Plain cement concrete is a mixture of cement, fine and coarse aggregates, and water that forms a rigid structure when cured. Reinforced cement concrete uses steel reinforcement within the concrete to resist tensile stresses that concrete is weak against. There are different types and grades of reinforcing steel like mild steel, TOR steel, and high tension bars with varying tensile strengths used for different purposes like prestressed concrete. Ready mix concrete is produced in a controlled factory environment and delivered to sites via transit mixers for precision and reduced work. It allows for specialized mixes but has limitations regarding transport distances and site access.

3. Concrete mainly consists of a binding material and filler material. If filler
material size is <5mm it is fine aggregate and > 5mm is coarse aggregate.
What is PCC (plain cement concrete)?
The intimate mixture of cement, sand, coarse aggregate (jelly) and water
is known as plain cement concrete. A small quantities of admixtures like
air entraining agents, water proofing agents, workability agents may also
be added to impart special properties to the plain cement concrete.

4. Concrete is good in resisting compressive stress but is very weak in
resisting tensile stresses. Hence reinforcement is provided in the
concrete wherever tensile stress is expected.
The best reinforcing material is steel, since its tensile strength is high
and bond between steel and concrete is good. Since elastic modulus
of steel is quite high compared to concrete, the force developed in
steel is high.
A cage of reinforcements is prepared as per the design requirements,
kept in the form work and then green concrete is poured. After the
concrete hardens, the form work is removed. The composite material
of steel and concrete, now called
R.C.C. acts as a structural member and can resist tensile as well as
compressive forces efficiently.

5. Plain Cement Concrete is a mixture of coarse (stone or brick chips) and
fine (generally sand or crushed stone) aggregates with a paste of binder
material (usually Portland cement) and water.
When cement is mixed with a small amount of water, it hydrates to
form microscopic opaque crystal lattices encapsulating and locking the
aggregate into a rigid structure.
The aggregates used for making concrete should be free from harmful
substances like organic impurities, silt, clay, lignite etc.
Typical concrete mixes have high resistance to compressive stresses
(about 4,000 psi (28 MPa)); however, any appreciable tension (e.g., due
to bending) will break the microscopic rigid lattice, resulting in
cracking and separation of the concrete. For this reason, typical non-
reinforced concrete must be well supported to prevent the development
of tension.

6. If a material with high strength in tension, such as steel, is placed
in concrete, then the composite material, reinforced concrete,
resists not only compression but also bending and other direct
tensile actions.
A reinforced concrete (i.e. reinforced cement concrete) section
where the concrete resists the compression and steel resists the
tension can be made into almost any shape and size for the
construction industry.

7. MATERIALS USES DISADVANTAGES (if added
extra)
Aggregates Used with binding material to
bind concrete properly.
May disintegrate the proper
setting of concrete.
Binding Materials Used for binding the
materials within concrete.
May make concrete rigid and
cause cracks after setting of
concrete.
Sharp Sand This material is also used for
binding the materials within
the concrete.
May make concrete to cause
cracks after setting of
concrete and disintegrate.
Cement This is used for binding as
well as strengthening the
places were applied and join
the masonry work
Even a single element
(lime,argilleous,silica,etc)
extra may develop cracks in
cement.
Water Used for mixing components May make extra moisture
containing cement take more
settling time and may not dry
nicely.
Steel Reinforcing cement and
concrete
If not properly used may get
corroded.

9. There are three types of reinforcing steel:
MILD STEEL- It contains carbon up to 0.23 to 0.25%. Higher value
is permitted for bars of 20 mm and above diameter. It is available in
diameters of 6, 10, 12, 16, 20, 25 and 32 mm. Its yield strength is 250
N/mm2 and young’s modulus 2 × 105 N/mm2. It was very commonly
used reinforcement in concrete
TOR STEEL- Two types of TOR steel bars are available. They are Fe-
415 and Fe-500. The number associated with the designation indicates
the tensile strength of bar in N/mm2. These bars are provided with ribs
deformation on surface so that bond between concrete and steel
improves. These bars are available in diameters 8, 10, 12, 16, 20, 22,
25, 28 and 32 mm. Nowadays these bars are replacing mild steel bars
as reinforcement since their strength in tension and bond is higher.

10. HIGH TENSION BARS-
High tensile steel bars are made with 0.8 % carbon and 0.6 %
manganese apart from small percentages of silicon, sulphur and
phosphorous.
The process of making these wires involve cold drawing and
tempering. They are usually available in 2, 3, 4, 5, 6, 7 mm
diameters. They may be bundled with number of them to form a
strand.
These bars are having tensile strength as high as 1400 N/mm2 to
1900 N/mm2. The young’s modulus of steels is also same as that
of mild steel.
High tensile bars are used as reinforcement in prestressed
concrete.

14. • Good Binding Between Steel and Concrete:-There is a very
good development of bond between steel and concrete.
• Stable Structure:-Concrete is strong in compression but week
in tension and steel as strong intension so their combination
give a strong stable structure.
• Less Chances of Buckling:-Concrete members are not slim
like steel members so chances of buckling are much less.
• Aesthetics:-concrete structures are aesthetically good and
cladding is not required
• Lesser Chances of Rusting:-steel reinforcement is enclosed
in concrete so chances of rusting are reduced

16. The requirements which form the basis of selection and
proportioning of mix ingredients are:-
a ) The minimum compressive strength required from structural
consideration
b)The adequate workability necessary for full compaction with the
compacting equipment available.
c)Maximum water-cement ratio and/or maximum cement content to give
adequate durability for the particular site conditions
d)Maximum cement content to avoid shrinkage cracking due to
temperature cycle in mass concrete.
Standard mixes:-
The nominal mixes of fixed cement-aggregate ratio (by volume) vary
widely in strength and may result in under- or over-rich mixes. For this
reason, the minimum compressive strength has been included in many
specifications. These mixes are termed standard mixes.

17. GRADES MIXES
M10 1:3:6
M15 1:2:4
M20 1:1:5:3
M25 1:1:2

18. • First Week in tension:-Concrete is week in tension so large
amount of steel is required.
• Increased Self Weight:-Concrete structures have more self
weight compared with steel structures so large cross-section
is required only to resist self weight, making structure costly.
• Cracking:-Unlike steel structures concrete structures can have
cracks. More cracks with smaller width are better than one
crack of larger width
• Unpredictable Behavior:-If same conditions are provided for
mixing, placing and curing even then properties can differ for
the concrete prepared at two different times.

19. Ready-mix concrete is concrete that
is manufactured in a factory or
batching plant, according to a set
recipe, and then delivered to a work
site, by truck mounted in–transit
mixers.
Allowing specialty concrete mixtures to be
developed and implemented on construction
sites.
It is sometimes preferred over on-site
concrete mixing because of the precision of
the mixture and reduced work site confusion
first ready-mix factory was built in the 1930s
referred as the customized concrete products
for commercial purpose
manufactured under controlled operations
and transported and placed at site using
sophisticated equipment and methods

20. The materials are batched at a
central plant, and the mixing begins at that plant, so the traveling
time from the plant to the site is critical over longer distances.
Some sites are just too far away, though this is usually a
commercial rather than a technical issue.
Generation of additional road traffic. Furthermore, access roads and
site access have to be able to carry the greater weight of the ready-
mix truck plus load. (Green concrete is approx. 2.5 tonne per m³.)
This problem can be overcome by utilizing so-called 'mini mix'
companies which use smaller 4m³ capacity mixers able to reach
more-restricted sites.
Concrete's limited time span between mixing and curing means that
ready-mix should be placed within 210 minutes of batching at the
plant. Modern admixtures can modify that time span precisely,
however, so the amount and type of admixture added to the mix is
very important.

21. A centralized concrete batching plant can serve a wide area. Site-
mix trucks can serve an even larger area including remote
locations that standard trucks can not.
The plants are located in areas zoned for industrial use, and yet
the delivery trucks can service residential districts or inner cities.
Site-mix trucks have the same capabilities.
Better quality concrete is produced. Site mix can produce higher
compression strength with less water than standard batching
methods