1. Special concrete refers to concrete made with special materials or techniques to achieve improved properties compared to normal concrete. Some examples are lightweight, high-strength, and fiber-reinforced concrete. 2. Special concretes are used for applications requiring reduced weight, increased durability, strength, or other optimized properties. Lightweight concrete for example reduces structural weight and is used in multi-story buildings. 3. Production methods vary depending on the type of special concrete but include using special aggregates, adding fibers or other materials, or applying processes like vacuum dewatering to improve properties. Each type has advantages and limitations for different construction needs.

1. Unit 2
Special concrete
Shruthi V
Asst Professor
SJCEM
Palghar

2. Special concrete
● Concrete which made up of some special materials
using special techniques and special methodologies.
● Lightweight aggregates, glass, steel and plastic fibres,
volcanic ashes etc.,

3. Need of special concrete
● To increase durability
● To reduce permeability
● To reduce shrinkage and creep action
● To increase compressive strength and tensile strength
● To reduce weight on structure.
● To give aesthetic view
● To improve the performance of concrete.
● To reduce the heat of hydration action.
● To reduce the section of structural members.

5. Special concrete
● Lightweight concrete
● Ultra lightweight concrete
● Vacuum Concrete
● Mass concrete
● Waste material based concrete
● Shotcrete
● Guniting
● Sulphur concrete
● Sulphur infiltrated concrete
● Jet concrete
● Gap graded concrete
● No fines concrete
● High strength concrete
● High performance concrete

6. 1. Lightweight concrete
● Lighter than conventional concrete.
● Density of this concrete is considerably low (300 kg/m3 to
1850 kg/m3)
● Max slump of 100mm
● Three types of LWC :
1. Lightweight aggregate concrete(UK, France & USA)
2. Aerated concrete (Scandinavian countries)
3. No – fines concrete (not so popular till now)

7. Types of LWC
1. Lightweight aggregate concrete
a. Natural aggregates – Pumice & Scoria
b. Artificial aggregates- Shale, Slate, Perlite, Vermiculite, etc.,
c. Density of concrete as low as 300 kg/m3 can be achieved.
2. Aerated concrete
a. Produced by introducing air into the concrete.
b. Two ways are there to induce the air in concrete.
i. Gas concrete
ii. Foamed concrete
c. Finely divided aluminum powder is generally used as gas
producing agent. (0.2% of weight of cement)

8. Cont..,
Types of LWC
3. No – fines concrete
a. Produced by omitting Fa from mix.
b. Compressive strength ranges from 5 to 15 MPa
c. W/c ratio of 0.4 to 0.45 is maintained, with an aggregate /cement ratio
of 1:6 to 1:8

9. cont..,
PRINCIPLE BEHIND LWC:
The basic principle behind the making of light weight concrete
is by inducing the air in concrete.
● To achieve the above principle practically, there are 3
different ways.
○ By replacing the conventional aggregates by cellular porous
aggregates (Lightweight agg. Concrete).
○ By incorporating the air or gas bubbles in concrete (Aerated
concrete).
○ By omitting the sand from the concrete (No- fines concrete).

10. Advantages of LWC
1. Reduces the dead load of the building.
2. Easy to handle and hence reduces the cost of transportation
and handling.
3. Improves the workability.
4. Relatively low thermal conductivity
5. Comparatively more durable.
6. Good resistance to freezing & thawing actio when compared to
conventional concrete.
7. Tall structures can be constructed on low SBC areas.

11. Disadvantages of LWC
1. Very Sensitive with water content in the mixture.
2. Mixing time is longer than conventional concrete to assure
proper mixing .
3. Lightweight Concrete are porous and shows poor resistance
4. Easily crackable.

12. Application of LWC
1. In multistoried buildings
2. As unreinforced blocks
3. As drainage layers.
4. As paver blocks.

13. 2. Ultra lightweight concrete
● Polystyrene beads (non- structural) or lightweight aggregates
(structural)
● Density of ULWC ranges from 600-1000 kg/m3
● Compressive strength of 15-20 MPa
● Uses
○ Manufacturing of hollow panels
○ Prefabricated non load bearing panes
○ Lightweight panel etc.,

14. Cont.., Ultra lightweight concrete
Advantage of ULWA
● High thermal insulation.
● Minimum compaction is required.
● Economical.
● Can be used in soils having low SBC.

15. 3. Vacuum concrete
● Includes high water content during the mixing to improve
the workability.
● After casting the member the excess water content can be
removed by application of vacuum thus the strength and
other properties of concrete.
● Invented by Billner in United state in 1935.
● Effective duration of dewatering will be 20-30 mins.
● 28 days compressive strength can be achieved within 10
days of time.

16. Cont.., Vacuum concrete
Uses
1. Used in manufacturing of prefabricated reinforced and
unreinforced structures
2. Manufacturing of thin structural members like slabs, walls etc.,
Advantages
1. Highly workable concrete.
2. Greater strength is achieved in shorter span.
3. Formwork can be removed early.

17. Mechanism involved in Vacuum concrete.

18. 4. Mass concrete
Mass concrete is any volume of
concrete with dimensions large
enough to require that measures be
taken to cope with the generation of
heat from hydration of the cement and
attendant volume change to minimize
cracking.

19. Cont.., Mass concrete
● It contains less percentage of cement and more aggregate
to avoid major problem of temperature shrinkage.
● Temperature control in mass concrete,
i. Low heat material
ii. Pre cooling of material
iii. Post cooling of material
iv. Surface insulation
● Compressive strength gained in first days is high, during
this heat of hydration will e more ad it leads to cracking.

20. Cont.., Mass concrete
Uses of Mass concrete
1. High rise building
(columns,foundations)
2. Construction of damsite
3. Reservoir site
4. Bridges, fly overs
5. Marine structure

21. 5. Waste material based concrete
● Concrete which is manufactured using waste
products
● It can also be called as sustainable concrete as
it has no impact on environment
● Basically 3 types of waste materials are used
in manufacturing
a. Organic Waste (Rice, wheat, groundnut husk)
b. Inorganic Waste ( Broken brick, broken
concrete)
c. Industrial Waste ( GGBS, Silica fumes, red mud,
Fly ash)

22. Cont.., WMBC
a. Organic Waste (Rice, wheat, groundnut husk)
● Used as lightweight aggregate
● Care must e take as they are easily eutralisale.
● Bulk density 100-150 kg/m3
b. Inorganic Waste ( Broken brick, broken concrete)
● Material should e sound, hard same as like natural. aggregate
● Ot so workable, requires extra 5-10% of water to be workable.
● Density of roke rick varies from 100-2000 kg/m3

23. Cont.., WMBC
C. Industrial Waste ( GGBS, Silica fumes, red mud, Fly ash)
● Fly ash and GGBS reduce heat evolution and chemical attack
● May be used as chemical admixture to achieve strength.
Uses of WMBC
1. Economy can be achieved.
2. Environment friendly.
3. Can produce high strength concrete.
4. Used as lightweight aggregate.

24. 6. Shotcrete
● Method of applying mortar or fine
concrete projected at high velocity
primarily on to a vertical or
overhead surface.
● The impact created by the
application consolidates the
concrete.
● Hardened properties of shotcrete
are similar to those of conventional
cast-in-place concrete.

25. Cont.., Shotcrete
Properties of Shotcrete
1. More durable as cement content and
FA is more.
2. Low permeable.
3. Highly resistant to disasters, fire mold etc.,
4. Less formwork is required.
5. Fast in casting and complex shape can be made
like arches and curved walls.
6. Minimum equipment requirement.

26. Cont.., Shotcrete
Applications of shotcrete
1. Highway and railroad tunnels.
2. Mining operations.
3. Stabilization of slopes.
4. Canal lining.
5. Repair and rehabilitation.
6. Bridge rehabilitation.
7. Seal the cracks.
8. Hydro power projects.

27. 7. Sulphur concrete
● Sulphur is heated into molten form then CA and FA is
added.
● On cooling it good strength, acid resistant and chemical
resistant.
● Uneconomical than conventional concrete.
● Some studies say that compressive strength of 100MPa can
be achieved in 2 days.

28. Mix Proportion of Sulphur Concrete:
● For optimum strength and
workability the typical mix
proportions are as 20% sulphur,
32% fine aggregate and 48%
coarse aggregate and 5% silica
flour, which come as 1:1.6:2.4. The
ratio of fine to coarse aggregate
comes as 1:1.5.

29. Cont.. Sulphur concrete
Manufacturing of Sulphur concrete
● All the components are heated till 140-150° C.
● Any type of aggregates can be used.
● Optimum amount for
a. Sulphur mortar - 30 % of the bond.
b. Sulphur concrete- 15 % of he bond.
● CA-4mm anf FA -150 mic to 4mm.
● Extenders in the form of volatile ashes, quartz dust of 150 mic. are
used as FA.
Used in manufacturing of sewer lines,precast roofing tiles, fencing elements
and railway sleepers.

30. 8. Sulphur infiltrated concrete
● The manufacturing procedure for this concrete is same as that o
sulphur concrete.
● The products manufactured with sulphur concrete need no curing
and the moulds can be stripped immediately as the sulphur solidifies
rapidly under normal temperatures.
Test result done on concrete.
● In a test procedure for sulphur infiltrated concrete shows more than
four times increase in splitting tensile strength.
● The elastic properties of sulphur infiltrated concrete improved 100
percent.
● Also its resistance to freezing and thawing increases.

31. Applications of sulphur impregnated concrete
1. They can be used in the precast industry
2. Precast roofing elements
3. Railway sleepers
4. Sewer pipes
5. When high corrosion resistance is required (Beach or coastal area
constructions).

32. 9. Guniting

33. Cont.., Guniting
● The guniting is the most effective
process of repairing concrete work
which has been damaged due to inferior
work or other reasons. It is also used for
providing an impervious layer.
● The gunite is a mixture of cement and
sand, the usual proportion being 1:3. A
cement gun is used to deposit this
mixture on the concrete surface under a
pressure of about 20 to 30 N/cm2

34. Applications of guniting
1. Slope stabilization certain rehabilitation
2. Retaining walls, swimming pool construction, tunnel construction, in fluid
tank construction, Concrete repair works.
Advantages
1. Highly versatile in nature. (structure of any shape can be formed.)
2. Quantity of water can be controlled.
3. No risk of segregation.
Disadvantages
1. Highly skilled and experienced labor so that there is proper check on the
pressure.
2. The guniting process will face the issue of rebound of the mix. As the mix is
sprayed on the surface of the material there is chances that the ingredients
get bounce off

35. Requirements of guiniting
1. Skillful operation and control of the nozzle.
2. The surface of application must be free from dirt, grease or any
other defective materials.
3. If the surface of treatment has high adsorption, then it must be
kept wet for a time period of 6 hours before undergoing guniting.
4. In order to reduce permeability, increase the resistance to
weather and chemical attack, it is necessary to have high quality
mortar.
5. If the surface of treatment has high adsorption, then it must be
kept wet for a time period of 6 hours before undergoing guniting

36. 11. No fine concrete
● Fines in the form of fillers
are omitted.
● Aggregates ranging from
10mm to 20mm is used.
● Light in weight.

37. Cont.. No fine concrete
Advantages
● It is a type of lightweight concrete
i.e. density is about 25 to 30% less
than the normal concrete.
● Better thermal insulating
characteristic
● As it has no fine aggregates, the
surface area required for cement
coating is reduced considerably.

38. Cont.. No fine concrete
Disadvantages
● Highly permeable.
● Not suitable for RCC.
● As it become porous, extra cement is required for
surface finishing.

39. Classification of concrete based on strength
1. Low strength concrete - <20 MPa
2. Normal strength concrete- 20 to 55 MPa
3. High strength concrete - >55 MPa
4. Ultra high strength concrete - >200 MPa

40. 12. High strength concrete
● Compressive strength building
greater than 35 MPa.
● High strength results in increase
in modulus of elasticity, decrease
in permeability and increase in
durability of concrete.
● Water cement ratio will be less
than 0.35.
● Superplasticizers are used to
increase the workability

41. Special methods of making High strength
concrete
1. Seeding
2. Use of admixtures
3. Revibration
4. High speed slurry mixing
5. Sulphur imprignation

42. Properties of materials used in high strength
concrete mix design
● Cement content should be around 415 kg/m3, but should not be
more than 650 kg/m3.
● Water cement ratio should be 0.24 to 0.35.
● Fine aggregate should be free from dirt and dust, it's fineness
modulus should be 3.0.
● Well graded strong and durable coarse aggregates are used.
● Superplasticizers are used to increase the workability.
● To achieve higher strength chemical admixtures like silica fumes,
metakaolin, pozzolanic materials and fly ash are used

43. Applications of high strength concrete
1. High strength concrete results in reduction of size columns
and reinforcement material.
2. Bridge construction with reduction in cross section of
concrete elements, dead load of the structure can be reduced.
3. It can be used in Offshore oil structures.
4. Bridge deck Overlays.
5. Heavy industrial slabs.

44. 13. High performance concrete
● It is having high strength, high workability, high durability and less
permeable, high density, resistance to chemical attack.
● A concrete that has been designs to be more durable and if
necessary stronger than conventional concrete - FHA.
● HPC should have one of the following characteristics-
○ 4 hour compressive strength greater than or equal to 20 MPa
○ 24 hours compressive strength greater than or equal to 35 MPa
○ 28 days compressive strength greater than or equal to 70 MPa

45. Characteristics of high performance concrete
1. Very easy to handle, place
2. Low permeability
3. High early strength
4. Compaction without segregation
5. High durability and long life in severe environment
Advantages of high performance concrete
1. Having different benefits for different applications
2. Highly economical in major project life high rise buildings, Dam
construction etc..,
3. Size of the structural members can be reduced (columns, beams)

46. Applications of high performance concrete
● High rise buildings
● bridges
● pavements
● Pier and abutments
● Overlays
● Girders
High performance concrete produced by adopting following
methodologies
1. Helical binding
2. Polymer concrete
3. Compaction by pressure

47. 14. Jet cement concrete (Ultra rapid hardening cement)
● Achieves high strength in less time.
● Normally the strength achieved by conventional cements in 7 days is
same as the strength achieved in 3 days.
Properties of Rapid Hardening Cement
1. It gains strength faster than OPC. In 3 days it develops 7 days strength of
OPC with same water cement ratio.
2. It emits more heat during setting so not suitable for mass concrete.
3. Soundness of this cement is, Autoclave – 0.8 %, Le – Chatelier's – 10mm
4. Its short curing period makes it economical.

48. Manufacture of Jet Cement
● The lime and shale clinker is then mixed with small amount of gypsum
and grinded very finely to form Ultra rapid hardening cement.
● All the difference of rapid hardening cement to conventional cement is
the quantity of limestone (tri-calcium silicate )used as raw material, which
gives the high early strength to the cement.
● The manufacture is done by dry process.
● In this cement, limestone and shale are
used as raw material and heated at
extremely high temperature to form
clinkers.

49. Uses of Jet Cement
1. It is used where formwork where quick removal is required.
2. It is used where high early strength is required.
3. It is generally used for constructing road pavements, where it is important to
open the road to traffic quickly.
4. It is used in industries which manufacture concrete products like slabs,
posts, electric poles, block fence, etc. because moulds can be released
quickly.
Advantages
1. It requires a short period of curing.
2. Shrinkage is reduced during curing and hardening of cement.
3. Used in road pavement where quick access is required.
4. Formwork can be removed early.

50. Thank you