This document summarizes various special concretes and concreting methods. It discusses light weight concrete using natural or artificial lightweight aggregates. It also discusses high density concrete using heavier aggregates, mass concrete for large structures, plum concrete using large stones, and fibre reinforced concrete to improve properties like ductility and impact resistance. Finally, it briefly discusses polymer concrete, ferroconcrete, and their applications.
Introduction to IEEE STANDARDS and its different types.pptx
Special Concretes and Methods
1. • Subject name :Concrete Technology
• Subject code :2140608
• Guided by:-Prof. Nilesh Parmar
Prof. Pritesh Rathod
2. Topic :- Special Concrete And
Concreting Method
Name Enrolment no.
Harshil R Gandhi 141100106018
Bhavik H Deshmukh 151103106002
Pritesh C Dudhat 151103106003
Aditya P Misrty 151103106009
Dhrumil D Pandya 151103106010
3. Outline
Introduction
Light weight concrete
High density concrete
Mass concrete
Plum concrete
Fibre reinforced concrete
Polymer concrete
Ferro concrete
4. Introduction
Special concrete are the concretes prepared for specific purpose like light weight, high
density, fire protection, radiation shielding etc.
Concrete is a versatile material possessing good compressive strength.
Modification have been made from time to time to overcome the deficiencies of cement
concrete.
Improvement in mechanical properties like compressive strength, tensile strength,
impact resistance etc.
Improvement in durability in terms of increased chemical and freeze resistances.
Improvement in impermeability, thermal insulation, abrasion, skid resistance etc.
Research work is going on in various concrete research laboratories to get improvement
in the performance of concrete.
5. Light weight aggregate concrete
The density of conventional concrete is in the order 2200 to 2600
kg/m³.
This heavy self weight will make it uneconomical structural material.
There are two type of light weight aggregate concrete:-
(a) Natural light weight aggregate
(b) Artificial light weight aggregate
Natural light weight aggregate
Pumice, scoria, Rice husk, saw dust.
artificial light weight aggregate
sintered fly ash ,formed slag, bloated clay, artificial cinders,
expanded clay, slate, shale, coke breeze, expanded perlite , exfoliated
vermiculite.
6. Light weight concrete is achieved by three
different ways
By replacing the normal mineral aggregate is known as ‘ light
weight aggregate concrete’.
By introducing air bubbles in mortar is known as ‘ aerated
concrete’.
By omitting sand fraction from the aggregate as ‘ no fines
concrete’.
7. Aerated concrete
Aerated concrete can be manufactured in this ways
1. By the formation of gas by chemical reaction within the mass
during liquid or plastic state.
2. By adding preformed stable foam with the slurry.
3. By adding a finely powdered expansive solid matter.
8. No fine aggregate
No fine aggregate is obtained by omitting fine aggregate fraction
from the conventional concrete.
It consist of cement, coarse aggregate and water only.
When conventional aggregate are used no fines concrete show a
density of about 1600 to 2000 kg/m³.
Strengths of the order of 15 n/mm² have been attained with no
fines concrete.
The bond strength of no fines concrete is very low and therefore
reinforcement is not used in no fines concrete.
9. High Density concrete
High density concrete is also known as ‘ Heavy weight concrete’.
High density concrete is produced by replacing the ordinary aggregate by a
material of very much higher specific gravity.
One of the more common natural aggregate is Barytes (barium sulphate).its
specific gravity of 4.1 and occurs as a natural rock with a purity of about 95%.
Another type of natural heavy weight aggregate is iron ore: magnetite, limonite,
hematite, goethite have been used.
By using iron ore aggregate concrete with densities of between 3000 to 3900
kg/m³.
Apart from biological hazards along with the nuclear reaction very high
temperature is also generated and shielding is necessary to protect the
electronic and other sensitive equipment's in the vicinity.
High density concrete is also suites for preparing counter-balance weight for lift
bridges and ballast blocks for ships.
10. • “An large volume of cast-in-place concrete with dimensions large
enough to require that measures be taken to cope with the
generation of heat and attendant volume change to minimize
cracking.”
• Mass concrete includes not only low-cement-content concrete
used in dams and other massive structures but also moderate to
high cement content concrete in structural members of bridges
and buildings.
• As the interior concrete increases in temperature and expands,
the surface concrete may be cooling and contracting.
• The width and depth of cracks depends upon the temperature
differential, physical properties of the concrete, and the
reinforcing steel.
Mass concrete:
11. Plum concrete
The original idea of the use of aggregate as an inert filler can be extended to
the inclusion of large stones up to 300 mm size in a normal concrete; thus the
apparent yield of concrete for a given amount of cement is increased this
result concrete is called ‘ plum concrete’.
These large stones are called ‘plum’ and used in a large concrete mass.
They can be as big as 300mm size but should not be greater than 1/3 of the
dimension to be concreted.
The volume of plums should not exceed 20 to 30% of the total volume of the
finished concrete and they to be well dispersed throughout the mass.
Care must be taken to ensure that no air is trapped underneath the stones.
The plums must have no adhering coating. Otherwise discontinuities between
the plums and concret
12. Fibre reinforced concrete
Fibre reinforced concrete can be define as a composite material consisting of
concrete and discontinuous , discrete, uniform dispersed fine fibres. The
continuous meshes , woven fibre and long wire or rod are not considered to
be discrete fibre.
The inclusion of fibre in concrete and shotcrete generally improve material
properties like ductility, flexural , toughness, impact resistance and fatigue
strength .
There is little improvement in compressive strength.
The type and amount of improvement is dependent upon the fibre
type,size,strength and configuration and amount of fibre
13. A numerical parameter describing of fibre is its ‘aspect ratio’ which is define
as the fibre length divided by an equivalent fibre diameter.
Typical aspect ratio range from 30 to150 for length dimensions 0.1 to 7.62cm.
Typical fibre diameters are 0.25 to 0.75 mm for steel and 0.02 to 0.5 mm for
plastic.
1. Steel fibre
2. Glass fibre
3. Plastic fibre
4. Carbon fibre
5. Asbestos fibre
14. Steel fibres
They are generally round .
The diameters may vary from 0.25 to 0.75 mm.
The steel fibre is lightly rusted and lose some of its strength.
Use of steel fibre makes significant improvements in flexural impact and
fatigue strength of the concrete.
Steel fibre has been used in overlays or roads, pavements, air fields. Bridge
decks, thin shells and floorings subjected to wear and tear and chemical
attack
15. Glass fibres
These are produces in three basic forms.
1. roving
2. strands
3. woven or chopped strand mats
majors problems in their use are breakage of fibres and the surface degradation
of glass by high alkalinity of hydrated cement paste.
glass fibre reinforced concrete is mostly used for decorative application rather
than structural purposes.
GFRC has very high tensile strength 1020 to 4080 N/mm² . They commonly used
verities of glass fibre are E-glass and AR-glass.
16. Plastic fibres
Fibres such as polypropylene, nylon, aramid and polyethylene have high
tensile strength but low young's modulus thus inhibiting reinforcing effect.
Polypropylene and nylon fibres are found to be suitable to increase the
impact strength.
Their addition to concrete has shown better distribute cracking and reduced
crack size.
The amount of plastic fibres added to concrete is about 0.25 to 1% by volume.
There are two type of polypropylene (1) mono filaments (2) film fibres.
17. Carbon fibres
Carbon fibres proses high tensile strength and high young's modulus.
The modulus of rupture of an aligned carbon fibres reinforced cement
composite with 8% fibres volume can be as high as 1623 N/mm² .
The use of carbon fibres in concrete is promising but is costly and availability
of carbon fibres in india is limited
18. Asbestos fibres
Asbestos is a mineral fibres and has proved to be the most successful fibres
which can be mixed with OPC .
The maximum length of asbestos fibres is 10 mm but generally fibres are
shorter than this
The composite has high flexural strength of asbestos varies between 500 to
980 N/mm²
19. Factors affecting properties of fibres
reinforced concrete
Volume of fibres
Aspect ratio of fibres
Orientation of fibres
Size of coarse aggregate
Workability and compaction of concrete
Mixing
20. Advantages of FRC
Reduction in shrinkage and cracking
Improvement in bond strength
Enhancement of fatigue strength and endurance limit
better toughness
Lower permeability of concrete
21. Application of FRC
Pavements and floors
Water retaining structures
Blast resistance structures
Precast products
Wearing surface to exiting bridges/ culverts
Repairs and rehabilitation works
22. Polymer concrete
There are three type of polymer concrete
(a) Polymer- impregnated concrete
(b) Polymer Portland cement concrete
(c) Polymer concrete
23. Polymer- impregnated concrete
Polymer- impregnated concrete is produced by impregnating or infiltrating a
hardened Portland cement concrete with n manometer and subsequently
polymerizing the manometer in situ
It is the widely used polymer composite.
The manometer used for impregnation are:
i. Methyl methacrylate
ii. Styrene
iii. Acrylonitrile
iv. T-butyle styrene
v. Epoxy
24. Application of polymer- impregnated
concrete
1) Prefabricated structural elements
2) Surface impregnation of bridges decks
3) Hydraulic structures
4) Marine works
5) Desalination plants
6) Nuclear power plants
25. Polymer Portland cement concrete
Polymer Portland cement concrete is a conventional Portland cement
concrete which is usually made by replacing a part of the mixing water a
latex.
There are two type of polymer employed in lattices
(a) Elastomeric polymers
(b) Glassy polymers
26. Elastomeric polymers
They are characterized by their rubber like elongation and low modulus of
elasticity
Examples are
- natural rubber latex
- styrene butadiene rubber latex
- neoprene
27. Glassy polymers
They are characterized by higher strength, higher modulus of elasticity and
relatively brittle type of failure.
Examples are
- polyester styrene
- epoxy styrene
- furans
- vinylidene chloride
28. Polymer concrete
Polymer concrete is a mixture of aggregate with a polymer as the sole binder.
There is no bonding material present.
Monomers or pre-polymers are added to the graded aggregate and the
mixture is thoroughly mixed by hand or machine.
The thoroughly mixed polymer concrete material is cast in moulds of wood,
steel or aluminium, etc.
Polymerization can be achieved by these methods :-
(a) Thermal catalytic reaction
(b) Catalyst promoter reaction
(c) Radiation
29. Application
The application of polymer concrete are repair for overlays, air field
pavements and industrial structure.
It is also used for repair of sluiceways and stilling basin of the dam.
It is also used in rock bolting
Polymer concretes possess good electrical properties and it can be used for
manufacturing poles.
30. Ferro cement
Ferro cement is a relatively new material consisting of wire meshes and
cement mortar.
It consists of closely spaced wire meshes which are impregnated with rich
cement mortar mix.
The Ferro cement possess high resistance against cracking high fatigue
resistance higher toughness and higher impermeability
31. Applications of Ferro cement
Mobile homes
Water tight structures
Silos and bins
Boat hulls
Biogas holder
Pipes
Folded plates
Shell roofs
Kiosks
Wind tunnel
Swimming pool
Curved benches for parks etc…
32. The construction in Ferro cement may be divided in to
four stages
(a)Fabrication of skeleton frame
(b)Fixing of bars and mesh
(c)Application of mortar
(d)Curing
33. Advantages of Ferro cement
Ferro cement structures are thin and light therefore self weight of structure
and foundation cost are reduced
The construction technique is simple and does not require highly skilled
labour
It is suitable for manufacturing the pre cast concrete elements
Partial or complete elimination of formwork is possible
It is very easy to repair the damaged Ferro cement work
34. Properties of Ferro cement
Thickness - 10 mm to 60 mm
Steel - 5 to 8%
Steel cover - 1.5 mm to 5 mm
Ultimate tensile strength - 34.5 N/mm²
Allowable tensile strength - 10.0 N/mm²
Compressive strength - 27.5 to 60 N/mm²