Brooks Concrete and Masonry Movements

1. Auflage 2014
ISBN: 978-0-12-801767-8
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 612 Seiten

Widely used in the construction of bridges, dams and pavements, concrete and masonry are two of the world's most utilized construction materials. However, many engineers lack a proper understanding of the methods for predicting and mitigating their movements within a structure. Concrete and Masonry Movements provides practical methods for predicting and preventing movement in concrete and masonry, saving time and money in retrofitting and repair cost. With this book in hand, engineers will discover new prediction models for masonry such as: irreversible moisture expansion of clay bricks, elasticity, creep and shrinkage. In addition, the book provides up-to-date information on the codes of practice. - Provides mathematical modelling tools for predicting movement in masonry - Up-to-date knowledge of codes of practice methods - Clearly explains the factors influencing all types of concrete and masonry movement - Fully worked out examples and set problems are included at the end of each chapter

Jeffrey J. Brooks, BSc; PhD; FIMS. Retired. Formerly Senior Lectures & Director of Postgraduate Studies in Civil Engineering at Leeds University. Has over 30 years of experience with over 150 papers as well as several textbooks.

Autoren/Hrsg.

Brooks, Jeffrey

Inhaltsverzeichnis

1;Front Cover;1
2;Concrete and Masonry Movements;4
3;Copyright;5
4;Contents;6
5;Preface;10
6;Acknowledgments;12
7;1 - Introduction;14
8;2 - Classification of Movements;18
8.1;Definition of Terms Used;19
8.2;References;29
9;3 - Composite Models;30
9.1;Concrete Models;31
9.2;Masonry Models;36
9.3;Summary;69
9.4;References;71
10;Chapter 4 - Elasticity of Concrete;74
10.1;Stress–Strain Behaviour;74
10.2;Static Modulus of Elasticity;83
10.3;Dynamic Modulus of Elasticity;89
10.4;Relationship of Modulus of Elasticity with Strength;91
10.5;Poisson's Ratio;100
10.6;References;103
11;5 - Elasticity of Masonry;108
11.1;Stress–Strain Behaviour;108
11.2;Poisson's Ratio;111
11.3;Geometry of Cross-Section;112
11.4;Type of Mortar;114
11.5;Type of Unit and Anisotropy;116
11.6;Unit/Mortar Interaction;125
11.7;Age;129
11.8;Prediction of Modulus of Elasticity of Masonry;129
11.9;Summary;145
11.10;References;147
12;Chapter 6 - Shrinkage of Concrete;150
12.1;Plastic Shrinkage;150
12.2;Swelling/Expansion;151
12.3;Carbonation Shrinkage;153
12.4;Drying Shrinkage;156
12.5;Shrinkage-Compensating Concrete;181
12.6;Autogenous Shrinkage;182
12.7;References;193
13;7 - Shrinkage of Calcium Silicate and Concrete Masonry;200
13.1;Type of Mortar;201
13.2;Type of Unit;205
13.3;Unit Moisture State and Absorption;208
13.4;Geometry of Cross-Section;217
13.5;Anisotropy;224
13.6;Prediction of Shrinkage;224
13.7;Concluding Remarks;231
13.8;References;232
14;8 - Moisture Movement of Clay Brick Masonry;236
14.1;Irreversible Moisture Expansion of Clay Units;236
14.2;Clay Brickwork;253
14.3;Composite Model Prediction;260
14.4;Design Code Guidelines;263
14.5;Concluding Remarks;264
14.6;References;265
15;9 - Enlarged Moisture Expansion due to Cryptoflorescence;268
15.1;Nature of Florescence;268
15.2;Hydration of Cement and Moisture Transfer Across the Brick/Mortar Interface;271
15.3;Factors Influencing Enlarged Expansion;273
15.4;Summary of Cryptoflorescence Mechanism;282
15.5;In-Plane Restraint;282
15.6;Quantification of Creep;288
15.7;Concluding Remarks;291
15.8;References;292
16;10 - Creep of Concrete;294
16.1;Categories of Creep;294
16.2;Factors Influencing Creep in Compression;298
16.3;Creep Recovery;341
16.4;Creep Poisson's Ratio;342
16.5;Tensile Creep;343
16.6;Cyclic Creep;346
16.7;Other Types of Load;353
16.8;References;355
17;11 - Methods of Predicting Elasticity, Shrinkage, and Creep of Concrete;362
17.1;Standard Methods of Prediction from Strength, Mix Composition, and Physical Conditions;363
17.2;Prediction Using Short-term Test Data;392
17.3;Case Study;400
17.4;References;411
18;12 - Creep of Masonry;416
18.1;Historical Background;416
18.2;Influencing Factors;418
18.3;Creep and Cryptoflorescence;437
18.4;Prediction of Creep;439
18.5;Summary;466
18.6;References;467
19;13 - Thermal Movement;470
19.1;Concrete;470
19.2;Masonry;479
19.3;References;485
20;14 - Effects of Movements, Restraint and Movement Joints;488
20.1;Effects of Movements;489
20.2;Restraint and Cracking;493
20.3;Movement Joints;501
20.4;References;522
21;15 - Theoretical Aspects of Creep and Shrinkage of Mortar and Concrete;524
21.1;Structure of Hydrated Cement Paste;524
21.2;The State of Water;528
21.3;Existing Mechanisms of Drying Shrinkage and Creep;532
21.4;Drying Creep Theory;535
21.5;Final Remarks;553
21.6;References;554
22;16 - Testing and Measurement;558
22.1;Methods of Load Application;559
22.2;Measurement of Movement;574
22.3;Standard Methods of Test for Creep Determination;582
22.4;Independent Shrinkage/Moisture Expansion Tests;588
22.5;References;592
23;Author Index;596
24;Subject Index;604

Leseproben

1

Introduction

Abstract

“Concrete and masonry movements” is a compilation of existing and up-to-date knowledge of movements of two traditional construction materials based upon the author's research and teaching and over a period of 30years. It is a reference book that brings together theory and engineering practice with worked examples and is suitable for the practising engineer, research student and undergraduate student studying civil engineering. Each type of movement of concrete and masonry is considered in separate chapters except where behaviour and features are so common that separate treatment is not warranted. The book emphasizes the property of clay brick units exhibiting irreversible moisture expansion which, under some circumstances when combined with mortar to build free-standing masonry, can manifest itself as an enlarged moisture expansion due to the occurrence of cryptoflorescence at the brick/bond interface.

Keywords

Civil Engineers; Concrete movements; Masonry movements; Postgraduate students; Research students; Undergraduate students

“Concrete and masonry movements” is a compilation of existing and up-to-date knowledge of movements of two traditional construction materials, based upon the author's research and teachingover a period of 30years. It is a reference book that brings together theory and engineering practice with worked examples and, consequently, is suitable for the practising engineer, research student, and undergraduate student studying civil engineering.

The presentation is somewhat different because it considers deformation properties of plain concrete and plain masonry together. Structural concrete and masonry containing steel reinforcing bars or prestressing tendons are not included. Conventionally, properties of concrete and masonry have been treated as separate composite materials by their respective professional institutions in spite of having common constituents: cement, sand, and coarse aggregate (brick or block). The theme of the book is to consider each type of movement of concrete and masonry in separate chapters, but to emphasize common features, except where behaviour and features are so common that treatment in different chapters is not warranted. It is the author's belief that the mutual exchange of knowledge in this manner will lead to a greater understanding of the movement properties of both materials.

What is essentially different about the two materials is when the clay brick or block is used as the “coarse aggregate” constituent, because of its behaviour under normal ambient conditions and how it can react with mortar to influence the movement of masonry. The book emphasizes the property of clay brick units exhibiting irreversible moisture expansion, which, under some circumstances, when combined with mortar to build free-standing masonry, can manifest itself as an enlarged moisture expansion due to the occurrence of cryptoflorescence at the brick/bond interface. When occurring in a control wall, this feature appears to increase creep of masonry because of the way in which creep is defined but, in practice, the enlarged moisture expansion is suppressed in masonry provided there is sufficient dead load or external load.

Summaries of all topics discussed are now presented chapter by chapter.

After defining terms and types of movement in Chapter 2, composite models for concrete and masonry are presented for: elasticity, creep, shrinkage or moisture expansion, and thermal movement. A new composite model is developed for masonry. Composite models are useful in understanding how individual components having different properties and quantities interact when combined. The models are applied and verified in other chapters, particularly for masonry, which has the advantage that movement properties of units can be physically measured in the laboratory. With concrete, this approach is not practicable because of the much smaller size of the coarse aggregate, a feature that makes it difficult to measure representative movement characteristics.

An example of the above-mentioned problem is in Chapter 4, which deals with elasticity of concrete. Modulus of elasticity is related to strength empirically because of the difficulty in measurement of aggregate modulus in order to apply theoretical composite models. Short-term stress–strain behaviour in compression leading to different definitions of modulus of elasticity is described together with Poisson's ratio. Main influencing factors are identified and effects of chemical and mineral admixtures are discussed in detail. Relations prescribed by U.S. and European standards are given for estimating modulus of elasticity from strength in tension as well as corresponding relations in compression, but there is a large scatter mainly because of the failure to quantify the influence of aggregate precisely.

Chapter 5 deals with elasticity of masonry and, besides presenting current empirical relations between modulus of elasticity and strength, composite models are tested and developed for practical application. In the first instance, it is demonstrated that modulus of elasticity of units and mortar may be expressed as functions of their respective strengths so that the composite model for modulus of elasticity of masonry can be expressed in terms of unit and mortar strengths. However, a limitation of the theoretical approach is demonstrated in the case of units laid dry, which causes moisture transfer at the unit/mortar bond during construction. This mainly affects the elastic properties of the bed joint mortar phase. However, this effect can be quantified in terms of the water absorption of the unit, which is thus an additional factor taken into account by the composite prediction model.

The different types of deformation arising from moisture movement that occur in concrete are described in Chapter 6. These range from plastic, autogenous, carbonation, swelling, and drying shrinkage, but emphasis is given to autogenous shrinkage and drying shrinkage especially, in view of the recent developments in the use of high strength concrete made with low water/binder ratios, very fine cementitious material, and chemical admixtures. Influencing factors are identified and quantified, such as the effects of mineral admixtures: fly ash, slag, microsilica, and metakaolin, and the effects of chemical admixtures: plasticizers, superplasticizers, and shrinkage-reducing agents. Methods of determining autogenous shrinkage are described and the latest methods of prediction are presented with worked examples.

The drying shrinkage behaviour of calcium silicate and concrete masonry, and their component units and mortar joints, are the subjects of Chapter 7. After considering influencing factors, the importance of the moisture state of the units at the time of laying is emphasized because of its effect on shrinkage of the bonded unit, mortar, and masonry. A mortar shrinkage-reducing factor is quantified in terms of water absorption and strength of the unit. The geometry of the cross section of masonry, quantified in terms of the ratio of its volume to the drying, exposed surface area, is also shown to be an important factor. The main influencing factors are accommodated in the composite models, which are developed for practical use to estimate shrinkage of calcium silicate and concrete masonry. Methods prescribed by Codes of Practice are also presented and their application is demonstrated with worked examples.

Moisture movement of masonry built from most types of clay units behaves in a different manner to other types of masonry and to concrete due to the property of irreversible expansion of clay units, which begins as soon as newly-made units have cooled after leaving the kiln. The effect is partially restrained when units are bonded with mortar since the mortar joints shrink, but the net effect in masonry depends on the type of clay used to manufacture the unit and the firing temperature. In fact, masonry shrinks in the long-term when constructed from a low, expanding clay brick. In Chapter 8, a detailed review of irreversible moisture expansion of clay units is undertaken before proposing a model to estimate ultimate values from knowing the type of clay and the firing temperature. Laboratory methods of measuring irreversible moisture expansion of clay units are given. It is then demonstrated that prediction of moisture movement of clay brick masonry can be achieved successfully by composite modeling.

The phenomenon of enlarged moisture expansion of clay brickwork is the subject of Chapter 9, which occurs in special circumstances when certain types of clay unit are bonded with mortar to create conditions for the development of cryptoflorescence at the interface of the brick/mortar bond. In many instances, the clay units responsible for the phenomena are of low strength, have high suction rate, and are laid dry. The degree of enlarged expansion also depends on in-plane restraint of the masonry and, hence, can be suppressed by wetting or docking units before laying, and ensuring there is sufficient dead load acting on the masonry. Enlarged moisture expansion is of particular relevance in measuring creep of clay brickwork by using laboratory-sized specimens, and recommended test procedures are suggested. The chapter examines the nature of efflorescence, the influencing factors, and the mechanisms involved.

Chapters 10 and 11, respectively, deal with creep of concrete and standard methods of prediction of creep. Two chapters are allocated because of the number of factors influencing creep, and...