Construction Materials Exam 2
Questions with Correct Answers
List a problem that can occur if concrete is not consolidated enough. - ANSWERSlow
durability/strength (lots of voids)
List a problem that can occur if concrete is consolidated too much. - ANSWERSlower
strength at concrete surface
Name two ways plastic shrinkage cracking can be mitigated. - ANSWERS1. decrease
concrete temperature
2. increase humidity
List 3 concrete admixtures and a reason you may want to use them. - ANSWERS1. air
entrainer (increase workability and helps with concrete freezing)
2. accelerator (increase early strength)
3. retarders (good for long delivery time)
Define f'c and f'cr. Which is higher? - ANSWERSf'c=specified compressive strength for
design
f'cr=required compressive strength for testing
f'cr>f'c
What are the two problems that steel corrosion causes in concrete? - ANSWERS1.
corroded steel is larger than non-corroded (expansion)
2. corroded steel is weaker
List three ways you can slow corrosion in concrete. - ANSWERS1. put more concrete
around the steel
2. make concrete less permeable
3. sacrificial anode
Name a way to mitigate Alkali Aggregate Reaction. - ANSWERSuse a different
aggregate
What is a reasonable compressive strength value for concrete? - ANSWERS3000-
6000psi
What is a reasonable tensile strength value for concrete? - ANSWERS100-500psi
Where is concrete most likely to crack (weak spot)? - ANSWERSspot between cement
and aggregate (ITZ)
, How would you expect compressive strength to vary based on: sample size, loading
rate, maximum aggregate size - ANSWERS1. smaller size is greater strength
2. increased loading rate is increased strength
3. smaller aggregate strength is greater strength
What rare crystal is responsible for Roman concrete's strength? -
ANSWERSTobermorite
What is one advantage of Roman concrete over today's concrete? -
ANSWERSEnvironmentally friendly as production does not emit toxic gases
What is fiber reinforced concrete? - ANSWERSUniformly distributed fibrouse materials
in concrete mix
Name the two types of synthetic fibers and at least two benefits of using each. -
ANSWERS1. Microfibers (decrease plastic shrinkage and increase uniformity in water
bleeding)
2. Macrofibers (increase durability and increase flexural toughness)
What is recycled concrete? - ANSWERSConcrete made from former concrete
structures or samples (Used as aggregate in new concrete)
What is an application of recycled concrete - ANSWERSLandscaping
What are two advantages and two disadvantages of 3-d printing concrete in
construction? - ANSWERSAdvantages:
1. quicker building times
2. can run 24/7
Disadvantages:
1. need technical expertise
2. cost of additives and mix design
What is the most common material used for the 3-D printing construction process? -
ANSWERSproprietary concrete
What is the range of compressive strength typically found in UHPC? -
ANSWERS17000-22000psi
What is the w/cm that is typically used in UHPC? - ANSWERS.25
What is a cement slurry? - ANSWERScement and water mixture
What is the most common application for soil cement? - ANSWERSpavements
Questions with Correct Answers
List a problem that can occur if concrete is not consolidated enough. - ANSWERSlow
durability/strength (lots of voids)
List a problem that can occur if concrete is consolidated too much. - ANSWERSlower
strength at concrete surface
Name two ways plastic shrinkage cracking can be mitigated. - ANSWERS1. decrease
concrete temperature
2. increase humidity
List 3 concrete admixtures and a reason you may want to use them. - ANSWERS1. air
entrainer (increase workability and helps with concrete freezing)
2. accelerator (increase early strength)
3. retarders (good for long delivery time)
Define f'c and f'cr. Which is higher? - ANSWERSf'c=specified compressive strength for
design
f'cr=required compressive strength for testing
f'cr>f'c
What are the two problems that steel corrosion causes in concrete? - ANSWERS1.
corroded steel is larger than non-corroded (expansion)
2. corroded steel is weaker
List three ways you can slow corrosion in concrete. - ANSWERS1. put more concrete
around the steel
2. make concrete less permeable
3. sacrificial anode
Name a way to mitigate Alkali Aggregate Reaction. - ANSWERSuse a different
aggregate
What is a reasonable compressive strength value for concrete? - ANSWERS3000-
6000psi
What is a reasonable tensile strength value for concrete? - ANSWERS100-500psi
Where is concrete most likely to crack (weak spot)? - ANSWERSspot between cement
and aggregate (ITZ)
, How would you expect compressive strength to vary based on: sample size, loading
rate, maximum aggregate size - ANSWERS1. smaller size is greater strength
2. increased loading rate is increased strength
3. smaller aggregate strength is greater strength
What rare crystal is responsible for Roman concrete's strength? -
ANSWERSTobermorite
What is one advantage of Roman concrete over today's concrete? -
ANSWERSEnvironmentally friendly as production does not emit toxic gases
What is fiber reinforced concrete? - ANSWERSUniformly distributed fibrouse materials
in concrete mix
Name the two types of synthetic fibers and at least two benefits of using each. -
ANSWERS1. Microfibers (decrease plastic shrinkage and increase uniformity in water
bleeding)
2. Macrofibers (increase durability and increase flexural toughness)
What is recycled concrete? - ANSWERSConcrete made from former concrete
structures or samples (Used as aggregate in new concrete)
What is an application of recycled concrete - ANSWERSLandscaping
What are two advantages and two disadvantages of 3-d printing concrete in
construction? - ANSWERSAdvantages:
1. quicker building times
2. can run 24/7
Disadvantages:
1. need technical expertise
2. cost of additives and mix design
What is the most common material used for the 3-D printing construction process? -
ANSWERSproprietary concrete
What is the range of compressive strength typically found in UHPC? -
ANSWERS17000-22000psi
What is the w/cm that is typically used in UHPC? - ANSWERS.25
What is a cement slurry? - ANSWERScement and water mixture
What is the most common application for soil cement? - ANSWERSpavements
