WACEL -Concrete II Technician Exam
and All Correct Answers.
What constitutes a valid set of 6"x12" or "x8" cylinders for the purposes of strength testing? -
Answer -cementitious and aggregates stored somewhere they won't be contaminated
-conform to all standards set by ASTM C94 or ASTM C685
-average strength of field-cured cylinders at a test age designated for determination of f'c is
equal to or at least 85% of the that cylinder’s standard-cured cylinders
-average strength of field-cured cylinders at test age exceed f'c by more than 500 psi
What is the minimum frequency of strength testing required to include when smaller quantities
of a given concrete mixture are placed on a project. - Answer -samples need to be collected
at least once a day
- at least once a day for each 150 yd3 of concrete (3 trucks)
-at least once a day for every 5,000 ft2 of surface area
- have about 5 different strength tests per project
- if less than 50 yd3 are used, you don't need strength tests if you have proper documentation
that it will work
Maximum coarse aggregate size in concrete mix (criteria and reasons). - Answer - 1/5
narrowest dimension between sides of forms
- 1/3 depth of slabs
- 3/4 minimum specified clear spacing between individual rebar, wires, bundles of bars,
prestressed tendons
* It should fit in and around any steel and not get clogged in any way.
What are the placement criteria and requirements of concrete? - Answer - Remove any
debris, ice, or standing water from spaces about to be poured.
- Masonry filler units that encounter concrete shall be prewetted.
- Any equipment used to move concrete from the mixer to the placement location shall have
capabilities to achieve the placement requirements
- Don't pump concrete through pipes made of aluminum or aluminum alloys.
- At a rate that provides an adequate supply of concrete to the location
- At a rate that allows sufficient workability such that it can be consolidated properly
- without segregate or loss of materials
- without interruptions that could cause cold joints
- placed as close to the final location as possible
, - remove any contaminated concrete or concrete that has lost its initial workability
- after starting the process, continue until completion of that section or panel
- concrete shall be consolidated by suitable means to get around any rebar and get into corners
-top surfaces of vertical formed lifts should be flat
Standard-cured vs. filed-cured cylinders. What are the differences and purposes of each? -
Answer - standard-cured are brought back to the lab and placed under controlled conditions
- field-cured are left on site and should reflect the placed concrete
Curing requirements for freshly-placed concrete - Answer - Everything but high-early-
strength concrete shall be maintained at temperatures of at least 50 F in moist conditions for at
least the first 7 days
- high-early-strength concrete shall be maintained at temperatures of at least 50 F in moist
conditions for at least the first 3 days
- You can use high-pressure steam, steam at atmospheric pressure, heat and moisture, or other
processes to accelerate strength gain
For field-cured cylinders to yield adequate results, what two things need to be satisfied? -
Answer - average strength at a test age designated for determination of f'c is equal to or at
least 85% of that standard-cured cylinders
- average strength at test age exceed f'c by more than 500 psi
Equilibrium vs. fresh density. What are the differences and how to apply each when inspecting
lightweight concrete? - Answer - equilibrium density is an estimate of the density of LWC
assuming some degree of drying after initial construction (ASTM C5670) (measured 7 days after
placement)
- fresh density is determined by the concrete supplier and varies based on moisture, air content,
mixture proportion, and type of LW aggregate
- establish a fresh density range that will result in the required equilibrium density
What are the components of batch water? - Answer all of the water added to the mixture,
including:
- mixing water
- ice
- surface moisture
- water introduced from admixtures
* should be measured to an accuracy of 1%
and All Correct Answers.
What constitutes a valid set of 6"x12" or "x8" cylinders for the purposes of strength testing? -
Answer -cementitious and aggregates stored somewhere they won't be contaminated
-conform to all standards set by ASTM C94 or ASTM C685
-average strength of field-cured cylinders at a test age designated for determination of f'c is
equal to or at least 85% of the that cylinder’s standard-cured cylinders
-average strength of field-cured cylinders at test age exceed f'c by more than 500 psi
What is the minimum frequency of strength testing required to include when smaller quantities
of a given concrete mixture are placed on a project. - Answer -samples need to be collected
at least once a day
- at least once a day for each 150 yd3 of concrete (3 trucks)
-at least once a day for every 5,000 ft2 of surface area
- have about 5 different strength tests per project
- if less than 50 yd3 are used, you don't need strength tests if you have proper documentation
that it will work
Maximum coarse aggregate size in concrete mix (criteria and reasons). - Answer - 1/5
narrowest dimension between sides of forms
- 1/3 depth of slabs
- 3/4 minimum specified clear spacing between individual rebar, wires, bundles of bars,
prestressed tendons
* It should fit in and around any steel and not get clogged in any way.
What are the placement criteria and requirements of concrete? - Answer - Remove any
debris, ice, or standing water from spaces about to be poured.
- Masonry filler units that encounter concrete shall be prewetted.
- Any equipment used to move concrete from the mixer to the placement location shall have
capabilities to achieve the placement requirements
- Don't pump concrete through pipes made of aluminum or aluminum alloys.
- At a rate that provides an adequate supply of concrete to the location
- At a rate that allows sufficient workability such that it can be consolidated properly
- without segregate or loss of materials
- without interruptions that could cause cold joints
- placed as close to the final location as possible
, - remove any contaminated concrete or concrete that has lost its initial workability
- after starting the process, continue until completion of that section or panel
- concrete shall be consolidated by suitable means to get around any rebar and get into corners
-top surfaces of vertical formed lifts should be flat
Standard-cured vs. filed-cured cylinders. What are the differences and purposes of each? -
Answer - standard-cured are brought back to the lab and placed under controlled conditions
- field-cured are left on site and should reflect the placed concrete
Curing requirements for freshly-placed concrete - Answer - Everything but high-early-
strength concrete shall be maintained at temperatures of at least 50 F in moist conditions for at
least the first 7 days
- high-early-strength concrete shall be maintained at temperatures of at least 50 F in moist
conditions for at least the first 3 days
- You can use high-pressure steam, steam at atmospheric pressure, heat and moisture, or other
processes to accelerate strength gain
For field-cured cylinders to yield adequate results, what two things need to be satisfied? -
Answer - average strength at a test age designated for determination of f'c is equal to or at
least 85% of that standard-cured cylinders
- average strength at test age exceed f'c by more than 500 psi
Equilibrium vs. fresh density. What are the differences and how to apply each when inspecting
lightweight concrete? - Answer - equilibrium density is an estimate of the density of LWC
assuming some degree of drying after initial construction (ASTM C5670) (measured 7 days after
placement)
- fresh density is determined by the concrete supplier and varies based on moisture, air content,
mixture proportion, and type of LW aggregate
- establish a fresh density range that will result in the required equilibrium density
What are the components of batch water? - Answer all of the water added to the mixture,
including:
- mixing water
- ice
- surface moisture
- water introduced from admixtures
* should be measured to an accuracy of 1%
