INTRODUCTIONTraditional mineral admixtures were derived mostly from natural volcanic materials and calcined clays or shales. Nowadays, solid waste management has become one of the major environmental concerns in the world. Utilization of waste materials and by-products is a partial solution to environmental and ecological problems.

Use of these materials not only helps in getting them utilized in cement, concrete, and other construction materials, it helps in reducing the cost of cement and concrete manufacturing, but also has numerous indirect benefits such as reduction in land-fill cost, saving in energy, and protecting the environment form possible pollution effects.

SILICA FUME

SILICA FUME IS REFERRED TO AS “FUME” BECAUSE IT IS SO FINELY DIVIDED THAT ITS PARTICLE SIZE APPROXIMATES THAT OF THE SOLID PARTICULATES IN SMOKE

The average diameter of the particles in silica fume has been established to be 0.1 m product, which is highly pozzolanic, is recovered by passing the outgoing flue gas through a bag house filter. 

FORMULA EQUATION

SiO2 + C Si + CO2 (main reaction-heat applied)

3SiO2 2C Si + 2SiO + 2CO2 (secondary reaction)

2SiO + O2 2 SiO2 (silica fume)

APPLICATIONS

Silica fume is added to Portland cement concrete to improve its properties, in particular its compressive strength, bond strength, and abrasion resistance.

Silica fume acts as both a filler, improving the physical structure by occupying the spaces between the

cement particles and as a 'pozzolan,' reacting chemically to impart far greater strength and

durability to concrete.

SILICA FUME HAS HIGH ELECTRICAL RESISTIVITY AND IMPERMEABILITY

silica fume also reduces the permeability of concrete to

chloride ions, which protects the reinforcing steel of concrete from

corrosion

METAKAOLIN

Metakaolin, generally called ‘‘calcined clay,’’ is a reactive alumina-silicate pozzolan produced by heating kaolinite at a specific temperature regime.

• Produced by: i. calcining pure clays at appropriate temperatures. ii. calcining waste sludge from the paper recycling industry.

• main parameters influence the pozzolanic activity: i. quantities of kaolinite in the inorganic fraction ii. calcium hydroxide derived from the calcite present in the sludge iii. particle sizes smaller than 10 μm.

• Metakaolin is white in color, affected by purity of kaolin.

• Reactivity of the metakaolin affected by: - grinding to a finer particle size - purity of the kaolin - amount of siliceous and aluminous material

METAKAOLIN TYPICALLY HAS AN AVERAGE PARTICLE SIZE OF ABOUT 1.5 ΜM IN DIAMETER, WHICH IS BETWEEN SILICA FUME (0.1 TO 0.12 ΜM) AND PORTLAND CEMENT (15 TO 20 ΜM).

Several benefits of utilization of metakaolin as a mineral admixture for cement and concrete:

• Reducing the permeability of concrete, including chloride permeability• Helping to control alkali-silica reactivity (ASR)• Increasing concrete durability• Lightening the colour of concrete making it possible to add lighter integral colours• Making concrete denser and reducing its shrinkage, due to “particle packing”; combined with fly ash the results are even better• Not substantially affecting set times when compared to the same mix without metakaolin• Increased compressive and flexural strengths• Reduced potential for efflorescence, which occurs when calcium is transported by water to the surface where it combines with carbon dioxide from the atmosphere to make calcium carbonate, which precipitates on the surface as a white residue.

RICE HUSK ASH (RHA)

Application.. as a fuel in the boilers for processing of paddy also used in power generation as a fuel..Effect.. RHA is a great environment threat causing damage to the land and the surrounding area in which it is dumped.

HOW TO PRODUCE RHA?..

During milling of paddy about 78 % of weight is received as rice, broken rice and bran. The rest 22% of the weight of paddy is received as husk .

This husk contains about 75 % organic volatile matter and the balance 25 % of the weight of this husk is converted into ash during the firing process is known as rice husk ash (RHA).

WHY RHA USED AS MINERAL ADMIXTURES ?

It increases the strength and density of the concrete and hence reduces the amount of cement in the concrete mix.

Because, particle size of the cement is about 35 microns. May be formation of void in the concrete, if curing is not properly. This reduces the strength and quality.

RHA is finer than cement. Its particle size only 25 microns, so that it fills the interstices in between the cement in the aggregate.

RHA AS A SUPER-POZZOLAN..

This super-pozzolan can be used in a big way to make special concrete mixes. There is a growing demand for fine amorphous silica in the production of special cement and concrete mixes, high performance concrete, high strength, low permeability concrete.

Used in bridges, marine environments and nuclear power plants.

OTHER ADVANTAGE RHA.

lower cost. enhance the workability, strength and

impermeability of concrete, while making concrete durable to chemical attacks, increasing compressive strength(10%-20%).

RHA has excellent water resistance properties and is used in waterproofing. It reduces water penetration. It also reducing chloride ion penetration in the structure and thus improving the life of building.

APPLICATION RHA

This product can be used in a variety of applications like: • green concrete• high performance concrete• refractory • ceramic glaze• insulator• waterproofing chemicals• insecticides and bio fertilizers 

Fly Ash

•First used in the U.S. in 1929 for the Hoover Dam•Fly ash is a fine, glass-like powder recovered from gases created by coal-fired electric power generation. containing aluminous and siliceous material

Fly Ash

• Cheap replacement for Portland cement used in concrete.

• easier to be used in cold weather compare to Portland cement.

• Gives better performance without higher cost.

• concrete containing fly ash stronger over time than concrete made only with cement because of the tiny, glassy beads which create a lubricating effect.

• More environmental friendly by reducing the need for cement production .

• Cost competitive with Portland cement because it less likely to crack .

• Using fly ash is an exceptional way to “Build Green,” without compromising cost or quality in concrete production.

BLAST FURNACE SLAG

GGBFS

blast furnace slag is the non-metallic by-product, consisting of silicates and alumino-silicates of lime and of other bases, that is developed simultaneously with iron in the blast furnace

GGBFS

GGBFS has been widely used as a supplementary cementitious material in Portland cement concrete,either as a mineral admixture or as a component of blended cement.GGBFS has been widely used in Europe,US and Asia(particularly in Japan and Singapore)

GGBFS

two major uses Of GGBFS is the production of quality-improved slag cement namely Portland Blastfurnace Cement(PBFC) and High Slag Blastfurnace Cement(HSBFC).

ENGINEERING PROPERTIES

Workability-concrete containing GGBFS as a partial cement has longer-lasting workability and low slump loss during hot weather construction

Heat of hydration-concrete containing GGBFS exhibits a lower heat of hydration than conventional Portland cement concrete

ENGINEERING PROPERTIES

Sulfate resistance-use of GGBFS as partial cement replacement gives concrete moderate resistance to sulfate attack

Alkali-aggregate reactivity-the use of GGBFS as a partial replacement for Portland ement can reduce available alkalies and can reduce the reaction between certain siliceous components of concrete aggregates and the alkalies in the concrete.

ENGINEERING PROPERTIES

Hydraulic reactivity-depending on the quenching process, the structure of pelletized blast furnace slag can range from crystalline(slow quench ) to vitreous(rapid quench)

Rapid quenching is important if cementitious properties are to be achieved.

MATERIALS PROCESSING REQUIREMENTS Dewatering-Moisture in blast furnace

slag, which occurs in the granulation process or in pelletized slag, should be removed by drying prior to the use of GGBFS as either an additive to Portland cement or a mineral admixture to Portland cement concrete.

MATERIALS PROCESSING REQUIREMENTS Grinding-Processing for use as a

supplementary cementitious material requires grinding of the slag, typically using the same or similar plant and equipment as for Portland cement production.

CONSTRUCTION PROCEDURES

Material Handling and Storage GGBFS (or cement containing GGBFS) is

handled and stored like conventional Portland cement.

Mixing, Placing, and Compacting The same equipment and procedures used

for conventional Portland cement concrete may be used to batch, mix, transport, place, and finish concrete containing GGBFS.

CONSTRUCTION PROCEDURES

Curing The slower strength development of concrete containing GGBFS

may require that the moisture be retained in the concrete for a longer period of time than what is normally required for conventional concrete. Scheduling of pavement construction should allow adequate time for the specified strength gain prior to the placement of traffic loads, the onset of freeze-thaw cycles, and the application of deicing salts.

Quality Control The same quality control procedures used for conventional

Portland cement concrete can be used for concrete containing GGBFS.

 

CONCLUSION

Nowadays the industrial by product and waste is increase from day to day, researches are continuously been done to produce the methods to transform this to something useful..The utilization of this by product gives us the choices to improve the desired properties of the cement.