SILICA FUME IN

CONCRETE

PRESENTED BY: KANAV CHANDAN 73-CE/L-12

CONTENTS

SILICA FUME (DEFINITION, SUMMARY, ETC.) METALS THAT PRODUCE SILICA FUME. SILICA FUME HEALTH ISSUES. PHYSICAL PROPERTIES. SILICA FUME IN CONCRETE & ITS EFFECT. SILICA FUME CONCRETE: TYPICAL STRENGTH CORROSION PROTECTION BY SILICA FUME. SILICA FUME & THE ENVIRONMENT.

SILICA FUME Very fine noncrystalline silica produced in electric arc furnaces as a byproduct of the production of

elemental silicon or alloys containing silicon; also known as

“condensed silica fume or

microsilica”

SILICA FUME

•The densified material is on the left and the as-produced material is on the right and slurried on the top.

•Silica Fume; ▫ Powdered ▫ Densified

SILICA FUME SUMMARY

• Smoke by-product from furnaces used in the production of ferrosilicon and silicon metals.• Amorphous silica with high SiO2 content, extremely small particle size, and large surface area.• Highly reactive pozzolan used to improve mortar and concrete.

SILICA FUME (ALSO KNOWN AS)

• Condensed silica fume• Microsilica• Micropoz (trademark)• Silica dust• Volatilized silica

SILICA FUME IS NOT

Precipitated silica. Fumed silica. Gel silica. Colloidal silica. Silica flour.

METALS THAT PRODUCESILICA FUME

• Silicon metal - typically greater than 97% silicon.• Ferrosilicon alloys -ranging from 40 to 90% silicon alloyed with iron.

PHYSICAL PROPERTIES

SILICA FUME IN CONCRETE

● Silica fume provides;

• Technical Advantages • Life-cycle cost Advantages • Resource Conservation;

EFFECT OF SILICA FUME IN CONCRETE

EFFECTS ON CONCRETE’S PROPERTIES

High Strength development. Water Demand Increased. No Bleeding of Concrete. Reduced Permeability. High Range Water Reducers Required. Increased Chloride Permeability. Increased Plastic Shrinkage.

SILICA FUME CONCRETE: TYPICAL STRENGHTS

SILICA FUME CONCRETE: TYPICAL STRENGTHS

● This previous slide(graph) shows the effects of adding increasing amounts of silica fume to a low water cementitious ratio, air-entrained concrete.

Note that;1. Increased strength will be seen at all ages.2. There is a diminishing that governs the

addition of silica fume. Strength will not continue to increase at the same rate with increased additions.

SILICA FUME CONCRETE: TYPICAL STRENGTHS

3. This concrete mixture is the typical of what has been used in many parking structures and bridge decks, where the amount of silica fume added would be approximately 7.5%.

SILICA FUME CONCRETE: TYPICAL STRENGTHS

CORROSION PROTECTION BY SILICA FUME IN CONCRETE

● 3-7% silica fume added by mass of cement.

● Mixture may include fly ash or slag.● W/C ratio < 0.40.● Total cementitious materials < 415

kg/m3.

CONCRETE WITH SILICA FUME

● 3-7% of mass of ● Cautions; cement. • > Plastic

Shrinkage● Adjust admixtures. • High Water

Demand.● Must be moist cured. • Stickiness. • Black-Gray

Color.

SILICA FUME AND THE ENVIRONMENT

● Recovered/recycled material.● Replaces Portland Cement. •Reduction of Co2 • Reduction of Sox and Nox● Reduced Material extraction

THE END

THANKS TO THE HEAD OF DEPARTMENT, TEACHERS OF CIVIL ENGINEERING.