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Title:Optimization of cellular concrete for impact-resistant infrastructure
Author(s):Clark, Jamie V
Director of Research:Lange, David A
Doctoral Committee Chair(s):Lange, David A
Doctoral Committee Member(s):Popovics, John S; Jasiuk, Iwona M; Garg, Nishant; Kurtis, Kimberly E
Department / Program:Civil & Environmental Eng
Discipline:Civil Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Cellular concrete
Cellular solids
Microstructural characterization
Abstract:Cellular concrete is an intentionally low strength, low density (300-1400 kg/m3) construction material with a cellular structure that has proven useful in the development of impact-resistant infrastructure such as explosion barriers in mines and military engineering projects as well as aircraft arresting systems. Like other cellular solids, energy absorbed during crushing is defined by the load-deformation response curve, in which a plateau is indicative of crushing behavior at a near-constant load. At the microstructural level, the energy absorbed from crushing is a combination of elastic buckling, plastic yield, and brittle fracture of the cellular microstructure. Therefore, the optimization of this cellular structure (e.g., bubble size and distribution) is paramount to the overall performance of these systems. Currently, however, the design of this material is largely an iterative process that can have adverse effects on the quality, reliability, and cost of impact-resistant infrastructure. The goal of this research is to inform better design of impact-resistant infrastructure by identifying cellular concrete microstructures which lead to optimal energy absorption in low-velocity impact events (e.g., automotive crashes). Specifically, this work explores a gap in the existing literature regarding the development of cellular concrete microstructures capable of effective energy absorption. Commercial foaming agents with varying interfacial properties were used to create cellular concrete samples at densities ranging from 20-60 % of the cementitious base. X-ray computed tomography investigations were implemented to quantify the three-dimensional nature of the resulting cellular concrete microstructures. Additionally, investigations of the hydration kinetics and early age properties of the cementitious base were completed to study the interaction between the amphiphilic surfactant molecules, which are the surface-active components of the commercial foaming agents, and cement grains. The effects of the observed microstructural variations on the mechanical properties of cellular concrete were investigated under quasi-static loading and low-velocity impact events. The experimental investigations show that independent of density, the cellular concrete microstructure can be controlled by foaming agents and that these microstructural variations influence the energy absorption capability of cellular concrete at densities below 1000 kg/m3. This builds on existing cellular concrete literature, which shows the mechanical properties are primarily controlled through the relative density of the material (i.e., foam content). Given the range of cellular concrete microstructures identified in this study, a new micromechanical model was developed to link the microscopic properties of cellular concrete with constitutive behaviors. Preliminary results are promising, demonstrating that it is possible to capture the effects of microstructural variation through numerical modeling efforts. Although this study focuses on cellular concrete, the findings are broadly applicable to other cellular solids that behave in a similar manner. Thus, this work has the potential to aid in the design of cellular ceramics, metals, and plastics for a variety of applications, including lightweight scaffolding, cushioning, filtration, insulation, and other crushable energy absorbers.
Issue Date:2020-11-23
Rights Information:Copyright 2020 Jamie Clark
Date Available in IDEALS:2021-03-05
Date Deposited:2020-12

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