CONCRETE Flashcards
is a building material which solidifies and hardens after
mixing with water and placement due to chemical process known as
hydration
CONCRETE
The chemical process that occurs when water is added to cement.
HYDRATION
is used to make pavements, pipe, engineering structures,
foundations, roads, bridges, walls, footings, etc.
CONCRETE
General Classification of Concrete
PLAIN CONCRETE
REINFORCED CONCRETE
A structural
concrete with no reinforcement or with less reinforcement than the
minimum amount specified for reinforced concrete.
PLAIN CONCRETE
A structural concrete reinforced with no less than the
minimum amounts of reinforcing bars, pre-stressing tendons or nonpre-stressed reinforcement.
REINFORCED CONCRETE
Classifications According to Proportion
CLASS AA
CLASS A
CLASS B
CLASS C
A rich concrete mixture that can be used for columns of
reinforced concrete building and for construction where a very
strong and dense concrete is required.
CLASS AA
A good concrete mixture that can be used for reinforced
concrete works of all kinds and best suited for general concrete
works.
CLASS A
A medium concrete mixture that can be used for plain
concrete foundations, walls, floors, etc. and for not much strength of
impermeability is required.
CLASS B
A lean concrete mixture that can be used for heavy masses.
CLASS C
1:1.5:3 , nature of work is concrete works for docks, water structure, and reservoir. , probable strength after 28 days is 3500 - 4000 psi
CLASS AA
1:2:4 , nature of work is reinforced concrete works buildings, bridges and tunnels. . probable strength after 28 days is 2500 - 3000 psi
CLASS A
1:2.5:5 , nature of work is heavy walls, retaining walls, piers, abutments, floor, and arches. , probable strength after 28 days is 1500 - 2000
CLASS B
1:3:6 , nature of work is mass concrete, backing for stone masonry, concrete blocks. , probable strength after 28 days is 500 - 1000
CLASS C
OTHER CLASSIFICATION OF CONCRETE
a. LIME CONCRETE
b. CEMCENT CONCRETE
c. SPECIAL TYPES OF CONCRETE
The main ingredient is slaked lime and used as a binding
material.
LIME CONCRETE
TYPES OF CEMENT CONCRETE
SPECIAL CEMENT CONCRETE
REINFORCED CEMENT CONCRETE
PRE-STRESSED CEMENT CONCRETE
AERATED CONCRETE
HEAVY WEIGHT CONCRETE
PRE-PACKED CONCRETE
. Produced to suit a variety of special requirements
of environmental condition.
SPECIAL CEMENT CONCRETE
Obtained by embedding steel bars in tension
zones of the structural member to offset tension weakness of plain cement
concrete.
REINFORCED CEMENT CONCRETE
Obtained with high graded steel wires or
tendon wires.
PRE-STRESSED CEMENT CONCRETE
Manufactured from calcareous and siliceous materials.
AERATED CONCRETE
Produced by using special heavy weight aggregates
and compacting well by mechanical means.
HEAVY WEIGHT CONCRETE
Obtained by injecting cement sand mortar under
pressure to fill voids already packed and fully compact coarse aggregates.
PRE-PACKED CONCRETE
SPECIAL TYPES CONCRETE
AIR ENTRAINED CONCRETE
HIGH-EARLY STRENGTH CONCRETE
LIGHTWEIGHT CONCRETE
Contains billions of microscopic cells per cubic ft and
produced by the use of air entraining Portland cement.
AIR ENTRAINED CONCRETE
. Produced by using high-early strength cement.
HIGH-EARLY STRENGTH CONCRETE
Made from light weight aggregates.
LIGHTWEIGHT CONCRETE
MIX PROPORTIONING METHOD
A. WEIGHT METHOD
B. ABSOLUTE-VOLUME METHOD
C. FINENESS MODULUS METHOD
D. ARBITRARY STANDARD METHOD
E. MINIMUM VOIDS METHOD
F. MAXIMUM DENSITY METHOD
G. WATER CEMENT RATIO
Fairly simple and quick for estimating mix proportion using
an assumed or known weight of concrete per unit volume.
WEIGHT METHOD
More accurate method involves used of specific
gravity values for all ingredients to calculate the absolute volume and each
will occupy in a unit volume of concrete.
ABSOLUTE-VOLUME METHOD
The term fineness modulus is used to indicate an
index number which is roughly proportional to the average size of the particle
in the entire quantity of aggregates.
FINENESS MODULUS METHOD
Ratio of fine aggregates and coarse aggregates
to develop a dense mix that lies between 1:1/2 and 1:2/1/2.
ARBITRARY STANDARD METHOD
The quantity of fine aggregate used in the mixed is
about 10% more than the voids in the coarse aggregates and the quantity of
cement is kept about 15% more than the voids in the fine aggregates.
MINIMUM VOIDS METHOD
In this method a box of fixed volume is filled with
varying proportion of fine and coarse aggregates.
MAXIMUM DENSITY METHOD
The amount of water in mixing concrete is the most
important factor affecting the strength of a given proportion.
WATER CEMENT RATIO
PROPERTIES OF CONCRETE
A.PLASTIC STAGE CONSISTENCY.
B. HARDENED STAGE
PLASTIC STAGE CONSISTENCY.
SLUMP TEST
SLUMP LOSS
WORKABILITY
SEGREGATION
BLEEDING
SETTLEMENT AND BLEEDING
SETTING
HYDRATION
AIR ENTRAINMENT
Commonly used to measure consistency of concrete.
SLUMP TEST
From the time of mixing, fresh concrete gradually loses
consistency. This gives rise to the problems only if the concrete becomes too
stiff to handle, place and compact properly
is caused
due to the following reasons: hydration of cement (generating more heat),
loss of water by evaporation, absorption of water by dry aggregates and
absorption of water by surfaces in contact with the concrete.
SLUMP LOSS
The ease which concrete can be compacted fully without
segregation and bleeding
is the relative
ease with which concrete can be placed, compacted and finished without
separation or segregation of the individual materials.
is not the
Construction Materials and Testing - MGSD
same thing as consistency.
if they are made with different sizes of stone, the smaller the
stone the more workable the concrete. It is not possible to measure
this but the slump test, together with an assessment of properties like
stone content, cohesiveness and plasticity; it gives a useful indication.
WORKABILITY
. Implies the separation of the coarser particles from the mix
which results in no homogeneity of the concrete mix.
SEGREGATION
The appearance of water along the cement particles on surface of
freshly laid concrete on compaction and finishing.
BLEEDING
Cement and aggregate particles have densities
about three times that of water. In fresh concrete they consequently tend to
settle and displace mixing water which migrates upward and may collect on
the top
SETTLEMENT AND BLEEDING
The hardening of concrete before its hydration is known as
SETTING
Concrete derives its strength by the hydration of cement particles.
The hydration of cement is not a momentary action but a process continuing
for a long time.
HYDRATION
reduces the density of concrete and
consequently reduces the strength.
AIR ENTRAINMENT
HARDENED STAGE
STRENGTH
DURABILITY
IMPERMEABILITY
DIMENSIONAL CHANGES
SHRINKAGE
CREEP
MODULUS OF ELASTICITY
WATER TIGHTNESS
THERMAL CONDUCTIVITY
is defined as the
compressive strength of 150 mm size cubes after 28 days of curing below
which not more than 5 % of the test results are expected to fail.
STRENGTH
Environmental forces such as weathering, chemical attack, heat,
freezing, and thawing mat deteriorate concrete. The period existence of
concrete without getting adversely affected by these forces is known as
the ability to maintain satisfactory
performance over and extended service life
DURABILITY
The resistance of concrete to the flow of water through its
pores. Excess water during concreting leaves a large number of continuous
pores leading to the permeability.
IMPERMEABILITY
Concrete shrinks with age and the total shrinkage
depends upon the constituents of concrete, size of the member and the
environmental conditions. Total shrinkage is approximately 0.0003 of original
dimension.
DIMENSIONAL CHANGES
The volume decreases of concrete caused by drying and chemical
changes. In another word, the reduction of volume for the setting and
hardening of concrete is defined as
SHRINKAGE
Deformation of concrete structure under sustained load is defined as
Long term pressure or stress on concrete can make changes
in shape. This deformation usually occurs in the direction the force is applied.
The permanent dimension changes due to loading over a long period is
termed as
CREEP
depends on the
Modulus of Elasticity of the concrete ingredients and their mix proportions.
As per ACI code, the modulus of Elasticity to be calculated using following
equation:
Ec= 33γc√fc′
MODULUS OF ELASTICITY
Sometimes
it is called impermeability of concrete.
e is directly
related to the durability of concrete. The lesser the permeability; the more
the durability of concrete.
WATER TIGHTNESS
Concrete has moderate thermal conductivity, much
lower than metals, but significantly higher than other building materials such
as wood, and it is a poor insulator. A layer of concrete is frequently used for
‘fireproofing’ of steel structures. However, the term fireproof is inappropriate,
for high temperature fires can be hot enough to induce chemical changes in
concrete, which in the extreme can cause considerable structural damage to
the concrete.
THERMAL CONDUCTIVITY
depends on percentage of
reinforcement, type of aggregate and number of voids.
UNIT WEIGHT
a method used to maintain a satisfactory moisture
content and temperature in some concrete for a period of time immediately
after placing and finishing to develop the desired properties for its intended
used.
CURING OF CONCRETE
