR is alkali silica reaction (ASR), which occurs with some types of silica minerals found in many of the rock types used as concrete aggregate. ASR is

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PDF Influence of Moisture on Alkali Silica Reaction

alkali silica reaction so as to avoid it in new structures. In this study, focus is placed on understanding how moisture affects the progression of alkali silica reaction, as moisture cannot be eliminated in concrete compared to other prerequisites for alkali silica reaction in concrete.

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Alkali-silica reaction in concrete - ICE Virtual Library

Alkali-silica reaction in concrete. Next > 7.8. Cement and Concrete Association mortar prism test. 7.9. Accelerated mortar prism tests. 7.10. Concrete prism tests. 7.11. Determining the potential for further expansion from concrete cores. Full Text References.

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Elastic Modulus of the Alkali-Silica Reaction Rim in a

The alkali-silica reaction (ASR) is a common durability problem affecting concrete structures. It contains a series of chemical and physical interactions between the reactive silica in the aggregates and the pore solution of the cement paste resulting in a slow, but severe expansive deterioration of the concrete.

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Effect of Alkali-Silica Reaction Expansion Rate and

Jan 01,  · Alkali-silica reaction (ASR) is a major deterioration mechanism that affects the durability of concrete structures. As the slow rate of ASR development and the restrained expansion in field concrete might affect the development of ASR damage, an experimental program was performed to investigate the

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Deleterious processes in concrete - Understanding Cement

In such a concrete, a particular form of sulfate attack known as delayed ettringite formation (DEF) could occur. DEF is often associated with alkali-silica reaction, if susceptible aggregate is also present. Both of these processes induce cracking in the concrete; this may allow water to percolate through the cracks, resulting in leaching.

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Monitoring Alkali-Silica Reaction Significance in Nuclear

Monitoring alkali-silica reaction significance in nuclear concrete structural members Simplified model for the transport of alkali-silica reaction gel in concrete porosity Laurent Charpin, Alain Ehrlacher Journal of Advanced Concrete Technology , volume 12 ( ), pp.1-6

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ASTM C1293 - 20a Standard Test Method for Determination of

4.5 This test method is intended for evaluating the behavior of aggregates in portland cement concrete with an alkali (alkali metal oxide) content of 5.25 kg/m 3 or in concrete containing pozzolan or slag with an alkali content proportionally reduced from 5.25 kg/m 3 Na 2 O equivalent by the amount of pozzolan or slag replacing portland cement. . This test method assesses the potential for

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PDF Cement and Concrete Research

A better understanding of silica dissolution-precipitation reactions at high pH aqueous solutions allows for promotion of favorable (e.g., pozzolanic) reactions and mitigation of deleterious (e.g., alkali-silica) reactions in concrete. In this paper, the kinetics and products of silica glass dissolution are studied as a function of solution

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PDF Alkali-silica Reactivity: an Overview of Research

accelerates alkali-silica reactions. Formation of Friedel's salt and other complex chloride containing salts complicates test results. Part II identifies 10 specific gaps in our knowledge of alkali-silica reactions in concrete that limit our ability to control these reactions or to predict performance of concrete with reactive aggregates.

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PDF) Correlation of Reaction Products and Expansion

Blended cements are effective in controlling the alkali-silica reaction (ASR) expansion by changing the chemical reactions, as well as improving the transport properties of concrete. Several models have been proposed to describe the mechanism by

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PDF Calcined Clay Pozzolan as an Admixture to Mitigate the

The alkali-silica reaction (ASR) is a chemical reaction within concrete between reactive siliceous constituents of coarse aggregates and the alkali hydroxides released during the hydration of a high alkali Portland cement, with an alkali content of over 0.6% [1], in the presence of sufficient moisture 2] [3][. The reaction products of ASR are

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