WMGT 101 - Quiz 5
[CONCRETE FUNDAMENTALS] Describe the constituents of concrete -
correct answer ✔-*Portland Cement
-*Aggregate (Coarse larger than #4 sieve + Fine between #4 and #200.
Anything below is considered deleterious)
-*Water
-Chemical Admixtures
-Supplementary Cementitious Materials
*The Big Three Ingredients
[CONCRETE FUNDAMENTALS]
Explain the goals of concrete mix design and how each constituent property
and quantity contributes to the ideal mix design - correct answer ✔In
concrete mix design you can cater your concrete to your specific location's
and application's needs by altering the percentages of each component and
mixing in additional ingredients.
Mix proportions: Material % By Volume
Cement 10-15%
Aggregate 60-75%
Water 15-20%
Air 5-8%
Paste = Cement + Water
Mortar = Paste + Sand
Water/Cement ratio is critical
,Type 1 - Normal
Type 2 - Moderate sulfate resistance
Type 3 - High Early Strength
Type 4 - Low heat of hydration
Type 5 - High sulfate resistance
[CONCRETE FUNDAMENTALS]
Describe the benefits and drawbacks of the following admixtures: air
entrainers, water reducers / superplasticizers, retarders, and accelerators. -
correct answer ✔Air Entrainers: Create air bubble structures within the
concrete to allow for freeze / thaw cycles preventing cracking or spalling.
Water reducers / superplasticizers: Aid in workability and pumping operations
Retarders: Used in hot climates during pour / hydration to slow down the
curing process.
Accelerators: Used to speed up the curing process, for use in cold climates
and schedule constraints.
[CONCRETE FUNDAMENTALS]
Describe when tests are performed in the design and construction process. -
correct answer ✔Samples taken for Laboratory compressive strength tests
and 3rd pt. flexural strength tests. Field quality control done through slump
tests. In-place non destructive tests include dynamic resonance and rebound
hammers.
[CONCRETE FUNDAMENTALS]
Explain the difference between flexural and compressive strength - correct
answer ✔Flexural strength is the ability to resist both compressive and tensile
stresses, generally for a beam or column with slenderness. Compressive
strengths are observed on the top half of flexural beams and for columns that
well above the slenderness ratio to be considered.
, [CONCRETE FUNDAMENTALS]
Describe the properties of reinforcement and why it is installed in concrete -
correct answer ✔Concrete is inherently weak in tension. Steel reinforcement
has high tensile strength and thus is added to concrete to improve this quality.
[CONCRETE FUNDAMENTALS]
Explain how development calculations are influenced by other material and
geometric properties of the concrete member being reinforced and
reinforcement type selected - correct answer ✔Development length is the
minimum embedment of reinforcement for strength. No greater than 0.75x
clear space between rebar
No greater than 0.33x member
[CONCRETE FUNDAMENTALS]
Describe where in the a concrete foundation we install reinforcement - correct
answer ✔Tension zone is the lower 1/3 portion of a beam. For shear, stirrups
are installed at a designated interval. Top bars are generally installed to hold
the stirrups in place during construction.
[CONCRETE FUNDAMENTALS]
Describe how unreinforced concrete member reacts to loading - correct
answer ✔It resists stresses almost linearly with comparison to the increased
loading until the tension strength is exceeded, which will induce catastrophic
failure.
[CONCRETE FUNDAMENTALS]
Explain how adding reinforcement changes the interactions within the
concrete - correct answer ✔Adding reinforcement in the tension zones of
concrete that become cast as one with the members improves the resistance
to tension stresses.
[CONCRETE FUNDAMENTALS] Describe the constituents of concrete -
correct answer ✔-*Portland Cement
-*Aggregate (Coarse larger than #4 sieve + Fine between #4 and #200.
Anything below is considered deleterious)
-*Water
-Chemical Admixtures
-Supplementary Cementitious Materials
*The Big Three Ingredients
[CONCRETE FUNDAMENTALS]
Explain the goals of concrete mix design and how each constituent property
and quantity contributes to the ideal mix design - correct answer ✔In
concrete mix design you can cater your concrete to your specific location's
and application's needs by altering the percentages of each component and
mixing in additional ingredients.
Mix proportions: Material % By Volume
Cement 10-15%
Aggregate 60-75%
Water 15-20%
Air 5-8%
Paste = Cement + Water
Mortar = Paste + Sand
Water/Cement ratio is critical
,Type 1 - Normal
Type 2 - Moderate sulfate resistance
Type 3 - High Early Strength
Type 4 - Low heat of hydration
Type 5 - High sulfate resistance
[CONCRETE FUNDAMENTALS]
Describe the benefits and drawbacks of the following admixtures: air
entrainers, water reducers / superplasticizers, retarders, and accelerators. -
correct answer ✔Air Entrainers: Create air bubble structures within the
concrete to allow for freeze / thaw cycles preventing cracking or spalling.
Water reducers / superplasticizers: Aid in workability and pumping operations
Retarders: Used in hot climates during pour / hydration to slow down the
curing process.
Accelerators: Used to speed up the curing process, for use in cold climates
and schedule constraints.
[CONCRETE FUNDAMENTALS]
Describe when tests are performed in the design and construction process. -
correct answer ✔Samples taken for Laboratory compressive strength tests
and 3rd pt. flexural strength tests. Field quality control done through slump
tests. In-place non destructive tests include dynamic resonance and rebound
hammers.
[CONCRETE FUNDAMENTALS]
Explain the difference between flexural and compressive strength - correct
answer ✔Flexural strength is the ability to resist both compressive and tensile
stresses, generally for a beam or column with slenderness. Compressive
strengths are observed on the top half of flexural beams and for columns that
well above the slenderness ratio to be considered.
, [CONCRETE FUNDAMENTALS]
Describe the properties of reinforcement and why it is installed in concrete -
correct answer ✔Concrete is inherently weak in tension. Steel reinforcement
has high tensile strength and thus is added to concrete to improve this quality.
[CONCRETE FUNDAMENTALS]
Explain how development calculations are influenced by other material and
geometric properties of the concrete member being reinforced and
reinforcement type selected - correct answer ✔Development length is the
minimum embedment of reinforcement for strength. No greater than 0.75x
clear space between rebar
No greater than 0.33x member
[CONCRETE FUNDAMENTALS]
Describe where in the a concrete foundation we install reinforcement - correct
answer ✔Tension zone is the lower 1/3 portion of a beam. For shear, stirrups
are installed at a designated interval. Top bars are generally installed to hold
the stirrups in place during construction.
[CONCRETE FUNDAMENTALS]
Describe how unreinforced concrete member reacts to loading - correct
answer ✔It resists stresses almost linearly with comparison to the increased
loading until the tension strength is exceeded, which will induce catastrophic
failure.
[CONCRETE FUNDAMENTALS]
Explain how adding reinforcement changes the interactions within the
concrete - correct answer ✔Adding reinforcement in the tension zones of
concrete that become cast as one with the members improves the resistance
to tension stresses.
