sustainable cements challenges and opportunities
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Sustainable CementsChallenges and Opportunities
Assistant Professor Claire E. WhiteDepartment of Civil and Environmental Engineering, and the Andlinger Center for Energy and the EnvironmentPrinceton UniversityAssociated Faculty:Princeton Environmental InstituteDepartment of Chemical and Biological EngineeringDepartment of Mechanical and Aerospace EngineeringPrinceton Institute for Science and Technology of MaterialsPrinceton Institute for Computational Science and Engineering
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Concrete, Sustainability and SocietyConcrete is the top engineering material contributing to anthropogenic CO2 emissions: ~8%
~95% of all concrete used around the world is based on Portland cement
4.1 billion tons of cement manufactured in 2017 (USGS)◦ ~1 ton of CO2 released into atmosphere per ton of cement◦ Also important to assess energy and water (for concrete)
requirements
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Binder for ConcretePortland Cement Powder Potable Water
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CO2 sources:- Chemistry ~ 55%
CaCO3 à CaO + CO2
- Fuel ~ 45%
Total ~1 t CO2 /t cement
Kiln temperature 1450 °C
Image from IEA 2009 (Cement Technology Roadmap 2009)
Cement Manufacturing
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Methods to Mitigate Energy and CO2 Impact
Carbon capture and storage◦ Any new cement plant should have associated CCS plant ($$)
Clinker substitution◦ Need to understand the structure and reactivity of industrial
by-products and processed minerals
Alternative fuels (e.g., biomass)
Energy efficiency ◦ Large cost but low savings in CO2 emissions
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Outlined by International
Energy Agency
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Cumulative CO2 Emissions Reduction from
2020 to 2050 (2 °C Scenario, Low Variability)
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Innovative technologies – Largely carbon capture and storage
Clinker substitution
Alternative fuels (e.g., biomass)
Energy efficiency
Technology Roadmap Low-Carbon Transition in the Cement Industry 2018
Total reduction = 7.7 Gt of CO2
Beyond 2 °C Scenario: Total reduction = 10.9 Gt of CO2
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Methods to Mitigate Energy and CO2 Impact
Carbon capture and storage◦ Any new cement plant should have associated CCS plant ($$)
Clinker substitution◦ Need to understand the structure and reactivity of industrial
by-products and processed minerals
Alternative fuels (e.g., biomass)
Energy efficiency ◦ Large cost but low savings in CO2 emissions
Alternative cementitious materials
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Outlined by International
Energy Agency
Innovative disruptive
technologies
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Status QuoModern day construction relies heavily on Portland cement concrete◦ Reproducible quality around the world◦ Heavily controlled by construction standards/codes
The main binder responsible for strength of concrete (and contributes to durability) is calcium-silicate-hydrate◦ Altering the chemistry of the binder may change macroscopic
properties (seen as a risky approach)
Conservative approaches making a dent on the CO2emissions◦ Clinker substitution (for example, limestone-calcined clay cements)◦ Still based on Portland cement chemistry
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Innovative Disruptive TechnologiesEliminate the need to produce Portland cement clinkerExamples include◦ Alkali-activated materials◦ Carbonate cements◦ Calcium aluminate cements◦ Super sulfated cements◦ Calcium sulfoaluminate cements◦ …
Varying levels of CO2 reduction compared with Portland cementChallenge to make inroads in an ultra-conservative industry
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Alternative Cements - Commercialization
9http://solidiatech.com/applications/; https://ctsrapidsetcement.com.au/gallery-videos/
Alkali-activated concrete
89% reduction of Portland cement using alkali activation
Carbonate concrete
Calcium sulfoaluminate concrete
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Fly AshMetallurgical Slags Calcined Clays Alkaline Activator
Aluminosilicate Rich Powders
Binder for Concrete
Alkali-activated Concrete
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Binder chemistry Cement Notation
Calcium-(sodium)-alumino-silicate-hydrate C-(N)-A-S-H◦ Alkali-activated high-Ca materials
(e.g., blast furnace slag)
Sodium-alumino-silicate-hydrate N-A-S-(H)◦ Alkali-activated low-Ca materials
(e.g., calcined kaolin)
~40-80% reduction in CO2
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Role of Fundamental ResearchLong-term performance of certain blended Portland cements and AAMs is not well established◦ Do not have 150 years of data on sustainable cements, in contrast
with Portland cements
Need to predict long-term performance◦ Key role of fundamental research (including modeling across length
scales) to provide this information
Long-term performance is linked to material durability◦ Performance can be compromised due to instabilities in the
atomic structure of the main binder gel◦ Performance is lost due to material degradation, which is
controlled by the concrete pore structure (and permeability)
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