Han / Yu / Ou Self-Sensing Concrete in Smart Structures

1. Auflage 2014
ISBN: 978-0-12-800658-0
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 398 Seiten

Concrete is the second most used building material in the world after water. The problem is that over time the material becomes weaker. As a response, researchers and designers are developing self-sensing concrete which not only increases longevity but also the strength of the material. Self-Sensing Concrete in Smart Structures provides researchers and designers with a guide to the composition, sensing mechanism, measurement, and sensing properties of self-healing concrete along with their structural applications - Provides a systematic discussion of the structure of intrinsic self-sensing concrete - Compositions of intrinsic self-sensing concrete and processing of intrinsic self-sensing concrete - Explains the sensing mechanism, measurement, and sensing properties of intrinsic self-sensing concrete

Baoguo Han is Professor of Civil Engineering, Dalian University of Technology, China. His research interests include multifunctional/smart materials and structures, high performance concrete and structures, and nanotechnology in civil engineering.

Autoren/Hrsg.

Han, Baoguo

Yu, Xun

Ou, Jinping

Inhaltsverzeichnis

1;Front Cover;1
2;Self-Sensing Concrete in Smart Structures;4
3;Copyright;5
4;Dedication;6
5;Contents;8
6;Preface;12
7;Chapter 1 - Structures of Self-Sensing Concrete;14
7.1;1.1 Introduction and Synopsis;14
7.2;1.2 Structures of Self-Sensing Concrete at the Macroscopic Level;15
7.3;1.3 Structures of Self-Sensing Concrete at the Microscopic Level;17
7.4;1.4 Summary and Conclusions;23
7.5;References;23
8;Chapter 2 - Compositions of Self-Sensing Concrete;26
8.1;2.1 Introduction and Synopsis;27
8.2;2.2 Matrix Material;27
8.3;2.3 Functional Filler;29
8.4;2.4 Dispersion Material;43
8.5;2.5 Mixing Proportion Design;50
8.6;2.6 Summary and Conclusions;51
8.7;References;53
9;Chapter 3 - Processing of Self-Sensing Concrete;58
9.1;3.1 Introduction and Synopsis;58
9.2;3.2 Mixing/Dispersing;60
9.3;3.3 Molding;70
9.4;3.4 Curing;74
9.5;3.5 Summary and Conclusions;76
9.6;References;76
10;Chapter 4 - Measurement of Sensing Signal of Self-Sensing Concrete;80
10.1;4.1 Introduction and Synopsis;80
10.2;4.2 Types of Sensing Signals;81
10.3;4.3 Electrode Fabrication Method;86
10.4;4.4 Measurement Method of Electrical Resistance;90
10.5;4.5 Acquisition and Processing of Sensing Signal;98
10.6;4.6 Summary and Conclusions;103
10.7;References;103
11;Chapter 5 - Sensing Properties of Self-Sensing Concrete;108
11.1;5.1 Introduction and Synopsis;109
11.2;5.2 Sensing Characteristics under Different Loading Conditions;109
11.3;5.3 Some Factors Affecting Sensing Properties;144
11.4;5.4 Summary and Conclusions;171
11.5;References;172
12;Chapter 6 - Sensing Mechanisms of Self-Sensing Concrete;176
12.1;6.1 Introduction and Synopsis;176
12.2;6.2 Type of Electrical Conduction;177
12.3;6.3 Conductive Mechanism Without Loading;181
12.4;6.4 Conductive Mechanism under External Force;186
12.5;6.5 Constitutive Model of Sensing Characteristic Behavior;191
12.6;6.6 Summary and Conclusions;198
12.7;References;198
13;Chapter 7 - Applications of Self-Sensing Concrete;202
13.1;7.1 Introduction and Synopsis;202
13.2;7.2 Structural Health Monitoring;203
13.3;7.3 Traffic Detection;228
13.4;7.4 Summary and Conclusions;241
13.5;References;242
14;Chapter 8 - Carbon-Fiber-Based Self-Sensing Concrete;244
14.1;8.1 Introduction and Synopsis;245
14.2;8.2 Fabrication of Carbon-Fiber-Based Self-Sensing Concrete;247
14.3;8.3 Measurement of Sensing Property of Carbon-Fiber-Based Self-Sensing Concrete;248
14.4;8.4 Sensing Property and Its Improvement of Carbon-Fiber-Based Self-Sensing Concrete;260
14.5;8.5 Performance of Carbon-Fiber-Based Self-Sensing Concrete Sensors;263
14.6;8.6 Effect of Temperature and Humidity on Sensing Property of Sensors;267
14.7;8.7 Self-Sensing Concrete Components Embedded with Sensors;270
14.8;8.8 Summary and Conclusions;279
14.9;References;281
15;Chapter 9 - Nickel-Powder-Based Self-Sensing Concrete;284
15.1;9.1 Introduction and Synopsis;285
15.2;9.2 Fabrication of Nickel-Powder-Based Self-Sensing Concrete;286
15.3;9.3 Measurement of Sensing Properties of Nickel-Powder-Based Self-Sensing Concrete;289
15.4;9.4 Sensing Mechanism of Nickel-Powder-Based Self-Sensing Concrete;293
15.5;9.5 Effect of Nickel Powder Content Level and Particle Size on Sensing Property of Concrete with Nickel Powder;301
15.6;9.6 Sensing Characteristic Model of Nickel-Powder-Based Self-Sensing Concrete;306
15.7;9.7 Nickel-Powder-Based Self-Sensing Concrete Sensors and Wireless Stress/Strain Measurement System Integrated with Them;312
15.8;9.8 Application of Nickel-Powder-Based Self-Sensing Concrete Sensors in Vehicle Detection;320
15.9;9.9 Summary and Conclusions;323
15.10;References;324
16;Chapter 10 - Carbon-Nanotube-Based Self-Sensing Concrete;328
16.1;10.1 Introduction and Synopsis;329
16.2;10.2 Fabrication of CNT-Based Self-Sensing Concrete;331
16.3;10.3 Measurement of Sensing Signal of CNT-Based Self-Sensing Concrete;333
16.4;10.4 Performances of CNT-Based Self-Sensing Concrete;341
16.5;10.5 Sensing Mechanism of CNT-Based Self-Sensing Concrete;355
16.6;10.6 Application of CNT-Based Self-Sensing Concrete in Traffic Detection;358
16.7;10.7 Summary and Conclusions;369
16.8;References;370
17;Chapter 11 - Challenges of Self-Sensing Concrete;374
17.1;11.1 Introduction and Synopsis;375
17.2;11.2 Smart Concrete;375
17.3;11.3 Stress/Strain Sensing for Concrete;379
17.4;11.4 Challenges for Development and Deployment of Self-Sensing Concrete;383
17.5;11.5 Summary and Conclusions;385
17.6;References;386
18;Index;390

Leseproben

Chapter 2

Compositions of Self-Sensing Concrete

Abstract

The composition of self-sensing concrete determines its structure and sensing properties. Self-sensing concrete consists of matrix material, functional filler, and a material to aid filler dispersion. Generally, all types of concrete can be used as the matrix of self-sensing concrete. By now, more than 10 types of functional fillers and hybrids of several types of fun[ctional fillers have proved effective for enhancing the sensing performance of concrete. These materials are helpful for dispersing functional fillers in a concrete matrix. The selection of composition materials and their mixing proportions is critical in fabricating self-sensing concrete.

Keywords

Composition; Filler dispersion material; Functional filler; Matrix material; Mixing proportion; Self-sensing concrete

Chapter Outline

2.1 Introduction and Synopsis?14

2.2 Matrix Material?14

2.3 Functional Filler?16

2.3.1 Types of Functional Filler?17

2.3.2 Some Representative Functional Fillers?21

2.3.2.1 Steel Fiber?21

2.3.2.2 Carbon Black?23

2.3.2.3 Steel Slag?24

2.3.2.4 Graphite Powder?27

2.3.2.5 Carbon Nanofiber?27

2.4 Dispersion Material?30

2.5 Mixing Proportion Design?37

2.6 Summary and Conclusions?38

References?40

2.1. Introduction and Synopsis

The structure of self-sensing concrete depends to a high degree on the composition of the composites. As a composite, self-sensing concrete consists mostly of matrix materials (i.e., conventional concrete materials) and functional filler. In addition, some auxiliary materials may be necessary to disperse functional fillers into matrix materials. The available composition materials for fabricating self-sensing concrete are varied. Therefore, selection of suitable materials and determination of their proportions are important for fabricating self-sensing concrete. Chapter 2 will introduce the composition of self-sensing concrete (including matrix material, functional filler, materials to aid filler dispersion, and the mixing proportion design), and the relationships between composition materials and the properties of the composites.

2.2. Matrix Material

The matrix material is the component that holds the functional filler together to form the bulk of the composite, so all types of concrete can be used as a matrix for self-sensing concrete. Here, concrete is a generalized concept that includes concrete (containing coarse and fine aggregates), mortar (containing fine aggregates), and paste (containing no aggregate, whether coarse or fine). In previous studies, typical Portland cement concrete (including cement concrete, cement mortar, and cement paste) was most frequently used as the matrix material for self-sensing concrete because Portland cement is the most widely used binder material. Recently, some new types of Portland cement concrete have been chosen as a matrix to develop self-sensing concrete. For example, Hong employed slurry-infiltrated fiber concrete as the matrix to obtain self-sensing concrete with high mechanical properties [1]. Fan used cementitious capillary crystalline waterproofing material as the matrix of self-sensing concrete to combine self-healing waterproofing with self-sensing ability [2]. Hou et al. and Lin et al. incorporated conductive fillers including carbon fiber, steel fiber, and carbon black into the engineered cementitious composite to enhance its self-sensing behavior while maintaining its tensile strain-hardening behavior [3,4]. Besides Portland cement, Cheng et al. tried to adopt sulphoaluminate cement as the binder in making self-sensing concrete [5]. Saafi et al. used geopolymer cement as a binder to fabricate self-sensing concrete with carbon nanotubes [6].

Since the potential application of self-sensing concrete in traffic detection was recognized, the use of asphalt concrete as a matrix to develop self-sensing concrete has increasingly been paid attention. Comprehensive research into intrinsic self-sensing asphalt concrete has been successfully performed [7–15]. In addition, Sett employed polymer concrete as a matrix to make self-sensing concrete [16]. Because previous research focused mainly on the sensing property of self-sensing concrete fabricated with a cement binder, in this chapter, self-sensing concrete refers to cement concrete unless otherwise specified.

Although the concrete matrix has no or poor sensing ability and contributes only slightly to the electrical conduction of the whole composite system, some properties of the concrete matrix have substantial effects on the sensing properties of self-sensing concrete. This is because the sensing ability of self-sensing concrete is strongly related to its mechanical behavior (i.e., stress, strain, damage, etc.) and electrical conduction, whereas the mechanical properties (e.g., ultimate stress and strain, Young’s modulus, and Poisson ratio) of self-sensing concrete depend heavily on the mechanical properties of the concrete matrix. In addition, the type and mixing proportions of the materials chosen as the matrix to prepare concrete also influence the dispersion of functional fillers, the distribution of functional fillers in the matrix, and the mechanical properties of the composites, thus affecting the sensing abilities of the composites. For example, Mao et al. observed that the sensing property of concrete with carbon fiber deteriorates with an increase in the water–cement ratio, and moderate heat dam cement paste with carbon fiber has better sensing properties compared with slag cement with carbon fiber [17]. Chen and Chung stated that the linearity of sensing properties is better for cement mortars containing methylcellulose than those containing hybrid methylcellulose and silica fume or latex [18]. Li [19] and Han et al. [20] suggested that increasing the water cement ratio can improve the self-sensing sensitivity of steel–slag concrete (as shown in Figure 2.1 [21]) and carbon nanotube–cement composites. Two factors contribute to the effect of the water–cement ratio on the sensing sensitivity of self-sensing concrete. One is the deformation capacity of the concrete matrix; the other is the dispersion of fillers in the concrete matrix. Concrete fabricated with a higher water–cement ratio has larger deformation than that fabricated with a lower water–cement ratio at the same compressive stress, so it is easier to change the conductive network in the former. This indicates that the electrical resistance of the composite with a higher water–cement ratio is more sensitive to loading. In addition, a higher water–cement ratio is beneficial for the dispersion of fillers in a concrete matrix [19,20]. Li and Jia observed that an increase in cement strength grade (as shown in Figure 2.2) [21] and the use of a water-reducing agent [19,22] cause a decrease in sensitivity of the steel–slag concrete, because they improve the strength of the concrete matrix and decrease its deformation capacity.

Figure 2.1 Sensing properties of self-sensing concrete containing steel–slag with different water–cement ratios (W/C) [21].

Figure 2.2 Sensing properties of self-sensing concrete containing steel–slag fabricated with different cement strength grades [21].

In addition, typical aggregates are electrically insulating in nature, and they will create some obstacles or cut the electron flow through the conductive network. The adoption of aggregates will decrease the conductivity of self-sensing concrete (as shown in Figure 2.3) [23,24]. Therefore, the concentration level of functional filler must be increased to achieve the expected self-sensing ability when aggregates, especially coarse ones, are included in the composites. All of these examples illustrate that the concrete matrix would affect the deformation capacity and inside conductive network of the composite, thus affecting the sensing property of self-sensing concrete.

2.3. Functional Filler

Functional filler is an essential and critical component of self-sensing concrete, because it dominates the sensing property of the self-sensing concrete. Since the sensing behavior of the self-sensing concrete was first observed, researchers have been trying to find or develop new functional fillers that can endow conventional concrete with high self-sensing performance.

Figure 2.3 Dependence of electrical resistivity of concrete on carbon fiber proportion and gravel–sand ratio [24].

2.3.1. Types of Functional Filler

By now, more than 10 types of functional fillers have proved effective for enhancing the sensing performance of concrete. In addition, a hybrid of two or several types of functional fillers can bring out preferable sensing properties of self-sensing concrete, which cannot be achieved by any of the functional fillers alone. This can contribute to the complementary effect of different functional fillers on the modification of sensing properties. For example, Azhari and Banthia observed that concrete with hybrid carbon fiber and carbon nanotube can provide better signal quality, improve reliability, and increase sensitivity over concrete carrying carbon fiber...