C-8 Concrete Contractor

What size of rebar is used to reinforce stem wall?

#4

What is the minimum size of anchor bolt can be used in seismic category D?

#4 Explanation: The building code requires 1/2" anchor bolt to be used in seismic category D or less.

What is the minimum size of anchor bolt can be used in seismic category E?

#5 Explanation: The building code requires 5/8" anchor bolt to be used in seismic category E.

If the concrete cost $90 per cubic yard, how much would you pay 2 ½ cubic yards of concrete with 8.75% CA sales tax?

$244.69 Calculate the price of the concrete for 2 ½ cubic yards.$90 x 2.5 = $225.00Calculate the sales tax.$225 x 8.75% (or 0.0875) = $19.69Calculate the total price including the sales tax.$225 + $19.69 = $244.69

Refer to the house plan. What is the total cost for the foundation slab if the contractor charges $3.54 per square foot?

$6524.90 Explanation: The easiest way to solve for the area of the slab is to image a full rectangle of the slab and subtract void areas from the area of the slab. Rectangle area: 28.167' x 71.5'= 2013.94 sq ftLeft void area: 6.667' x 1.83' = 12.2 sq ftCenter void area: 11.5' x 1.83' = 21.045 sq ftRight void area: 9.167' x 15' = 137.505Net area of the foundation slab: 2013.94 - 12.2 - 21.045 - 137.505 = 1843.19 sq ft.Calculate the price of the slab.1843.19 sq ft x $3.54 = $6524.90

You have 5 employees that work for eight hours. How much would you have to pay your employees, if one of them is an apprentice who makes $17/hour, supervisor makes $33/hour, and three journeymen make $22/hour?

$928.00 Explanation: Apprentice: $17 x 8 hours = $136Supervisor: $33 x 8 hours = $264Journeymen: 3 x $22 x 8 hours = $528Total: $136 + $264 + $528 = $928

The normal tolerance for the location of bends and ends of reinforcing bar is:

+/- 2 inches

In a beam not exposed to weather or soil; what is the minimum coverage for #4 reinforcing bar:

1 inch

What is the minimum spacing of parallel reinforcing bars placed in two or more layers?

1 inch Explanation: According to the American Concrete Institute, where parallel reinforcement is placed in two or more layers, bars in the upper layers shall be placed directly above bars in the bottom layer with clear distance between layers not less than 1 inch.

What is the minimum mixing time for a mixture of 1 cubic yard?

1 minute Explanation: Specifications usually require a minimum of 1 minute mixing for mixtures of 1 cu yd capacity. It increases 15 seconds for each additional ½ cu yd of additional mixture.

What is the minimum depth of a footing below the soil?

12"

What is the minimum width of the footing for a 1-story house?

12"

What size of footing required for a 2-story building with a load bearing value of 1,500psf?

15

What is the minimum width of the footing for a 2-story house?

15"

What is the standard overlap for #4 rebar?

15" Explanation: According to the California Building Code, the standard overlap should be 30 times the diameter of the rebar.30 x ½" = 15"

The sides of the main field of the slab must be reinforced with an ___ by ___ grid.

15"...18"

The average deadload of dry concrete, including reinforcement, is:

150 lbs/sq ft.

What is the maximum spacing of the rebar in the stem wall?

18"

The main field of the slab must be reinforced with an ___ by ___ grid.

18"...18"

Refer to the house plan. How many square feet is the foundation slab?

1844 sq ft Rectangle area: 28.167' x 71.5'= 2013.94 sq ftLeft void area: 6.667' x 1.83' = 12.2 sq ftCenter void area: 11.5' x 1.83' = 21.045 sq ftRight void area: 9.167' x 15' = 137.505Net area of the foundation slab: 2013.94 - 12.2 - 21.045 - 137.505 = 1843.19 sq ft.

How many cubic yard of concrete is required for the footing shown, if it is 85 feet long?

2 ½ cubic yards Explanation: Step 1: Figure out the area of the face of the footing.Top area = 6" x 9" = 54 square inchesBottom area = 6" x 12" = 72 square inchesTotal area = 54 + 72 = 126 square inchesStep 2: Convert square inches into square feet.126 ÷ 144 = 0.875 square feetStep 3: Get volume by multiplying the previous answer by the length.0.875 x 75 = 65.625 cubic feetStep 4: Convert cubic feet into cubic yards.65.625 ÷ 27 = 2.43 cubic yardsSince there is no exact answer, round up the number.

How many cubic yard of concrete is required for a 4" slab with the diameter of 15 feet?

2 ½ cubic yards Explanation: Traditional MethodUse the following formula:Area of the circle = π x r x rWhere π = 3.14 and radius (r) = 7.5 feet (half of the diameter length)Area = 3.14 x 7.5 x 7.5Area = 176.625 sq. ft.Multiply area by the depth of the slab (in feet) to find the volume in cubic feet.176.625 x .333 = 58.82 cubic feetConvert cubic feet into cubic yards.58.82 ÷ 27 = 2.18 cubic yardsSince 2.18 is not a given option, round up the number to 2.5 cubic yardsShortcut MethodThis problem can be solved using a much simpler method. First is to find the area of the square, then convert it into the area of the circle by multiplying it by 78.5%.Area of the square = 15' x 15' = 225 square feetArea of the circle = 225 x .785 = 176.625 square feetDivide the volume by 81 to solve for the cubic yards for a 4" slab.176.625 ÷ 81 = 2.18 cubic yardsSince 2.18 is not a given option, round up the number to 2.5 cubic yards

To ensure proper grounding, the grounding electrode must be encased by how many inches of concrete?

2" Explanation: To ensure proper grounding, the electrode must meet the following criteria:1. Must be encased by 2 or more inches of concrete2. Electrode must be at or near the bottom of the footing or foundation3. Concrete must be in contact with the ground4. At least 20 feet of rebar that is at least ½" thick or 20 feet of solid copper as a conductor

What is the maximum spacing of control joints in driveways?

20' Explanation: The control joints in driveways should be spaced equal to the width of the slab, but the maximum permissible spacing is 20 feet.

Refer to the house plan. How many cubic yards of concrete needs to be ordered for the foundation slab that is 4 inches thick?

23 cubic yards Explanation: The easiest way to solve for the area of the slab is to image a full rectangle of the slab and subtract void areas from the area of the slab.Rectangle area: 28.167' x 71.5'= 2013.94 sq ftLeft void area: 6.667' x 1.83' = 12.2 sq ftCenter void area: 11.5' x 1.83' = 21.045 sq ftRight void area: 9.167' x 15' = 137.505Net area of the foundation slab: 2013.94 - 12.2 - 21.045 - 137.505 = 1843.19 sq ft.Traditional Method:Multiply the area of the slab by the thickness of the slab (in inches).1843.19 x 0.333' = 613.78 cubic feetConvert the volume into cubic yards.613.78 ÷ 27 = 22.73 cubic yards (rounded up to 23 cubic yards)Industry Method:Divide the area by 81 to get cubic yards.1843.19 sq ft ÷ 81 = 22.76 cubic yards (rounded up to 23 cubic yards)

When batching concrete, what percentage of concrete powder is commonly used?

25% to 40% cement powder

What is the area of a cylinder that has a radius of 6 inches and height of 8 feet?

25.12 sq. ft. Explanation: To solve for the area of a cylinder, multiply circumference by the height of the cylinder. Don't forget that the radius is given in inches, but height is given in feet.Step 1: Find Circumference.Diameter = radius x 2Diameter = 6" x 2 = 12 inches or 1 footCircumference = D x π (or 3.14)1 x 3.14 = 3.14 feetStep 2. Find the Area.Area = circumference x heightArea = 3.14 x 8Area = 25.12

From an engineering perspective, concrete has the advantage of high compressive strength. Maximum strength is reached after:

28 days

Bundled reinforcing bars are normally required to have a minimum cover of at least the diameter of the bundle, except in the case of permanent proximity to earth where the minimum will be:

3 inches

Rebar should be encased in concrete at minimum:

3 inches Explanation: Concrete cover as protection of reinforcement against weather and other effects is measured from the concrete surface to the outermost surface of the steel. This is also known as concrete tolerance for reinforcement. In most cases, this means that rebar should be encased 3 inches in concrete. If the concrete is not in direct contact with soil/weather, then the encasement can be less than 3 inches.

What is the minimum required thickness for a slab?

3 ½" Explanation: Although most concrete slabs are 4", according to code the minimum permissible thickness for the slab is 3 ½".

The concrete stem walls must have #4 rebar ___ from the top of the footing as well as ___ from the bottom of the footing.

3"

How many cubic yards of concrete is required for a 4" slab with the radius of 10 feet?

3.87 cubic yards Traditional MethodUse the following formula:Area of the circle = π x r x rWhere π = 3.14 and radius (r) = 10 feet (half of the diameter length)Area = 3.14 x 10 x 10Area = 314 sq. ft.Multiply area by the depth of the slab (in feet) to find the volume in cubic feet.314 x .333 = 104.562 cubic feetConvert cubic feet into cubic yards.104.562 ÷ 27 = 3.87 cubic yardsShortcut MethodThis problem can be solved using a much simpler method. First is to find the area of the square, then convert it into the area of the circle by multiplying it by 78.5%.Diameter = radius x 2 = 20'Area of the square = 20' x 20' = 400 square feetArea of the circle = 400 x .785 = 314 square feetDivide the volume by 81 to solve for the cubic yards for a 4" slab.314 ÷ 81 = 3.87 cubic yards

How many cubic yards of concrete is required for a 4" slab with the circumference of 25 feet?

3/4 cubic yard(s) Explanation: Since the circumference was provided to calculate the area of the circle, we need to figure out the diameter and/or radius to solve the problem.Circumference = 25Diameter = Circumference (25') ÷ π (or 3.14) = 7.96 feetRadius = Diameter (7.96') ÷ 2 = 3.98 feetTraditional MethodUse the following formula:Area of the circle = π x r x rWhere π = 3.14 and radius (r) = 3.98 feetArea = 3.14 x 3.98 x 3.98Area = 49.74 sq. ft.Multiply area by the depth of the slab (in feet) to find the volume in cubic feet.49.74 x .333 = 16.56 cubic feetConvert cubic feet into cubic yards.16.56 ÷ 27 = 0.61 cu yds (round up to 3/4)Shortcut MethodThis problem can be solved using a much simpler method. First is to find the area of the square, then convert it into the area of the circle by multiplying it by 78.5%.Diameter = 7.96'Area of the square = 7.96' x 7.96' = 63.36 square feetArea of the circle = 63.36 x .785 = 49.74 square feetDivide the volume by 81 to solve for the cubic yards for a 4" slab.49.74 ÷ 81 = 0.61 cu yds (round up to 3/4)

What size is the #3 rebar?

3/8" Explanation: The rebar comes with 1/8" increments. #1 rebar is 1/8", whereas #3 rebar is 3/8" thick.

What is the area of the circle if the diameter is 20 feet?

314 sq. ft. Explanation: There are two ways to solve for the area of the circle.Traditional MethodUse the following formula:Area of the circle = π x r x rWhere π = 3.14 and radius (r) = 10 (half of the diameter)Area = 3.14 x 10 x 10Area = 314 sq. ft. Shortcut MethodArea of the circle is 78.5% of the square. Treat the circle as a square and solve for the area.Step 1. Find the area of the square instead of the circle.20' x 20' = 400 sq. ft.Step 2. Since a circle is 78.5% of the square, multiply the area of the square by 78.5% (or .785 if there is no percentage sign on the calculator).400 sq. ft. x .785 = 314 sq ft

What is the maximum number of parallel bars that can be bundled together and still be considered a single unit?

4 bars Explanation: According to the American Concrete Institute, groups of parallel reinforcing bars bundles in contact to act as a unit shall be limited to four in any one bundle.

Que 37. What is the spacing of anchor bolts from ends of sill plates?

4" min, 12" max

What is the maximum spacing of the anchor bolts for a 2-story house?

4' o. c.

How long can a batch of concrete be in the truck before considerations of quality arise?

45 minutes

Please refer to the house plan. How many square feet does the patio cover (excluding sidewalk)?

460 sq ft Explanation: Break down the area of the patio into 4 sections as shown in this diagram.

What is the maximum spacing of the anchor bolts for 1-story house?

6' o. c.

Please refer to the house plan. How many cubic yards of concrete is required for the patio (excluding sidewalk), if the slab is 4 inches thick?

6.25 cubic yards Explanation: From the previous question, we figured out that the area of the slab is 487 sq ft.Traditional MethodMultiply area of the slab by the thickness of the slab to get the volume in cubic feet.487 x 4" or .333 = 162.171 cubic feetConvert cubic feet into cubic yards by diving the cubic feet by 27.162.171 ÷ 27 = 6.006Industry MethodDivide the area of the slab (sq ft) by 81 to get cubic yards.487 sq ft ÷ 81 = 6.01Round up to select the best answer, which is 6.25 cubic yards.

The anchor bolt must be embedded ___ into the slab.

7"

Which of the following is a normal curing temperature?

75°F Explanation: The normal curing temperature is 75°F. Most manufacturers specify a range between 50 and 85°F.

How many cubic yards of backfill are required for a 3' x 5' trench, 1500 ft long, with a 1 foot diameter pipe?

789.72 Explanation: Step 1. Find the net face area of the trench deducting for pipe.Face area including pipe: 3 x 5 = 15 square feetArea of the pipe: 𝐴=𝜋𝑟2A = 3.14 x .5 x .5A = 0.785Find the face area of the trench minus area of the pipe, which will give you the net area for the backfill.15 - 0.785 = 14.215Step 2. Find the total volume of the backfill.14.215 x 1500 = 21322.5 cubic feetConvert the volume into cubic yards.21322.5 ÷ 27 = 789.72 cubic yards

What is the volume of a cylinder if the diameter equals 3 feet and the length equals to 12 feet?

84.78 cubic feet Explanation: There are two ways to solve the problem. However, regardless of which method is used, you need to first determine the area of the circle then multiply it by the length.Traditional MethodUse the following formula:Area of the circle = π x r x rWhere π = 3.14 and radius (r) = 1.5 feet (half of the diameter length)Area = 3.14 x 1.5 x 1.5Area = 7.065 sq. ft.Multiply area by the length to find the volume.7.065 x 12 = 84.78Shortcut MethodArea of the circle is 78.5% of the square. Treat the circle as a square and solve for the area.Find the area of the square instead of the circle.3' x 3' = 9 sq. ft.Since circle is 78.5% of the square, multiply area of the square by 78.5% (or .785 if there is no percentage sign on the calculator).9 sq. ft. x .785 = 7.065 square feetMultiply area by the length to find the volume.7.065 x 12 = 84.78 cubic feet

One cubic foot of cement weighs approximately:

95 lbs

There are many ornamental uses of concrete, including casting architectural elements, ornaments, and faux finishes. How would you describe terrazzo in the simplest terms?

A special combination of colored rock and glass for floors.

In some cases it may be necessary to use stronger or double ties. Why?

As a safety precaution when workers may need to climb on reinforcement.

Which of the following has the highest Load Bearing-Value?

Bedrock

A mix with a higher percentage of rock has the advantage of:

Being less expensive.

What would be the easiest way to avoid puddling under a slab?

Careful grading

What class of formwork is used for temporary or light loads?

Class I Explanation: Class I - used for temporary or for light loadsClass II - used for structures that will encounter heavy loads

Green concrete is:

Concrete that has been treated for water exposure

What is the purpose of the deformed rebar?

Deformations improve the bond between steel and concrete

There are many surface finishes that can be applied to smooth finished concrete, including: Stain, Paint, Stenciling Oil, Varnish, Epoxy. What considerations should be taken into account before application?

Depends on finish to be applied.

Control joints in sidewalks should be spaced at what intervals?

Equal to the width of the slab Explanation: Generally the control joints in sidewalks should be spaced equal to the width of the slab, but not more than 6 feet apart.

Shotcrete can be wet or dry. What are the advantages of wet?

Exact batching

Finishing with a steel float:

Finishing with a steel float:

Weather conditions may make placing concrete inadvisable, including:

High winds and high temperatures

Compacting placed concrete is advisable because of:

Higher cured strength.

Air-entraining:

Improves the working life of concrete.

At what times, during set-up, is it important to pay special attention to keeping concrete sufficiently moist?

In hot and cold weather.Explanation: Cold weather reduces air humidity, hot weather increases evaporation.

When applying concrete to concrete there are several factors to consider. Which is most important?

In most cases the most important is the bond.

Where are spiral rebar ties used?

In round columns

High-early:

Is cured after 7 days.

Construction joints are:

Joints designed to separate one pour from another.

When can the live load be calculated by multiplying the height, width and length of a pour and dividing by the deadload?

Never

Releasing agent is used on forms, why is over use a problem?

Oil in the water makes concrete that is less strong.

A standard truck load of concrete is around 10 cubic yards of material. In a pour with an average depth of 8 inches, and a width and length of 12 by 32 feet, how much will the second truck need to bring?

One load was enough Explanation: Step 1. Solve for the volume of the pour: 12 x 32 x 8/12 (or 0.667) = 256.128 cubic feetStep 2. Convert cubic feet into cubic yards.256.128 ÷ 27 = 9.49 cubic yardsSince one truck carries 10 cubic yards of concrete, one truck will be enough for the pour.

What is the minimum width of the footing for a 2-story house?

Required reinforcement bar splicing length or lap length is a function of:

Which of the following tests used to measure the consistency of the concrete?

Slump test Explanation: Slump test is used to measure the consistency of the concrete.Compressive test is used to determine whether a concrete has the specified compressive strength.

Pitch in a spiral reinforcing is a measure of:

Spacing between turns.

What is the concrete mixture ratio of 1:2:4?

Standard The mixture ratio of 1:2:4 stands for 1 part cement, 2 parts of sand or fine aggregate, and 3 parts of coarse aggregate.Here is all of the mixture ratios:Lean 1:3:6Medium 1:2 ½:5Standard 1:2:4Rich 1:2:3

Strength tests are normally:

The average of 2 tests at a specified time, taken from the same pour.

When welding bars on sight, special attention should be paid to safety and ____________.

The exact composition of the materials to be welded Explanation: Not all alloys used in reinforcing bar are compatible.

Construction loads are:

The maximum loads to which a structure will ever be subjected.

Tensile strength in concrete is achieved by:

The use of steel reinforcement.

Proper curing is essential. What factors are most important to consider?

There are many factors, each with appropriate responses

What is the purpose of the rebar?

To increase the tensile strength

It is important to keep the work site tidy and clear of debris, especially used lumber and used forms. Why?

To reduce risk of accidents.

On concrete paving or roadway, it is normal to use transverse joints at regular intervals. These joints are best filled and sealed. Why?

To reduce risk of exposure to the reinforcing.

When would a slab be double reinforced?

To strengthen a slab that would otherwise need to be thicker, to meet expected loads.

Which of the following will cause the concrete to lose its strength?

Too much water

For quick dry applications you would most commonly use which kind of concrete?

Type 3

What is the maximum spacing of the control joints in a slab that is to receive a floor finish?

joints are not necessary Explanation: If the carpet, hardwood floor, or other floor finishes are to be installed on the slab, the control joints are not necessary since the floor finishes will cover unsightly cracks in the slab.