high volume fly ash concrete - bookspar.com

Lecture-7

Normal Concrete

IS-456: 2000 Provisions.

• Cement: 300-450Kg /m3

• Max.W/C Ratio: 0.55-0.4

• Grade of Concrete: M20 - M40

• Permits the use of :

o Mineral Admixtures (Fly Ash, Silica Fume, GGBS, Rice Husk Ash, Metakaoline)

o Chemical Admixtures

Eco-Smart Concrete (HVFC)

• EcoSmart or Green concrete uses large volumes of by-products to reduce green house

emissions for preservation of ecology

• Concrete optimally uses industrial and agriculture wastes in form of cementitious, pozzolanic

and or inert as its ingredients without scarifying its structural properties and imparting

improved performance and life.

Eco-Smart Concrete(HVFC)

� EcoSmart or Green concrete uses large volumes of by-products to reduce green house

emissions for preservation of ecology

� Concrete optimally uses industrial and agriculture wastes in form of cementitious, pozzolanic

and or inert as its ingredients without scarifying its structural properties and imparting

improved performance and life.

WHY HVFC

• Annually, more than 90 million tonnes of Fly Ash is being generated in India.

• Requires 65,000 acres of land for disposal

• By 2015, 1000 square Km of land required.

• Current production of Cement is about 70 million tonnes

HVFA Concrete

High volume fly ash concrete is designated as EcoSmart or Green concrete and have following

properties:

1. Structural capability

2. Durability

3. Cost efficiency

4. Aesthetics

5. Schedule of construction



Lecture-7

6. Better utilisation of large volume of co-product

7. Sustainability of depleting resources

Why use EcoSmart Concrete (HVFC)

• Adequate structural strength

• Improved flexural and tensile strengths

• Results in less bleeding

• Cohesive flow able concrete

• Improves resistance to sulphate and other chemicals

• Gives a superior appearance

• Costs less

• Is environmentally sound

HVFA Concrete

High volume fly ash concrete is defined as concrete with following attributes

1. Fly ash replacing cement by 30 – 60%

2. W/B < 0.40

3. Very low water, Chloride & oxygen penetrability

4. Almost double design life with least maintenance

5. Better fresh concrete properties

6. Better finishes and hence Aesthetics

7. Does not affects the schedule of construction

8. Economical than conventional concrete

9. Offers sustainability of depleting resources

HVFC

Disadvantages

1. All fly ashes can not be used in structural concrete

2. Replacement level depends on fly ash properties

3. Requires a good knowledge of mix proportioning

4. If not handled properly, may be dangerous

5. Requires better quality control at site

6. Slower rate of hardening and hence behaves differently to steam curing

7. Requires good curing for minimum 7 days



Lecture-7

E.A. Abdun- Nur, 1984.

“In the world of modern concrete, fly ash is as essential an ingredient of the mixture as are Portland

cement, aggregates, water and chemical admixtures. In most concretes, I use it in larger amounts ( by

volume) than Portland cement, and therefore it is not an admixture, i.e. an addition to the mixture.

Concrete without fly ash and chemical admixtures should only be found in museum showcases”.

Fly Ash

What is Fly ash?

• Fly ash is a fine powder, produced as a by-product of the combustion of coal in thermoelectric

power plants.

Types of fly ash

• Low-lime fly ash (CaO < 10% )

o Exhibit Pozzolanic properties produces cementitious properties with the help of an activator

(cement or lime).

• High-lime fly ash (CaO > 10% )

o Exhibit Cementitious properties itself.

Chemical Composition

• Major constituents of most fly ashes are

SiO2, Al2O3, Fe2O3 ,CaO and Loss on Ignition (LOI).

• Other elements are MgO, Na2O, K2O, SO3, MnO, TiO2.

Morphology

Smooth, glassy surface



Lecture-7

Properties of HVFC

FA absorptions, % 40 50 60

Total Binder, kg 435

Cement, kg 260 215 175

W/B 0.42 0.42 0.42

Slump, mm 75 85 95

Air content, % 3.5 3.8 4.0

Bleeding, ml/cm2 0.020 0.024 0.025

Density, kg/m3 2500 2495 2490

Hardened concrete properties


0

10

20

30

40

50

60

70

80

0 50 100 150 200

Age, days

Compressive strength, MPa

40 50 60

0

1

2

3

4

5

6

7

8

0 50 100 150 200

Age, days

MOR, MPa

40 50 60



Lecture-7


Water Permeability

Chloride Permeability

0

10

20

30

40

50

28 60 90 180

Age, days

Water pen

etration

,mm

40 50 60

0

200

400

600

800

1000

0 50 100 150 200Age, days

Chan

ge p

assed, Cou

lomb

40 50 60



Lecture-7

Variety in HVFAC mixes

Fly ash %

Compressive strength, MPa 0 25 40 56

1 day 27.8 26.2 18.1 10.0

3 day 41.4 33.5 30.1 26.9

7 day 46.1 43.5 42.6 41.6

28 day 61.6 59.2 60.4 57.7

182 day 62.6 60.9 62.1 64.5

Sky Trains

• Work of Fast + Epp structural Engineers and Busby Architectural Associates in Vancouver.

• To construct two sky train stations, on elevated platforms with HVFA concrete with the support

of CANMET

Brentwood Station



Lecture-7

Precast Prestressed Platform Beams

South Concrete Frame

Gilmore Station



Lecture-7

Indian Case studies

Hiranandani Builders, Mumbai

1. Frame structures with buildings up to 20 stories, both in Powai, Thane and other locations

2. Uses 30% fly ash in all structural concrete of grade M35

3. Uses 40% fly ash in non-structural concrete

4. Uses 50% Fly ash in Masonry

Hiranandani Builders, Mumbai

Typical concrete mix

Cement = 300 kg

FA = 130 kg

Water = 165 kg

W/B = 0.40

Aggregates = 1975 kg

Grade = M35

Other Builders

• Almost every builder in Mumbai uses fly ash based concrete, varying between 15 to 35 %

for various structural applications.

• Builders in Delhi have started using fly ash in structural concrete of residential and

commercial building

• Masonry and plasters uses about 60% fly ash as cement replacement

Delhi metro rail

Delhi metro rail under construction have about 100 km of underground portion, subjected to aggressive

environment



Lecture-7

Delhi metro rail

Used 30% fly ash in all structural concrete & 70% slag in underground sections

Concrete road in Ropar

700 m long, 7 m wide demonstration project undertaken under the guidance of CIDA

Concrete road in Ropar

Details Values

Grade of concrete M40

Cement 280

Fly ash 200

Water 180



Lecture-7

SP 2.8

Aggregates 1830

Compressive strength, MPa 7 day

28 day

90 day

27.0

40.2

?

Flexural strength, MPa at 28 days 6.4

Water permeability, DIN test, mm 17

RCPT, ASTM 1202, Coulomb 551

Concluding Remarks

� It is possible in our country to have HVFAC structures

� It is economically required for our country

� Cooperative Owner/Contractor/Architect critical

� Be Balanced – don’t “force it”

� Ideal Conditions:

• warm weather

• large pours

• no schedule/form stripping constraints

� Take higher strengths into consideration when designing

Concluding Remarks

Engineer’s of the future have to shoulder the additional responsibility of conserving the increasingly

depleting natural resources by adopting ECO-FRIENDLY technologies.

CONCRETE PUMPS

Pumps

• Pumps are available in different sizes

• Pipes diameter must be at least 3 times greater than max aggregate size

• A slump of 40 to 100 mm is generally recommended

Direct acting concrete pump



Lecture-7

Direct acting concrete pump

• Horizontal

Piston type with semi rotary valves

• Concrete

is fed by gravity and partially sucked during suction stroke

• Moved up

to 450m horizontally, 40 m vertically

• 60 cum of

concrete can be achieved per hour

Squeeze-type concrete pumps

Squeeze-type concrete pumps

• Concrete is placed in collecting hopper

• Used with small pipes (up to 100 mm dia)

• The vacuum inside the chamber is about 660 mm of Hg.



Lecture-7

• Two rotating rollers progressively squeeze the tube, thus pump the concrete in the suction

pipe towards delivery pipe.

• Moved up to 90m horizontally, 30 m vertically

• 20 cum of concrete can be achieved per hour

Advantages

• Concrete can be delivered to points over a wide area otherwise not easily accessible

• Pumping delivers the concrete direct from the mixer to the form and so avoids double

handling

• Placing can proceed at the rate of the out put of the mixer

• It is not held back by the limitations of the transportation and placing equipment

Limitation/ problems faced

• Unsatisfactory concrete cannot be pumped

• Control of mix is affordable by the force required to stir it in the hopper and by the pressure

required to pump it

• Blockage can occur

o Water escapes through the mix so that pressure is not transmitted to the solids,

therefore cannot move

o If the fines are very high, the friction resistance of the mix is so large that pressure

exerted by the piston is not sufficient to move the concrete, which becomes stuck

Moderon concrete pumps

• The first type of concrete pump is attached to a truck.

• It is known as a trailer-mounted boom concrete pump because it uses a remote- controlled

articulating robotic arm (called a boom) to place concrete with pinpoint accuracy.

• Boom pumps are used on most of the larger construction projects as they are capable of

pumping at very high volumes and because of the labour saving nature of the placing boom.

• They are a revolutionary alternative to truck-mounted concrete pumps.

Truck-mounted concrete pump

• The second main type of concrete pump is either mounted on a truck or trailer and are

called as truck-mounted concrete pump

• it is commonly referred to as a line pump or trailer-mounted concrete pump.

• This pump requires steel or rubber concrete placing hoses to be manually attached to the

outlet of the machine.



Lecture-7

• Line pumps normally pump concrete at lower volumes than boom pumps and are used for

smaller volume concrete placing applications

Under Water Concreting

• In the

tremie process, concrete is placed through a vertical steel pipe with an open, funnel-shaped

upper end. The lower end of the tremie is kept immersed in plastic concrete so that freshly

placed concrete doesn’t come into contact with the water.



Lecture-7



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