CONCRETE TECH EXAM 2 QUESTIONS AND CORRECT
ANSWERS (NEWEST)
Workability of concrete is best defined as: - ANSWER ability of the
concrete to be mixed, placed, consolidated, and surface finished
Which of the following are mixture design proportioning methods?
ACI 211 Absolute Volume
all these above
1:2:3 OR 3:2:1
Iteration (Trial Batching) method - ANSWER all these above
What does 3:2:1 mixture design mean? - ANSWER 3 portions of rock,
2 portions of sand, 1 portion of cement
ACI 211 only provides guidance into designing a concrete mixture. T/F -
ANSWER True
Which of the following are aggregate proportioning methods?
all these above
By Weight or Volume
Maximum voids content
Combined gradation
Range of Voids Content
Surface Area - ANSWER all these above
Both ACI 318 and 301 have been commonly referenced for meeting a
concrete mixture. T/F - ANSWER True
Trial batches are not necessary if the concrete mixture was designed
properly. T/F - ANSWER False
Quality testing of concrete isn't required if the concrete was designed
properly. T/F - ANSWER False
, Increasing the water-to-cement ratio will always improves the strength of
a given concrete mixture. T/F - ANSWER False
What are common design parameters in the concrete mixture? -
ANSWER Strength
What are mixture design parameters for durability of concrete? -
ANSWER W/cm, air content, and scms
What are durability issues related to concrete? - ANSWER corrosion,
freeze-thaw, sulfates, alkali silica reaction (ASR)
When using ACI 318 or 301 for determining durability requirements,
each durability parameter is based on: - ANSWER exposure
classification (environmental conditions)
How does air-entrainment impact the strength of the concrete? -
ANSWER decreases the strength of the concrete
What is the largest mixture design parameter to influence compressive
strength? - ANSWER w/cm
What does w/cm mean? - ANSWER ratio between the weight of water
to the weight of cementitious materials (cement, fly ash, slag etc.)
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? - ANSWER 250 lbs
At what value should concrete be designed for strength? - ANSWER at
an adjusted compressive strength value using a safety factor
According to ACI 301, if one concrete cylinder breaks below the
minimum specified f'c, the concrete must be replaced. T/F - ANSWER
False
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)? - ANSWER
5700 psi
What modification factor would be used for a compressive strength
standard deviation if only 25 sets of strength data was available (per ACI
318)? - ANSWER 1.03
ANSWERS (NEWEST)
Workability of concrete is best defined as: - ANSWER ability of the
concrete to be mixed, placed, consolidated, and surface finished
Which of the following are mixture design proportioning methods?
ACI 211 Absolute Volume
all these above
1:2:3 OR 3:2:1
Iteration (Trial Batching) method - ANSWER all these above
What does 3:2:1 mixture design mean? - ANSWER 3 portions of rock,
2 portions of sand, 1 portion of cement
ACI 211 only provides guidance into designing a concrete mixture. T/F -
ANSWER True
Which of the following are aggregate proportioning methods?
all these above
By Weight or Volume
Maximum voids content
Combined gradation
Range of Voids Content
Surface Area - ANSWER all these above
Both ACI 318 and 301 have been commonly referenced for meeting a
concrete mixture. T/F - ANSWER True
Trial batches are not necessary if the concrete mixture was designed
properly. T/F - ANSWER False
Quality testing of concrete isn't required if the concrete was designed
properly. T/F - ANSWER False
, Increasing the water-to-cement ratio will always improves the strength of
a given concrete mixture. T/F - ANSWER False
What are common design parameters in the concrete mixture? -
ANSWER Strength
What are mixture design parameters for durability of concrete? -
ANSWER W/cm, air content, and scms
What are durability issues related to concrete? - ANSWER corrosion,
freeze-thaw, sulfates, alkali silica reaction (ASR)
When using ACI 318 or 301 for determining durability requirements,
each durability parameter is based on: - ANSWER exposure
classification (environmental conditions)
How does air-entrainment impact the strength of the concrete? -
ANSWER decreases the strength of the concrete
What is the largest mixture design parameter to influence compressive
strength? - ANSWER w/cm
What does w/cm mean? - ANSWER ratio between the weight of water
to the weight of cementitious materials (cement, fly ash, slag etc.)
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? - ANSWER 250 lbs
At what value should concrete be designed for strength? - ANSWER at
an adjusted compressive strength value using a safety factor
According to ACI 301, if one concrete cylinder breaks below the
minimum specified f'c, the concrete must be replaced. T/F - ANSWER
False
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)? - ANSWER
5700 psi
What modification factor would be used for a compressive strength
standard deviation if only 25 sets of strength data was available (per ACI
318)? - ANSWER 1.03
