Concrete Flashcards
Which of the different types of cement is best to use in concrete when the soil has a high alkali content
type V
the minimum thickness of a concrete non-bearing tilt-up wall is:
4 inches
when erecting precast concrete walls, the bracing used to hold the walls in place shall be designed to withstand a wind load of at least:
10 lbs per sq ft
Portland cement is a manufactured cement. The name portland is not a brand name; it refers to a type of cement. (T/F)
True
a retaining and breast wall are the same (T/F)
True
which of the following cements is most commonly used in masonry units
Type I
What is an accumulation of fine particles on the surface of freshly painted concrete caused by an upward movement of water through the concrete called?
Laitance
The type of construction where columns are used and concrete is poured as a slab and lifted into place to form the walls is know as tilty up or tilt slab construction(T/F)
True
For a three story building, how thick is the foundation wall for a concrete foundation, in accordance with the code?
10”
for a single story building, how wide is the footing for a unit masonry foundation, in accordance with the code
12”
for a two story building, how thick is the thickness of the footing, in accordance with the code
7”
for a two story building, how deep in the soil must the base of the footing be, in accordance with the code?
18”
For a two story building, how wide is the foundation wall, in accordance with the code?
8”
Space holder
for a single story building, how deep in the soil is the base of the foundation
12”
for a three story building, how deep in the soil is the base of the foundation?
24”
space holder
which type of float should be used on air entrained concrete
aluminim
if a #5 rebar is overlapped 32 bar diameters, what is the total length of the splice?
20”
a saddle tie is used for
cross tie rebar
unless a curing compound is used, the number of days recommended for the moist curing of concrete is:
7
vibrating the concrete durring placement is useful for
consolidation only
which of the following concrete joints allows both verticle and horizontal movement of a slab
isolation
which of the following will achieve highest water tightness in concret
water/cement ratio should be as low as possible
which of the following causes plastic shrinkage cracks in concrete
rapid drying of the concrete at the slab surface
In order for the visible section of concrete tie to be broken off after pouring a concrete wall, the tie is manufactured with what type of special feature
breakoff
what is the minimum thickness of a concrete floor slab supported directly on the ground, according to the code
3-1/2”
which of the following additives is used to accelerate concrete curring?
calcium chloride
how soon should curing commence after finishing a concrete slab
immediately
air-entrained concrete requires which of the following
less mixing water
air-entrained concrete is used primarily to provide which of hte following results
improve resistance to freezing and thawing deterioration
what is a flat steel tool, of different sizes and shapes used to spread and smotth plaster, mortat or concret called
a trowel
the maximum allowable size of coarse aggregate in a concrete slab is ____, according to the code.
1/3 the slab thickness
the purpose of bull floating or darbying is to
embed the larger agregate and level the surfce
which of the following designates concrete strength
pounds per square inch compressing
a paste is formed when portland cement is mixed with water making a chemical reaction take place that is called
hydration
Dampening of wood concrete forms before placement will
prevent the rapid extraction of mixing water
when concrete foundations or grade beams and floors are poured in one single operation, it is reffered to as what type of pour
monolithic
The normal portland cement used in pavement and sidewalk construction as well as reinforced concrete buildings is
type 1
which of the following types of portland cement is used where concrete is subject to exposure to water or soil of high alkali or sulphate content
type V
when high strength is desired at an early period of cure, which type of portland cement is used
type III
what is the wood or metal straightedge used to strike off or level newly placed concrete called?
a screed
in concrete flatwork, what is a flat tool used as a smoothing device immediatley after screeding called
a darby
what is the trademark for a construction material composed of cement, snad or crusehd slag and water mixed together and forced through a cement gun by a pneumatic pressure
gunite
portland cement is manufactured from
lime
silica
aluminia
portland cement is kilned at
2700 degrees F
Sand is classified as fine aggregate. Fine aggregate used in concrete should be able to pass through a seive number
4
aggregate having a density of ____ pcf or less is known as lightweight aggregate
70
sand that is used in concrete is called
fine aggregate
which tool is usually used to finish lightweight concrete
bull float or darby
what is the primary ingredient of pertland cement
lime
what ingredients constitute the cement paste portion of concrete
cement, air, water
when cement and water combine, the chemical reaction is known as hydration. This process produces
heat
the most commonly used type of cement is
type1
cement sets and hardens due to the chemical reaction called
hydration
what is the main use in construction of portland-pozzolan cement
large hydralic structures
it is necessary to take precautions to protect the skin from direct contact with fresh concrete. not doing so may result in:
painful burns
what is the most common form of fine aggregate
sand
Of what materials are the best aggregates composed of
hard and durable
aggregates for concrete are separated into what two general sizes
coarse and fine
aggregates for concrete should be sound and durable. waht are two desirable characteristics
well graded and clean
aggregates comprise approximately ____ to ____ percent of the total volume of a concrete mix
60
75
what is the minimum particle size for coarse aggregates
1/4 inch
what are some qualities of water that usually make it satisfactory for making concrete without testing it
drinkable and no objectionable odeor
temperature below 90 degrees f
temperature above 40 degrees f
the proper time to put the final finish on concrete is
after the bleed water has left the surface
curring of concrete is necessary because of which of the following
keeps moisture in the concrete so that it develops its full strength
about ____ pounds of water are required to completely hydrate 100 pounds of cement
30
after all materials are charged into the truck mixer, the drum should be rotated at mixing speed for completion of mixing under normal conditions what are the maximum minimum revolutions commonly used in specifications
70 to 100
the compressive strength of a molded test cylinder at ____ after placement is the standard for specifying concrete strength
28 days
How many minutes should be allowed for mixing 3 cu yd batch of concrete mixer after all the materials have been placed in the mixer
1.5 minutes
1 min first yard 15 seconds for each extra yard
what must be taken into consideration regarding the method used for conveying concrete from the mixer to the place of final deposit on the job
prevent separation of the concrete materials
concrete should be placed in forms at a temperature of approximately
50 to 70 degrees
how long after placement should normal concrete be kept moist
5 days
the strength of concrete is in direct relationship to the proportions of water and cement. This is referred to as the ____ ratio.
water/cement
hot weather affects concrete in which of the following ways
-increased water demand
-faster rate of setting
-increased slump lost
the test for consistency of a concrete mix is called
slump test
how many inches high is a standard slump cone mold
12
when starting the slump test, the slump cone should be
damp
the most important factor of wooden forms is
the size should be correct and the forms should be even
the type of footing that is sunk deepest is:
Spread footing
Which of the materials requires the use of a form sealer
wood
the proper procedure for preparing steel forms prior to pouring is to
oil them
the minimum thickness of a plain concrete pad poured directly on the ground is:
3-1/2”
the process of pouring cement under water is called
tremie pouring
which forms do not need oiling
cardboard
which of the following causes compaction in concrete
vibration
why should a supervisor be present when concrete is poured
to make sure the concrete is vibrated properly
the term aggregate means
sand, stone and gravel
when air bubbles appear next to where the form was, this is reffered to as
honey comb
adding additional sand and aggregate to a normal concrete mis will
weaken it
space holder
in concrete an admixture is used to
cure faster and strengthen the mix
the best type of footing for a single column is
spread footign
which of the following is the best answer for what vibrating does to concrete
consolidates concrete
a sack of prtland cement weighs
94 lbs
a sack of portland cement is equal to ____ cubic feet
1
the weight of reinforced concrete is approximately how many pounds per cubic foot
140 to 160
the initial set in concrete should usually occur within not more than ____ of the pour
1 hour
it is commonly required that concrete be poured within how many minutes after mixing
30 to 90 minutes
the inside surface of forms are oiled to
all the form to strip easier
rapid pouring of concrete
may burst the forms
if footings are not placed below the frost line
the foundation will heave and crack
spreaders for footing forms are used
because they maintain the footing width
the horizontal surface of a stepped footing must be minimum of
twice the vertical distance
what is the usual size of a standard wall panel
3 feet x 8 feet
when you reinforce the walers at the corners with vertical 2x4s this is called
yoking the corners
to guide the screeding of the top of a foundation wall
use the top of the form as a guide
when erecting concrete formwork
use duplex nails throughout
if using the slump test for concrete to be used in a large slab, the slump should be
1-4 inches
if using the slump test for concrete to be used in a reinforced concrete wall other than thin walls, the slump should be
3-6 inches
if using the slump test for concrete to be used in a thin reinforced concrete wall, the slump should be
4-8 inches
normal portland cement is used whenever
sulfate hazards are absent
type 2 cement is commonly refered to as
moderate portland cement
cement after being ground will pass through a sieve number
325.
what material does not effect concrete
creosote
what type of tool is used for bonding an expansion joint
trowel
which of the following materials requires the use of a form sealer
wood
the proper procedure for using steel forms prior to pouring is to
oil them
the typpe of concrete known as high early strength is
type III
which of the following will increase the durability of concrete
curing
which property of concrete increases its resistance to bending, pullout, temperature changes and freezing
tensile strength
if the size of the largest aggregate in a given mix increases, what will the water and cement do
both decrease in ratio
which of the following will make up for strength lost due to air
decrease the water/cement ratio
he tremic process is used to
pour concrete under water
when paving with cement, the layer underneath should be
damp
which of the form materials do not need oiling
cardboard
vertical steel bars in a concrete upright are refered to as
column bars
when mixing mortar in a mechanical mixer the mixing should be completed in
1 minute
there are various standards for mixing time which necessarily allow for different mixers and ingridients. The absolute minimum time to mix a batch of concrete is
40 seconds
which of the following are joints used in concrete pavements
contraction
expansion
construction
the bent end of an anchor bolt must extend at least ____ into the concrete (15” into masonry)
7”
at lest two anchor bolts, spaced not more than ____ apart must be used for each piece of mudsill and there must be an anchor bolt within ____ of each end of each piece
6 ft
12 inches
if a concrete wall (Not considering the footing) measures 8” thick x 6’8” high x 150 yards long, how many cubic yards of concrete is required to construct the wall.
74
air entrained concrete has increased durability and workability. It contains approximately ____ air by volume
7%
When constructing forms, the ACI 347 recommends that both vertical and horizontal framing components be designed for a minimum live load of ____ per square foot to sustain the weight of workers, runways, screeds, etc
50 psf
the slump test is used to test
liquidity
what is the size of a slump test
cone 4” top, 8” base, 12” high
edgers should be used right after
bull floating or darbying
when concreting in hot weather, one of the biggest problems is the
hardening too fst
for expansion and contraction of concrete in sidewalks ____ betwenn control joints should be allowed.
5 to 10 feet
on a concrete slabs what are a couple of the basic joints
constructio
control
isolation
to give a smooth finish, which of the following is used
steel trowel
when placing concrete, which of the following is not important
transportation method
a non steel form has greater longevity if it is kept
oiled and clean
which of the following is not used in a slump test
wood float
test cylinder compressive strength is machine tested to the closest ____ psi
10
when using entrained air, whic of the following may be reduced in concrete
water adn sand
air entrained agents improve which of the following qualities of concrete?
expansion ability
