Symbols and Abbreviations 10 
1 Introduction 16 
1.1 Motivation 16 
1.2 Overall Objectives 17 

2 State of the Art 21 
2.1 Fiber-Reinforced Concrete Composites—General Aspects 21 
2.2 Polymer Fibers in Strain-Hardening Cement-Based Composites 25 
2.2.1 Properties of Polymer Fibers 25 
2.2.2 Polymer Fibers in Concrete Composites 27 
2.3 Polypropylene Fibers 29 
2.3.1 Chemical Structure of Polypropylene 29 
2.3.2 Melt-Spinning and Core/Shell Bicomponent Melt-Spinning Process 30 
2.4 Surface Modification of Polyolefin Fibers to Enhance the Fiber-Matrix Adhesion in Fiber-Reinforced Cement-Based Composites 35 
2.4.1 Surface Chemical Modification of Fibers 35 
2.4.2 Incorporation of Fillers onto the Surface of Fibers 35 
2.4.3 Exploring Fiber Manufacturing with Varied Configurations 37 
2.5 Fiber Recycling and Environmental Impact 38 
2.6 Low-Cement Content and Alternative Binders 40
 
3 Materials 42 
3.1 Material Selection 42 
3.1.1 Types of Polypropylene 42 
3.1.2 Types of Fillers 42 
3.2 Commercial Monocomponent PP Fibers 44 
3.3 Mixture Design Mineral Binders 45 
3.3.1 Cement-Based Composite 45 
3.3.2 LC3-Based Composites 47 

4 Methods 49 
4.1 Raw Materials Analysis  49 
4.1.1 Confocal Laser Scanning Diffractometer 49
4.1.2 High-Temperature Size Exclusion Chromatography 49 
4.1.3 Rheological Analysis 50 
4.2 Designing Bicomponent PP Fibers 51 
4.2.1 Pretested Fiber Manufacturing 51 
4.2.1.1 Micro Compounding 51 
4.2.1.2 Piston Melt-Spinning Equipment and Offline Drawing 51 
4.2.1.3 Core/Shell Diameter Calculation of the Fibers 55 
4.2.2 Upscaled Fiber Manufacturing 56 
4.2.2.1 Melt-Compounding 56 
4.2.2.2 Pilot Melt-Spinning Equipment and Online Drawing 56 
4.3 Characterization of Single PP Fibers 58 
4.3.1 Morphology Analysis of Surface and Cross-Sectional Areas 58 
4.3.1.1 SEM-EDX 58 
4.3.1.2 Confocal Microscopy 59 
4.3.2 Tensile Test 59 
4.4 Mechanical Testing of Composite Materials 60 
4.4.1 Micro Scale—Single-Fiber Pull-Out Test 60 
4.4.1.1 Single-Fiber Embedment Technique 65 
4.4.1.2 Sample Preparation—Quasi-Static Pull-Out Test 66 
4.4.1.3 Sample Preparation—Dynamic Pull-Out Test 67 
4.4.2 Macro Scale—Fiber-Reinforced Concrete Composites 69 
4.4.2.1 Sample Preparation 69 
4.4.2.2 Compression Test 70 
4.4.2.3 Flexural and Quasi-Static Uniaxial Tension Tests 70 
4.4.2.4 Digital Image Correlation Postprocessing 71 

5 Results and Discussion 72 
5.1 Raw Materials 72 
5.1.1 Particle Size Distribution 72 
5.1.2 Molecular Weight Distribution Analysis 73 
5.1.3 Rheological Analysis 75 
5.1.3.1 Viscosity Analysis  75 
5.1.3.2 Thermal Analysis 76 
5.2 Single PP Fibers 78 
5.2.1 Pretested Bicomponent Polypropylene Fibers  79 
5.2.1.1 Core/Shell Ratio Optimization 79 
5.2.1.2 Throughput Optimization 82 
5.2.1.3 Die Size and Elevated Filler Amount Optimization 83 
5.2.2 Upscaled Bicomponent Polypropylene Fibers 90 
5.2.2.1 Optimization of Spinning Parameters 90 
5.3 Mechanical Behavior of Composite Materials 96 
5.3.1 Micro Scale—Single-Fiber Model Composites 96 
5.3.1.1 Failure Mode and Interfacial Bond at Low Strain Rate 96 
5.3.1.2 Failure Mode and Interfacial Bond at High Strain Rate 101 
5.3.2 Macro Scale—Mechanical Tests 106 
5.3.2.1 Compression Test 106 
5.3.2.2 Flexural and Uniaxial Tensile Tests 107 
5.3.2.3 Examination of Cracked Cross Sections 112
 
6 Conclusion and Future Prospects 113 
6.1 Conclusion of the Investigation Program 113 
6.2 Outlook 114 
6.2.1 Material Level 114 
6.2.2 Fiber Level 115 
6.2.3 Composite Level 116 

Bibliography 118 

Appendix 131 
Micro Scale Analysis 131 
A. Particle Size Distribution 131 
B. Molecular Weight and Polydispersity Index 131 
C. Viscosity Analysis 131 
D. Thermal Analysis 132 
E. Diameter and Roughness Analysis 133 
F. Density Analysis 134 
G. Tensile Test 134 
H. Quasi-Static Pull-Out Test 136 
I. Dynamic Pull-Out Test 137 
Macro Scale Analysis 138 
J. Compression Tests 138 
K. Bending and Tensile Tests 139