1. REINFORCED CEMENT CONCRETE AND
PLAIN CEMENT CONCRETE
SUB:- BUILDING CONSTRUCTION
• INTRODUCTION TO CONCRETE
• ELEMENTAL ANALYSIS
• TYPES OF REINFORCING STEEL
• CHARACTERS OF CONCRETE STRUCTURES
• MIX INGREDIENTS
• DEMERITS OF CONCRETE CONSTRUCTION
• READY MIX CONCRETE
3. What is CONCRETE?
Concrete is a mixture of cement, fine and coarse aggregate.
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.
What is RCC (reinforced cement concrete)?
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.
4. COMPOSITION OF CONCRETE:
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.
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.
5. USES AND DISADVANTAGES (IF EXTRA) OF THE COMPOSITION MATERIALS:-
MATERIALS USES DISADVANTAGES (if added
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
Sharp Sand This material is also used for
binding the materials within
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
extra may develop cracks in
Water Used for mixing components May make extra moisture
containing cement take
more settling time and may
not dry nicely.
Steel Reinforcing cement and
If not properly used may get
6. HOW IS REINFORCEMENT DONE
This animated video will explain you how exterior walls are reinforced with steel and then
coated with cement.
Function of structure is to transfer all the loads safely to ground. A particular structural
member transfers load to other structural member
8. 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.
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.
TYPES OF REINFORCING STEEL BARS IN RCC
11. CHARACTERISTICS OF CONCRETE STRUCTURES
• Good Control over cross sectional dimensions and Shape:-One of the major
advantage of concrete structures is the full control over the dimensions and
structural shape. Any size and shape can be obtained by preparing the formwork
• Availability of Materials:-All the constituent materials are earthen materials
(cement, sand, crush) and easily available in abundance.
• Economic Structures:-All the materials are easily available so structures are
• Good Insulation:-Concrete is a good insulator of Noise & heat and does not
allow them to transmit completely.
• 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
13. PROPORTIONS Of MIX INGREDIENTS
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
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
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.
IS 456-2000 has designated the concrete mixes into a number of grades as M10, M15, M20,
M25, M30, M35 and M40. In this designation the letter M refers to the mix and the number to
the specified 28 day cube strength of mix in N/mm2. The mixes of grades (if we consider them in
the ratio a:b:c then a-cement, b-sand, c-aggregates)
14. DEMERITS OF CONCRETE CONSTRUCTION
• 1. Week in tension:-Concrete is week in tension so large amount of steel is
• 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
• 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
• Inelastic Behavior:-concrete is an inelastic material, its stress-strains curve is not
straight so its behavior is more difficult to understand.
• Shrinkage and Creep:-Shrinkage is reduction in volume. It takes place due to loss
of water even when no load is acting over it. Creep is reduction in volume due to
sustained loading when it acts for long duration. This problem is not in steel
• Limited Industrial Behavior:-Most of the time concrete is cast-in-situ so it has
limited industrial behavior
15. READY MIX CONCRETE
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.
• 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
• referred as the customized
concrete products for commercial
• manufactured under controlled
operations and transported and
placed at site using sophisticated
equipment and methods TRANSIT MIXER
Inside the mixer
16. Disadvantages of ready-mix concrete:-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
Standard ready-mix concrete vs. site-mix concrete:-
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