A
concrete is a homogeneous mixture of Cement, fine aggregate (Sand) and coarse
aggregate (20 mm & 10 mm) with required amount of water. Homogeneous
mixture means properly mix on the basis of ratio is fixed or provided. Concrete
technology deals with the properties and practical approaches.
Concrete
play a massive level role in construction industry.
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Composition Of Concrete:-
(1.)
Cement
(2.)
Fine
Aggregate (Sand )
(3.)
Coarse
Aggregate (20 mm & 10 mm )
(4.)
Water
(5.)
Admixture
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Type of Concrete:-
(1.)
RCC
(Reinforced Cement Concrete)-When reinforcement is used in concrete, then it is
known as RCC.
(2.)
PCC
(Plain Cement Concrete) - When reinforcement is not present during concreting,
it is known as PCC. PCC is very lean and thin layered concrete. Generally M-5,
M-7.5 and present sinario M-10 grade
of concrete is used. PCC is provided not for strength purpose, its only for the
layer which is provided between soil and reinforcement. Its main purpose is to
break the contact between soil and steel and provide hard strata below the
concrete.
Grade of Concrete –
(1.)
Nominal Grade Of
Concrete-
Grade
Of Concrete
|
Mix
Ratio
|
Min. Compressive Strength
|
M-5
|
1:5:10
|
5 N/MM2
|
M-7.5
|
1:4:8
|
7.5 N/MM2
|
M-10
|
1: 3: 6
|
10 N/MM2
|
M-15
|
1:2:4
|
15 N/MM2
|
M-20
|
1:1.5:3
|
20 N/MM2
|
(2.)
Standard Grade of Concrete-
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Grade
Of Concrete
|
Mix Ratio
|
Min. Compressive Strength
|
M-25
|
1:1:2
|
25 N/MM2
|
M-30
|
Design Mix
|
30 N/MM2
|
M-35
|
Design Mix
|
35 N/MM2
|
M-40
|
Design Mix
|
40 N/MM2
|
M-45
|
Design Mix
|
45 N/MM2
|
(3.) High Strength Concrete Grade-
Grade
Of Concrete
|
Mix Ratio
|
Min. Compressive Strength
|
M-50
|
Design Mix
|
50 N/MM2
|
M-55
|
Design Mix
|
55 N/MM2
|
M-60
|
Design Mix
|
60 N/MM2
|
M-65
|
Design Mix
|
65 N/MM2
|
M-70
|
Design Mix
|
70 N/MM2
|
Types of Concrete Mix:-
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(1.) Nominal Mix-Its
ratio is fixed. Not required to change, but from M-15 and upper grades of concrete generally design mix is required from third party (like as IIT
college, NIT college and other reputed govt. colleges) as per client
requirements.
(2.) Design Mix-Its
ratio is not fixed, it is designed by third party and on the basis of many
times trial mixes is done.
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During
the concrete mixing following parts will be consider:-
(1.) Water-Cement
Ratio
(2.) Workability
Of Concrete to be check through Slump-Cone and check the required slump is ok or not as per requirement?
(3.)
Durability of concrete and
(4.)
Strength
(5.)
Curing will also be considered
Note:-
As per IS Code:456, Page no.-11, Degree of workability and required slump value is described:-
Sl.
No.
|
Placing
Condition
|
Degree
Of Workabilty
|
Slump
(In mm)
|
1
|
Blinding Concrete, Shallow
Sections, Pavement using Pavers
|
Vey Low
|
|
2
|
Mass Concrete, Lightly Reinforced
Sections in slabs, beams, wall, Column, Floors, Hand placed pavements, Canal
Linning,Strip Footings
|
Low
|
25-75
|
3
|
Heavily reinforced sections in
slabs, Beams, Walls, Columns
|
Medium
|
50-100
|
4
|
Slipform Work, Pumped Concrete
|
Medium
|
75-100
|
5
|
Trench Fill , In-Situ Pilling
|
Very High
|
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Procedure of Concreting:-
(1.)
Mixing
(2.)
Placing
(3.)
Transportation
(4.)
Placing
(5.)
Pouring
(6.)
Proper
Compaction through Vibration
(7.)
Removal
of formwork after required duration of setting time of concrete
(8.)
Curing
with pond method , sprinkling method as required on laying of hessian
cloth/gunny bags/jute bags/Sacks
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Environmental
Exposure Conditions:-
(1.)
Mild
(2.)
Moderate
(3.)
Severe
(4.)
Very
Severe
(5.)
Extreme
Another Types of Concrete-
(1.) Lime
Concrete- Lime is used for concrete.
(2.)
Asphalt Concrete- Bitumen is used in asphalt
concrete for road construction.
Note:-
(1.) Concrete is strong in
compression, but steel is strong in tension.
(2.) More water
mixing in concrete is decreased the strength of concrete.
(3.) During hand
mixing of concrete, 10% of extra cement is required.
(4.) Mixing of concrete will be proper for any
structure casting , it will be simply check we will take some concrete in our
hand, if it is not more loose and gain a shape like as a ball,then it is ok.
Mixing of concrete will also check, on its colour.
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Test Of Concrete:-
(1.) Cube Test
(2.) Core Cutter Test
(3.) Ultra-sonic Pulse Velocity Test
(4.) Rebound Hammer Test
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Written By-
Ritesh Raj
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