CSLB C-8 Concrete (Trade Exam) — All Questions

A shed slab is 16 ft by 20 ft and 4 in thick. How much concrete does it contain?

• a.About 3.5 cubic yards
• b.About 4.0 cubic yards✓
• c.About 47.4 cubic yards
• d.About 11.9 cubic yards

16 × 20 = 320 sq ft; 4 in = 0.333 ft; 320 × 0.333 = 106.7 cu ft; ÷ 27 = 4.0 cu yd. Dividing by 9 gives 11.9, and multiplying by 4 without converting inches gives 47.4.NIST Handbook 44 (2026), Appendix C

A sidewalk is 5 ft wide, 120 ft long and 4 in thick. How much concrete does it need?

• a.About 6.2 cubic yards
• b.About 22.2 cubic yards
• c.About 88.9 cubic yards
• d.About 7.4 cubic yards✓

5 × 120 = 600 sq ft × 0.333 ft = 200 cu ft ÷ 27 = 7.4 cu yd. 22.2 comes from dividing by 9 instead of 27, and 88.9 from treating 4 in as 4 ft.NIST Handbook 44 (2026), Appendix C

About how many square feet does one cubic yard of concrete cover at 4 inches thick?

• a.81 square feet✓
• b.324 square feet
• c.27 square feet
• d.108 square feet

One cubic yard is 27 cu ft; 27 ÷ 0.333 ft = 81 sq ft. 27 is the cubic feet in a yard, not the area it covers, and 324 comes from multiplying by 12 instead of dividing by the thickness in feet.NIST Handbook 44 (2026), Appendix C

About how many square feet does one cubic yard of concrete cover at 6 inches thick?

• a.54 square feet✓
• b.162 square feet
• c.81 square feet
• d.36 square feet

27 cu ft ÷ 0.5 ft = 54 sq ft. 81 sq ft is the coverage at 4 in; a thicker slab covers less area per yard, not more.NIST Handbook 44 (2026), Appendix C

Twelve piers are 12 in in diameter and 6 ft deep. About how much concrete do they take?

• a.About 6.3 cubic yards
• b.About 8.4 cubic yards
• c.About 2.1 cubic yards✓
• d.About 2.7 cubic yards

Area = 0.785 × 1² = 0.785 sq ft; one pier = 0.785 × 6 = 4.71 cu ft; twelve = 56.5 cu ft ÷ 27 = 2.1 cu yd. Treating each pier as a 1-ft square gives 2.7, and using the diameter as the radius gives 8.4.NIST Handbook 44 (2026), Appendix C

A continuous footing is 24 in wide and 12 in deep with a centerline length of 150 ft. How much concrete does it hold?

• a.About 11.1 cubic yards✓
• b.About 33.3 cubic yards
• c.About 5.6 cubic yards
• d.About 13.3 cubic yards

150 × 2 × 1 = 300 cu ft ÷ 27 = 11.1 cu yd. Dividing by 9 gives 33.3, and using a 12-in width by mistake gives 5.6.NIST Handbook 44 (2026), Appendix C

Bars will be spaced 18 in on center across a 30-ft-wide slab. How many bars run the other way?

• a.22
• b.18
• c.21✓
• d.20

30 ft = 360 in; 360 ÷ 18 = 20 spaces; bars = spaces + 1 = 21. Answering 20 counts the spaces rather than the bars.NIST Handbook 44 (2026), Appendix C

What is the nominal diameter of a #7 reinforcing bar?

• a.7 millimeters
• b.7/16 inch
• c.7/8 inch✓
• d.3/4 inch

U.S. bar sizes are identified in eighths of an inch, so #7 is 7/8 in. 3/4 in is a #6, and reading the number as sixteenths or millimeters is a common error.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 4

A takeoff totals 1,350 cubic feet of concrete. How many cubic yards is that?

• a.150 cubic yards
• b.112.5 cubic yards
• c.45 cubic yards
• d.50 cubic yards✓

1,350 ÷ 27 = 50 cu yd. Dividing by 9 gives 150, and dividing by 12 gives 112.5, neither of which converts cubic feet to cubic yards.NIST Handbook 44 (2026), Appendix C

A square column is 12 in by 12 in and 10 ft tall. How much form contact area do its four sides need?

• a.10 square feet
• b.40 square feet✓
• c.120 square feet
• d.20 square feet

Each side is 1 ft × 10 ft = 10 sq ft, and four sides give 40 sq ft. 10 sq ft is one side, and 120 comes from using inches for the side width.Estimating practice (form contact area)

A 23-cubic-yard pour will come in trucks carrying 10 cubic yards each. How many loads must be ordered?

• a.4
• b.2
• c.1
• d.3✓

23 ÷ 10 = 2.3, and a partial load is still a truck, so 3 loads. Two loads bring only 20 cu yd.NIST Handbook 44 (2026), Appendix C

A single, stand-alone project will disturb 30,000 square feet of soil and is not part of a larger plan. Does it need state Construction Stormwater General Permit coverage?

• a.No, it is under one acre.✓
• b.Yes, over 10,000 square feet needs it.
• c.Only if it is a public project.
• d.Yes, all grading needs coverage.

One acre is 43,560 sq ft; the State Water Board's permit applies to projects disturbing one or more acres, or less if part of a larger common plan that disturbs an acre. Local stormwater rules still apply.State Water Resources Control Board, Order 2022-0057-DWQ

On public concrete work, what does a "rebar factor" describe?

• a.Average pounds of rebar per cubic yard✓
• b.The ratio of bar length to lap length
• c.The yield strength of the steel
• d.The number of bars per square foot

Caltrans describes establishing the average pounds of rebar per cubic yard of a concrete item, the "rebar factor," to pay for reinforcement in step with concrete quantities. Yield strength is shown by the grade mark.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 2

A winter pour needs faster setting. Which ASTM C494 admixture type accelerates?

• a.Type C✓
• b.Type D
• c.Type B
• d.Type F

Type C is accelerating. Type B and Type D retard setting, which is the opposite of what a cold pour needs, and Type F is a high-range water reducer.IMCP Manual for Concrete Pavement, 2nd ed. (FHWA/CP Tech Center, 2019)

Which portland cement type offers moderate sulfate resistance?

• a.Type IV
• b.Type III
• c.Type I
• d.Type II✓

Type II is moderate sulfate resistance (Type V is high). Type III is high early strength and Type IV is low heat of hydration.IMCP Manual for Concrete Pavement, 2nd ed. (FHWA/CP Tech Center, 2019)

Why is an air-entraining admixture specified for exterior concrete in freezing areas?

• a.To reduce the need for curing
• b.To speed up the set
• c.To raise the compressive strength
• d.For freeze-thaw and scaling resistance✓

Air-entraining admixtures stabilize microscopic bubbles that provide freeze-thaw resistance and improve resistance to deicer salt scaling. They do not raise strength, speed setting or replace curing.IMCP Manual for Concrete Pavement, 2nd ed. (FHWA/CP Tech Center, 2019)

A load has stiffened in the truck. The driver offers to add water and remix it. What is the rule?

• a.It may be re-tempered if the slump is low.
• b.It may be re-tempered below 90 °F.
• c.It may be re-tempered once.
• d.Re-tempering it with water is prohibited.✓

Caltrans states that re-tempering partially hardened concrete with additional water is expressly prohibited, because it can markedly reduce strength. Low slump from stiffening is the symptom, not a reason to add water.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 5

A load without a retarder is 95 minutes from batching and has turned 200 drum revolutions. Under the Caltrans limits, may it be placed?

• a.No, it is past 90 minutes.✓
• b.Yes, it is under 250 revolutions.
• c.Yes, if it is placed quickly.
• d.Yes, the limit is 120 minutes.

Without a retarder the limit is 250 revolutions or 90 minutes, whichever occurs first; 95 minutes exceeds the time limit even though the revolutions are under 250. The 120-minute limit applies only with a retarder.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 5

Water held back at the plant is added to a truck on site within the mix design. What must happen before discharge continues?

• a.Add an equal amount of cement
• b.Mix at least 30 drum revolutions✓
• c.Wait 30 minutes for it to absorb
• d.Mix for at least 5 revolutions

Caltrans requires added water to be introduced only once and mixed for at least 30 drum revolutions before more than a quarter cubic yard of the load has been discharged. Waiting without mixing does not blend it.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 5

Which item belongs on the equipment list for a large wall pour, in case of breakdown?

• a.Extra form oil
• b.A spare slump cone
• c.A second finishing crew only
• d.A standby vibrator and generator✓

Caltrans calls it best practice to always have a standby vibrator and generator on hand, and lists backup equipment among pre-pour items. A breakdown with no spare leaves unconsolidated concrete and cold joints.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 5

Why might a pump be chosen over a crane and bucket under a low roof or canopy?

• a.Pumps allow water to be added.
• b.Pumps need less overhead clearance.✓
• c.Pumps place concrete more slowly.
• d.Pumps need no setup inspection.

Caltrans notes that pumps normally require less headroom than a crane and bucket. Pumps also place faster, and they still require inspection and follow the water limits.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 5

What is the main placing drawback of a belt conveyor?

• a.It cannot reach more than 20 feet
• b.It requires aluminum pipe
• c.Segregation where it transfers✓
• d.It only works with low slump

Caltrans identifies a tendency for concrete to segregate at intermediate transfer points and at the discharge point as a major disadvantage of belts; hoppers or baffles at discharge help.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 5

Heavy rain begins on a slab being placed. What is the concern for the surface?

• a.Rain speeds up the set.
• b.Rain only matters after finishing.
• c.Rain improves surface strength.
• d.Diluted paste, higher w/c ratio✓

Rain dilutes the mortar at the surface and may increase the water-cement ratio enough to decrease strength and durability there, so placement should be protected or suspended.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 5

A plan sheet references a standard detail from a Standard Plans book. How binding is that detail?

• a.It is part of the contract.✓
• b.It is only a suggestion.
• c.It is binding only on public work.
• d.It applies only if drawn on the sheet.

Caltrans states that Standard Plans are contractual supplements to the project plans; a referenced detail is as binding as the sheet. On any job, referenced details are part of the documents you build to.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 2

Workers will enter a 4-ft-deep footing trench. Does the trench need a Cal/OSHA excavation permit?

• a.Yes, if it is longer than 50 ft.
• b.Only if the soil is Type C.
• c.Yes, every entered trench needs one.
• d.No; that permit starts at 5 ft.✓

Title 8 §341 requires a permit for trenches or excavations 5 feet or deeper into which any person must descend. A 4-ft trench still needs a competent person's check for cave-in signs, but no permit.Cal. Code Regs. tit. 8, §341

An excavator's 811 ticket expires while trenching is still going on. What must happen?

• a.Keep going if marks are visible.
• b.Finish that day, then renew.
• c.Call the operator directly instead.
• d.Stop and get a new ticket.✓

If a ticket expires while work is ongoing, the excavator must immediately cease excavation, contact the regional notification center and get a new ticket before resuming.Cal. Gov. Code §§4216–4216.9

An applicant has 2 years at an accredited construction program and 3 years as a journey-level concrete finisher. How much of the program can count toward the 4-year requirement?

• a.Only 6 months per year attended
• b.None, school never counts
• c.All of it, plus up to 4 years
• d.Up to 2 years; never over 3✓

Under 16 CCR §825, accredited training or apprenticeship can count as experience, but never for more than 3 years; here the 2 years can count, giving 5 years total.Cal. Code Regs. tit. 16, §825

Which field change lowers concrete strength the most directly?

• a.Consolidating with a vibrator
• b.Curing for the full specified time
• c.Using a water-reducing admixture
• d.Water beyond the mix design✓

Strength increases as the water-cementitious ratio decreases, so water beyond the mix design raises the ratio and lowers strength. Water reducers, curing and vibration all help strength.IMCP Manual for Concrete Pavement, 2nd ed. (FHWA/CP Tech Center, 2019)