Exploring the potential of chlorellestadite and calcium chlorosilicate as low-carbon binders

Abdelrahman, Mohamed Ahmed Moussa

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https://hdl.handle.net/2142/127513 Copy

Description

Title

Exploring the potential of chlorellestadite and calcium chlorosilicate as low-carbon binders

Author(s)

Abdelrahman, Mohamed Ahmed Moussa

Issue Date

2024-12-12

Director of Research (if dissertation) or Advisor (if thesis)

Garg, Nishant

Department of Study

Civil & Environmental Eng

Discipline

Civil Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Chlorellestadite
• Calcium Chlorosilicate
• Cement
• Carbonatable Binder
• Sequestration
• CO2 Curing
• Waste-to-Energy Ash

Abstract

The urgent need for sustainable construction materials has driven research into alternatives that can reduce cement consumption and facilitate CO₂ sequestration. This thesis investigates the potential of calcium chlorosilicate (CCS) and chlorellestadite (CE) as supplementary binders in cementitious systems. Chlorellestadite (Ca10(SiO4)3(SO4)3Cl2) is the main phase in thermally treated waste-to-energy ashes and can also be found in eco-cements, which exhibit higher compressive strength after carbonation curing. In this thesis, the carbonation reaction mechanism of chlorellestadite was investigated. It was determined that 3 reactions occur during CE carbonation. The first reaction involves the carbonation of chlorellestadite, the second pertains to the carbonation of calcium chlorosilicate (Ca3SiO4Cl2), and the third involves carbonation of sinjarite (CaCl2.2H2O). These reactions enabled a CO2 uptake of up to 29.7%. Additionally, blended cement paste samples with 20% CE have shown higher strength than pure cement, demonstrating potential for inclusion in concrete. Calcium chlorosilicate is a byproduct of alinite cement production and can be found in eco-cement, often associated with chlorellestadite. In this research, the optimal conditions for calcium chlorosilicate hydration were determined to be 18% relative humidity and 45 °C at atmospheric CO2 concentration. Although pure calcium chlorosilicate (CCS) binders exhibit relatively low compressive strength compared to pure ordinary Portland cement (OPC), blended binders containing up to 30% CCS demonstrated higher early compressive strength, achieving values greater than 31 MPa, compared to 26 MPa for pure OPC. This is likely driven by the rapid formation of calcium silicate hydrate (CSH), which provides nucleation sites that accelerate cement hydration. Additionally, carbonated blended binders with up 25% CCS resulted in comparable early compressive strength to carbonated OPC, with values of 44.9 MPa and 47.6 MPa, respectively. The findings elucidate pathways for utilizing relatively inexpensive sources of calcium and highlight the possible benefits of integrating CCS and CE into cementitious systems: reducing reliance on traditional OPC to lower carbon emissions and utilizing treated WTE ashes in concrete. This approach addresses the dual challenges of carbon mitigation and waste management. Since the chloride content in both materials limits their use in steel reinforced concrete, they could be more suitable for non-reinforced or fiber-reinforced applications. Future research should aim towards optimizing the hydration and carbonation conditions, performing durability tests, exploring the rheological influence of both materials, and performing large-scale concrete testing.

Graduation Semester

2024-12

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/127513

Copyright and License Information

Copyright 2024 Mohamed Abdelrahman

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