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Concrete Exam 2

Terms in this set (60)

Workability of concrete is best defined as:

A) ability of the concrete to be mixed, placed, consolidated, and surface finished
B) amount of water added to the concrete
C) slump of the concrete
D) flowability of the concrete
F) stiffness of the concrete
A
Which of the following are mixture design proportioning methods?

A) 1:2:3 OR 3:2:1
B) all these above
C) Iteration (Trial Batching) method
D) ACI 211 Absolute Volume
B
What does 3:2:1 mixture design mean?

A) 3 portions of cement, 2 portions of rock, 1 portions of sand
B) zero
C) 3 portions of rock, 2 portions of sand, 1 portion of cement
D)3+2+1=6
C
ACI 211 only provides guidance into designing a concrete mixture.

True
False
T
Which of the following are aggregate proportioning methods?

A)Maximum voids content
B)Combined gradation
C)all these above
D)By Weight or Volume
E)Range of Voids Content
F)Surface Area
C
Both ACI 318 and 301 have been commonly referenced for meeting a concrete mixture.
True
False
T
Trial batches are not necessary if the concrete mixture was designed properly.
True
False
F
Quality testing of concrete isn't required if the concrete was designed properly.

True
False
F
Increasing the water-to-cement ratio will always improves the strength of a given concrete mixture.
True
False
F
Which of the following are common design parameters in the concrete mixture?
A)Strength
B)Workability
C)Durability
D)all these above
A
Which of the following are mixture design parameters for durability of concrete?

A)W/cm, air content, and scms
B)slump
C)only SCMs
D)Both w/cm and air content
E)only w/cm
F)only air content
A
Which of the following are durability issues related to concrete?

A) corrosion, freeze-thaw, sulfates, alkali silica reaction (ASR)
B) stress and strain
C) CSH, CH, ettringite, Afm
D) C3S, C2S, C3A, C4AF
E) compressive strength, flexural strength, modulus of elasticity
A
When using ACI 318 or 301 for determining durability requirements, each durability parameter is based on:

A) compressive strength
B) air content
C) exposure classification (environmental conditions)
D) workability
C
How does air-entrainment impact the strength of the concrete?
A) increases the strength of the concrete
B) depends on air entrainer type
C) decreases the strength of the concrete
D) it may increase or decrease
C
What is the largest mixture design parameter to influence compressive strength?
A) Blaine fineness of cement
B) only water content
C) only cement content
D) w/cm
E) environmental conditions
F) accelerator dosage
D
What does w/cm mean?
A) ratio between volume of water to volume of cement
B) ratio between the weight of water to the weight of cementitious materials (cement, fly ash, slag etc.)
C) cement to water ratio
D) nothing
B
If a concrete mixture with a 0.50 w/cm has 500 lbs of cement per cubic yard, how much water is contained in the mixture?
A) 200 lbs
B) 250 lbs
C) 500 lbs
D) 280 lbs
B
At what value should concrete be designed for strength?
A) at an adjusted compressive strength value using a safety factor
B) at the design compressive strength as provided on project specifications
C) 3,000 psi
D) at the minimum required compressive strength for the project
E) Just add water until strengths it adequate
A
According to ACI 301, if one concrete cylinder breaks below the minimum specified f'c, the concrete must be replaced.
True
False
F
What is the required average compressive strength (f'cr) when the specified compressive strength (f'c) is 4500 psi and data are not available to establish a standard deviation (per ACI 318)?
A) 5000 psi
B) 5700 psi
C) 4500 psi
D) 5200 psi
B
What modification factor would be used for a compressive strength standard deviation if only 25 sets of strength data was available (per ACI 318)?
A) 1.16
B) 1.03
C) 1.08
D) 1.00
B
For a 30 cylinder set standard deviation of 448 psi, what is the required average compressive strength (f'cr) when 3500 psi is the specified compressive strength (f'c) (per ACI 318)?
A) 4100 psi
B) 4300 psi
C) 4600 psi
D) 4000 psi
A
Convert 5 gallons of water per sack of cement (94 lbs.) to water-cement ratio by weight (to the nearest 0.01). (hint: 1 gallon of water =8.32 lbs)
A) 0.43
B) 0.44
C) 0.42
D) 0.46
E) 0.45
B
How much volume within the concrete is 5% air content?
A) 2.25 cft
B) 5 cft
C) 25.65 cft
D) 2 cft
E) 1.35 cft
E
What is the estimated average compressive strength (psi) based on the mix design procedure outlined in ACI 211?

Cement: 650 lbs.
#67 Limestone: 1820 lbs.
Manufactured Sand: 1275 lbs.
Water: 286 lbs.
Design Air Content: 5 %

A) 5,000 psi
B) 3,500 psi
C) 4,500 psi
D) 3,000 psi
E) 4,000 psi

Compressive Strgth W/C (by mass)
at 28 days Non-Air Air Entrained

7,000 psi 0.33 ---
6,000 psi 0.41 0.32
5,000 psi 0.48 0.40
4,000 psi 0.57 0.48
3,000 psi 0.68 0.59
2,000 psi 0.82 0.74
C
How much volume is 1820 lbs of crushed limestone with a SG of 2.76?
A) 5.38 cft
B) 10.57 cft
C) 27 cft
D) 16.43 cft
E) 8.43 cft
B
Based on the ACI 211 table below, what is the water content of an air-entrained concrete mixture with a 1.5 inch slump and a nominal maximum coarse aggregate size of 3/4 inch?

A) 270 lbs
B) 280 lbs
C )295 lbs
D) 300 lbs
E) 315 lbs
F) 320 lbs
G) 325 lbs
B
Based on the ACI 211 table below, what is the water content of a non-air entrained concrete mixture with a 6 inch slump and a nominal maximum coarse aggregate size of 1 inch?
A) 300 lbs
B) 310 lbs
C) 325 lbs
D) 340 lbs
E) 360 lbs
F) 315 lbs
D
Based on the chart below, what is the w/cm of a 5,500 psi non-air entrained concrete mixture? (5,500 psi has safety factor for strength built in)

Compressive Strgth W/C (by mass)
at 28 days Non-Air Air Entrained

7,000 psi 0.33 ---
6,000 psi 0.41 0.32
5,000 psi 0.48 0.40
4,000 psi 0.57 0.48
3,000 psi 0.68 0.59
2,000 psi 0.82 0.74

A) 0.33
B) 0.41
C) 0.43
D) 0.45
E) 0.47
F) 0.49
G) 0.57
D
Based on the chart below, what is the w/cm of a 5,500 psi air-entrained concrete mixture? (5,500 psi has safety factor for strength built in)

Compressive Strgth W/C (by mass)
at 28 days Non-Air Air Entrained

7,000 psi 0.33 ---
6,000 psi 0.41 0.32
5,000 psi 0.48 0.40
4,000 psi 0.57 0.48
3,000 psi 0.68 0.59
2,000 psi 0.82 0.74

A) 0.32
B) 0.33
C) 0.36
D) 0.39
E) 0.40
F) 0.41
G) 0.43
C
BASED ON THE CHART BELOW, What is the bulk volume of coarse aggregate per unit volume of concrete for a coarse aggregate with a 1-inch NM and a fine aggregate with a FM of 2.70?

A) 0.63
B) 0.66
C) 0.67
D) 0.68
E) 0.69
F) 0.70
D
Based on ACI 211 mixture design, what is the coarse aggregate weight with a unit weight of 106 lbs/cft and bulk volume (b/bo) of 0.64?

A) 1832 lbs
B) 1869 lbs
C) 1924 lbs
D) 2198 lbs
F) 1758 lbs
A
The following mixture design needs to be modified due to a material change. The current #67 limestone A with a SG of 2.52 needs to be replaced with a #67 limestone B with a SG of 2.66. What is the new mixture design by weight?

Material Weight
Cement 564 lbs
Limestone A 1825 lbs
Fine agg. 1160 lbs
Water 320 lbs
Total 3868 lbs

Cement = ?
Limestone B = ?
Fine Agg. = ?
Water = ?

A) 1160 lbs
B) 564 lbs
C) 300 lbs
D) 1926 lbs
E) 320 lbs
B
D
A
E
The following non-air entrained mixture design needs to be modified for 6.0% air. Adjust the volume of the fine aggregate to allow the modified mixture design to properly yield 27.0 cft. The SG of cement is 3.15, SG of coarse agg is 2.66, and SG of fine agg is 2.58. What are the volumes of the individual materials of this modified mixture design?

Material Weight Volume
Cement 517 lbs 2.63 cft
Coarse agg 1750 lbs 10.54 cft
Fine agg 1262 lbs 7.84 cft
Water 3240 lbs 5.45 cft
Air 2% 0.54 cft
Total 3869 lbs 27.0 cft

Cement = ?
Coarse Aggregate = ?
Fine Aggregate = ?
Water = ?
Air = ?

A) 5.45
B) 1.62
C) 2.63
D) 10.54
E) 6.76
C
D
E
A
B
The following non-air entrained mixture design needs to become more economical by using 20% fly ash replcement. Adjust the volume of the fine aggregate to allow the modified mixture design to properly yield 27.0 cft. The SG of cement is 3.15, SG of fly ash is 2.52, SG of coarse agg is 2.66, and SG of fine agg is 2.58. What are the volumes of the individual materials of this modified mixture design?

Material Weight Volume
Cement 517 lbs 2.63 cft
Coarse agg 1750 lbs 10.54 cft
Fine agg 1262 lbs 7.84 cft
Water 340 lbs 5.45 cft
Air 2% 0.54 cft
Total 3869 lbs 27.0 cft

Cement = ?
Fly ash = ?
Coarse Aggregate = ?
Fine Aggregate = ?
Water = ?
Air Content = ?

A) 10.54
B) 7.71
C) 2.10
D) 5.45
E) .54
D) .66
F) .25
G) 7.99
C
D
A
B
D
E
The following non-air entrained mixture design needs to become more economical by using 20% fly ash replcement. Adjust the volume of the fine aggregate to allow the modified mixture design to properly yield 27.0 cft. The SG of cement is 3.15, SG of fly ash is 2.52, SG of coarse agg is 2.66, and SG of fine agg is 2.58. What are the weights of the individual materials of this modified mixture design?

Material Weight Volume
Cement 517 lbs 2.63 cft
Coarse agg 1750 lbs 10.54 cft
Fine agg 1262 lbs 7.84 cft
Water 3240 lbs 5.45 cft
Air 2% 0.54 cft
Total 3869 lbs 27.0 cft

Cement = ?
Fly Ash = ?
Coarse Aggregate = ?
Fine Aggregate = ?
Water = ?

A) 1750 lbs
B) 103 lbs
C) 414 lbs
D) 1500 lbs
E) 340 lbs
F) 1241 lbs
G) 3850 lbs
C
B
A
F
E
For concrete being transported with a dump truck and dumped in front of a slip formed paver, what is the minimum increments must be obtained to be combined together into a composite sample? (According to ASTM C172)
A) 1
B) 2
C) 3
D) 4
E) 5
E
At least two portions must be taken when sampling from a revolving drum truck. (According to ASTM C172)
True
False
T
Concrete samples must be obtained before any water or admixtures are added to the mixer at the job site.
True
False
F
Samples for strength should be taken before 10% or after 90% of the batch has been discharged in a revolving drum truck.
True
False
F
According to ASTM C 94, only slump and air content tests are required to be measured when making compressive strength cylinders.
True
False
F
The Slump test is not a workability test, but a test to measure consistency according to the standard ASTM C143.
True
False
T
The curing procedure for cylinders is not important and just wastes both time and money.
True
False
F
ASTM C 94 the minimum temperatures of concrete at placement and also provides text to caution about concrete with a maximum temperature close-to or exceeding 90F.
True
False
T
ASTM C 94 requires that if the measured air content of concrete falls outside the specified limits, a check test shall be made immediately on another portion of the same sample prior to rejecting the concrete.
True
False
T
According to ASTM C 94, the purchaser shall ensure that the manufacturer (ready mix producer) is provided copies of all reports of tests performed on concrete taken to determine compliance with specification requirements.
True
False
T
According to ASTM C 94, compliance testing shall be made by a certified ACI Concrete Field Testing Technician Grade I, or equivalent.
True
False
T
How long does a technician have to obtain a composite sample?
A) 5 minutes
B) 10 minutes
C) 15 minutes
D) 20 minutes
E) 25 minutes
F) 30 minutes
C
Match the test description in Column A with the test process in Column B for which they are used.
Weight of concrete within a known volume = ?
Compressive strength of concrete = ?
Measurement of concrete consistency = ?
Freeze-thaw durability of the concrete = ?
Measuring temperature of concrete = ?
Method of curing cylinders = ?


A) Cylinders
B) Air content
C) Unit Weight
D) Slump
E) Water bath
F) Therometer
G) Sampling
H) Volume
I) Beams
C
A
D
B
F
E
After how many minutes does the technician have to start testing slump, temperature, unit weight, and air after obtaining the composite sample?
A) 5 minutes
B) 10 minutes
C) 15 minutes
D) 20 minutes
E) 25 minutes
F) 30 minutes
A
After how many minutes does the technician have to start making strength specimen(s) after obtaining the composite sample?
A) 5 minutes
B) 10 minutes
C) 15 minutes
D) 20 minutes
E) 30 minutes
C
When determining the temperature of fresh concrete, what is the minimum amount of concrete cover (inch) in all directions around the thermometer?
A) 1 inch
B) 2 inches
C) 3 inches
D) 4 inches
C
What is the time limit for conducting Slump?
A) 1 min
B) 2.5 min
C) 5 min
D) 15 minutes
B
After properly consolidating the concrete into the slump cone and striking off the top, how many seconds must it take for the technician to vertically lift the slump cone at least 12 inches?
A) 15 minutes
B) 5 minutes
C) 2.5 minutes
D) 10 seconds
E) 5 +/- 2 seconds
F) maximum of 3 seconds
E
According to the ASTM standards if a concrete mixture has a slump less than 1 inch, the technician should use a vibrator to adequately consolidate the samples for unit weight, air, and cylinders.
True
False
T
Calculate the unit weight of the concrete based on the following data:
Volume of Unit Wt. Bucket: 0.255 cu. ft.
Weight of Bucket with Concrete: 42.60 lbs.
Weight of Empty Bucket: 7.35 lbs.
A) 135.7 lbs/cft
B) 138.2 lbs/cft
C) 145.5 lbs/cft
D) 150.3 lbs/cft
E) 137.9 lbs/cft
F) 143.3 lbs/cft
B
What type of curing should be conducted for quality control, quality assurance, and trial batching?
A) standard (lab) cure
B) field cure
C) in-place cure
D) no cure
A
What is the basic formula used to calculate compressive strength?
A) maximum load
B) maximum load/cross-sectional area, which sometimes is called P/A
C) stress/strain
D) length change/original length
B
Yeild of the concrete in ft^3 and yd^3
Unit weight = 148.2 lbs/ft^3
Design weight = 20,000 lbs
4.988
Calculate relative yield
Theoritical yield = 12yd^3
Actual Yeild = 12.3 yd^3
1.025
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