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CONCRETE AS BUILDING MATERIALS
IN CONSTRUCTION

1

PART I : CONCRETE INGREDIENTS

2

1
...

Or
Concrete is a composite man-made materials, most
widely used building materials in the construction
industry which consist of rationally chosen mixture of
binding materials such as lime, or cement, well graded
fine and coarse aggregates and water , sometimes
admixture is added to produce concrete with special
properties
...
CONCRETE IS A MAJOR BUILDING MATERIALS
BECAUSE OF THE FOLLOWING REASONS;
• It can be readily moulded into durable structural
items of various sizes and shapes at practically no
considerable labour expenditure
...

• It is possible to mechanise completely its preparation
and placing processes
...

4

3
...

• It is free from corrosion and there is no appreciable
effect of atmospheric agents on it
...

• It is proved to be more economical than steel
...
The
formwork which is of steel or timber , can be used over
and over again or for other purposes after it is removed
...
This is termed as the
Reinforced Cement Concrete (R
...
C)
...

(i) There is initial shrinkage of cement concrete which
is mainly due the loss of water through forms, absorption
by surface of forms etc
...

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PROPERTIES OF CEMENT CONCRETE CONT…
• It has a tendency to be porous
...
The two precautions necessary to avoid
this tendency are as follows:
(i) There should be proper grading and consolidating
of the aggregates
...

• It forms a hard surface, capable of resisting abrasion
...
FUNCTION OF EACH CONCRETE CONSTITUENT
4
...

-The matrix is usually 22-34% of the total volume
...


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4
...
Aggregates
-These are the inert or chemically inactive
materials which forms the bulk of cement
concrete
...

-They are derived from igneous, sedimentary
and metamorphic rocks or manufactured from
blast furnace slag etc
...

-They occupy about 70 – 80% of the volume of concrete,
therefore it is necessary to obtain right type and quality of
aggregates at site
-They should be clean, hard, strong, durable and graded in
size

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Aggregates cont…
-Aggregates are mass of crushed stone, gravel, sand
composed of individual particles, in some cases clays &
silts
-The largest particle size in aggregates may have a
diameter as large as 150 mm and the smallest particle
can be as fine as 5 to 10 microns
...
2
...

-According to Source:
Natural aggregate : Native deposits with no change in
their natural state other than washing, crushing &
grading
...
(blast furnace slag, Fired expanded shale &
clays )
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Classification of aggregates cont…
-According to Petrological Characteristics:
Igneous rocks : are formed by solidification of molten
lava
...
(limestone, shale)
Metamorphic rocks : are formed under high heat &
pressure alteration of either igneous & sedimentary
rocks (marble, slate)
...

15

Classification of aggregates cont…
- Rounded : Completely water worn & fully shaped by
attrition
...
(Land Gravel)
-Angular: Has sharp corners, show little evidence of wear
...
(Laminated Rocks)
- Elongated : Have lengths considerably larger than two
other dimensions
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Classification of aggregates cont…

-According to Size:

Fine aggregate F
...
A
...
2
...

-Volume is occupied by both the aggregates and the voids between
the
aggregate particles
...

-Specific gravity is the mass of a material divided by
the mass of an equal volume of distilled water
...

23

(c) Particle Shape and Surface Texture
-Shape

of

the

individual

aggregate

particles,

determines how the material will pack into a dense
configuration and also determines the mobility of the
stones within a mix
...

• Smooth: Bond b/w cement paste & agg is weak
...
is strong
...
having rough
surface texture perform better under flexural & tensile
stresses
...
08 percent shrinkage occurs, the
aggregate is considered undesirable
...
7 to
16 MPa , while the compressive strength ranges from 35
to 350 Mpa
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(b) Toughness and hardness
-The ability of aggregates to resist the damaging effect of
loads is related to the hardness of the aggregate particles
and is described as the toughness resistance
...

-Resistance to wear (abrasion) is determined by LosAngeles abrasion test
...
2
...

-In other words; graded aggregates are those with
particles of known size
...
5 mm
Coarse aggregate- 13 sieves with openings from 1
...


36

Grading of aggregates cont…

-The particle size distribution in an aggregate sample is
known as “gradation”
...

• Fine Particles → higher cost
• Coarse Particles → less workability
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Grading of aggregates cont…
-A reasonable combination of fine & coarse aggregate must
be used
...

-A s agg
...
grading:
- The grading of the particles in an agg
...
The sieve analysis is
conducted by the use of “standard test sieves”
...

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Ex:A 500gr sample of a Fine Agg
...
Determine FM?
Sieve

Amount Retained on
(gr)

Amount Retained on
(%)

% Cumulative Retained
on

9
...
75

30

6

6

2
...
18

100

20

42

0
...


= 3
...

-The larger the size of agg, the smaller the surface area to
be wetted per unit weight
...
So, for the same workability & cement content
higher strength will be obtained
...

-Studies have shown that concrete’s made with max agg
size greater than 40mm have lower strength
...
Volume changes in the paste causes larger stresses
at the interface
...


43

Grading of aggregates cont…
-Frequently, a dense gradation, but not necessarily the
maximum

possible

density,

is

desired

in

many

construction applications because of its high stability
...


44

Grading of aggregates cont…

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Grading of aggregates cont…

46

4
...
4 Tests of aggregates

The following tests are conducted to ensure satisfactory
performance of aggregates
(a) Flakiness Index (F
...
I) test
(b) Particle size distribution test
(c) Specific gravity and water absorption test
(d) Bulk density and void test
(e) Aggregate impact value test (AIV)
(f) Soundness test
(g) Aggregate crushing value test (ACV)
(h) Ten per cent fines value test (TFV)

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(a) Flakiness Index (F
...
I) test
-The sample of aggregate as required to be tested are
taken in sufficient quantities
...


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Flakiness Index (F
...
I) test cont…
-F
...
Aggregates retained on each sieve are
separated
...
I = weight of aggregate retained on length gauge divided by total
weight of the sample times 100
49

Flakiness Index (F
...
I) test cont…

50

(b) Particle size distribution test
-The sample of aggregate as required to be tested are
taken in sufficient quantities
...


51

Particle size distribution test cont…
-Typical sieve size;
80,63,40,20,16,10,4
...
36,1
...

-From the graph relative amount of various sizes of aggregates
can be compared
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Particle size distribution test cont…

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(c) Specific gravity and water absorption test
-The specific gravity of an aggregate is considered to be
a measure of strength or quality of the material
...


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(d) Aggregates Impact value Test (AIV)
-Test sample aggregates passing 12
...
36mm sieve, and weigh the
fraction passing 2
...

-18 hours of immersion
-Dry at 105°C+5°C to constant weight
-After 5 cycles determine the loss in weight of the agg
...

Na2SO4

MgSO4

Fine Agg
...


15%

22%

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(f) Aggregate Crushing Value Test (ACV)
-Aggregate crushing value gives a relative measure of
resistance of aggregate to crushing under a gradually
applied compressive load
-The aggregate crushing strength value is useful factor to
know the behavior of aggregates when subjected to wear

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Aggregate Crushing Value Test (ACV) cont…
-The sample consist of aggregate passing 12
...

-The aggregate are tested in surface dry condition
-The weight of the sample is determined as A
-The cylinder of the test apparatus is positioned on the
base plate and the test sample added in thirds each
subjected to 25 strokes from the tamping road
61

Aggregate Crushing Value Test (ACV) cont…
-The apparatus with the test sample and plunger in
position is placed in compression machine and load
applied gradually to maximum of 400kN
-The load is released and sample sieved on a 2
...

-Then Crushing value is obtained as (B/A) x 100

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Aggregate Crushing Value Test (ACV) cont…

-Low ACV – high strength
while high ACV implies
Low strength of aggregate

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(g) Ten per cent Fines Test (TFV)
The procedure are the same as for ACV except the
formula to calculate TFV is given as;

64

65

(h) Los Angeles Abrasion Test (LAA)
-The aggregate abrasion value gives a relative measure of
resistance of an aggregate to wear when it is rotated in a
cylinder along with some abrasive charge

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Los Angeles Abrasion Test (LAA) cont…
-The agg with a specified grading is placed inside the L
...

Testing Machine
-Loose steel balls are placed inside the drum
-The apparatus is rotated for a specified cycles
- Finally the loss in weight is determined
...


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4
...


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Water cont
...

-Mixing water in concrete includes batch water
measured and added to the mixer at the batch plant,
free moisture on aggregates, water included in any
significant quantity with chemical admixtures, and
water added after batching during delivery or at the
jobsite
...

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Water cont
...

-When non - potable sources of water are used, it is
important to verify and document that the impurities in
the water do no harm to concrete
...
3
...

-Mixing and curing with sea water shall not be
permitted
-The pH value shall not be less than 6
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Effects on Concrete due to Chemicals in Mixing Water
-Chlorides - High chloride levels promote steel
corrosion
-Sulfate - High sulfate levels promote expansive
reactions due to sulfate attack
-Sugars - Small amounts of sugars can retard setting
time
...


73

Test of Water for concrete
-A simple way of determining the suitability of water for
mixing is to compare the setting time of cement and the
strength of mortar cubes using the water in question
with the corresponding results obtained using deionized or distilled water
...

-Final setting time shall not exceed 12 hours and also be
within 25% with the distilled water
...

-Those requirements may be compared with BS 3146:
1980, which suggests a tolerance of 30 min in the
initial setting time and recommends a tolerance of 10
per cent for strength
...


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4
...
2 : Chemical Admixtures
A material other than water, aggregates, hydraulic
cement, used as an ingredient of concrete or mortar and
added to the batch immediately before or during its
mixing
...
To reduce the cost of concrete construction
2
...
To maintain the quality of concrete during the stages
of mixing, transporting, placing, and

curing in

adverse weather conditions
4
...
Air-entraining admixtures
2
...
Plasticizers
4
...
Retarding admixtures
6
...

-Air-entrainment will dramatically improve the
durability of concrete
...

79

Water-Reducing Admixtures
-used to reduce the quantity of mixing water required to
produce concrete of a certain slump, reduce watercementing materials ratio, reduce cement content, or
increase slump
...


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Water-Reducing Admixtures cont
...

– Carbohydrates
...


81

Super-plasticizers (High-Range Water Reducers)
-These admixtures are added to concrete with a low-tonormal slump and water-cementing materials ratio to
make high-slump flowing concrete
...

82

Super-plasticizers cont
...
thin-section placements,
2
...
pumped concrete to reduce pump pressure, thereby
increasing lift and distance capacity,
4
...
for reducing handling costs
...

Typical super-plasticizers include:
– Sulfonated melamine formaldehyde
condensates
...

– Lignosulfonates
...

-One of the most practical methods of counteracting this
effect is to reduce the temperature of the concrete by
cooling the mixing water or the aggregates
...


85

Retarding Admixtures cont
...


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Retarding Admixtures cont
...
offset the accelerating effect of hot weather on
the setting of concrete,
2
...
delay the set for special finishing processes such
as an exposed aggregate surface
...


v Typical Materials are:
– Calcium chloride: most commonly used for plain
concrete
...

– Calcium formate
...

– Calcium nitrite
...

-Ferrous oxide and ferric oxide form on the surface of
reinforcing steel in concrete
...


89

Corrosion Inhibitors cont
...


• Commercially available corrosion inhibitors include:
– calcium nitrite,
– sodium nitrite,
– amines,
– phosphates
90

Shrinkage-Reducing Admixtures
-Shrinkage cracks, such as shown on this bridge
deck, can be reduced with the use of good
concreting practices and shrinkage reducing
admixtures

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