07-11-2012, 11:23 AM
Geopolymer Concretes pdf
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Geopolymer Concretes
Geopolymers refer to alkali‐activated binders
(AAB’s).
Geopolymers studied for the last 40+ years.
Applications in replacing Portland cement‐based
concrete materials.
Geopolymers are a cement‐free concrete.
Performance often exceeds that of Portland cement
concretes.
Increased
• durability,
• resistance to chemical attack,
• fire protection.
Geopolymer Concretes
Produced from natural and synthetic pozzolanic solids,
activated with alkaline solutions.
Originally metakaolinite with siliceous solutions.
Use of other synthetic reactive aluminosilicate pozzolans
and alkaline activators possible.
Waste‐stream or by‐product pozzolans readily available ,
e.g. PFA, GGBS, etc.
Using PFA‐based geopolymers will have an impact on
national and international targets on CO2 reduction.
Environmental Considerations of PFA: Landfill
Waste‐stream pozzolans such as PFA not recycled to
their full capacity, and excesses are stockpiled or
“landfilled”.
Commercialisation of PFA in geopolymers will help
to reduce landfill.
Future demand may help to utilise existing stocks.
Our starting work on geopolymers
At Liverpool: Investigated mortars using PFA.
Effect of different lab‐grade alkali activators and
curing temperatures on strength development.
Alkalis tested include:
• Sodium hydroxide, NaOH,
• Potassium hydroxide, KOH,
• Sodium silicate
Problems and benefits of porosity
Porosity is closed‐cell, hence permeability is low.
Potential problems:
• Percolation of atmospheric acid solutions and
sulphates. Effects on paste not yet fully
investigated. Deterioration of re‐bar expected.
Benefits of porosity:
• Resilience to freeze‐thaw weathering.
• Thermal insulation.
Ways to manage porosity:
• Use more suitable surfactants/ defoamers/
wetting agents/ superplasticisers.