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Construction Materials Exam 1
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Gravity
Terms in this set (47)
From the list below which is the largest Coarse aggregate size?
No. 3 (smallest No. is largest Coarse aggregate size)
When an aggregate's voids are filled with water but no moisture exists on the surface it is in...
A saturated surface dry state
A typical value for specific gravity of a SSD sample of coarse aggregate is:
2.65
ASTM standards fall into which categories?
All of the above:
Standard practices
Standard Test Methods
Standard Specifications
By definition, "Fine" aggregate particles are smaller than what sieve size?
No. 4 ( The sieve size No. is the number of holes within one inch length)
An aggregate sample in a saturated surface dry state dry state weighs 100 grams. After oven drying it weigh s 92 games the absorption of this sample is
8.7% (absorption % equation)
A sieve that is classified as a No. 40 sieve
Has 40 openings per lineal inch
A sample of gravel has a weight of 5 ibs and occupies a volume of 0.0297 cubic feet. If the density of water is taken as 62.4 pounds per cubic foot, the specific gravity of the gravel is?
2.7 (specific gravity equation)
A dense gradation of aggregate in a concrete/asphalt mix
All of the above:
-Would probably be more cost effective
-Would reduce the amount of void space between the pieces of aggregate
-Would mean aggregate is occupying most of the volume
Absorption is the moisture content of an aggregate in what moisture state?
Saturated Surface Dry
an example of a supplementary cementitious material is
All of these:
-Fly ash
-Silica Fume
-Slag cement
Air entrainment is used for
Increasing the freeze-thaw durability of concrete
If cement is ground into finer particles it will result in
All of the above:
-Faster hydration
-Greater generation of heat
-Faster strength development
In the production of cement, the raw materials are burned which produces a product known as _______ which ultimately goes through a grinding process
cement clinker
Strength gain in concrete is primarily linked to the production of what?
C-S-H
The specific gravity of portland cement is typically ________
3.15
How could a retarding admixture be useful?
allowing for long haul distances
The type of cement which may be used to develop early strength gain is
Type III
The volume of entrapped air in concrete would typically range between
1%-3%
Fly ash
All of the above:
-increases workability
-may be used to replace a portion of cement in the mix
-is a mineral admixture
You are asked to proportion a concrete mix for 5000 psi (air entrained) which uses a 1" nominal maximum coarse aggregate is designed for a 6 to 7 inch slump. What is the approximate amount of water you will need per cubic yard?
310 Ib (use ACI211 table)
If you are proportioning a concrete mix with a water-to-cement ratio of .40 and know that you are using 320 pounds of water per cubic yard, how much cement would you need to use?
800 Ibs (320/.4)
In a concrete mix design you select a value of 0.55 from ACI table 6.3.6. If the oven dry-rodded unit weight of the coarse aggregate is 108 pcf, what is the approximate amount of oven dry coarse aggregate that you would need in a cubic yard
1604 Ibs ((.55
27)
108)
The amount of SSD fine aggregate that you proportion a concrete mix to use is 1200 Ibs. But the actual fine aggregate being used has a moisture content of 2% and an absorption of 1%. How much fine aggregate will you need to use?
1212 Ibs (2%-1%)--> (1%*1200=12Ibs)-->1212 Ibs
The amount of SSD coarse aggregate that you proportion a concrete mix to use is 1400 Ibs. But when adjusting it for the actual moisture content and absorption you find out that you need to use 1430 Ibs of coarse aggregate. Which is a true statement ?
The coarse aggregate will add 30 Ibs of water to the mix
Curing focuses on which two elements in concrete in order to optimize hydration?
moisture and temperature
The air test that uses a piece of equipment that pushing pressurized air down into the concrete is which method?
Pressure method
Consolidation of concrete on commercial jo s is typically accomplished by
vibrating
A slump test is performed and the "slumped pile" of concrete is 4" high after removing the slump cone (i.e. the actual height of the pile of concrete is 4"). The slump is?
8"
When a slump test is performed, there are 3 layers - each of which are rodded 15 times
False
Type I
Normal
Type II
moderate sulfate resistance (Normal)
Type III
High Early Strength
(cheaper & common, strip form earlier and speeds up production)
Type IV
Low Heat of Hydration (used for large and massive pours to control heat of hydration)
Type V
High Sulfate Resistance
Order of Operations for Concrete
Specific operations must be performed in a certain order-final quality is influenced by every step
I.mix design (proportioning)
II.trial mixes & testing
III. batching----------start the clock
IV. mixing
V. transporting
VI. pouring (placing)
VII.vibrating (consolidating)----initial set here
VIII. finishing-------------------final set here
IX.curing
X.maintenance
Cylinders
-6 x 12 standard
-Place concrete in three lifts, rod each 25 times•Cure on site 24 hrs
-Temperature
-Humidity / submerged in lime water
-4 x 8 can be used, make in 2 lifts, smaller rod
Improving strength
•Strength is improved by strengthening the aggregate/paste bond and the strengthening the paste.
•Bond and paste strength are improved by:
-Low w/c ratio
-Use of pozzolans •Bond can be improved by
-Smaller aggregates
-Fractured aggregate (more surface area)
Cement paste
cement + water
Mortar
Cement paste + sand
Concrete
= cement + water + sand + aggregates
Fineness
Smaller cement particles have more surface area to react with water
Specific Gravity
Gcement ~ 3.15
Fly Ash
-most commonly used pozzolan in CE structures
-by-product of the coal industry
-Class N, F, and C
-increases workability and extends the hydration process
Slag Cement
-made from iron blast furnace slag
-used as a cementitious material in concrete
Silica Fume
-byproduct of the production of silicon metal or ferrosilicon alloys
-increases strength and durability
-reduces concrete corrosion induced by deicing or marine salts
Natural Pozzolans
-Not cementitious, but react with calcium hydroxide to form compounds possessing cementitious properties
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