SILICA FUME CONCRETE

PRESENTED BY,D.SELVAGANESH,

A.R.BAWA ABUL HASSAN,3rd YEAR, DEPARTMENT OF CIVIL,

FATIMA MICHAEL COLLEGE OF ENGINEERING AND TECHNOLOGY,MADURAI – 20.

CONTENTS Introduction to silica fume concrete.Function of silica fume in concrete.Chemical composition.Physical characteristics.Available forms of silica fume.Properties of fresh concrete while using the

silica fume.Properties of hardened concrete by the usage of

silica fume.Applications of silica fume concrete.Advantages of silica fume material.Conclusion.

SILICA FUME CONCRETESilica fume is an artificial pozzolona

having high pozzolonic activity.It is a By- product from an electric

arc furnace used in manufacture of silicon metal or silicon alloy.

It has high silica content of more than 80%.

It is an excellent for use as a portland cement supplement.

SILICA FUME CONCRETE

FUNCTION OF SILICA FUMESilica fume works on Two levels.The hydration of Portland cement produces

many components, including silicate hydrates(CSH) and calcium hydroxide(CH).

The silica fume is added to the CH for produce the additional CSH to obtain a very good compressive strength can exceed 15000 psi.

The additional CSH produced by the silica fume is more resistant to attack from aggressive chemicals then the weaker CH.

CHEMICAL COMPOSITIONChemical composition depends on the product

being made by the furnace.Composition is also influenced by the furnace

design. It is mostly made of silica having percentage of

more than 80.The other chemical composition include

Fe2O3,Al2O3,Cao,Na2O,K2o in small percentages.

Unlike the other By- products like Fly Ash, Silica fume from a single source has little or no variation in chemical composition from one day to another.

PHYSICAL CHARACTERISTICSIt should be in premium white and

standard grey colors.The specific gravity of the silica fume

concrete is 2.2.Its specific surface area is to be 20,000

sq.meters / kg.Particle size is less than 1 micron with

average diameter of 0.1 micron.The shape of the particle is spherical. It should be in Amorphous in nature.

AVAILABLE FORMS IN SILICA FUME CONCRETE

Undensified forms with a bulk density 200 – 300 kg/m3.

Densified forms with a bulk density 500 – 600 kg/m3.

Pelletised forms with a bulk density 600 – 800 kg/m3.

Slurry form.

PROPERTIES OF FRESH CONCRETE USING THE SILICA FUME

WORKABILITY.BLEEDING AND SEGREGATION.SETTING TIME.PLASTIC SHRINKAGE.

PROPERTIES OF HARDENED CONCRETE

DRYING SHRINKAGE.CREEP.STRENGTH.

PROPERTIES OF FRESH CONCRETE USING SILIC FUME

WORKABILITY: Workability is reduced Water demand

increases in proportion to silica fume added.

Water demand is 1% for every 1% of replacement of cement.

Lower slump and & more cohesive mix.

BLEEDING AND SEGREGATION:

Bleeding is reduced as silica fume particles find their way between two cement grains.

Segregation is reduced as the concrete mix is more cohesive due to increase in number of solid to solid contact points.

From the above two discussion we had cleared that the silica fume reduce the bleeding and segregation property of the fresh concrete.

SETTING TIMETime results have shown that the initial

setting time and final setting time is not greatly influenced.

This increase may be 30 minutes or so.PLASTIC SHRINKAGE

Fresh concrete is subjected to surface cracking is known as plastic shrinkage.Since the silica fume concrete show no bleeding, fresh concrete is subjected to the plastic shrinkage.Precautions should be taken ass per normal concrete.

PROPERTIES OF HARDENED CONCRETE

DRYING SHRINKAGE:Drying shrinkage test by different

researcher show that the long time shrinkage of concrete is not affected significantly by the addition of silica fume to the concrete.

CREEP:The creep of the concrete containing silica

fume will be lower than the corresponding Portland cement concrete.

STRENGTHConcrete containing silica fume

show outstanding performance in development of strength.

Strength of 62 – 80 Mpa can be easily achieved.

Silica fume forms backbone of high performance concrete due to early high strength properties.

APPLICATIONSIt is used to construct a New TJ ORN

Bridge in sweeden which having the high strength, workability, durability and free from any deformations and cracks.

Girders using silica fume concrete.It is mostly used in high rise structures

to increase the life time of the structure without any affects.

It is most widely used in important structures which had a high strength when compared with another.

HIGHRISE BUILDINGS USING SILICA FUME

Since 1990’s high rise structures or buildings uses the silica fume content to yield the high strength concrete , high compression strength, without affecting of wind forces , high abrasion resistance and high corrosion resistance.

GRIDERS REDUCED USING SILICA FUME CONCRETE

NEW TJ ORN BRIDGE IN SWEEDEN

ADVANTAGES OF SILICA FUME CONCRETE

High early compressive strength.High tensile flexural strength and

modulus of elasticity.Very low permeability to chloride

and water intrusion.High bond strength.High electrical resistivity and low

permeability.

CONCLUSIONFrom the above discussions we have

conclude the points about silica fume concrete.

Silica fume can be used to manufacturing of concrete of very high strength at early age.

Forms the backbone of modern day high performance.

Strengths upto 200 Mpa can be achieved by using silica fume.