Doctoral Theses
Ongoing Ph.D. projects at SCiM.
Title: Decoupling the Dehydroxylation and Amorphization of Kaolinite upon Thermal and Mechanical Activation for Use in Low-Carbon Cements
Ph.D. student: Hao Chen – start Fall 2025
Hao Chen is a Ph.D. student in Civil and Environmental Engineering at UC Berkeley since September 2025. Driven by the goal of decarbonizing the construction industry through Limestone Calcined Clay Cement (LC3), his research focuses on the fundamental activation mechanisms of clay minerals. Specifically, Hao utilizes a combination of advanced and traditional characterization tools—including Synchrotron XRD, TEM, SEM and NMR—to investigate how kaolinite transforms during thermal and mechanical processing. By decoupling the distinct mechanisms of dehydroxylation and amorphization, his work aims to provide the foundational insights needed to optimize clay activation procedures and advance low-carbon cement technologies.
Title: Coupling Aluminum Incorporation with Structural Changes, Transport Properties, and Densification Mechanisms in C-A-S-H from Blended Cements
Ph.D. student: Kyle Wong – start Fall 2025
Grant: This project is supported by the NSF CAREER award #2540556
Calcium aluminosilicate hydrates (C-A-S-H) are the main binding product produced in the hydration of blended cements and are responsible for a majority of the strength and durability properties of blended cement concrete. Unlike the calcium silicate hydrates (C-S-H) found in ordinary Portland cement pastes, C-A-S-H incorporates greater amounts of Al3+ ions in the silicate chains at SiO42- bridges which results in significant property changes. A critical property change is “densification” of the C-A-S-H structure where a tightening of the silicate sheets may reduces the interlayer spacing and thus reduces ion transport through the structure. This property is especially important for chemical durability as this densification reduces ion ingress and diffusion that leads to chemical attack. While these properties have been observed, the exact mechanism behind densification of C-A-S-H in blended cements remains unknown and direct causation of the phenomenon and aluminum incorporation is unproven.
This study provides a fundamental investigation of the microstructural changes that occur in C-A-S-H from aluminum incorporation and correlates the amount Al3+ substitution with transport rates and pore networks. The project uses synthetic single-phase C-A-S-H that reflects the chemical and structural properties of real C-A-S-H from blended cements and characterizes the pore network properties through nuclear magnetic resonance (NMR), X-ray nanotomography (nano-CT), and electrochemical impedance spectroscopy (EIS). Zeta potential analysis (ZPA) is then used to relate surface charges of the C-A-S-H with decalcification tovalidate the densification mechanism. The project will conclude with determination of an optimal Al3+ substitution percentage and explore practical methods to reach these levels of substitutions in real blended cements through the use of high-aluminum SCMs.
Title: Optimization of Low Paste Volume Concrete – Integrating the Compressible Packing Model (CPM) with Particle Filler/Aggregate Effect Boundary for Enhanced Sustainability
Ph.D. student: Marcus Cheung – start Fall 2025
Grant: This project is supported by industry award SFO Westfield (Webcor) #062791
The Ultra-Green Concrete project shifts the decarbonization paradigm from alternative, low-carbon binders toward direct clinker reduction through aggregate skeleton optimization – a pathway offering immediate scalability within the ready-mix industry. This research designs low-paste volume concrete (LPVC) by minimizing inter-particle voids using the Compressible Packing Model (CPM). We systematically investigate two distinct formulation pathways targeted at equivalent compressive strengths:
(1) direct cement paste reduction via optimized granular packing, and
(2) the incorporation of filler particles.
Crucially, this work aims to define the fundamental particle size boundary where a material transitions from a functional “filler” (and hence providing filler effects) to a passive micro-aggregate. The resulting microstructural evolution of the Interfacial Transition Zone (ITZ) is characterized via Scanning Electron Microscopy (SEM) and Micro-Computed Tomography (CT). Ultimately, the project validates these green formulations across a spectrum of performance metrics – including volumetric stability, rheological robustness, and structural rebar-bond integrity – ensuring durability is not compromised for sustainability.
Title: Elucidating Metakaolin Reactivity and Hydration Pathways in Low-Carbon Cement via Isotopic Labeling and Advanced Solid-State NMR
Ph.D. student: Paolo Camesasca – start Fall 2022 (ETH Zurich)
Grant: This project is partly supported by the SNSF Ambizione Grant #208719
Calcined kaolinite (metakaolin, MK) serves as the primary reactive phase in natural calcined clays used in highly substituted, low-carbon cement blends such as LC3. Despite extensive research, the fundamental reactivity of constituent phases in MK during early-age hydration and the fresh state remains unresolved due to the inherent variability and impurities of natural clays.
This project investigates the fundamental reaction kinetics and hydration product selectivity of metakaolin in cementitious matrices using a bottom-up synthetic approach and high-sensitivity characterization.
To isolate reaction mechanisms from natural clay variability, this project utilizes a novel hydrothermal synthesis protocol to produce custom kaolinite with precise control over:
- Crystallinity and pozzolanic potential
- Impurity profiles
- Isotopic labeling and targeted paramagnetic doping
By strategically doping the synthetic matrix with paramagnetic impurities, NMR relaxation times are significantly reduced, boosting analytical efficiency by up to two orders of magnitude. When combined with isotopic labeling, this method yields quantitative solid-state MAS-NMR measurements with unprecedented signal-to-noise ratios. This breakthrough allows for the clear differentiation of MK-derived silicate hydration products from other silicon sources within complex cementitious blends.
