Engineering Fly Ash-based Geopolymer Concrete Geopolymer Concrete E. Ivan Diaz-Loya Ph.D. Candidate Erez N. Allouche Ph.D., P.E. 1 2010 International Concrete Sustainability Conference, Dubai, UAE
Engineering fly ash-based geopolymer concrete OUTLINE • Geopolymers ▫ Structure ▫ Reactions ▫ Properties ▫ Properties • Sustainability • Engineering fly ash-based GPC • Results • Results ▫ Fly ash analysis ▫ Mechanical characterization of GPC ▫ Data analysis y • Conclusions 2 2010 International Concrete Sustainability Conference, Dubai, UAE
Engineering fly ash-based geopolymer concrete Geopolymers • Geopolymers are cementitious materials that do not require the presence of OPC to harden or gain strength. g g • Geopolymers are formed by a 3d network of Si & Al mineral molecules linked through covalent bonds with oxygen covalent bonds with oxygen molecules. • A positive ion must be provided to allow aluminum to b become tetravalent. t t l t 3 2010 International Concrete Sustainability Conference, Dubai, UAE
Engineering fly ash-based geopolymer concrete Geopolymers • The source of Si & Al for geopolymers can be any mineral (e.g. metakaolin) or by-product (e.g. fly ash) ( g y ) • The positive ion is usually provided by a hydroxide solution of Na or K, etc. • Water glass provides the • Water glass provides the monomers from which the polymeric chains grow. • In most cases a slightly elevated temperature is required to kick i i d ki k start the geopolymerization reaction 4 2010 International Concrete Sustainability Conference, Dubai, UAE
Engineering fly ash-based geopolymer concrete Geopolymerization Geopolymeric reaction occurs can be divided into three steps: 1. Dissolution of species Si and Al dissolve in 1 Dissolution of species - Si and Al dissolve in the alkaline media providing monomers. 2. Transportation/Initial gelation- Orientation of th the precursors takes place. t k l 3. Condensation/setting- Hydrolyzed aluminate and silicate species policondensate and p p harden. 5 2010 International Concrete Sustainability Conference, Dubai, UAE
Engineering fly ash-based geopolymer concrete MIXING MIXING Geopolymer paste can be mixed with the same aggregates used for Portland cement for its use as mortar or cement, for its use as mortar or concrete. FINE & COARSE ACTIVATOR FLY ASH SOLUTION AGGREGATES 6 2010 International Concrete Sustainability Conference, Dubai, UAE
Engineering fly ash-based geopolymer concrete PROPERTIES PROPERTIES COMPRESSIVE STRENGTH COMPRESSIVE STRENGTH 80 70 70 e strength (MPa) 60 50 40 Geopolymer Geopolymer Compressive 30 20 OPC 10 0 0 0 20 40 60 80 100 Age (days ) Typical compressive strength curve of Geopolymer vs. Portland cement. Observe the high early strength of geopolymer (up to 12,000 Ob h hi h l h f l ( psi after 3 day of curing). 7 2010 International Concrete Sustainability Conference, Dubai, UAE
Engineering fly ash-based geopolymer concrete PROPERTIES PROPERTIES CHEMICAL RESISTANCE CHEMICAL RESISTANCE Geopolymer made from class C fly ash REMAINING COMPRESSIVE STRENGTH REMAINING COMPRESSIVE STRENGTH after sulfuric acid immersion test (pH = 0.6) 120 ENGTH (%) 100 Geopolymer made from class F fly ash 80 COMPRESSIVE STRE Class F fly ash- based 60 geopolymer Class C fly ash-based 40 geopolymer OPC 20 Ordinary Portland Cement 0 0 1 2 4 6 8 WEEK Geopolymer’s corrosion resistance to the attack of sulfuric acids is significantly greater than that of Portland cement. It is practically inert to sulfate salts attack. 8 2010 International Concrete Sustainability Conference, Dubai, UAE
Engineering fly ash-based geopolymer concrete Sustainabilit y POLLUTION AND POLLUTION AND ECOLLOGICAL FOOTPRINT ECOLLOGICAL FOOTPRINT Actual production of Portland cement p contributes 13.5 billion tons of CO 2 per year. Approximately 5% of the total global emission of CO2 to the atmosphere. Geopolymer made out of waste Geopolymer made out of waste materials like fly ash not only have a smaller footprint but help reduce the footprint of other industries namely, coal-fired power plants. p p 9 2010 International Concrete Sustainability Conference, Dubai, UAE
Engineering fly ash-based geopolymer concrete Sustainability Sustainability ENERGY CONSUMPTION ENERGY CONSUMPTION • Portland cement production requires heating raw materials over 2550 F • Fly ash based-geopolymers are a much less energy consuming alternative. 10 2010 International Concrete Sustainability Conference, Dubai, UAE
Engineering fly ash-based geopolymer concrete Sustainability Sustainability • 480 Million Tons of fly ash produced in 2001 480 Million Tons of fly ash produced in 2001 • World wide utilization ranges 20 to 80% 11 2010 International Concrete Sustainability Conference, Dubai, UAE
Engineering fly ash-based geopolymer concrete Sustainability Sustainability Energy production sources in the Coal reserves in the U.S. U.S. • 72 million tons of fly ash produced in 2008 • 72 million tons of fly ash produced in 2008 • Only 30 million tons were used sending around 42 m illion tons to the landfills 12 2010 International Concrete Sustainability Conference, Dubai, UAE
Engineering fly ash-based geopolymer concrete Sustainabilit y Monthly Fuel Cost to U.S. Electric Utilities 1995 – 2009, I n 2009 cents per kilowatt-hour Source: Ventyx Velocity Suite Updated: 5/10 13 2010 International Concrete Sustainability Conference, Dubai, UAE
Engineering fly ash-based geopolymer concrete Sustainability Sustainability POTENTIAL RISKS OF FLY ASH STORAGE LAGOONS POTENTIAL RISKS OF FLY ASH STORAGE LAGOONS • In December 2008 a TVA’s fly ash storage lagoon ruptured in Kingston, TN • 1.1 billion gal. of fly ash slurry 1.1 billion gal. of fly ash slurry were spilled into the Emory and Clinch Rivers • 300 acres of the surrounding land were contaminated land were contaminated • Estimated clean-up costs: 675 to 975 million 14 2010 International Concrete Sustainability Conference, Dubai, UAE
Engineering fly ash-based geopolymer concrete New Opportunities in the US • Increasing Cost Of Fly Ash Disposal Disposal ▫ New regulations proposed by the EPA are expected to tighten fly ash disposal requirements increasing its cost. • Fly Ash Only For Encapsulated Applications Applications ▫ EPA’s new regulations may only allow fly ash to be recycled in encapsulated applications. • Green Construction Boom ▫ LEED Certification is aimed at improving p g performance across all the metrics that matter most: energy savings, water efficiency, CO 2 em issions reduction , improved indoor environmental quality, and stewardship of resources and sensitivity to their impacts. • Carbon Trading ▫ Geopolymer offers the possibility to offset carbon emissions. 15 2010 International Concrete Sustainability Conference, Dubai, UAE
Engineering fly ash-based geopolymer concrete Challenges of fly ash-based geopolymer concrete • Fly ash Variability 16 2010 International Concrete Sustainability Conference, Dubai, UAE
Engineering fly ash-based geopolymer concrete Challenges of fly ash-based geopolymer concrete Add Calcination Hydration aggregates reactions reactions Raw Cement Cement paste Ordinary Materials concrete • Limestone • C3S • C-S-H • f c ’ • Sand • C2S • C-A-H • f r • Clay • C3A • AFt • E c • Shale Shale • C4AF C4AF • AFm AFm • µ µ • Iron ore Add Geopolymerization aggregates reactions Geopolymer Fly ash Geopolymer ? ? concrete concrete paste paste • f c ’ • Mostly • Poly-sialate • f r amorphous • Poly-sialate siloxo • E c • Poly-sialate disiloxo • µ 17 2010 International Concrete Sustainability Conference, Dubai, UAE
Engineering fly ash-based geopolymer concrete Challenges of fly ash-based geopolymer concrete Add Calcinations Hydration aggregates reactions reactions Raw Cement Cement paste Ordinary Materials concrete • Limestone • C3S • C-S-H • f c ’ • Sand • C2S • C-A-H • f r • Clay • C3A • AFt • E c • Shale Shale • C4AF C4AF • AFm AFm • µ µ • Iron ore Fly ash Fly ash Geopolymer Geopolymer concrete Regression Model • Mostly • f c ’ amorphous • f r • E c • µ 18 2010 International Concrete Sustainability Conference, Dubai, UAE
Engineering fly ash-based geopolymer concrete Engineering fly ash-based geopolymer concrete 1. Identify the fly ash characteristics that significantly impact GPC Collect fly ash samples � Keep mix design constant Keep mix design constant � Full mechanical characterization of GPC samples � 2. Evaluate the mechanical behavior of GPC made from each of the fly ash samples Compressive vs. tensile strength C i t il t th � Compressive vs. elastic modulus � Density vs. fly ash fineness � 3. Determine the feasibility of establishing a 3 y g regression model to predict GPC’s mechanical properties using the characteristics fly ash 19 2010 International Concrete Sustainability Conference, Dubai, UAE
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