Concrete Technology Unit-II

1. Concrete Technology
Unit-II

2. Syllabus
• General:
• Historical background, composition of
concrete, general note on strength
mechanism, current practice and future
trends.

3. General
• Historical Background
• The use of cementing material dates back to several
hundred years. The ancient Egyptians used claimed
impure gypsum to grout the space between huge rocks
of stone in pyramid.
• The Greeks and Romans used claimed limestone and
later learned to add to lime and water, sand and
crushed stone or brick and broken tiles. This was first
concrete in History.

4. Historical Background

5. General
• Lime mortar does not harden under water, and for
construction under water the Romans ground
together lime and a volcanic ash or finely ground
burnt clay tiles. Roman builders used volcanic tuff
found near Pozzuoli village near mount Vesuvius in
Italy. This Volcanic tuff or ash mostly siliceous in
nature thus acquired the name pozzolana, having
nearly the same composition as that of volcanic tuff
or ash found at Pozzuoli.

6. Historical Background

7. General
• Some of the structures in which masonry was bonded
by mortar, such as the Coliseum in Rome and the Pont
du Gard near Nimes, have survived to this day, with
the cementations material still hard and firm. In the
ruins at Pompeii, the mortar is often less weathered
than the rather soft stone. The superiority of Roman
mortar has been attributed to thoroughness of mixing
and long continued ramming.
• It is learnt that the Romans added milk, blood and lard
to their mortar and concrete to achieve better
workability. Hemoglobin is a powerful air-entraining
agent and plasticizer, which perhaps is yet another
reason for the durability of roman structures Probably
they didn’t knew about the durability aspect but used
them as workability agents.

8. Historical Background

9. General
• In India, powdered brick named surkhi has been
used in mortar. The Indian practice of thoroughly
mixing and long continued ramming of lime mortar
with or without addition of surkhi yielded strong
and impervious mortar which conformed the secret
of superiority of roman Mortars. However, not much
light has been thrown on cementing material used
in the construction of the cities of Harappa and
Mohenjo-Daro.

10. Historical Background

11. History of Modern Cement
• John Smeaton was called upon to rebuild the
Eddystone lighthouse in 1756. He made extensive
inquiry in the state of art existing in those days and
also conducted experiments to view to find out the
material to withstand the severe action of sea water.
He found that the best mortar was produced when
pozzolana was mixed with limestone containing a
high proportion of clayey matter. He was the first to
understand the chemical properties of limestone.

12. History of Modern Cement

13. History of Modern Cement
• In 1796, hydraulic cement was produced by calcining
nodules of argillaceous lime-by calcining an intimate
mixture of limestone and clay.
• In 1811, James Frost patented a cement and
established a factory in london district.
• In 1824. Joseph Aspdin , a Leeds builder took the
patent of Portland cement
• The fancy name of Portland was given owing to the
resemblance of this hardened cement to the natural
stone occurring at Portland In England, Hard
limestone and finely divided clay were used as raw
materials.

14. History of Modern Cement
Portland, UK

15. History of Modern Cement:
• In India, the South India Industrial ltd, first manufactured
Portlands cement near madras in 1904.
• In 1912, the Indian Cement Co. Ltd. Was established at
Porbandar (Gujarat) and by 1914 this company was able to
deliver about 1000 tonnes of Portland Cement.
• Prior to the manufacture of Portland Cement in India, it
was imported from U.K. A three storeyed structure build at
Byculla, Bombay is one of the oldest RCC structures built
using Portland cement.
• The Cement Corporation of India, a government owned
company is set up with the aim of surveying prospecting
and providing limestone deposits in the country and
establishing cement manufacturing capacity.

16. Concrete
• Concrete= Cement + Sand+ Aggregate+ Water+
Admixture+ Air
• The mixture of Cement and water is paste. The
function of paste is to bind sand and aggregate
particles by chemical process of hydration. It also
fills the voids between sand and aggregate particles.
• The strength of concrete depends upon the property
of cement, sand, aggregate, etc.

17. Composition of Concrete
• Concrete is composed of,
• Concrete= Cement + Sand + aggregate+ water+ admixtures +
air
• Cement: The funtion of cement is to bind the aggregates. It
also fills the void between sand and aggregate.
• Aggregate:
• The aggregate occupy about 75 % of the volume and hence
their influence on various properties of concrete is
considerable. Aggregates are generally cheaper than cement
and impart greater volume, stability, and durability to
concrete. The aggregate generally provides bulk to the
concrete.

18. Composition of Concrete
• Water: Water is required for carrying out chemical
reactions in cement. If the water content is less the heat of
hydration is not possible, hence the strength of concrete
will be reduced. If water content is in excess water will
cause undesirable capillary cavities and concrete becomes
porous.
• Admixtures: Admixtures is defined as a material other than
the basic ingredient of concrete mixed immediately before
or during mixing to modify some properties of concrete in
the fresh or hardened state.
• The use of admixtures like accelerators, retarders, air-
entraining agents, pozzolanic material, water proofing
admixtures etc.

19. Cement

20. Aggregate

21. Admixtures

22. Admixtures

23. Composition of Concrete
• The properties commonly modified using
admixtures are setting time, workability, air
entrainment, dispersion etc. The admixtures are
generally added in small quantity from 0.005 to
2 % by cement weight. Overuse of admixtures
have detrimental effect on the properties of
concrete.
• Air: The voids in the mass of concrete can be
classified into two groups
• Entrapped air
• Entrained air

24. Composition of Concrete
• Entrapped air: The entrapped air is the void
present in the concrete due to insufficient
compaction
• Entrained air: The entrained air is the
intentionally incorporated minute spherical
bubbles

25. Entraped Air

26. Entrained Air

27. Ingredients of Concrete

28. Strength Mechanism
• When water is added to cement, ingredients of cement
react chemically with water and form various
complicated chemical compounds. The chemical
reaction that takes place between cement and water is
reffered as hydration of cement.
• Anhydrous cement does not bind fine and course
aggregates. It acquire adhesive property only when
water is mixed.
• The silicates (C3S, C2S) and aluminates of cement react
with water and form hydro silicates and hydro
aluminates These products are thick and sticky. It is
called gel. Gel posses adhesive property and binds
aggregate and sand together. It also fill the voids
between sand and aggregate.

29. Strength Mechanism
• The hydration of cement may happen in two ways. The
one is ‘through solution’ mechanism in which the
cement compound dissolve in water to produce a
supersaturated solution from which different hydrated
products gets precipitated. The second theory is that
water attack cement compound in the solid state
converting them into hydrated products.
• It is possible that both the ‘ through solution’ and solid
state’ type of mechanism occur during the so called
reaction between cement and water. Obviously the
through solution mechanism take place in the early
stages of hydration when large quantity of water is
available. The ‘solid state’ mechanism may occur
during the later stage of hydration

30. Current Practice and Future Trends
• Concrete is a versatile material possessing good
compressive strength. But it suffers from many
drawbacks like low tensile strength, permeability
to liquids, corrosion of reinforcements
susceptibility to chemical attack and low
durability.
• Modifications has been made from time to time
to overcome the deficiencies of cement concrete.
The recent developments in the material and
construction technology have led to significant
changes resulting in improved performance,
wider and more economical use.

31. Current Practice and Future Trends
• Research work is going on in various concrete
research laboratories to get improvement in the
performance of concrete. Attempts are being
made for improvements in the following areas.
• Improvement in mechanical properties like
compressive strength, tensile strength, impact
resistance etc.
• Improvement in durability in terms of increased
chemical and freeze resistance
• Improvements in impermeability, thermal
insulation, abrasion, skid resistance etc.

32. Current Practice and Future Trends

33. Current Practice and Future Trends
• Ready Mix Concrete
• Self Compacting Concrete
• High Performance Concrete
• Fly ash Concrete.
• Translucent Concrete
• Biological Concrete (Self Healing Concrete)

34. Current Practice and Future Trends
• Ready mix Concrete
• Ready Mixed Concrete, or RMC as it is popularly called,
refers to concrete that is specifically manufactured for
delivery to the customer's construction site in a freshly mixed
and plastic or unhardened state. Concrete itself is a mixture
of Portland cement, water and aggregates comprising sand
and gravel or crushed stone. In traditional work sites, each of
these materials is procured separately and mixed in specified
proportions at site to make concrete. Ready Mixed Concrete is
bought and sold by volume - usually expressed in cubic
meters. RMC can be custom-made to suit different
applications.
• Ready Mixed Concrete is manufactured under computer-
controlled operations and transported and placed at site
using sophisticated equipment and methods. RMC assures its
customers numerous benefits..

35. Current Practice and Future Trends

36. Current Practice and Future Trends
• Self Compacting Concrete:
• Self-consolidating concrete or self-compacting
concrete (SCC) is characterized by a low yield, high
deformability, and moderate viscosity necessary to
ensure uniform suspension of solid particles during
transportation, placement (without external
compaction), and thereafter until the concrete sets.
• Such concrete can be used for casting heavily
reinforced sections, places where there can be no
access to vibrators for compaction and in complex
shapes of formwork which may otherwise be
impossible to cast, giving a far superior surface than
conventional concrete.

37. Self Compacting Concrete

38. Self Compacting Concrete:
• The first generation of SCC was characterized by the use of
relatively high content of binder as well as high dosages of
chemicals admixtures, usually super plasticizer to enhance
flowability and stability. Such high-performance concrete
had been used mostly in repair applications and for casting
concrete in restricted areas. The first generation of SCC
was therefore characterized and specified for specialized
applications.
• The relatively high cost of material used in such concrete
continues to hinder its widespread use in various segments
of the construction industry, including commercial
construction, however the productivity economics take
over in achieving favorable performance benefits and
works out to be economical in pre-cast industry.

39. Current Practice and Future Trends
• High Performance Concrete: (HPC)
• The development of high performance concrete (HPC) is a
giant step in making concrete a high-tech material with
enhanced characteristics and durability. High performance
concrete is an engineered concrete obtained through a
careful selection and proportioning of its constituents. The
concrete is with the same basic ingredients but has a totally
different microstructure than ordinary concrete.
• The low water cement ratio of HPC results in a very dense
microstructure having a very fine and more or less well
connected capillary system.
• High performance concrete can hence be defined as an
engineered concrete with low water/ binder ratio to control its
dimensional stability and when receive an adequate curing.

40. High Performance Concrete
(HPC)

41. Current Practice and Future Trends
• Translucent concrete (concrete) is a concrete based
building material with light-transmissive properties
due to embedded light optical elements - usually
Optical fibers. Light is conducted through the stone
from one end to the other. Therefore the fibers have to
go through the whole object. This results into a certain
light pattern on the other surface, depending on the
fiber structure..
• Translucent concrete is used in fine architecture as a
façade material and for cladding of interior walls. But
light-transmitting concrete has also been applied to
various design products.

42. Translucent Concrete

43. Current Practice and Future Trends
• Fly Ash Concrete
• Owing to its pozzolanic properties, fly ash is used as a replacement for
some of the Portland cement content of concrete.
• Use of fly ash can replace up to 30% by mass of Portland cement, and
can add to the concrete’s final strength and increase its chemical
resistance and durability. Due to the spherical shape of fly ash
particles, it can also increase workability of cement while reducing
water demand. The replacement of Portland cement with fly ash is
considered to reduce the greenhouse gas "footprint" of concrete, as the
production of one ton of Portland cement produces approximately one
ton of CO2 as compared to zero CO2 being produced using existing fly
ash. Since the worldwide production of Portland cement is expected to
increase replacement of any large portion of this cement by fly ash
could significantly reduce carbon emissions associated with
construction.

44. Fly Ash Concrete

45. Current Practice and Future Trends
• Biological Concrete (Self Healing Concrete)
• In manufacturing of biological concrete a specially selected
bacteria of the genus Bacillus, alongside a combination of
calcium lactate, nitrogen and phosphorus, is used to
create a healing agent within the concrete.
• If untouched, these agents can remain dormant in the
concrete for centuries. But if water begins to seep into the
cracks, the spores of the bacteria start to germinate and
feed on the calcium lactate. This consumes oxygen, which
in turn converts the calcium lactate into limestone that
solidifies and seals the surface. The removal of oxygen also
improves the durability of the steel reinforcement.

46. Biological Concrete
(Self Healing Concrete)

47. Authorities in the Field of Concrete
Research
• Concrete Related Institutes and Associations
• 1. Asian Concrete Federation
• 2. Concrete Institute of Australia
• 3. Portland Cement Association
• 4. FIB International Federation for Structural Concrete
• 5. The Institution Of Engineers(Malaysia)
• 6. Concrete Reinforcing Steel Institute
• 7. American Concrete Institute
• 8. American Society of Concrete Contractors
• 9. Institution of Civil Engineers , UK
• 10. National Information Center for Earthquake Engineerings
• 11. Korean Concrete Institute

48. Authorities in the Field of Concrete
Research
• 12. Indian Roads Congress
• 13. Precast Prestressed Concrete Institute
• 14. International Association for Bridge and Structural engineering
• 15.Institution of Structural Engineers, UK.
• 16. Japan Concrete Institute
• 17. The Institution of Engineers (India)
• 18. Thai Concrete Association
• 19. American Society of Civil Engineers
• 20. ASTM Standards
• 21. For Civil Engineer
• 22. RILEM
• 23 Indian Concrete Institute

49. References
• Concrete Technology by: R.P. Rethaliya
• Concrete Technology by . M.S. Shetty
• Internet websites
• http://www.foundationsakc.org/

50. Thanks….