High-performance strain-hardening geopolymer composites with optimized fiber aspect ratio for improving its tensile performance

다국어 초록 (Multilingual Abstract)

This study developed high-strength strain-hardening geopolymer composites (SHGC) containing 2% (by volume) polyethylene (PE) fibers. A high-strength geopolymer matrix with a compressive strength of over 100 MPa was achieved using liquid crystal display glass powder and ground granulated blast furnace slag. To determine the optimum aspect ratio of PE fibers, five different types of PE fibers with aspect ratios ranging from 300 – 900 were considered. The average bond strength of PE fibers in the high-strength geopolymer matrix was 1.55 MPa, similar to that of high-strength cement matrices. The PE fibers with higher aspect ratios were more effective for improving the tensile performance of high-strength SHGC than those with lower aspect ratios, and a robust strain-hardening characteristic with saturated micro-crack patterns was obtained when the fiber aspect ratio exceeded 600. The energy-based pseudo strain-hardening index (\sfrac{J_b^\prime}{J_{tip}}) was found to be 25.3 at a fiber aspect ratio of 600, and it increased to 104.3 with the increase in the fiber aspect ratio up to 900. The best tensile performance tensile strength of 5.73 MPa, strain capacity of 7.58%, and strain energy density of 309.6 kJ/m3 was achieved in the high-strength SHGC reinforced with PE fibers having an aspect ratio of 900.

목차 (Table of Contents)

• TABLE OF CONTENTS i
• LIST OF TABLES iii
• LIST OF FIGURES iv
• ABSTRACT vi
• Chapter 1. INTRODUCTION 1
• 1.1 Background 1
• 1.2 Research purpose 4
• Chapter 2. TEST PROGRAM 7
• 2.1 Chemical and physical properties of materials 7
• 2.2 Mixture proportions and curing method 12
• 2.3 Test setup 14
• 2.3.1 Compressive tests 14
• 2.3.2 Three point bending test using notched beams 16
• 2.3.3 Single fiber pullout test 18
• 2.3.4 Direct tensile test 20
• Chapter 3. TEST RESULT AND DISCUSSION 23
• 3.1 Reaction products of geopolymer 23
• 3.2 Compressive strength and elastic modulus 25
• 3.3 Pullout behavior of single fibers 29
• 3.4 Tensile behaviors 32
• 3.4.1 Effect of the aspect ratio on the tensile behavior 32
• 3.4.2 PSH index 38
• 3.4.3 Crack patterns 44
• 3.4.4 SEM image analysis after the tensile tests 48
• Chapter 4. CONCLUSIONS 50
• REFERENCES 52
• 국문요지 58
• ACKNOWLEDGEMENT 60
• DECLARATION OF ETHICAL CONDUCT IN RESEARCH IN ENGLISH 61
• DECLARATION OF ETHICAL CONDUCT IN RESEARCH IN KOREAN 62