Doctoral Dissertations

Abstract

This study explored the potential of using high-calcium class C fly ash (FA) as the main precursor for synthesizing alkali-activated mortar (AAM) suitable for 3D-printed concrete (3DPC) applications. The objective was to broaden the selection of AAMs, designed to suit various printing techniques, including continuous mixing and pumping, large batch mixing, and set-on-demand processes. The study began by assessing the fresh properties of various mixtures, utilizing tests such as open time (OT), initial setting time (IST), immediate axial deformation, and penetration test (PT), to determine the mixtures' extrudability and buildability. The study optimized mixtures with a broad spectrum of cycle times (CT) and OT designed to meet predetermined thresholds for excessive and axial deformations, making them adaptable to diverse 3DPC applications. This was achieved by fine-tuning the ratios of water to fly ash (W/FA), alkali activators to fly ash (Alk/FA), and sodium silicate to sodium hydroxide (SS/SH). The mechanical properties of the various mixtures were evaluated at different CTs. The mixtures underwent 3D-printing and subsequent evaluation. The CT was determined by analyzing the rate of static yield stress evolution and the shear stress resulting from gravity. As the CT increased, there was a noticeable decline in the compressive, pull-off, flexural, and direct shear strengths of 3DPC specimens compared to their monolithic counterparts. Successful 3D-printing was achieved across different alkali-activated mortars (AAMs) at a nozzle speed of 50 mm/s. In conclusion, AAMs offer customization flexibility based on the specific 3DPC technique and the tools available, facilitating adaptability to a range of printing conditions.

Advisor(s)

ElGawady, Mohamed

Committee Member(s)

Kumar, Aditya
Gheni, Ahmed
Feys, Dimitri
Yan, Guirong Grace

Department(s)

Civil, Architectural and Environmental Engineering

Degree Name

Ph. D. in Civil Engineering

Publisher

Missouri University of Science and Technology

Publication Date

Spring 2025

Journal article titles appearing in thesis/dissertation

This dissertation consists of the following four articles, formatted in the style used by the Missouri University of Science and Technology:

Paper I, found on pages 12–42 “Evaluation of Fresh Properties of High Calcium Content Fly Ash-Based Alkali-Activated 3D-Printed Concrete”, has been submitted for publication to ACI Materials Journal.

Paper II, found on pages 43–83 “Mechanical Properties of 3D-Printined Alkali-Activated Class C Fly Ash Concrete”, has been submitted to the Cement and Concrete Research Journal.

Paper III, found on pages 84–117 “Performance of 3D-Printed Alkali-Activated Concrete Utilizing Class C Fly Ash with Extrusion-Based 3D-Printing Technology”, has been submitted to the Construction and Building Materials Journal.

Paper IV, found on pages 118–149 “Utilizing Set-On-Demand Technique for 3D-Printed Concrete-Based Alkali-Activated Mixtures, Presenting Two Approaches”, is currently undergoing review and will be submitted to the Transportation Research Board Journal.

Pagination

xviii, 160 pages

Note about bibliography

Includes_bibliographical_references_(pages 154-159)

Rights

© 2025 Fareh Abudawaba , All Rights Reserved

Document Type

Dissertation - Open Access

File Type

text

Language

English

Thesis Number

T 12493

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