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Über dieses Buch

This book describes procedures and methodologies used predominantly to obtain a diagnosis of damaged concrete possibly caused by Alkali-Aggregate Reaction (AAR). It has two primary objectives, namely firstly to identify the presence of AAR reaction, and whether or not the reaction is the primary or contributory cause of damage in the concrete; and secondly, to establish its intensity (severity) in various members of a structure. It includes aspects such as field inspection of the structure, sampling, petrographic examination of core samples, and supplementary tests and analyses on cores, such as mechanical tests and chemical analysis. Evaluation of test data for prognosis, consequences and appraisal will be more fully set out in AAR-6.2.

Inhaltsverzeichnis

Frontmatter

Introduction

Diagnosis of damage to concrete in structures caused by Alkali-Aggregate Reaction (AAR) often involves complex processes because of the resemblance of the external characteristics of the damage with those caused by other actions, such as e.g. frost attack or shrinkage. The wide variety of aggregate types used in concrete worldwide, the different reactivity and proportions of the reactive constituents in the aggregates involved and the wide range factors that influence the reaction result in wide variability found in site samples. This makes diagnosis difficult and has sometimes led to subjective or even erroneous interpretations and conclusions.
Bruno Godart, Mario de Rooij, Jonathan G. M. Wood

Alkali-Aggregate Reaction

Alkali-aggregate reaction in concrete is the name given to a group of reactions leading to expansion caused by a chemical reaction between the alkalis contained in the cement paste and certain reactive forms of (usually silica containing) minerals in the aggregates, see Figure 4. The alkalis in the pore solution are derived from the hydration of the cement but may be augmented by alkalis in some aggregates or alkaline salts from the environment [5].
Bruno Godart, Mario de Rooij, Jonathan G. M. Wood

Symptoms of an Expansive Reaction during Routine Inspection

For any existing structure, a routine inspection is ordinarily a starting point of a cyclic process to maintain the safety and reliability of the structure (Figure 9). It is part of an inspection process where detailed inspection and in depth investigation are important actions. This chapter covers review of existing records, field equipment and materials, personnel and expertise and so on. Also some general field symptoms of AAR are given to recognize first signs of AAR.
Bruno Godart, Mario de Rooij, Jonathan G. M. Wood

Confirmation Investigation

When routine inspection results, like examples given in the previous chapter, show indications which could point in the direction of AAR, it is wise decision to bring in the specialists. As these specialists are normally brought in when something odd has been observed, the first step to be taken is to establish what the cause of the ”strange” results is.
Bruno Godart, Mario de Rooij, Jonathan G. M. Wood

Severity Investigation

From the confirmation inspection and its subsequent test results the presense of AAR has either been confirmed or eliminated. Assuming the first outcome, the next step is to investigate the severity of the situation, see Figure 23. One should keep in mind that it is possible that some evidence of AAR may be found in concrete where siliceous material forms part or all of the aggregates, whether or not the concrete has cracked or expanded as a consequence of AAR.
Bruno Godart, Mario de Rooij, Jonathan G. M. Wood

Reporting

The purpose of the report is to present an accurate summary of the results of the investigation and to establish whether or not the damage to the concrete in the structure was caused at least in part by AAR.
Bruno Godart, Mario de Rooij, Jonathan G. M. Wood

Backmatter

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