Thesis
Synthesis of calcium silicate hydrate (C-S-H) and novel cementitious materials : characterisation, engineering applications and environmental aspects
- Creator
- Awarding institution
- University of Strathclyde
- Date of award
- 2018
- Thesis identifier
- T14864
- Person Identifier (Local)
- 201469248
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- This doctoral dissertation describes the synthesis and characterisation of calcium silicate hydrate (C-S-H) phase and other cementitious materials. C-S-H is the most important mineral phase in ordinary Portland cement (OPC), accounting for strength and hardening. Its characterisation has been the subject of research in the past 70 years and yet there are still gaps in knowledge and understanding. In this work the development of a novel method process for direct synthesis of solid calcium silicate hydrate (C-S-H) phases is proposed, by mixing calcium hydroxide and silica. This method allows crystal structural determination of the synthetic mineral, and permits characterisation at the atomic scale and also mechanical-hydraulic measurements on monoliths, rather than the more traditional slurry format. The method is easy, relatively fast and highly reproducible. In particular, structure evolution of synthetic C-S-H is studied under varying calcium to silica ratio, curing time and silica particle size, using either silica fume or nano-silica (particle size). While this method advantageously produces solid C-S-H, its production at bulk-scale is also evaluated by means of a life cycle assessment and compared to other OPC-free binder materials. Novel OPC-free cementitious binders are in fact developed and characterised in terms of mechanical and thermal performance. Proposed as an environmentally friendly alternative to Portland cement, these innovative cementitious materials have a lower carbon footprint and contribute to reduce Portland cement consumption and its CO2 emissions. Hydrothermal synthesis of C-S-H is carried out to investigate the response to hot and wet conditions, typical of cement encapsulation in deep geological storage of radioactive waste. As a result of these investigations, synthesis conditions have been proven to be the key in "tailoring" and designing the C-S-H structure at the nano-scale. C-S-H produced is used as a crack-sealing agent in aqueous injection. A lab-scale investigation shows that aqueous nano-silica injected through a hardened cement matrix reacts with calcium hydroxide naturally present in hydrated Portland cement producing additional C-S-H and reducing the overall porosity and permeability. This study explores the potential use of solid C-S-H to repair large scale structures which are wet or under water, such as legacy ponds in nuclear waste storage facilities.
- Advisor / supervisor
- Hamilton, Andrea
- Resource Type
- Note
- This thesis was previously held under moratorium from 4th June 2018 until 4th June 2023.
- DOI
- Date Created
- 2018
- Former identifier
- 9912601293502996
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