Civil Engineering ETDs

Publication Date

Spring 5-13-2023

Abstract

In recent years, digital manufacturing techniques in the architecture and construction industry have rapidly gained attention, especially with 3D printing, also called additive manufacturing. The use of cement has been common in modern construction and is now being explored for 3D printing. However, due to cement's contribution to approximately 7 percent of global carbon emissions and its high cost, research on sustainable and greener materials has gained attention. Previous studies on alternative construction have examined the mechanical and rheological properties of soil mixes, but not much attention has been given to printability evaluation, shrinkage, and cracking, which can affect the serviceability of 3D-printed components in the long term. This thesis focuses on studying the mix-design of earthen material to address some of the issues concerning printability, shrinkage, and mechanical properties. Firstly, the collected soil from six different locations in Albuquerque was characterized according to Atterberg’s limit (plasticity tests), and the most suitable soil with a high level of clay content was selected. The amount and type of clay were determined by X-Ray Diffraction (XRD) and X-ray fluorescence spectroscopy (XRF) for the specific soil, which passed the preliminary tests. It was found that the soil was rich in silica and aluminum oxide (63% of SiO2 and 15.5% of Al2O3) with the clay minerals kaolinite, nontronite, and Illite. Other than soil, the designed earthen mixes include locally available materials in New Mexico, such as natural stabilizers (i.e., hydraulic lime), natural pozzolana (Tephra Natural pozzolana), biological waste and degradable natural fibers( wheat straw fiber) to achieve carbon-zero construction. Thus, the rheological characteristics (i.e., viscosity, yield stress, and flow table test), hardened properties (i.e., shrinkage, compressive strength, and flexural strength), and printability assessment (i.e., extrudability and buildability) of designed earthen mixes were studied. The presence of nontronite clay mineral in the soil was responsible for causing shrinkages in the test specimens and the addition of lime stabilized the mix, and fibers helped to control the cracks and shrinkage. However, the lime was found to reduce the mechanical performance: compressive strength and flexure. Adding pozzolana to soil mixes improved flowability but resulted in negative outcomes, especially higher thixotropy and deformations for the lowermost filament layer in printed geometry.

Keywords

3D printing, Earthen Materials, New Mexico, Carbon Zero Construction Materials, Sustainable Construction, Clay Minerals, Shrinkage

Document Type

Thesis

Language

English

Degree Name

Civil Engineering

Level of Degree

Masters

Department Name

Civil Engineering

First Committee Member (Chair)

Dr. Maryam Hojati

Second Committee Member

Dr. Rafiqul Tarefder

Third Committee Member

Francisco Uviña-Contreras

Comments

Hi Mayra,

Please let me know if I need to submit it in the word format.

Thank you.

Sincerely,

Shiva Bhusal

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