Seminar by : Arivusudar Nagarajan Seminar by : Arivusudar Nagarajan

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CEMENT REPLACEMENT MATERIALS

FLY ASH It is finely divided residue resulting from the

combustion of powdered coal and transported by the flue gases and collected by electrostatic precipitator ( Thermal Power plants)

Mostly used pozzolonic material Reference IS-3812

Contd…

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Savings in cement Reducing heat of hydration Reducing water demand Spherical shape and smooth surface of flyash

helps to reduce the inter-particle friction and thus facilitates mobility.

Reduce Bleeding and drying shrinkage. Fly ash particles plasticize cement paste and

improves flowability and rheology of the mix. Contributes to strength

Contd…

ADVANTAGES OF FLY ASH

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CEMENT + C-S-H Gel + Ca(OH)2

WATER FLYASH C-S-H Gel

SECONDARY HYDRATION OF FLY ASH

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PETROGRAPHIC VIEW OF FLY ASH

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FLYASH-PARTICLE PACKING EFFECT

FLYASH

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Cement Flyash

BALL BEARING EFFECT

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Trapped Water

DISPERSION OF CEMENT PARTICLES WITH FLY ASH

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By-product from steel Industries. Specific surface of about 400-600 m2/kg Higher cement replacement levels upto 70% Glass content 85% (Min) Blended with cement Secondary hydration

Slag (GGBS)

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Reduces water demand Water can be reduced based on slag content and

fineness of slag Reduces bleeding Water retention Improves workability Increases Pumpability

Effect of GGBS on Fresh Concrete

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Reduces heat of hydration Improves the pore structure Reduces permeability Improves resistance to corrosion of reinforcement Increased resistance to chemical attack Higher ultimate strength Saving cement in concrete mix

Effect of GGBS on Hardened Concrete

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Condensed Silica Fume is a by product of ferro-Silicon alloy industry and it is the dust which is collected from furnace exhaust system

Fineness of silica fume is @ 15000 m2/kg as against 280 to 290 m2/kg of Cement

Contributes significantly to compressive strength due to micro-filler effect and excellent pozzolanic properties

Leads to increase in density and reduction of permeability in concrete

It’s use is must for manufacturing of concrete above M50 Contd…

SILICA FUME (Micro Silica)

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SILICA FUME

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Admixtures are materials mostly chemicals that are added in small quantities during the preparation of concrete to impart certain specific properties to it.The requirements may be

Improving the workability of concrete during placing Retarding or accelerating setting Improving the impermeability and water tightness of the

cast concrete. Imparting corrosion inhibition etc Entraining air in concrete

Chemical Admixtures

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Compatibility test by Marsh Cone Apparatus

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DEFLOCCULATION OF CEMENT PARTICLES

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DISPERSION OF MECHANISM

Dispersion Mechanism

Electro static repulsion Steric Hindrance

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EFFECT OF SUPER PLASTICISERON WORKABILITY

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SLUMP : Collapse

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EFFECT OF SUPER PLASTICISERON WORKABILITY

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PUMPABLE CONCRETE

1. Air entrainers :

TYPES OF ADMIXTURES

They entrain air in the form of micro air bubbles which helps in improving the durability of concrete in freezing environment, sulphate and alkali attack.

2. Water reducers

To reduce the water-cement ratio and yet retain workability. It is possible to reduce water upto 12%. The only precaution is that it should be mixed thoroughly

3. Accelerating admixtures :To accelerate setting of cement in cold environment or where early setting is desired.It assists in early removal of form work

4. Retarding admixtures :

To delay the setting time of concrete, for RMC supplied to far off sites.Prolongs setting time, giving higher strength at later stages, also results in reduction in micro cracks.

5. Super plasticisers :To make flowing concrete for concreting in heavily reinforced sections, tremie concrete, for pumping concrete.(when added to normal concrete with 75mm slump upto 250mm can be achieved)

6. High range water reducers :

PC based admixturesWater reduction capacity of about 25-40%High performanceEarly strength and early setting

7. Bonding agents :

To increase bond strength, old and new concrete(in repair and rehabilitation works), they are usually modified latex or polymer compounds

8. Corrosion inhibitors :To inhibit corrosion

Aggregate is the word used to describe any inert material . Usually rock derivative generally between 50mm down to

75 micron used to produce concrete . It is divided into coarse aggregate and fine aggregate Those which are 4.75mm to 50mm are classified as coarse

aggregates Those below 4.75mm to 75 micron as fine aggregates Except for mass concrete in dams etc. which may contain

upto 150mm size aggregate, the maximum size of aggregate is normally 20mm in most cases

But it may be 40mm for plain concrete or massive works.

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AGGREGATES

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Specific gravity: it should have good crushing strength and density

Surface texture: it should be smooth,slightly rough but not honeycombed

Particle shape : it should not be flaky or elongated.

Porosity : it should have very low water absorption

Should not be Reactive

PROPERTIES OF COARSE AGGREGATES

Water demand, Workability Cohesion of concrete in plastic state Strength, Density, Durability Porosity of hardened concrete Stability : it should be chemically inert. Impurities: it should be free from impurities

(like silt, clay) Compactness: it should be graded, as then

only the voids can be less.

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PROPERTIES OF AGGREGATE EFFECT

Specific gravity implies the absolute weight per unit volume of aggregates

A low specific gravity may indicate high porosity poor durability low strength.

Specific gravity of aggregates is used in arriving at mix design

Generally the specific gravity of good aggregates is greater than 2.5 g/cm3

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SPECIFIC GRAVITY

Surface texture reveals how grainy or smooth the surface of the aggregate is.

It indicates bonding strength and porosity. Higher the smoothness of the particle, lesser is

the bonding between aggregate and cement matrix.

rough textured aggregates develop higher bond strength than smooth textured aggregates,

This property is especially considered while producing high strength concretes.

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SURFACE TEXTURE

Particle shapes are classified as Irregular Rounded Flaky Angular Aggregates should be as much cubical as

possible in shape

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PARTICLE SHAPE

Grading of aggregates means particle size distribution of the aggregates.

Principle of grading is that smaller size particles fill up the voids left in larger size particles.

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GRADING

IS sieve Designatio

n

Percentage passing for single size aggregate of nominal size by weight

63 mm 40mm 20 mm 16 mm 12.5 mm

10 mm Remarks

80 mm 100 - - -63 mm 85-100 100 - -40 mm 0-30 85-100 100 -20 mm 0-5 0-20 85-100 10016 mm - - 85-100 100

12.5 mm - - - 85-100 10010 mm 0-5 0-5 0-20 0-30 0-45 85-100

4.75 mm 0-5 0-5 0-10 0-202.26 mm - - - 0-5

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GRADING OF COARSE AGGREGATE

Indian standards divides the sand into four zones

zone-I to zone-IV based on the sieve analysis

Sand falling in zone-I is coarse and that falling in zone-IV is fine.

Sand falling in zone IV shall not be used for reinforced concrete work.

Fineness modulus for sand : ranges from 2.2 to 3.2, higher value indicates coarser grading

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SAND

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IS sieve designation

Percentage passingZone-I Zone-II Zone-III Zone-IV

10 mm 100 100 100 1004.75 mm 90-100 90-100 90-100 90-1002.36 mm 60-95 75-100 85-100 95-1001.18 mm 36-70 55-90 75-100 90-100

600 microns 15-34 35-59 60-79 80-100300 microns 5-20 8-30 12-40 15-50150 microns 0-10 0-10 0-10 0-15

Remarks Very coarse Coarse Medium Fine

REQUIREMENT OF FINE AGGREGATES

Water helps in dispersing the cement evenly

Quality of water for making concrete and for curing

Water should be free from salts, oils, acids, alkalis, sugar and organic materials

pH value shall not be less than 6 Sea water is not suitable for making

concrete

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WATER

SL. No.

Description Tested as per Permissible limit (max) mg/l

1 Organic IS-3025(part-18) 2002 Inorganic IS-3025(part-18) 30003 Sulphates (as SO3)

Sulphates (as SO4)IS-3025(part-24) IS-3025(part-24)

400500

4 Chlorides (as Cl) IS-3025(part-32) 2000 mg/l for concrete not containing embedded steel

1000 mg/l for RCC work

5 Suspended matter IS-3025(part-17) 2000

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PERMISSIBLE LIMITS FOR SOLIDS IN WATER

FRESH CONCRETE Fresh concrete is a freshly mixed material

which can be moulded into any shape. Workability: is the ease with which fresh

concrete can be mixed, transported, placed and compacted in the moulds or forms

Apart from water-cement ratio the concrete has to be compacted well to get the required strength

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UNDERSTANDING CONCRETE

TESTS ON FRESH CONCRETE

WORKABILITY 1. Slump Test 2. Compaction Factor Test 3. Flow Test. Yield Test

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It is the science of the deformation and flow of materials and is concerned with relationships between stress, strain, rate of strain and time.

The term Rheology deals with the materials whose flow properties are more complicated than those of fluids (liquids or gases)

RHEOLOGY OF CONCRETE

Factors affecting workability: Water content Mix proportions Size of aggregates Shape of aggregates Surface texture of aggregate Grading of aggregate Use of admixture

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Segregation: Segregation can be defined as the separation of

the constituent materials of concrete.Bleeding: Sometimes referred as water gain It’s a particular form of segregation

due to highly wet mix If water cement ratio is more than 0.7 Badly proportioned and insufficiently

mixed concrete

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BLEEDING

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While traversing from bottom to top Bleeding channels responsible for

permeability It may be interrupted by aggregates

(flaky) It may be interrupted by reinforcement Reduces bond between reinforcement,

aggregate and paste Remedy— re-vibration, delayed finishing

Cement – 3.15Coarse aggregate – 2.70Sand – 2.60Water – 1.00Fly ash– 2.15Silica Fume - 2.20

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SPECIFIC GRAVITY

Compaction of concrete is the process adopted for expelling the entrapped air from the concrete.

The entrapped air in the form of voids reduces the strength of concrete.

For every 1% of entrapped air, the strength of concrete falls about 5% to 6%.

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COMPACTION

Hand compaction Tamping Ramming : generally permitted for

unreinforced foundation concrete RCC should never be rammed Compaction by vibration: common

needle vibrator dia is 25mm to 40mm External vibrators Surface vibrators

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METHODS OF COMPACTION

Contd…

When inserting a needle vibrator, allow it to penetrate the bottom of the layer as quickly as possible.

If it is done slowly, the upper part of the concrete will get compacted and prevent the air in the bottom layer from escaping.

The vibrator should be left in the concrete for about 10 sec. and then withdrawn slowly. If it is withdrawn fast, a hole will be left in the concrete.

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PRECAUTIONS

Contd…

The vibrator should be inserted again at a distance of not more than 50 cm from its last position.

The vibrator should not be allowed to touch the face of the form work or the reinforcement to prevent the reinforcement from losing bond with concrete

Do not stop the vibrator when the needle is in the concrete.

Do not over vibrate or under vibrate

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The rate of levelling should not be less than the rate placing of concrete

FINISHING OF CONCRETE

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Effect of Water-Cement ratio Effect of maximum size of aggregate

on strength Grades of concrete: Concrete in construction is specified

by grade like M20,M25 etc. Usually increments of five.

M20 means the specified crushing strength is 20 N/mm2

STRENGTH OF CONCRETE

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CURING Why Curing ? To prevent loss of moisture from the

Concrete due to combined effect of hot sun and drying wind

Creation of conditions for promotion of uninterrupted and progressive hydration of cement during the period immediately after placing

Curing does not mean only application of water

HARDENED CONCRETE

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1. WATER CURING2. MEMBRANE CURING3. APPLICATION OF HEAT (Steam Curing)4. ACCELERATED CURING

CURING METHODS

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Sampling Criteria Cube Testing Acceptance Criteria Non Destructive Testing of Concrete

1. Rebound Hammer Test 2. Ultra sonic pulse velocity testing Core Test

COMPRESSIVE STRENGTH

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OTHER CONCRETES : High strength concrete High performance concrete Mass Concrete Light-weight concrete High-density concrete No-fines concrete Roller compacted concrete Ferrocement Self compacting concrete.

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HIGH STRENGTH CONCRETE

CONCRETE GRADE FROM M60 ONWARDS REGARDED AS HIGH STRENGTH CONCRETE

FOR HIGH STRENGTH CONCRETE DESIGN STANDARDS GIVEN IN THE CODE IS-456-2000 MAY NOT BE APPLICABLE

THEY HAVE TO BE OBTAINED FROM SPECIFIED LITERATURES OR BY EXPERIMENTAL RESULTS

SPECIAL CONCRETES

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POSSESSING1. HIGH WORKABILITY2. HIGH STRENGTH3. HIGH DENSITY4. HIGH DIMENSIONAL STABILITY5. LOW PERMEABILITY6. RESISTANCE TO CHEMICAL ATTACK

HIGH PERFORMANCE CONCRETE

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NORMAL CONCRETE HEAVY SELF WEIGHT

(DENSITY 2200 to 2600 KG/M3)

LIGHT WEIGHT CONCRETE DENSITY (300 to 1850 KG/M3) LOW THERMAL CONDUCTIVITY

LIGHT WEIGHT CONCRETE

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DENSITY 3360 TO 3840 KG/M3 EVEN 5280 KG/M3 USING IRON AS BOTH F.A. AND C.A

DENSITY 50% HIGHER THAN THE CONVENTIONAL CONCRETE

USED AS A SHIELDING MATERIAL FOR PROTECTION FROM RADIATION

HIGH DENSITY CONCRETE

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It is made by introducing air or gas into the slurry composed of cement and finely crushed sand by alluminium powder.

Uniformly cellular structure is formed. Also called as gas concrete, foam

concrete, cellular concrete

AERATED CONCRETE

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By Omitting fine aggregate fraction Made by cement, water and single sized

coarse aggregates Having large voids and hence light in weight Applications

Temporary structures In external walls for Thermal insulation Rough texture gives good base for plastering Free from dampness because of low capillary

action on account of large voids

NO-FINES CONCRETE

ROLLER COMPACTING CONCRETE

Recent development particularly in the field of Dam construction.

Lean mix No slump concrete High volume fly ash to the extent of

60 to 65% Compacted by Rollers. Compressive strength of about 7

Mpa to 30 Mpa

FERRO CEMENT It is a relatively new material consisting

of wire meshes and cement morar. Thickness of elements is 2 to 3 cm Water –cement ratio 0.4 to 0.45 Cement -sand ratio 1:2 External cover to reinforcement is 2 to

3mm

APPLICATIONS OF FERROCEMNT

FOR CASTING DOMESTIC OVER-HEAD WATER TANKS

FOR TANKS USED AS GRAIN SILOS IN VILLAGES

FOR CONTAINER USED AS GAS HOLDER UNIT IN “GOBBAR GAS” PLANTS.

IDEAL MATERIAL FOR BOAT BUILDING FOR MANHOLE COVER

SELF COMPACTING CONCRETE

Self levelling concrete With Super plasticizer (Glenium ) Fines Should not be vibrated Applications Precast units.

MASS CONCRETE It’s is a concrete having considerable

dimensions that may get affected by thermal behavior of Concrete. Ex-Concrete Dam

Members with minimum cross sectional dimension of a solid concrete member approaches or exceeds 2 to 3 ft

Cement contents above 364 kg/m3

It is a latest development in the construction industry

Concrete is batched and mixed in a centralised Plant and transported to the sites far-away from the plant through Transit-Mixers and placed through pumps to the required height and distances.

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RMC (READY MIX CONCRETE)

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RMC PLANT

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PLANT LAYOUTPLANT LAYOUT

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CONVEYOR BELT

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DOUBLE SHAFT MIXER

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BATCHING PLANTBATCHING PLANT

CONCRETE PUMPS

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TRUCK MOUNTED BOOM PUMPS

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RMC PLACEMENT THROUGH BOOM PUMPS

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RMC PLACEMENT THROUGH BOOM PUMPS

ANY QUESTIONS ?

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THANK YOU

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