All ETDs from UAB

Advisory Committee Chair

Thomas L Attard

Advisory Committee Members

Cristopher Waldron

Vinoy Thomas

Document Type

Thesis

Date of Award

2018

Degree Name by School

Master of Science in Civil Engineering (MSCE) School of Engineering

Abstract

In this study, the thermal resistance, flexural behavior, and impact resistance via hurricane impact loads of two-wythe precast concrete composite sandwich beams comprised of an intermediate carbon-fiber epoxy inter-facially bonded to a dual Hybrid Matrix Composite (HMC) were investigated as an affordable alternative for enhancing thermal and mechanical (debris-impact and flexural) properties. The study is a precursor to the design of Precast Concrete Sandwich Panels (PCSP). HMC is a chemical reaction between a thermosetting epoxy network and a fast-setting, yet highly reactive, isocyanate-amine system at a pre-polymerized stage. The interfacial reaction of HMC is a function of epoxy curing kinetics, resin viscosity, and polyurea-type, enabling mechanical and thermal behaviors to be aptly modified. Thirteen thin two-wythe (2.5-in per wythe) concrete beams were quasi-statically tested under 4-point loading; twelve HMC specimens were tested for thermal conductivity and resistivity (R-Value); and nine concrete panels were impact-tested, engendering enhanced mechanical and thermal behavior relative to conventional fiber-reinforced composites (FRP) and also to current industry-standard expanded polystyrene (EPS) and extruded polystyrene (XPS) insulation. Test results indicate that panels integrated with HMC designed with a lower-viscosity resin ( = 696 cps) and an epoxy curing time of 0.5 hours, where the epoxy network reacts with an aliphatic polyurea to elicit excellent dual thermal-mechanical performance. In this scenario, energy absorption, and R-value, using a heat flow meter apparatus, were calculated as 7.9 kJ and 4.71 hr∙ft2∙°F/(Btu∙in) respectively. Although thermal resistance (R-value) in counterpart XPS standard insulation systems was found to reach R-4.76 hr∙ft2∙°F/(Btu∙in), strength, energy absorption, and ductility were limited. Furthermore, composite beam action, or the shear transfer mechanism, at service and ultimate conditions in the highest-performing sample was calculated using stiffness and strength methods that elicited 22% and 337% respectively, deducing that HMC is an affordable dual-purpose insulation alternative in the multi-wythe construction of large precast tilt-up walls. A finite element model was developed to simulate PCSPs with HMC intermediate layer materials. indicating enormous potential of HMC as a dual thermal-mechanical system in tilt-up wall constructions.

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