KMH459 Geopolymer Production and Applications
Dr. Öğr. Üyesi Evren ARIÖZ
Hafta 03
Raw Materials for Geopolymer Synthesis
Ground Granulated Blast Furnace Slag
Ground granulated blast furnace slag (GGBS) is a by-product from the
blast furnaces used to make iron.
Blast-furnaces are fed with controlled mixture of iron ore, coke and
limestone, and operated at a temperature of about 1,500°C.
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Ground Granulated Blast Furnace Slag
When iron-ore, coke and limestone melt in the blast furnace, two
products are produced - molten iron, and molten slag.
The molten slag is lighter and floats on the top of the molten iron.
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Ground Granulated Blast Furnace Slag
The molten slag comprises mostly silicates and alumina from the original
iron ore, combined with some oxides from the limestone.
The process of granulating the slag involves cooling of molten slag
through high pressure water jets.
This rapidly quenches the slag and forms granular particles generally not
bigger than 5 mm.
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Ground Granulated Blast Furnace Slag
The rapid cooling prevents the formation of larger crystals, and the
resulting granular material comprises around 95% non-crystalline
calcium-aluminosilicates.
The granulated slag is further processed by drying and then grinding in a
rotating ball mill to a very fine powder, which is GGBS.
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Ground Granulated Blast Furnace Slag
Ground granulated blast-furnace slag is a
glassy material. The colour of GGBS
varies from beige to dark to off-white
depending on moisture content, chemistry
and efficiency of granulation. When it is
ground it has usually white colour. It
imparts
a
lighter,
brighter
color
to
concrete.
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Ground Granulated Blast Furnace Slag
Advantages of Using GGBS
❖
Improved workability and compaction characteristics
❖
Increased pumpability
❖
Increased strength
❖
Enhanced durability
❖
Reduced permeability
❖
High resistance to chloride penetration
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Ground Granulated Blast Furnace Slag
Advantages of Using GGBS
❖
High resistance to sulfate attack
❖
High resistance to ASR (alkali silica reaction)
❖
Low heat of hydration
❖
Improved surface finish
❖
Enhanced architectural appearance
❖
Suppresses efflorescence
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Ground Granulated Blast Furnace Slag
Advantages of Using GGBS
❖
Enhancement of the life cycle of concrete structures
❖
Reduction in maintenance and repair costs
❖
Slashes lifetime construction costs
❖
Production of GGBS involves virtually zero CO2 emissions, and no
emissions of SO2 and NOx
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Metakaolin
Metakaolin (MK) is a pozzolanic material. It is a dehydroxylated form of
the clay mineral kaolinite. It is obtained by calcination of kaolinitic clay
at a temperature between 500°C and 800°C.
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Metakaolin
Between 100 and 200°C, clay minerals lose most of
their adsorbed water.
Between 500 and 800°C kaolinite becomes calcined
by losing water through dehydroxilization.
The raw material input in the manufacture of
metakaolin (Al2Si2O7) is kaolin clay.
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Kaolin
Kaolin is a fine, white, clay mineral that has been traditionally used in the
manufacture of porcelain.
Kaolinite is the mineralogical term that is applicable to kaolin clays.
Kaolinite is defined as a common mineral, hydrated aluminum disilicate, the
most common constituent of kaolin.
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Metakaolin
Advantages of Using Metakaolin
➢
Enhanced workability
➢
Increased compressive strength
➢
Increased tensile and flexural strengths
➢
Increased durability
➢
Reduced permeability
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Metakaolin
Advantages of Using Metakaolin
➢
Increased resistance to chemical attack
➢
Reduction in alkali–silica reactivity (ASR)
➢
Reduced shrinkage due to particle packing
➢
Reduced potential for efflorescence
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Rice Husk Ash
Rice husk is an agricultural residue obtained from the outer covering of rice
grains during milling process. Current rice production in the world is more
than 700 million tons.
Rice husk constitutes about 20% of the weight of rice. It contains about 50%
cellulose, 25–30% lignin, and 15–20% of silica.
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Rice Husk Ash
Rice husk ash (RHA) is generated by burning rice husk. On burning,
cellulose and lignin are removed leaving behind silica ash.
The controlled temperature and environment of burning yields better quality
of rice-husk ash as its particle size and specific surface area are dependent
on burning condition.
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Rice Husk Ash
The production of rice husk ash is primarily in areas where rice crops are
abundant.
Fully burned rice husk ash could be gray, purple or white, depending on the
impurities present and the burning conditions.
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Rice Husk Ash
Advantages of Using RHA
➢
Improved strength
➢
Enhanced durability properties
➢
Reduced materials costs due to cement savings
➢
Environmental benefits related to the disposal of waste materials and to
reduced carbon dioxide emissions.
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