CONCRETE CONSTITUENTS OF CONCRETE LIGHTWEIGHT CONCRETE ADVANTAGES DISADVANTAGES APPLICATIONS PRINCIPLE TECHNIQUES BEHIND LIGHTWEIGHT CONCRETE LIGHTWEIGHT AGGREGATE CONCRETE PRODUCTION OF LIGHTWEIGHT AGGREGATE CONCRETE CLASSIFICATION OF LIGHTWEIGHT AGGREGATE CONCRETE NATURAL AGGREGATE ARTIFICIAL AGGREGATE LOW-DENSITY CONCRETES STRUCTURAL LIGHTWEIGHT CONCRETE MODERATE-STRENGTH LIGHTWEIGHT CONCRETE PROPERTIES OF LIGHTWEIGHT AGGREGATE CONCRETE AERATED OR FOAMED CONCRETE MANUFACTURING OF FOAMED CONCRETE PROPERTIES OF FOAMED CONCRETE APPLICATIONS OF FOAMED CONCRETE NO FINES CONCRETE PROPERTIES NO FINES CONCRETE APPLICATIONS NO FINES CONCRETE HIGH DENSITY CONCRETE Man-made (Synthetic) Aggregates ADMIXTURE High Strength Concrete SPECIAL METHODS OF MAKING HIGH STRENGTH CONCRETE

1. BUILDING CONSTRUCTION - IV
(ARCH- 220)
AMITY SCHOOL OF ARCHITECTURE &
PLANNING
Sem-IV (2020-2021), Section-A
B. Arch 2019-24
ASAP, Noida

2. CONCRETE
 Concrete is a construction material composed of cement, fine aggregates
and coarse aggregates mixed with water which hardens with time.
 In building construction, concrete is used for the construction of
foundations, columns ,beams , slabs and other load bearing elements.
CONSTITUENTS OF CONCRETE:-
 Fine Aggregates: 25 - 30%
 Coarse Aggregates: 30 to 50%
 Matrix (paste):
• Water: 15 – 20%
• Cementitious materials (cement, pozzolans & slag): 7 – 15%
• Air: 1 – 8%
• Chemical Admixtures: < 2%

3.  Lightweight concrete is a special concrete which weighs lighter than
conventional concrete.
 Lightweight concrete can be defined as a type of concrete which includes an
expanding agent in that it increases the volume of the mixture while giving
additional qualities such as durability and lessened the dead weight.
 Lightweight concrete mixture is made with a lightweight coarse aggregate and
sometimes a portion or entire fine aggregates may be lightweight instead of
normal aggregates.
 Lightweight concrete is a mixture made with lightweight coarse aggregates such
as shale, clay, or slate, which give it its characteristic low density.
 Structural lightweight concrete has an in-place density of 90 to 115 lb./ft³,
whereas the density of regular weight concrete ranges from 140 to 150 lb/ft³.
LIGHTWEIGHT CONCRETE

4.  Reduction in dead loads making savings in foundations and reinforcement.
 Easy to handle and hence reduces the cost of transportation and handling.
 Improves the workability.
 Relatively low thermal conductivity
 Comparatively more durable
 Good resistance to freezing & thawing action when compared to conventional concrete.
ADVANTAGES
 Very Sensitive with water content in the mixture.
 Due to its light weight it maybe difficult to mix with the aggregate and may
float on the surface.
 Mixing time is longer than conventional concrete to assure proper mixing .
 Lightweight Concrete are porous and shows poor resistance
DISADVANTAGES

5. APPLICATIONS
 The strength of L.W.C. is low, it is used in the construction of roof slabs,
small houses with load bearing walls etc.
 It is also used in the construction of stairs, windows, garden walls, etc.
 These are moulded in the form of slabs and used as thermal insulators
inside the building.
 The structural lightweight concrete can use for the construction of residential
and non-residential buildings in seismic areas.
 This concrete can also be used for the construction of underground bunkers.
 The lightweight concrete can use for making a structure such as Precast wall
blocks and panels, homes on weak foundations, roof and building aprons,
partitions, boats, shipbuilding, lightweight blocks/bricks, thin shell roof
structures, roof section in high-rise structures, doors, bridge decks, and
girders, etc.
 Construction of partition walls and panel walls in frame structures.
A LIGHTWEIGHT BUILDING

6. The principal techniques used for producing lightweight concrete can be summarized as follows:
 By omitting thesand from the concrete(no-fines concrete).
 By incorporating the air or gas bubbles in concrete(aerated or foamed concrete).
 By replacing the conventional aggregates by cellular porous aggregates (lightweight aggregate concretes).
PRINCIPLE TECHNIQUES BEHIND LIGHTWEIGHT CONCRETE
NO-FINES AERATED OR FOAMED LIGHTWEIGHT AGGREGATE

7.  Lightweight aggregate is a type of coarse aggregate that is used in the
production of lightweight concrete products such as concrete block, structural
concrete, and pavement.
 Most lightweight aggregate is produced from materials such as clay, shale, or
slate. Blast furnace slag, natural pumice, vermiculite, and perlite can be used
as substitutes, however.
 To produce lightweight aggregate, the raw material (excluding pumice) is
expanded to about twice the original volume of the raw material. The
expanded material has properties similar to natural aggregate, but is less
dense and therefore yields a lighter concrete product.
 The weight of the lightweight aggregate concrete is around 115 pounds per
cubic foot, whereas the weight of the normal weight concrete is 145 pounds
per cubic foot.
 The less weight of light weight concrete is due to the usage of fine and
course lightweight aggregate. When the complete aggregate is replaced with
lightweight aggregate, the weight decreases the concrete density of by
approx. 10 kilogram per cubic meter.
LIGHTWEIGHT AGGREGATE CONCRETE

8.  The production of lightweight aggregate begins with mining or quarrying the
raw material.
 The material is crushed with cone crushers, jaw crushers, hammer mills, or
pug mills and is screened for size.
 Oversized material is returned to the crushers, and the material that passes
through the screens is transferred to hoppers.
 From the hoppers, the material is fed to a rotary kiln, which is fired with
coal,coke, natural gas, or fuel oil, to temperatures of about 1200°C
(2200°F).
 As the material is heated, it liquefies and carbonaceous compounds in the
material form gas bubbles, which expand the material; in the process,
volatile organic compounds (VOC) are released.
 From the kiln, the expanded product(clinker) is transferred by conveyor into
the clinker cooler where it is cooled by air, forming a porous material.
 After cooling, the lightweight aggregate is screened for size, crushed if
necessary, stockpiled,and shipped.
PRODUCTION OF LIGHTWEIGHT AGGREGATE CONCRETE

9. CLASSIFICATION OF LIGHTWEIGHT AGGREGATE CONCRETE
ON THE BASIS OF MATERIAL
 Natural aggregate
 Artificial aggregate
 Lightweight aggregate concrete is made with lightweight aggregates, either natural or manufactured,
comprising gravel or crushed stone.
 Therefore it has substantially lower bulk density than concrete.
 Natural light weight aggregates are less preferred over artificial aggregates.
 The natural aggregates are available naturally. These aggregates are chemically inert and usually has a
relatively high amount of silica about 75%
 Artificial aggregate are mostly produced in the rotary kiln. The raw materials are clay, shale, slate or
pulverized fuel ash. These are subjected to either expansion or agglomeration.

10. NATURAL AGGREGATE
 Pumice: These are rocks of volcanic origin. They are light coloured or nearly white and has a fairly even
texture of interconnected voids.It is used for reinforced concrete roof slab, mainly for industrial roofs.
 Scoria: Scoria is light weight aggregate of volcanic origin. They are dark in colour .It is slightly weaker than
pumice.
 Rice Husk: Use of rice husk or groundnut husk has been reported as light weight aggregate.
 Saw dust: Saw dust is used as light weight aggregate in the flooring and in the manufacture of precast
elements. But the presence of carbohydrates in the wood, adversely affect the setting and hardening of
Portland cement.
 Diatomite: It is derived from the remains of microscopic aquatic plants called diatoms. It is also used as a
pozzolanic material.
 Volcanic cinders: cinders are applied as surfacing material primarily on unpaved roads, such as logging,
forest ac- cess, and low-traffic roads. On higher type roads cinders are used as subbase and base material
and for asphalt-stabilized surfacing.
PUMICE SCORIA RICE HUSK SAW DUST DIATOMITE CINDERS

11. ARTIFICIAl AGGREGATE
 Sintered flash (Pulverized fuel ash): it is used as as aggregate in concrete; in horticulture as a growth
media; as a thermal insulator; as a refractory material; and as a specialist surface for sport facilities.
 Foamed Slag: Foamed slag is a by product produced in the manufacture of pig iron. It is a porous,
honeycombed material which resembles pumice.
 Bloated Clay: When special grade of clay and shales are heated to the point of incipient fusion, there will
be expansion due to formation of gas within the mass. The expansion is known as bloating and the product
so formed is used as light weight aggregate.
 Exfoliated vermiculite: The concrete made with vermiculate as aggregate will have very low density and
very low strength.
 Ciders, clinkers, breeze: The partly fused or sintered particles arising from the combustion of coal, is
termed as cinder or clinker or breeze. These are used for making building blocks for partition walls, for
making screening over flat roofs and for plastering purposes.
PULVERIZED FUEL ASH FOAMED SLAG BLOATED CLAY VERMICULITE CIDERS

12. ON THE BASIS OF DENSITY AND STRENGTH
 Low-density concretes
 Structural lightweight concretes
 Moderate-strength lightweight concretes.
LOW-DENSITY CONCRETES :
 Low-density concretes are generally used for insulation as they have high thermal
insulation values.
 They have a density of 800 kg/m3 or lower. Being of low density, they have a low
compressive strength between 0.7 and 7.0 MPa.
 Vermiculite and perlite are commonly used aggregates.
 They are known to have bulk density in the range from 96 to 192 kg/m3.
 During a rise in temperature, with vermiculite, being a micaeous mineral, layers of
combined water in the mica’s laminar structure are converted to steam.
 Due to this, successive layers are peeled off, leading to material disintegration.
 At the same time, perlite, being a volcanic glass, contains combined water
making the internally generated steam expand violently.

13. STRUCTURAL LIGHTWEIGHT CONCRETE :
 Structural lightweight concretes are produced using aggregates such as expanded slags ; sintering grate
expanded shale, clay, or FA; and rotary kiln expanded shale, clay, or slate.
 These aggregates produce concretes that have densities ranging from 1360 to 1920 kg/m3 and minimum
compressive strengths of 17.0 MPa.
 Although the insulating efficiency is lower than that of low-density concretes, it is still higher than that of
normal-weight concretes.
 It is light in weight and sufficiently strong to be used in conjunction with steel reinforcement and is a
material which is more economical than the conventional concrete
 Workability is less due to water absorption by the aggregates.
 Drying shrinkage is more and less thermal expansion than normal concrete.
 Is good in sound proofing, sound absorption & thermal insulation.
MODERATE-STRENGTH LIGHTWEIGHT CONCRETE :
 Moderate-strength lightweight concretes are made from pumice which is spongy lava, or scoria aggregate
which is volcanic cinder .
 As a result of a rise in temperature, steam or gas escapes from the lava while pumice is hot, creating tube-
like, interconnected void pores.
 Scoria has a pore structure and possesses isolated voids.
 These concretes have a density and strength approximately midway between those of low-density and
structural concretes. They are also called fill concrete.

15. PROPERTIES OF LIGHTWEIGHT AGGREGATE CONCRETE
1. Particle Shape and Texture of Aggregate
 The shape of the lightweight aggregate used in concrete may be in cubical, rounded, angular, or irregular
shape.
 Textures may range from the fine pore, relatively smooth skins to highly irregular surfaces with large
exposed pores.
2. Compressive Strength
 Compressive strength levels commonly required by the construction industry for design strengths of cast-in-
place, precast, or prestressed concrete is around 3,000 to 5,000 psi which can be easily obtained by
lightweight aggregate concrete.
3.Density
 The fresh density of lightweight concretes is a function of mixture proportions, air contents, water demand,
particle density, and moisture content of the lightweight aggregate.
4. Absorption
 Studies have revealed that high-quality lightweight concretes absorbed very little water and thus maintained
their low density. The permeability of lightweight concrete was extremely low and generally equal to or
significantly lower than that reported for normal weight concrete.

16. PROPERTIES OF LIGHTWEIGHT AGGREGATE CONCRETE
5. Internal Curing
 Lightweight aggregate batched at a high degree of saturation may be substituted for normal weight
aggregates to provide internal curing in concrete containing a high volume of cementitious materials.
 The reason is better hydration of the cementitious fraction provided by moisture available from the slowly
released reservoir of absorbed water within the pores of the lightweight aggregate.
6. Thermal Conductivity
 The thermal conductivity of concrete depends mainly on its density and moisture content but is also
influenced by the size and distribution of the pores, the chemical composition of the solid components,
their internal structure of light weight concrete.
 The LWC is low in density and moisture conduct is more due to pores, the thermal conductivity of this
concrete is less when compared to normal concrete.
7. Fire Resistance
 When tested according to the procedures of ASTM E 119, structural lightweight concrete slabs, walls, and
beams have demonstrated greater fire-endurance periods than equivalent-thickness members made with
concretes containing ordinary aggregate.

17. AERATED OR FOAMED CONCRETE
 Foam concrete, also known as Lightweight Cellular Concrete (LCC), Low Density Cellular Concrete (LDCC),
and other terms is defined as a cement-based slurry, with a minimum of 20% (per volume) foam entrained
into the plastic mortar.
 As mostly no coarse aggregate is used for production of foam concrete the correct term would be called
mortar instead of concrete; it may be called "foamed cement" as well.
 The density of foam concrete usually varies from 400 kg/m3 to 1600 kg/m3.
 The density is normally controlled by substituting fully or part of the fine aggregate with foam.
MATERIAL USED IN FOAM CONCRETE

18. MANUFACTURING OF FOAMED CONCRETE
 Foamed concrete typically consists of a slurry of cement or fly ash and sand and water, although some
suppliers recommend pure cement and water with the foaming agent for very lightweight mixes.
 This slurry is further mixed with a synthetic aerated foam in a concrete mixing plant.
 The foam is created using a foaming agent, mixed with water and air from a generator.
 The foaming agent used must be able to produce air bubbles with a high level of stability, resistant to the
physical and chemical processes of mixing, placing and hardening.
 Foamed concrete mixture may be poured or pumped into moulds, or directly into structural elements. The
foam enables the slurry to flow freely due to the thixotropic behaviour of the foam bubbles, allowing it to be
easily poured into the chosen form or mould.
 The viscous material requires up to 24 hours to solidify (or as little as two hours if steam cured with
temperatures up to 70 °C to accelerate the process.
 Depending on variables including ambient temperature and humidity. Once solidified, the formed produce
may be released from its mold.
 New application in foam concrete manufacturing is to cut the big size concrete cakes into blocks of different
sizes by a cutting machine using special steel wires. The cutting action takes place when concrete is still
soft.

19. MANUFACTURING OF FOAM
MANUFACTURING OF FOAM
CONCRETE

20. 1. Low heat transfer.
 Foamed concrete porous structure provides good insulation, so walls and floors made of foamed
concrete do not need additional insulation.
2. Good acoustic insulation.
 Foamed concrete provides low noise transmission.
 This feature is necessary for making acoustical blanket on floor slabs made of structural concrete.
3. Ecological properties.
 Foamed concrete is one of the most eco-friendly and non-hazardous materials, also it doesn’t educe any
harmful substances in operation.
 It is inferior in environmental compatibility only to wood, but at the same time foamed concrete has
longer lifetime and is more reliable.
4. Fire safety.
 Due to low heat transfer foamed concrete secures from fire and it is highly recommended for fire-
resistant constructions.
PROPERTIES OF FOAMED CONCRETE

21.  As load bearing masonry walls using cellular concrete blocks.
 As partition walls in residential, institutional and industrial buildings.
 As precast composite wall or floor panels
 As a filler wall in the form of precast reinforced wall panels in high-rise building
 As precast floor and roof panels in all types of buildings.
 As insulation cladding to exterior walls of all types of buildings.
APPLICATIONS OF FOAMED CONCRETE

22. NO FINES CONCRETE
 No fines concrete is one type of light weight concrete. As the name
indicates, this a concrete mix without fine aggregate or sand. This type of
concrete consists of only water, cement and coarse aggregate.
 The aggregates to cement ratio of no fines concrete generally vary from
6:1 to 10:1.
 The water cement ratio is kept within the range of 38 to 0.52. Water
cement ratio should be chosen very carefully considering the
cohesiveness of the mixture.
 Density of no fines concrete with normal aggregate vary from 1600 to
1900 kg/m3. When light weight aggregates are used density can be as
low as 300 kg/m3.
 The compressive strength of no fines concrete varies between 4 MPa to
14 MPa.

23. PROPERTIES NO FINES CONCRETE
 There is no workability test for no fines concrete. The
visual check for ensuring even coating of aggregate
particles with cement paste is sufficient.
 As no fines concrete segregates, it can be dropped from
a considerable height and placed in high lifts.
 The modulus of rupture of no fines concrete is about
30% of its compressive strength. This proportion is
higher than the normal weight concrete.
 The thermal movement of no fines concrete is about
70% of that of normal weight concrete. The actual value
of coefficient of thermal expansion depends on the type
of aggregate used.

24.  No fines concrete normally is not used in reinforced
concrete. However if it is essential to use no fines concrete
in reinforced concrete, then the reinforcement has to be
coated with a thin layer of about 3 mm of cement paste to
improve its bond and prevent corrosion. Shot creating may
be applied for coating the reinforcement.
 In spite of its lower weight and strength it can be used for
even of many storyed buildings.
APPLICATIONS NO FINES CONCRETE

25. HIGH DENSITY CONCRETE

26. HIGH DENSITY CONCRETE
 The density of high density concrete is about 50% more than
the density of conventional concrete. However this concrete
can be produced of density upto 5200 kg/m3 using iron as
both fine and coarse aggregate.
With the advent of the nuclear energy, there is a considerable
demand of the concrete technologists in the market. Due to
the use of nuclear energy producing reactors, large scale
production of penetrating radiation and radioactive materials
also has taken place.
 High density concrete (HDC) consists of concrete with
a density higher than normal 2300 to 2550 kg/m³ and is used
for special purposes such as radiation shielding, counter
weights, ballasts, safe walls and safe roofs

27. HIGH DENSITY CONCRETE
 High Density=Heavyweight
 Density should be more than 2600 kg/m3
 Offers more strength
 Can be used everywhere, in all construction practices
 Resistant to extreme weather

28. MAIN COMPONENTS
 Cement
 Provides limited strength
 Not that useful in high density concrete
 Used as binding material
 Water
 Aggregates
 Admixtures
NATURALAGGREGATES
 Aggregates are obtained from iron ores
 Large amount of iron content
 Varying densities so variety of high density concrete
can be produced

29. Man-made (Synthetic) Aggregates
Iron Shots
Lead Shots
Chilcon
Fergran
Synthetic
Aggregates

30.  Water reducing admixture is used
 Consists Lignosulfonic acid, carboxylic acids
 Use of Water reducing admixture in high density concrete.
 Increase workabilityy
 Reduces water requirement
 Reduces cement content requirement
 High early strength
ADMIXTURE
APPLICATION
 High density radiation shielding
 Precast blocks
 Mass concrete projects
 High density concrete applications columns
 Gravity seawall, coastal protection & breakwater
structures
 Bridge counterweights
 Ballast for ocean vessels
 Off shore platforms noise and vibration dampening

31. High Strength Concrete:
 Using Type I Portland cement, gravel or crushed limestone coarse
aggregate, sand from a local deposit, and for some mixes a water-
reducing retarding admixture.
 Water-cement ratios ranged from 0.70 to 0.32
 Concrete strength of 90-120 MPa
 Uniaxial compressive strengths ranged from about 21 to 76 MPa.

32. SPECIAL METHODS OF MAKING HIGH STRENGTH CONCRETE
 Seeding: This involves adding a small percentage of finely ground, fully hydrated
Portland cement to the fresh concrete mix.
 This method may not hold much promise.
 Revibration: Controlled revibration removes all the defects like bleeding, water
accumulates, plastic shrinkage, continuous capillary channels and increases the
strength of concrete.
 High speed slurry mixing: This process involves the advance preparation of
cement - water mixture which is then blended with aggregate to produce
concrete.
 Use of admixtures: Use of water reducing agents are known to produce increased
compressive strength.

33. FIRE RESISTANCE OF HIGH STRENGTH CONCRETE:

34. STRENGTH-WEIGHT RATIO BECOMES COMPARABLE TO STEEL:
4 5
4 0
3 5
3 0
2 5
2 0
1 5
1 0
5
0
Structural steel C o n c r e t e H ig h s t r e n g t h
c o n c r e t e
Lightweight H S C
S t r e n g t h - W e ig h t Ratio

35. HIGH PERFOMANCE CONCRETE:
“A high performance concrete is a concrete in which certain characteristics are developed for a particular
application and environments”
 Ease of placemen
 Compaction without segregationn
 Early-age strength
 Long term mechanical properties
 Permeability
 Durability
 Heat of hydration
 Toughness
 Volume stability
 Long life in severe environments
 High resistance to frost and deicer scaling damage
 Toughness and impact resistance
 Volume stability

36. The required durability characteristics are governed by the application of concrete and by conditions expected
to be encountered at the time of placement. These characteristics should be listed.
DURABILITY

37. MATERIALS USED IN HIGH-PERFORMANCE CONCRETE
Material Primary contribution/Desired property
Portland cement Cementing material/durability
Blended cement Cementing material/durability/high strength
Fly ash Cementing material/durability/high strength
Slag Cementing material/durability/high strength
Silica fume Cementing material/durability/high strength
Calcined clay Cementing material/durability/high strength
Metakaolin Cementing material/durability/high strength
Calcined shale Cementing material/durability/high strength

38. Super plasticizers Flow ability
High-range water reducers Reduce water to cement ratio
Hydration control admixtures Control setting
Retarders Control setting
Accelerators Accelerate setting
Corrosion inhibitors Control steel corrosion
Water reducers Reduce cement and water content
Shrinkage reducers Reduce shrinkage
ASR inhibitors Control alkali-silica reactivity
Polymer/latex modifiers Durability
Optimally graded aggregate Improve workability and reduce paste

39. PROPERTIES OF HIGH DENSITY CONCRETE:
The strength of this concrete measured on standard cylinders has been found 42 MPa at 28 days for a
water/cement ratio 0.58 and 24 MPa at water/cement ratio 0.9.
The coefficient of thermal expansion of barite concrete measured in the range of temperature of 4°C to 38°C
is found about twice that of normal concrete.
The modulus of elasticity and poisson’s ratio of high density concrete and normal concrete are approximately
the same.
 Shrinkage of high density concrete is about 1/4 to 1/3 of the normal concrete
 Thermal conductivity, diffusivity etc. of high strength concrete is considerably lower than corresponding
values for normal aggregate concrete.
Concrete made with barite aggregate does not stand well to weathering No entrained air should be permitted
in this concrete.

40. SHIELDING ABILITY OF HIGH DENSITY CONCRETE:
Due to the following characteristics, concrete has
been found an excellent shielding material:
 It has sufficient capacity to absorb the radiation
both of neutron and gamma rays, reducing the
radiation to a very weak state.
 It has good mechanical properties as strength and
durability.
 it can be moulded into any shape. Thus the ease of
construction makes concrete a specially suitable
material for radiation shielding.
 Its initial and maintenance cost is also relatively
low.

41. SHIELDING ABILITY OF HIGH DENSITY CONCRETE
DISADVANTAGES
 As the sections of the structure are heavy, they need more space. Thus the use of concrete as shielding
against radiation needs more space.
 The weight of shielding concrete is very high in the range of 3360 to 3840 kg/m3.
TYPES OF RADIATION IN HIGH DENSITY CONCRETE
1. Electro-magnetic waves.
 These waves are of high frequency and have high energy. These waves are known as X and gamma rays.
These are the only electro-magnetic waves which need shields for the protection of personnel.
 These waves are of high frequency and have high energy. These waves are known as X and gamma rays.
These are the only electro-magnetic waves which need shields for the protection of personnel
2. Nuclear particles.
 Nuclear particles consist of nuclei of atoms or their fragments. These fragments are known as neutrons,
protons, alpha and beta particles.

42. AGGREGATES TO BE USED IN SHIELDING
 For making shielding concrete heavy weight aggregate having a specific gravity between 3.5 to 4.0 is needed.
There are many aggregates whose specific gravity is more than 3.5 for making a heavy weight concrete.
 Some of natural commercially used aggregates are as follows:
1. Barite
2. Magnetite
3. Ilmenite
4. Limonite, and
5. Hematite etc.

43. Proportioning, mixing and placing of High Density Concrete
 The mix proportions for these high density concrete is same as that of normal concrete.
 Conventional method of mixing and placing is used in high density concrete. The most important thing is to
prevent overloading the mixer especially when heavy weight aggregates such as steels are used.
 Batch sizes should be reduced to 40 to 50% of the allowable mixer capacity.
 Also avoid excess mixing because it will result in workability of concrete.
 Preplaced aggregate methods can be adopted when placing heavy weight concrete.
 In this method the aggregates are placed in forms, the appropriate grout made of cement, sand and water is
pumped over the placed aggregates, so that they can fill the voids in between the aggregates.
 This method prevents the segregation of coarse aggregates also reduces drying shrinkage and helps us to
achieve concrete of uniform density and composition.
 Puddling method can also be adopted. In this method, the mortar is placed in forms of 2″ thick and the
coarse aggregates are placed over it and vibrated internally.
 Pumping of heavy weight concrete can be adopted only the height is limited. The heavy weight concrete
cannot be pumped to larger distances because of their greater densities.
 They are mainly used in the construction of radiation shields (medical or nuclear).
 The ideal property of normal and high density concrete are high modulus of elasticity , low thermal
expansion , and creep deformation.
 Because of high density of concrete there will be tendency for segregation. To avoid this pre placed
aggregate method of concreting is adopted.

44.  High Modulus of Elasticity, Low thermal Expansion, Low elasticity and creep deformation are ideal
properties.
 The high density. Concrete is used in construction of radiation shields. They are effective and economic
construction material for permanent shielding purpose.
 Most of the aggregate specific gravity is more than 3.5

45. THANK YOU