Doctoral Dissertations

Eslam Gomaa

Keywords and Phrases

Alkali-activated Concrete; Class C; Compressive Strength; Fly Ash; Repair; SEM

Abstract

“This study has investigated the feasibility of using locally available fly ashes (FAs) to synthesize alkali-activated concrete (AAC) for different structural and repair applications. Using AAC made of 100% FA reduces global CO2 emissions, saves energy, and decreases raw material consumption during the production process of ordinary Portland cement. Class C FAs, sourced from Labadie, Jeffery City, Kansas City, Thomas Hill, and Sikeston power plants in the state of Missouri, were used to synthesize the AAC. Sodium silicate (SS), Na2SiO3, and sodium hydroxide (SH), NaOH were used as the alkali activators. Slag, crumb rubber, and air-entraining admixture were used as additives to improve the durability of the AAC. Mixing procedure, water/FA, Alk/FA, SS/SH, curing regime, fresh properties, mechanical properties, durability, and repair applicability of the AAC were studied. A conventional concrete (CC) mixture was prepared for comparison purposes. Three curing regimes (oven, ambient, and moist) were applied to the AAC.

This study revealed that AAC can be used as a replacement for CC. AAC showed good workability and adequate compressive strength for structural applications ranging from 3,660 psi to 7,465 psi based on the curing regime and source of FA. Some AAC mixtures successfully passed 300 cycles of freeze and thaw per ASTM C666-15 procedures A and B. AAC also presents higher corrosion resistance compared to CC. AAC mixtures have a low to moderate permeability and chloride ion penetrability, while the CC mixture showed a high permeability and chloride ion penetrability. Finally, AAC can be used as a repair material for existing concrete structures. The bond between AAC as a repair material and CC as a host material was adequate and comparable to the bond between CC and CC”--Abstract, page iv.

Advisor(s)

ElGawady, Mohamed

Committee Member(s)

Feys, Dimitri
Yan, Guirong Grace
Wu, Chenglin
Kumar, Aditya

Department(s)

Civil, Architectural and Environmental Engineering

Degree Name

Ph. D. in Civil Engineering

Comments

The author extends gratitude to who made this work possible through financial contributions including Missouri Department of Transportation (MoDOT), Missouri Department of Natural Resources (MoDNR), and Ameren Corporation.

Publisher

Missouri University of Science and Technology

Publication Date

Spring 2022

Journal article titles appearing in thesis/dissertation

  • Fresh Properties and Compressive Strength of High Calcium Alkali Activated Fly Ash Mortar
  • Mechanical Properties of High Early Strength Class C Fly Ash-Based Alkali Activated Concrete
  • The Relationship between Microstructure and Strength Development of High Calcium Fly Ashes Based Alkali Activated Concrete Under Different Curing Regimes
  • Bond Strength of Eco-Friendly Class C Fly Ash Based Alkali-Activated Concrete to Portland Cement Concrete
  • Interface Bond Strength for Repair of Ordinary Portland Cement Concrete and Ambient-Cured Alkali-Activated
  • Durability of Class C Fa-Based Alkali-Activated Concrete

Pagination

xxiv, 269 pages

Note about bibliography

Includes bibliographic references.

Rights

© 2022 Eslam Yehia Mohamed Elsayed Gomaa, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Thesis Number

T 12111

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