Quiz 2 Flashcards
Properties of the hardened concrete
important to the materials engineer are:
- Strength
- Modulus of Elasticity
- Durability
- Porosity
is generally the controlling design
factor. Unless otherwise specified, concrete
strength f′c refers to the average
compressive strength of three tests.
Strength
is
desired for mixes with low cement content to
promote workability.
Low Fineness Modulus
is defined as the ease of
placing, consolidating, and finishing freshly
mixed concrete.
Workability
is an indicator of
workability when evaluating similar
mixtures. This test consists of filling a
truncated cone with concrete, removing
the cone, then measuring the distance
the concrete slumps (ASTM C143).
Slump Test
is measuring and introducing the concrete
ingredients into the mixer.
Batching
is
mixed in a central plant
and delivered to the job
site in mixing trucks
ready for placing.
Ready-mixed Concrete
3 mixing methods can be used for
ready-mixed concrete:
- Central-mixed concrete
- Shrink-mixed concrete
- Truck-mixed concrete
is mixed
completely in a stationary mixer and
delivered in an agitator truck (2 rpm to 6
rpm).
Central-mixed concrete
is partially mixed
in a stationary mixer and completed in a
mixer truck (4 to 16 rpm).
Shrink-mixed Concrete
is mixed
completely in a mixer truck (4 to 16 rpm)
Truck-mixed Concrete
It can be mixed in a mobile
batcher mixer at the job site.
Mobile Batcher Mixed Concrete
should be
deposited continuously as close as possible
to its final position.
Depositing Concrete
is frequently used for large
construction projects. Special pumps deliver the concrete directly into the forms.
Pump Concrete
Quality concrete requires thorough
consolidation to reduce the entrapped air
in the mix
Vibration of Concrete
The pressure
method is based on _______, which
relates pressure to volume.
Boyle’s Law
compares the unit weight of freshly mixed
concrete with the theoretical maximum
unit weight of the mix.
Gravimetric Method
can be used
for concrete made with any type of
aggregate. The basic process involves
placing concrete in a fixed volume
cylinder
Volumetric Method
is a
quick method used to determine the air
content of freshly mixed concrete
Chace Air Indicator Test
is the process of maintaining
satisfactory moisture content and
temperature in the concrete for a definite
period of time.
Curing
is a
long-term process and requires water and
proper temperature.
Hydration of Cement
involves covering the exposed
surface of the concrete structure with
water.
Ponding
A system of nozzles or sprayers can provide
continuous spraying or fogging This
method requires a large amount of water
and could be expensive. It is most suitable
in high-temperature and low humidity envi
ronments.
SPRAYING / FOGGING
Moisture-retaining fabric coverings saturated
with water, such as burlap, cotton mats, and
rugs, are used in many applications
Wet Coverings
which is the most common technique
for evaluating workability acrossthe world.
Slump Test
is better suited for adequately measure
the workability of stiff and dry mixes.
Vee Bee Test
a given
volume of concrete undergoes free fall from
one hopper to the second, and then into a
cylindrical container.
Compaction Factor Test
involves the spread of a
truncated cone of concrete on a table that is
dropped a number of times.
Flow Table Test
is a quality index, because
its correlates with other characteristics
as: compaction, mechanical strength,
permeability, freeze – thaw resistance
and etc.
Specific Weight
It is considered only when it is required as
a necessity in the design project that
establishes the maximum and minimum
valuesfor concrete temperature.
Temperature
defined as the largest stress that does
not cause a measurable permanent
strain.
Elastic Limit
is commonly used in designing concrete
structures. Since the stress-strain relationship is not exactly linear, the classic definition of the
modulus of elasticity (Young’s modulus) is not
applicable.
Modulus of Elasticity
s used in advanced structural
analysis of shell roofs, flat-plate roofs, and mat foundations. Poisson’s ratio of concrete varies between 0.11 and 0.21,
POISSON’S RATIO
is an important property of
concrete because concrete structures are
highly vulnerable to tensile cracking due to
various kinds of effects and applied loading
itself.
Tensile Strength
is used to evaluate the shear resistance provided by concrete in reinforced lightweight
aggregate concrete members.
Split Tensile Strength
measures the
tensile strength of concrete. In this test, a 0.15-m by 0.30-m (6-in. by 12-in.) concrete cylinder is subjected to a compressive load at a constant rate along the vertical diameter until failure.
SPLIT TENSION TEST
The specimen is prepared
either in the lab or in the field in accordance with ASTM C192 or C31, respectively.
FLEXURE STRENGTH TEST
It is a measure of an unreinforced concrete
beam or slab to resist failure in bending.
Flexture Strength
also known as the Schmidt hammer test, is a
nondestruc tive test performed on hardened
concrete to determine the hardness of the
surface
Rebound Hammer Test
also known as the Windsor Probe test, is standardized by ASTM C803.
PENETRATION RESISTANCE TEST
measures the
velocity of an ultra sonic wave passing through the concrete. This test is used to detect cracks, discontinuities, or internal deterioration in the structure of concrete.
ULTRASONIC PULSE VELOCITY TEST
is defined as the degree of cement hydration, which varies as a function of both time and
temperature.
Maturity
an ultimate strength pertaining to the
failure of beams by flexure equal to the
bending moment at rupture divided by the
section modulus of the beam
Modulus of Rupture
