Doctoral Dissertations

Zemei Wu

Keywords and Phrases

Fiber-Matrix Bond; Mechanical Properties; Microstructure; Nano-Particles; Ultra-High Performance Concrete

Abstract

"The main objective of this study is to provide new insights into enhancing fiber-matrix bond and mechanical properties of ultra-high performance concrete (UHPC). Three main strategies were investigated: 1) use of supplementary cementitious materials; 2) use of nano-particles; and 3) use of deformed fibers. A multi-scale investigation involving the evaluation of non-fibrous UHPC mortar phase (matrix), fiber-matrix interface phase, and then UHPC composite material was undertaken to determine microstructural characteristics, fiber bond to matrix, and key mechanical properties of the UHPC matrix and UHPC. Test results indicate that the incorporation of 10%-20% silica fume effectively improved the fiber-matrix bond and mechanical properties due to increased C-S-H content and decreased porosity. The flexural and tensile strengths of UHPC were found to increase by approximately 15%-30% and 35%-70%, respectively. Optimal nano-CaCO₃ and nano-SiO₂ contents were found to be 3.2% and 1.0%, respectively, by mass of binder. High nano-particle content decreased the fiber-matrix bond and mechanical properties of matrix and UHPC due to the increased porosity and introduction of weak zone at fiber-matrix interface. The use of deformed fibers enhanced bond given additional mechanical interlocking and enhanced friction. Compared to straight fibers, the corrugated and hooked fibers improved the bond strengths by approximately three and seven times, respectively. Such values were three and four times greater for pullout energy. The flexural strengths of UHPC made with 2% corrugated and hooked fibers were enhanced by approximately 10%-30% and 15%-50%, respectively. The tensile/flexural strengths of UHPC can be predicted based on the composite theory given fiber-matrix bond strength, strength of matrix, and fiber characteristics"--Abstract, page iii.

Advisor(s)

Khayat, Kamal

Committee Member(s)

Feys, Dimitri
Ma, Hongyan
Smith, Jeffrey D.
Shi, Caijun

Department(s)

Civil, Architectural and Environmental Engineering

Degree Name

Ph. D. in Civil Engineering

Sponsor(s)

Missouri University of Science and Technology RE-CAST Tier-1 University Transportation Center
National Science Foundation of China

Comments

Financial support from RE-CAST University Transportation Center at Missouri S&T under grant No. DTRT13-G-UTC45, as well as the National Science Foundation of China under project Nos. U1305243 and 51378196

Publisher

Missouri University of Science and Technology

Publication Date

Summer 2018

Pagination

xvi, 190 pages

Note about bibliography

Includes bibliographic references (pages 172-189).

Rights

© 2018 Zemei Wu, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Thesis Number

T 11401

Electronic OCLC #

1051223591

Download

Share

 
COinS