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ACI SCC Testing practice questions

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Question 1Self-Consolidating Concrete Field Testing

Which test method is the standard field measure of the filling ability of self-consolidating concrete using a slump cone inverted in orientation?

  1. Segregation resistance sieve test
  2. Slump flow test (ASTM C1611) Correct answer.
  3. V-funnel test
  4. L-box test

Explanation

The slump flow test uses an inverted slump cone filled without tamping and measures the resulting spread diameter, which characterizes filling ability and flow. Other listed tests measure passing ability, viscosity, or segregation resistance rather than free flow spread.

Question 2Self-Consolidating Concrete Field Testing

In the slump flow test, the T50 time is measured as the elapsed time until the concrete spread reaches what diameter?

  1. 500 mm Correct answer.
  2. 800 mm
  3. 300 mm
  4. 650 mm

Explanation

T50 is the time for the inverted cone slump flow to reach a 500 mm spread circle. It is used as an indicator of the concrete's viscosity and rate of flow.

Question 3Self-Consolidating Concrete Field Testing

A slump flow spread of 660 mm with no visible segregation is measured. Into which general SCC slump flow class does this value most likely fall?

  1. Below the range of the standard classes
  2. SF2 Correct answer.
  3. SF1
  4. SF3

Explanation

SF2 covers approximately 660 to 750 mm spread. SF1 is roughly 550 to 650 mm and SF3 is roughly 760 to 850 mm, so 660 mm sits in SF2.

Question 4Self-Consolidating Concrete Field Testing

Which field test is specifically intended to assess the passing ability of SCC through closely spaced reinforcement?

  1. Siege segregation test
  2. Setting time test
  3. L-box test Correct answer.
  4. Slump flow test

Explanation

The L-box measures the ability of SCC to flow through reinforcing bars and reach the far end of the horizontal section, which is passing ability. Slump flow measures free filling ability and the sieve test measures segregation resistance.

Question 5Self-Consolidating Concrete Field Testing

In the L-box test, the result is typically reported as which ratio?

  1. The ratio of mass retained to total mass
  2. The ratio of flow time to spread
  3. The ratio of heights at the two ends of the horizontal section Correct answer.
  4. The ratio of spread diameter to cone height

Explanation

The L-box blocking ratio is the height of concrete at the far end divided by the height at the near end after the gate is lifted. A ratio close to 1 indicates good passing ability.

Question 6Self-Consolidating Concrete Field Testing

An L-box blocking ratio of 0.85 is obtained. How should this result be interpreted?

  1. The concrete is too viscous to flow at all
  2. The concrete has failed the segregation resistance requirement
  3. The concrete shows good passing ability through the reinforcement Correct answer.
  4. The concrete has poor passing ability and likely blocked

Explanation

Higher blocking ratios indicate better passing ability, and values near 0.8 to 1.0 generally indicate acceptable performance. A ratio of 0.85 reflects good flow past the obstacles with little blocking.

Question 7Self-Consolidating Concrete Field Testing

The V-funnel test in SCC field testing is primarily used to evaluate which property?

  1. Static segregation resistance
  2. Air content
  3. Compressive strength development
  4. Viscosity and filling ability via flow time Correct answer.

Explanation

The V-funnel measures the time for a fixed volume of SCC to flow through a funnel-shaped outlet, which reflects viscosity and filling ability. Longer times indicate higher viscosity.

Question 8Self-Consolidating Concrete Field Testing

The T50 slump flow time of an SCC mixture is unusually long while the final spread is acceptable. What does this most likely indicate?

  1. Insufficient cement content only
  2. High viscosity and slower flow Correct answer.
  3. Excessive segregation
  4. Low viscosity and high flow rate

Explanation

A longer T50 time means the concrete takes more time to reach the 500 mm circle, which reflects higher viscosity and a slower rate of flow. Final spread can still be acceptable even when the flow rate is slow.

Question 9Self-Consolidating Concrete Field Testing

Which test is used to assess the static segregation resistance of SCC in the field by measuring the mass passing through a sieve?

  1. Slump flow test
  2. V-funnel test
  3. L-box test
  4. Segregation resistance sieve test Correct answer.

Explanation

The segregation resistance sieve test pours a sample over a sieve and measures the mass of mortar that passes through, indicating the tendency for aggregate to separate from paste. A higher passing mass indicates greater segregation.

Question 10Self-Consolidating Concrete Field Testing

When performing the slump flow test, how is the slump cone prepared before filling?

  1. It is placed inverted and vibrated during filling
  2. It is placed upright and filled in two layers with tamping
  3. It is placed inverted on a level base plate and filled in one lift without rodding Correct answer.
  4. It is placed upright and rodded in three layers

Explanation

For SCC slump flow, the cone is inverted (smaller opening down) on a level, moistened base plate and filled in a single lift without tamping or vibration. The concrete is allowed to spread freely once the cone is lifted.

Question 11Self-Consolidating Concrete Field Testing

During a slump flow test, the base plate must be level and free of vibration. Why is this requirement important?

  1. To prevent the concrete from setting too quickly
  2. To ensure the spread is not biased by tilt or external disturbance Correct answer.
  3. To reduce the air content of the sample
  4. To increase the measured T50 time

Explanation

A level, undisturbed base plate ensures the measured spread reflects the concrete's flow rather than gravity-driven bias or vibration. Tilt or vibration would distort both the final spread and the T50 time.

Question 12Self-Consolidating Concrete Field Testing

A field technician observes a visible ring of mortar around the perimeter of the slump flow patty with coarse aggregate concentrated in the center. This observation most likely indicates what?

  1. Insufficient filling ability
  2. Excessive viscosity
  3. Excellent stability with uniform aggregate distribution
  4. Segregation or bleeding of the mixture Correct answer.

Explanation

A halo of mortar at the edge with aggregate concentrated centrally is a visual sign of segregation or bleeding. Visual stability assessment is a standard part of the slump flow test.

Question 13Self-Consolidating Concrete Field Testing

What is the typical minimum curing or conditioning consideration for SCC field test samples before testing fresh properties?

  1. Samples should be remixed gently just before testing to ensure homogeneity Correct answer.
  2. Samples should be vibrated to remove air before testing
  3. Samples should be allowed to set for 30 minutes before testing
  4. Samples should be tested immediately after mixing with no conditioning

Explanation

Fresh SCC samples should be gently remixed before testing to counteract any segregation that occurred during transport or standing. Testing should proceed promptly after remixing.

Question 14Self-Consolidating Concrete Field Testing

The V-funnel flow time for a mixture is measured, then the test is repeated after a 5-minute rest period. What is the purpose of the second measurement?

  1. To assess the viscosity increase due to thixotropy or setting Correct answer.
  2. To measure the segregation resistance over time
  3. To measure the air content loss
  4. To determine the compressive strength gain

Explanation

The V-funnel test at 5 minutes (T5min) assesses how flow time changes with rest, reflecting thixotropic behavior or viscosity increase. A large increase indicates the mixture stiffens significantly when left static.

Question 15Self-Consolidating Concrete Field Testing

Which of the following best describes the purpose of the J-ring test in SCC field testing?

  1. To determine the setting time of the concrete
  2. To measure the static segregation resistance of the mixture
  3. To assess passing ability by measuring flow spread through an array of vertical bars Correct answer.
  4. To measure the air content of the fresh mixture

Explanation

The J-ring test places a ring of vertical bars around the slump flow setup and measures the spread and height difference, assessing passing ability through obstacles. It complements the L-box for passing ability evaluation.

Question 16Self-Consolidating Concrete Field Testing

In the J-ring test, a large difference in concrete height between inside and outside the ring indicates what?

  1. Excessive air content
  2. Excellent passing ability
  3. Rapid setting
  4. Blocking or poor passing ability Correct answer.

Explanation

The J-ring height difference (and the difference between J-ring spread and slump flow spread) quantifies blocking. A large height difference indicates the bars impeded flow, signaling poor passing ability.

Question 17Self-Consolidating Concrete Field Testing

What is the correct orientation of the slump cone for the SCC slump flow test?

  1. Either orientation gives equivalent results
  2. Larger opening down, smaller opening up
  3. Lying on its side
  4. Smaller opening down, larger opening up Correct answer.

Explanation

The SCC slump flow test uses the cone inverted so the smaller opening rests on the base plate and the larger opening faces up. This differs from the conventional slump test orientation.

Question 18Self-Consolidating Concrete Field Testing

A slump flow test yields a spread of 780 mm. Which slump flow class does this correspond to?

  1. SF1
  2. SF2
  3. SF3 Correct answer.
  4. It exceeds all defined classes

Explanation

SF3 covers approximately 760 to 850 mm spread. A value of 780 mm falls within the SF3 range, indicating high filling ability.

Question 19Self-Consolidating Concrete Field Testing

Which factor most directly affects the T50 time measured during the slump flow test?

  1. The mass of the slump cone
  2. The ambient noise level
  3. The viscosity of the paste and mortar phase Correct answer.
  4. The color of the base plate

Explanation

T50 reflects the rate at which the concrete spreads, which is governed primarily by the viscosity of the paste and mortar. Higher viscosity slows the spread and lengthens T50.

Question 20Self-Consolidating Concrete Field Testing

In the segregation resistance sieve test, a higher mass of mortar passing through the sieve generally indicates what?

  1. Lower air content
  2. Greater segregation tendency Correct answer.
  3. Lower segregation tendency
  4. Higher compressive strength

Explanation

More mortar passing through the sieve means more paste separated from the aggregate, indicating a greater tendency to segregate. Lower passing mass indicates better stability.

Question 21Self-Consolidating Concrete Field Testing

A contractor needs to verify that an SCC mixture can flow through heavily congested reinforcement without blocking. Which test is most appropriate?

  1. L-box or J-ring test Correct answer.
  2. Slump flow test alone
  3. Segregation resistance sieve test
  4. Setting time test

Explanation

Passing ability through congested reinforcement is assessed with the L-box or J-ring test, both of which introduce obstacles to flow. Slump flow alone measures free filling ability without obstacles.

Question 22Self-Consolidating Concrete Field Testing

Why is it important to moisten the base plate and cone before performing a slump flow test?

  1. To reduce the air content of the sample
  2. To accelerate the setting of the concrete
  3. To prevent the concrete from adhering to the equipment and to reduce friction effects Correct answer.
  4. To increase the measured spread artificially

Explanation

Moistening the equipment prevents fresh concrete from sticking and reduces surface friction that could bias the measured spread. It does not intentionally alter the concrete's properties.

Question 23Self-Consolidating Concrete Field Testing

Which combination of tests would best characterize both the filling ability and the passing ability of an SCC mixture in the field?

  1. Slump flow and setting time
  2. Slump flow and L-box Correct answer.
  3. Segregation sieve and setting time
  4. Air content and compressive strength

Explanation

Slump flow characterizes filling ability, while the L-box characterizes passing ability through reinforcement. Together they cover two key workability properties of SCC.

Question 24Self-Consolidating Concrete Field Testing

An SCC mixture shows a slump flow of 700 mm, a T50 of 2 seconds, and a visible mortar halo at the patty edge. Which property is most clearly deficient?

  1. Viscosity
  2. Passing ability
  3. Stability against segregation Correct answer.
  4. Filling ability

Explanation

The mortar halo is a visual indicator of segregation, meaning the mixture lacks stability even though filling ability and viscosity appear acceptable. Stability is assessed by visual observation and segregation tests.

Question 25Self-Consolidating Concrete Field Testing

The V-funnel flow time for a mixture is very short. What does this most likely suggest about the mixture?

  1. Low viscosity and rapid flow Correct answer.
  2. High compressive strength
  3. High viscosity and slow flow
  4. High segregation resistance

Explanation

A short V-funnel flow time indicates the concrete flows quickly through the funnel, reflecting low viscosity. Excessively short times can also suggest a risk of segregation.

Question 26Self-Consolidating Concrete Field Testing

What does the slump flow test primarily measure in self-consolidating concrete?

  1. Bleeding rate under pressure
  2. Passing ability through congested reinforcement
  3. Filling ability under its own weight Correct answer.
  4. Resistance to segregation after setting

Explanation

The slump flow test measures the horizontal spread of concrete after the cone is lifted, which indicates the mixture's ability to flow and fill under its own weight without mechanical vibration. It does not directly assess passing ability or segregation resistance.

Question 27Self-Consolidating Concrete Field Testing

According to common SCC guidelines, a slump flow spread of 550 mm would typically classify the mixture as:

  1. SF2
  2. SF1 Correct answer.
  3. SF3
  4. Not classifiable

Explanation

Slump flow classes are defined by ranges: SF1 typically covers 550–650 mm, SF2 covers 660–750 mm, and SF3 covers 760–850 mm. A spread of 550 mm falls at the lower bound of SF1.

Question 28Self-Consolidating Concrete Field Testing

In the V-funnel test, what does a flow time of less than 8 seconds typically indicate about the SCC mixture?

  1. High viscosity and low flowability
  2. Excessive air content
  3. High segregation resistance
  4. Low viscosity and high flowability Correct answer.

Explanation

The V-funnel flow time measures the time for a set volume of concrete to flow through the funnel. Shorter times indicate lower viscosity and higher flowability, while longer times indicate higher viscosity.

Question 29Self-Consolidating Concrete Field Testing

Which test is commonly used in the field to evaluate the passing ability of SCC through narrow openings?

  1. L-box test Correct answer.
  2. Setting time test
  3. Slump flow test
  4. Segregation sieve test

Explanation

The L-box test measures the ability of SCC to flow through a simulated obstacle (reinforcement bars) and is a standard method for assessing passing ability. The slump flow test assesses filling ability without obstacles.

Question 30Self-Consolidating Concrete Field Testing

During the slump flow test, what is the specified height to which the slump cone should be filled?

  1. Completely to the top Correct answer.
  2. One-third of its height
  3. Half of its height
  4. Two-thirds of its height

Explanation

The slump cone is filled completely to the top in a single layer without tamping or vibration. This ensures a consistent volume of concrete for the test.

Question 31Self-Consolidating Concrete Field Testing

What does a segregation index of 15% in the sieve segregation test indicate?

  1. The mixture has poor segregation resistance Correct answer.
  2. The mixture has high passing ability
  3. The mixture is highly resistant to segregation
  4. The mixture has excessive air content

Explanation

The sieve segregation test measures the mass of mortar that passes through a sieve relative to the total sample mass. A segregation index above about 10-15% typically indicates poor segregation resistance, with higher values meaning more segregation.

Question 32Self-Consolidating Concrete Field Testing

In the J-ring test, what does a small difference in concrete height inside and outside the ring indicate?

  1. Low filling ability
  2. Good passing ability Correct answer.
  3. High segregation
  4. Poor passing ability

Explanation

The J-ring test measures the difference in height of concrete inside and outside the ring after flow. A small difference indicates that the concrete flowed through the obstacles without blocking, meaning good passing ability.

Question 33Self-Consolidating Concrete Field Testing

What is the typical duration for which the slump flow spread is measured after lifting the cone?

  1. Immediately after lifting Correct answer.
  2. After 1 minute
  3. After 30 seconds
  4. After 5 minutes

Explanation

The slump flow spread is measured immediately after the cone is lifted, once the concrete has stopped flowing. Waiting would allow the concrete to spread further and give incorrect results.

Question 34Self-Consolidating Concrete Field Testing

A T50 time of 2 seconds in the slump flow test indicates:

  1. A mixture with low flowability and high viscosity
  2. A mixture with high passing ability
  3. A mixture with poor segregation resistance
  4. A mixture with high flowability and low viscosity Correct answer.

Explanation

T50 is the time for the concrete to spread to a diameter of 500 mm. A short T50 (e.g., 2 seconds) indicates rapid flow and low viscosity, typical of highly flowable SCC.

Question 35Self-Consolidating Concrete Field Testing

When performing the L-box test, what is the purpose of the vertical bars in the apparatus?

  1. To evaluate segregation resistance
  2. To measure the flow time of the concrete
  3. To simulate reinforcement and assess passing ability Correct answer.
  4. To determine the air content

Explanation

The L-box test uses vertical bars to simulate congested reinforcement. The ability of the concrete to flow through these bars and reach a certain height in the horizontal section indicates its passing ability.

Question 36Self-Consolidating Concrete Field Testing

Which of the following is a correct procedure for sampling SCC from a truck mixer for field testing?

  1. Take samples from the top of the drum
  2. Take samples only from the end of the discharge
  3. Take samples only from the beginning of the discharge
  4. Take samples from the middle of the discharge Correct answer.

Explanation

Standard practice for sampling fresh concrete is to take samples from the middle portion of the discharge to ensure representativeness. Sampling from the beginning or end may not be representative of the entire batch.

Question 37Self-Consolidating Concrete Field Testing

What does a visual stability index (VSI) of 1 indicate for an SCC mixture?

  1. Severe segregation
  2. Moderate segregation
  3. No evidence of segregation Correct answer.
  4. Slight bleeding or segregation

Explanation

The VSI is a visual rating from 0 to 3. A VSI of 0 indicates no segregation, VSI 1 indicates slight bleeding or segregation, VSI 2 indicates moderate segregation, and VSI 3 indicates severe segregation.

Question 38Self-Consolidating Concrete Field Testing

In the V-funnel test, what is the purpose of the 5-minute rest period before the second flow time measurement?

  1. To allow the concrete to cool to room temperature
  2. To measure the setting time of the concrete
  3. To determine the air content of the mixture
  4. To assess the ability of the mixture to resist segregation and retain flowability Correct answer.

Explanation

The V-funnel test can be performed with a 5-minute rest period to evaluate the static segregation resistance and thixotropic behavior of the SCC. The difference between the initial and the 5-minute flow times indicates whether the mixture retains its flowability or segregates.

Question 39Self-Consolidating Concrete Field Testing

A field technician is conducting a slump flow test and observes that the concrete spread has reached 500 mm at 3 seconds. What is this 3-second value called?

  1. Segregation index
  2. T50 time Correct answer.
  3. J-ring difference
  4. V-funnel time

Explanation

The time required for the concrete to spread to a diameter of 500 mm is defined as the T50 time. It is used as an indicator of the viscosity of the SCC mixture.

Question 40Self-Consolidating Concrete Field Testing

When using the L-box test, the blocking ratio is calculated as the ratio of:

  1. H1/H2, where H1 is the height at the horizontal end and H2 is the height at the vertical section
  2. H2/H1, where H1 is the height at the horizontal end and H2 is the height at the vertical section
  3. H1/H2, where H1 is the height at the vertical section and H2 is the height at the horizontal end
  4. H2/H1, where H1 is the height at the vertical section and H2 is the height at the horizontal end Correct answer.

Explanation

The blocking ratio (or passing ability ratio) is the height of concrete at the end of the horizontal section (H2) divided by the height at the vertical section (H1). A ratio closer to 1 indicates better passing ability.

Question 41Self-Consolidating Concrete Field Testing

What is the primary purpose of the sieve segregation test for SCC?

  1. To determine the air content of the fresh concrete
  2. To assess the resistance of the mixture to static segregation Correct answer.
  3. To evaluate the passing ability through reinforcement
  4. To measure the flow rate through a funnel

Explanation

The sieve segregation test measures the mass of mortar that passes through a sieve from a sample of concrete, providing an indication of the static segregation resistance of the SCC.

Question 42Self-Consolidating Concrete Field Testing

A slump flow test yields a spread of 680 mm. Which slump flow class does this correspond to?

  1. SF3
  2. SF2 Correct answer.
  3. SF4
  4. SF1

Explanation

Slump flow class SF2 typically covers spreads from 660 to 750 mm. A spread of 680 mm falls within this range.

Question 43Self-Consolidating Concrete Field Testing

During the J-ring test, the concrete is allowed to flow and then the height difference between the concrete inside and outside the ring is measured. What does a large height difference indicate?

  1. Low viscosity
  2. Poor passing ability Correct answer.
  3. High filling ability
  4. High segregation resistance

Explanation

A large height difference indicates that the concrete had difficulty flowing through the obstacles, which is a sign of poor passing ability.

Question 44Self-Consolidating Concrete Field Testing

Which of the following is a recommended practice for curing SCC test specimens before testing hardened properties?

  1. Air cure at ambient temperature
  2. Seal in a plastic bag without moisture
  3. Oven dry at 100 °C
  4. Moist cure at 20 ± 2 °C until the time of test Correct answer.

Explanation

Standard curing for test specimens typically involves moist curing at a controlled temperature (20 ± 2 °C) until the time of testing to ensure representative strength development.

Question 45Self-Consolidating Concrete Field Testing

What does a V-funnel flow time of 15 seconds typically indicate about an SCC mixture?

  1. Low viscosity
  2. High viscosity Correct answer.
  3. High passing ability
  4. High segregation resistance

Explanation

Longer V-funnel flow times indicate higher viscosity and slower flow. A time of 15 seconds is relatively long and suggests a viscous mixture.

Question 46Self-Consolidating Concrete Field Testing

In the slump flow test, if the concrete spread is non-circular or asymmetric, what is the most likely cause?

  1. Too high a slump flow
  2. Excessive air content
  3. Segregation or inconsistent mixture Correct answer.
  4. Too low a viscosity

Explanation

An asymmetric spread often indicates segregation or inconsistency in the mixture, such as uneven distribution of coarse aggregate or mortar.

Question 47Self-Consolidating Concrete Field Testing

A concrete mixture has a slump flow of 720 mm, a T50 of 1.5 seconds, and a V-funnel time of 6 seconds. Which of the following best describes this mixture?

  1. High flowability with low viscosity Correct answer.
  2. Low flowability with high viscosity
  3. High passing ability
  4. High segregation resistance

Explanation

A large slump flow (720 mm) indicates high flowability, and short T50 (1.5 s) and V-funnel (6 s) times indicate low viscosity. These characteristics are typical of a highly flowable SCC.

Question 48Self-Consolidating Concrete Field Testing

During a slump flow test, the concrete is observed to have a visible ring of mortar around the perimeter of the spread. What does this most likely indicate?

  1. High passing ability
  2. Segregation of the mixture Correct answer.
  3. Excessive air content
  4. Low viscosity

Explanation

A mortar halo or ring around the perimeter indicates that the coarse aggregate has segregated from the mortar, which is a sign of segregation.

Question 49Self-Consolidating Concrete Field Testing

A field technician performs a J-ring test and obtains a height difference of 15 mm. According to typical acceptance criteria for SCC, how should this result be interpreted?

  1. Indicates high segregation
  2. Indicates low filling ability
  3. Acceptable passing ability Correct answer.
  4. Unacceptable passing ability

Explanation

A height difference of 15 mm is generally within acceptable limits for passing ability (often ≤ 10-15 mm depending on specification). It indicates that the concrete flows through the obstacles without significant blocking.

Question 50Self-Consolidating Concrete Field Testing

An SCC mixture is tested using the L-box, and the blocking ratio is found to be 0.65. What does this value indicate about the mixture's passing ability?

  1. Excellent passing ability
  2. High segregation resistance
  3. Low viscosity
  4. Poor passing ability Correct answer.

Explanation

A blocking ratio of 0.65 means that the concrete height at the end of the horizontal section is only 65% of the height at the vertical section. This indicates significant blocking and poor passing ability. Typically, a ratio of at least 0.8 is required for adequate passing ability.