Explanation of different types of concrete are as below:
1. Normal Concrete
The concrete in which common ingredients i.e.
aggregate, water, cement are used is known as normal
concrete. It is also called normal weight concrete or
normal strength concrete.
It has a setting time of 30 – 90 minutes depending upon
moisture in atmosphere, fineness of cement etc.
The development of the strength starts after 7 days the
common strength values is 10 MPa (1450 psi) to 40 MPa
(5800 psi). At about 28 days 75 – 80% of the total
strength is attained.
Almost at 90 days 95% of the strength is achieved.
See Also: Concrete Tests | Properties of Concrete
Air Entrained Admixures Properties of Fresh
Concrete Hardened Concrete Properties High
Strength Concrete
Properties of Normal Concrete
Its slump varies from 1 – 4 inches.
Density ranges from 140 pcf to 175 pcf.
It is strong in compression and weak in tension.
Air content 1 – 2 %.
Normal concrete is not durable against severe conditions
e.g. freezing and thawing.
2. High strength concrete
Compressive strength of high strength concrete mix is
usually greater than 6,000 pounds per square inch.
High strength concrete is made by lowering the water
cement (W/C) ratio to 0.35 or lower.
Often silica fume is added to prevent the formation of
free calcium hydroxide crystals in the cement, which
might reduce the strength at the cement aggregate bond.
Low w/c ratios and the use of silica fume make concrete
mixes significantly less workable, which is particularly
likely to be a problem in high-strength concrete
applications where dense rebar cages are likely to be
used. To compensate for the reduced workability in the
high strength concrete mix, superplasticizers are
commonly added to high-strength mixtures.
Aggregate must be selected carefully for high strength
mixes, as weaker aggregates may not be strong enough
to resist the loads imposed on the concrete and cause
failure to start in the aggregate.
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3. High Performance Concrete
This mix has the following main properties:
High strength.
High workability.
High durability.
Ease of placement.
Compaction without segregation.
Early age strength.
Long-term mechanical properties.
Permeability.
Density.
Heat of hydration.
Toughness.
Volume stability.
Long life in severe environments.
Preparation
High strength concrete mix can be prepared with careful
selection of ingredients and optimization of mix design.
High workability is attained by super plasticizers , they
lower the water cement ratio to 0.25 which is the amount
required only for hydration process.
High durability is attributed to fly ash and silica fume
which modify the e mineralogy of the cement; it
enhances the compatibility of ingredients in concrete
mass and reduces the CH amount. Fly ash also causes
ball bearing effect increasing workability.
The admixtures are 20-25% fly ash of partial replacement
of cement and rest 70% is Ordinary Portland Cement.
As it is not usually durable against freezing and thawing
so air entrained agents can also be utilized.
Properties of high performance concrete mix
Strength of high performance concrete ranges from
10000 psi – 15000 psi
Water cement ratio can be reduced to 0.25
► Types of Concrete
► Concrete Design
► Concrete Testing
► Concrete Mix
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4. Air Entrained Concrete
One of the greatest achievements in field of concrete
technology is development of air entrained concrete. It is
used where the concrete is vulnerable to freezing and
thawing action.
It is used where the concrete is vulnerable to freezing
and thawing action. It is prepared by adding the air
entraining admixture.
The air entrainment in concrete does the following
functions:.
1. It lowers the surface tension of water and thus
bubbles are created.
2. Secondly the air entraining agents prevents
coalescing i.e. the combining of bubbles. The
diameter of these bubbles ranges form 10 micrometer
to 1000 micrometer and in entrapped air the diameter
of bubble is greater than 1mm.
Air entraining agents OR air entrained admixtures are used
for the purpose of making entrained air in concrete.
FREEZING AND THAWING:
There are two phenomenons regarding the freezing and
thawing action on concrete.
1. when water inside concrete mass freezes it expands
9-10% due to this increase in the size it exerts
pressure on its surrounding and thus creating a
tensile force due to which micro cracks appear in the
concrete. Due to freezing these micro cracks develop
into fissures which results in disruption of concrete.
When the air entrained agents are present, extra amount of
air is there as water expands these air bubble provide them
thin space and the exertion of pressure is prevented.
2. Second is of osmotic pressure: In a concrete structure
there are two parts, frozen and unfrozen. As the
water content is higher in the frozen part, the osmotic
pressure is developed and water tends to flow
towards the low water concentration part. If
capillaries are not available, the water develops
cracks.
Normal concrete can not sustain 3-4 cycles of freezing
and thawing where as the AEA concrete can sustain 100
cycles of it.
DRAW BACKS of Air Entrained Concrete:
It has low strength as compare to normal concrete.
► Concrete Testing
► Concrete Blocks
► Concrete Additive
► Mixture Concrete
5. LIGHT WEIGHT CONCRETE
The concrete which has substantially lower mass per
unit volume then the concrete made of ordinary
ingredients is called lightweight concrete. The
aggregates used are lighter in weight.
Density of light weight concrete is 240 kg/m³ (15pcf)
-1850 kg/m³ (115 pcf).
Strength of light weight concrete blocks varies from 7
MPa (1000 psi) – 40 MPa (5800 psi).
Some times Air Entrained Admixtures are also added to it
giving resistance to freezing and thawing along with
strength .
Uses of Light weight concrete:
Used where extra load is not applied e.g. parapet wall,
road lining etc. or to reduce dead load.
6. SELF COMPACTING CONCRETE
The concrete where no vibration is required. The concrete is
compacted due to its own weight. It is also called self
consolidated concrete or flowing concrete. It can be also
categorized as high performance concrete as the
ingredients are the same, but in this type of concrete
workability is increased. This self-consolidating concrete is
characterized by:
Extreme fluidity as measured by flow, typically between
650-750 mm on a flow table, rather than slump (height).
No need for vibrators to compact the concrete.
Placement being easier.
No bleed water, or aggregate segregation.
Uses and Applications of Self Compacting Concrete:
1. It is used in location unreachable for vibrations. e.g.
underground structure, deep wells or at bottom of
deep sea.
2. SCC can save up to 50% in labor costs due to 80%
faster pouring and reduced wear and tear on
formwork.
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► Concrete Additive
► Mixture Concrete
► Micro Concrete
► On Site Concrete
7. Shotcrete
Shotcrete concrete uses compressed air to shoot
concrete onto (or into) a frame or structure.
Shotcrete is mortar or (usually) concrete conveyed
through a hose and pneumatically projected at through a
shortcrete nozzle with high velocity onto a surface.
Shotcrete undergoes placement and compaction at the
same time due to the force with which it is projected
from the nozzle.
It can be impacted onto any type or shape of surface,
including vertical or overhead areas.
Shotcrete is frequently used against vertical soil or rock
surfaces, as it eliminates the need for formwork.
It is sometimes used for rock support, especially in
tunneling.
Shotcrete is also used for applications where seepage is
an issue to limit the amount of water entering a
construction site due to a high water table or other
subterranean sources.
This type of concrete is often used as a quick fix for
weathering for loose soil types in construction zones.
8. Pervious concrete
Pervious concrete contains a network of holes or voids,
to allow air or water to move through the concrete. This
allows water to drain naturally through it, and can both
remove the normal surface water drainage infrastructure,
and allow replenishment of groundwater when
conventional concrete does not.
It is formed by leaving out some or the entire fine
aggregate (fines), the remaining large aggregate then is
bound by a relatively small amount of Portland cement.
When set, typically between 15% and 25% of the concrete
volumes are voids, allowing water to drain.
The majority of pervious concrete pavements function
well with little or no maintenance. Maintenance of
pervious concrete pavement consists primarily of
prevention of clogging of the void structure.
In preparing the site prior to construction, drainage of
surrounding landscaping should be designed to prevent
flow of materials onto pavement surfaces. Soil, rock,
leaves, and other debris may infiltrate the voids and
hinder the flow of water, decreasing the utility of the
pervious concrete pavement.
9. Roller compacted concrete
Roller compacted concrete, sometimes called rollcrete, is
a low-cement-content stiff concrete placed using
techniques borrowed from earthmoving and paving work.
The concrete is placed on the surface to be covered, and
is compacted in place using large heavy rollers typically
used in earthwork.
The concrete mix achieves a high density and cures over
time into a strong monolithic block.
Roller compacted concrete is typically used for concrete
pavement. Roller compacted concrete dams can also be
built, as the low cement content causes less heat to be
generated while curing than typical for conventionally
placed massive concrete pours.

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