Doctoral Dissertations

Date of Award

12-2023

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Civil Engineering

Major Professor

Hongyu Zhou

Committee Members

Som Shrestha, Baoshan Huang, Shuai Li

Abstract

With a growing energy demand, the development of sustainable and energy efficient building materials is growing rapidly. Numerous researches have focused on low carbon footprint construction materials, high-performance thermal insulations, high-performance façade, and thermal energy storage. Among these, the development of functional cementitious composites has attracted significant attention due to its potential utilities in building energy reduction and decarbonatization efforts. For example, fly ash cenospheres have been used as micro-size lightweight fillers to achieve low density and thermal conductivity. The use of phase change materials (PCM) in concrete has been studied to answer energy demands. While their inclusion into concrete has been achieved, the encapsulation methods have left questions about their implementation and use. Current research uses micro-encapsulation in a soft polymer shell, resulting in low strengths and greatly limiting their applicability.

This research aims to address these concerns by studying the synergistic role of micro-size functional additives (MSFA), specifically core-shell particles (CSP) with rigid shells, in developing functional cementitious composites that can be used in buildings to enable reduction in thermal loads and energy consumption while maintaining their ability to support mechanical loads as well as to serve architectural functionalities. This was achieved through a series of multiscale experimental and numerical studies. First, a broad scale study of MSFA were conducted on cementitious composites with CPSs by investigating both the thermal conductivities and mechanical performance. This study demonstrated the ability of rigid CSPs to reduce the self-weight and thermal conductivity while maintaining/increasing the mortars strength. Based on this study, cenospheres were used in further studies to identify the hierarchical relationship with both normal and light weight aggregates in concrete and component forms. At the same time the rigid shell MSFA were used to replace the polymer shell in the micro-encapsulation process to achieve both high thermal storage capabilities while maintaining high strength. Component level panels were poured using cenosphere encapsulated PCM to evaluate their performance in an active thermal energy storage system, and testing is ongoing. Finally, micro-encapsulated PCM was evaluated for the use in the emerging additive manufacturing of cementitious composites by incorporating it into 3d printing “inks”.

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