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Title: HARDENED CONCRETE
Description: Now this here guys is the real deal.all that you want to know about HARDENED concrete is in here you don't have to peruse through websites to get the information just did it for you.

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Hardened Concrete
vIt is important for the engineer to understand the basic
properties of hardened Portland cement concrete and to
be able to evaluate these properties
...
Strength

Strength = ability to resist stress without failure

v

The most important property that is often required, simply
because Concrete is used for compressive loads
...
3 to 5
...


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Ø The strength of a concrete specimen prepared,
cured and tested under specified conditions at a
given age depends on:

ü
Amount of Cement
ü
Water-Cement Ratio
ü
Other influencing
factors:
§ Admixture(s)
§ Aggregate
Selection &
Gradation
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Typical sizes of test specimen
150 x 150mm cubes – British standard

Other sizes:
Cylinder:
Cubes:

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100 × 200 or 150 × 300 mm
100 × 100 × 100 mm3

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Typical Failure Modes for Test Cubes: (a) Non
-explosive; (b) explosive

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Tensile strength
Ø Tensile Strength can be obtained either by direct
methods or indirect methods
...


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SPLIT TENSILE STRENGTH
vThe split-tension test (ASTM C496) measures the
tensile strength of concrete

vConcrete cylinder of 150mm by 300mm is subjected
to a compressive load at constant rate along a
vertical diameter until failure

v

Failure is due to tension developed in the

transverse direction
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SPLIT TENSILE STRENGTH CONT…

Due to applied compression load a fairly uniform
tensile stress is induced over nearly 2/3 of the
diameter of the cylinder perpendicular to the
direction of load application
...

• The test is simple to perform and gives uniform
results than other tension tests
...

The results
obtained are useful
because concrete
is subjected to
flexural loads more
often than it is
subjected to tensile
loads
...


vThe length of beams should be at least three times
the depth of the beam plus 50 mm
...

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2
...

However, specially for
cylindrical specimens
with h/D=2, it can be
assumed as linear
upto 40-50% of σult

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Modulus of Elasticity
As per ASTM

S2 = stress at 40% of ultimate load with a strain
of ε2
S1 = stress at ε1 equal to 0
...
5 [f’c]0
...

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Calculation example
For normal-weight concrete, the relationship used in
the United States for designing concrete structures is
defined by the ACI Building Code as

A normal-weight concrete has an average
compressive strength of 30 MPa
...
Durability of Concrete

vDurability of concrete performs satisfactory under
anticipated exposure conditions towards life time of
the structure

vConcrete is very durable, but concrete structures
have shown poor durability and strength loss within
few year of their service

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Durability of concrete is based on:

üResistant to freezing and thawing
üAppearance of cracks
Resistance to freezing and thawing can be minimized:

ØControl Air entrainment
Ø
Control w/c
Cracking

ü
Path of harmful materials to get into concrete
§ Sulphate causes severe expansion and deterioration
§ Chloride initiate corrosion
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Factors affecting durability of concrete includes:

vPermeability
ü
Permeability is an important factor that largely affects the
durability of hardened concrete
...


ü
Water that permeates into reinforced concrete causes
corrosion of steel reinforcements
...
:

vThe  permeability  of  concrete  is  due  to  presence  of  air 
voids

vThe  air  voids  that  affect  permeability  of  hardened 
concrete are obtained from two main sources: incomplete 
consolidation  of  fresh  concrete  and  voids  resulting  from 
evaporation of mixing water that is not used for hydration 
of cement

vTherefore,  increasing  the  water–cement  ratio  in  fresh 
concrete has a severe effect on permeability
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Factors affecting durability of concrete cont
...
 

vAge reduces the permeability, since hydration products 
fill the spaces between cement grains
...
 
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Factors affecting durability of concrete cont
...


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4
...
 

vCreep of concrete is a long-term process, and it takes place over 
many years
...
 

vThe effect of creep varies with the type of structure
...
 

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vShrinkage is a negative volume change due to 

drying and hardening causes water to evaporate 
from cement paste
vShrinkage:
ü Increases with decreasing humidity, 
 with 
ü Increases with increasing cement-to-aggregate 
 with 
ratio: Cement paste shrinks, aggregate does not 
shrink
vIncreases with increasing water-to-cement ratio: 
 with 
More water, less aggregate, 
l water evaporates, paste shrinks, aggregate 
does not shrink
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vIncreases with increasing fineness of cement,
 with 
l Finer 

cement  absorbs  more  water,  water 

evaporates, more shrinkage
...

shrinkage

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vThe  rate  of  creep  decreases  with  time  and  the  creep  strains  at 
five years are taken as terminal values
...


Ø
Depth is inversely related to the strength
...

Ø
Rebound  hammer  tests  only  the  surface  while 
penetration  resistance  test  make  measurements  into 
the depth of the sample
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Ultrasonic Pulse Velocity Test (ASTM C597)

Ø
Measures the velocity of an ultrasonic wave passing through the 
concrete

Ø
The length between transducers/the travel time = average 
velocity of wave propagation

Ø
It is used to detect discontinuities, cracks and internal 
deterioration in the structure of concrete

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Title: HARDENED CONCRETE
Description: Now this here guys is the real deal.all that you want to know about HARDENED concrete is in here you don't have to peruse through websites to get the information just did it for you.