Concrete, Aggregates, Admixtures Flashcards
of cement is usually measured indirectly by measuring
the surface area with Blaine air permeability.
Soundness
Wagner turbidimeter is used to determines the surface area by
measuring the rate of sedimentation of cement suspended in
kerosene
Fineness can also be measured by determining the percent
passing the sieve diameter of
0.045 mm
Refers to the stiffening of the cement paste or the change from a
plastic state to a solid state
Setting
set time must allow for handling and placing the
concrete before stiffening.
initial setting
Refers to its ability to retain its volume after setting of the cement
paste
Soundness
The autoclave expansion test is used to check the ____ of the
cement paste.
Soundness
The acceptance criteria for questionable water are specified in
ASTM __
C94
After 7 days, the average compressive strength of mortar cubes
made with the questionable water should not be less than _____
of the average strength of cubes made with potable water.
90%
Aggregate particles that are retained on a 4.75 mm sieve (No. 4)
Coarse
Aggregate particles that pass a 4.75 mm sieve (No. 4).
Fine
One sieve size larger than the nominal maximum aggregate size
Maximum size
One sieve larger than the first sieve to retain more than 10% of the
aggregates.
Nominal Maximum
Two considerations in the shape of the material: angularity
and_____.
flakiness
Referred to as flat and elongated, describes the relationship
between the dimensions of the aggregate.
Flakiness
It is desirable to use rounded and smooth aggregates to improve
the ____ of fresh concrete during mixing.
workability
Angular and rough particles are desirable for asphalt concrete and
base courses to increase the ____of the materials in the field.
Stability
The Superpave mix design method recognizes an angularity test,
Test Method for Uncompacted Void Content. A test for ___.
Fine
The ability of aggregate to withstand weathering is defined as ___.
Toughness
The ability of aggregates to resist the damaging effect of loads is
related to the ____of the aggregate particles and is described as
abrasion resistance.
hardness
The aggregate may have some moisture but the saturation state is
not quantified.
air dry condition
The aggregate contains no moisture; this requires drying the
aggregate in an oven to a constant mass.
Bone dry
Defined as the moisture content in the SSD condition
Absorption
The aggregate’s voids are filled with moisture but the main surface
area of the aggregate particles is dry
(SSD) condition
The moisture content in the aggregate in excess of the moisture
content in the SSD condition.
Free moisture
Field samples must be reduced using the following except:
slump
There are four major reasons for using admixtures except:
to substitute the quality of aggregates in the concrete mix
This admixture is recommended for all concrete exposed to
freezing.
Air entraining
When superplasticizers are used, the fresh concrete stays
workable for a short time, _____ minutes, and is followed by
rapid loss in workability.
30-60mins
Advantages of retarding admixtures except
increase the time between the initial and final set
an ultrafine gray powder, binds sand and
rocks into a matrix
of
concrete.
Cement
A cement which possesses
the property of hardening
in combination with water
HYDRAULIC CEMENT
It is the product obtained by pulverizing
clinker consisting of hydraulic calcium
silicates
Portland Cement
Hydrates
and hardens rapidly and is largely
responsible for initial set and
early strength.
Tricalcium silicate
Hydrates and hardens
slowly and is largely
responsible for strength
increases beyond one week.
Dicalcium silicate
Hydrates
and hardens the quickest.
Tricalcium aluminate
___ undergo a series of chemical
reactions that cause it to harden or set.
Hydration
a siliceous and aluminous
material in finely divided form react with
calcium hydroxide at ordinary
temperatures to form compounds having
cementitious properties.
Pozzolan Cement
Apperance of water on the surface of the
concrete after it has consolidated but
before it is set.
Bleeding
