Civil Engineering ETDs

Publication Date

Fall 12-16-2023

Abstract

The time-dependent rheological and early-age strength parameters of Polymer concrete (PC) were investigated. PC flow decreased, and the static yield stress and thixotropy increased as the specimen aged, while the dynamic yield stress remained unchanged. The study found that the Herschel-Bulkley model can accurately describe the PC’s rheological behavior over time. The change in cohesion strength and internal friction angle over time was observed using uniaxial unconfined compression and direct shear tests of fresh PC. A time-dependent MohrCoulomb failure criterion was established. Temperature analysis was used to determine the gel time and explain the evolution of the time-dependent early-age strength of PC.

To simulate 3D printing of PC, two finite element models were created. These models, one axisymmetric and one 3D, differed in their layer addition methods. These models provided insights into optimizing construction durability. Both models highlighted elastic buckling as the main failure mode, becoming more pronounced with added layers. The 3D model's mesh studies suggested a maximum print height of nine layers before buckling initiated.

Euler's buckling theory was used to estimate buildability, but it overestimated by 320%, mainly due to idealized structural assumptions and material elasticity. Real 3D-printed structures exhibit inconsistencies, with factors like vibrations, deposition speed, and printing strategies impacting outcomes. The study observed consistent elastic buckling failures by the tenth layer in actual printing tests. Comparatively, theoretical and experimental results aligned closely. Overall, the research emphasizes the significance of balancing theoretical models with real-world 3D printing challenges.

Keywords

Early-age strength, Rheology, Polymer concrete, 3D Printing, Mechanical properties, Gelation time, Finite element Modeling, Experimental validation, Elastic buckling

Sponsors

Dana C. Wood Endowment at the University of New Mexico

Document Type

Dissertation

Language

English

Degree Name

Civil Engineering

Level of Degree

Doctoral

Department Name

Civil Engineering

First Committee Member (Chair)

Mahmoud Reda Taha

Second Committee Member

John Stormont

Third Committee Member

Yu-Lin Shen

Fourth Committee Member

Eslam Soliman

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