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)

Which document must accompany every load of ready-mixed concrete delivered to a Caltrans-type job?

• a.A weighmaster certificate, commonly called the concrete ticket✓
• b.A batch-plant inspection report signed by the project engineer
• c.The 811 ticket number for the delivery address
• d.A manufacturer's certificate of compliance for the cement alone

The weighmaster certificate (concrete ticket) travels with each load, and its quantities are compared with the mix design. A certificate of compliance for one material does not replace it, and material that does not meet the contract can be rejected even with one. A plant inspection report is not the delivery document, and the 811 number belongs to excavation, not delivery.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 5

Under Caltrans guidance, what is the lowest temperature mixed concrete may have immediately before it is placed?

• a.32 °F
• b.50 °F✓
• c.60 °F
• d.40 °F

Caltrans checks that mixed concrete is between 50 °F and 90 °F just before placing, so 50 °F is the floor. 32 °F is the freezing point, which is far too cold for placing. 40 °F appears later as a curing-period minimum, not a placing limit. 60 °F is not a stated limit and would reject acceptable loads.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 5

As a starting estimate when planning deliveries, what is the longest gap Caltrans suggests between concrete trucks?

• a.About 5 minutes
• b.About 90 minutes
• c.About 45 minutes
• d.About 20 minutes✓

The interval between deliveries should not exceed about 20 minutes so that fresh concrete is still plastic when the next load is placed against it and cold joints are avoided. 5 minutes is not a limit and would stack trucks on site. 45 and 90 minutes would let earlier concrete begin to set.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 5

Caltrans gives a typical placing rate for a crane-and-bucket operation of about how many cubic yards per hour per crane?

• a.20 to 30✓
• b.5 to 10
• c.100 to 120
• d.65 to 80

A crane and bucket typically places about 20 to 30 cubic yards per hour per crane. 5 to 10 is below the stated rate. 65 is the figure given for belt conveyors, and 100 is the pumping rate described as easily attainable.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 5

How are concrete and bar reinforcing steel usually paid for on public work?

• a.Together as a single unit price per cubic yard
• b.By the pound of steel, with concrete included
• c.As separate pay items, one for each material✓
• d.After the 28-day cylinders have been broken

Concrete and rebar are usually separate pay items, which is why the average pounds of rebar per cubic yard (the rebar factor) is worked out. A combined unit price, steel-only pay, and payment tied to cylinder breaks are not how the items are described.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 2

Which two documents are the primary components of the contract documents on a Caltrans job?

• a.The Standard Plans and the weighmaster tickets
• b.The pre-pour meeting notes and the mix design
• c.The contract specifications and the project plans✓
• d.The bar lists and the concrete delivery schedule

Specifications and project plans are the primary components of the contract. The Standard Plans are contractual supplements to the plans, not one of the two primary parts. Meeting notes, mix designs, bar lists and delivery schedules are working documents that follow from the contract.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 2

During a preliminary review of project plans, which item is a typical flag for something that could complicate the work?

• a.Dimensions given along horizontal and vertical planes
• b.One mix design allowed for several concrete types
• c.Congestion of reinforcing steel✓
• d.A 28-day strength shown in the General Notes

Rebar congestion, along with added embeds and blockouts, can make placing and vibrating hard and is worth catching early. Strength in the General Notes, a single mix design that meets every requirement, and dimensions along vertical and horizontal planes are all normal plan features.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 2

What minimum experience does California's license law require of a contractor-license applicant in the class applied for?

• a.Four years as a journeyman, foreman or supervising employee✓
• b.Two years of general labor on any type of construction job
• c.Six years as a licensed contractor in any class of work
• d.One year of supervised work plus a trade-school diploma

The law requires not less than four years' experience in the particular class at journeyman, foreman, supervising employee or contractor level. Two years as a general laborer and one year with a diploma fall short, and six years in any class is neither required nor class-specific.Cal. Code Regs. tit. 16, §825 (as printed in the 2026 CSLB Law Book)

How far ahead of digging may an excavator make the first call to the regional notification center, at most?

• a.28 calendar days
• b.7 calendar days
• c.21 calendar days
• d.14 calendar days✓

Notice is due at least two working days and not more than 14 calendar days before the excavation starts. 7 and 21 days are not the limits, and 28 days is how long the ticket stays valid, not how early the call may be made.2026 CSLB Contractors License Law & Reference Book (Underground Service Alert)

At the site, how does an excavator mark the boundaries of the work area for the 811 process?

• a.Outline it, usually with white paint✓
• b.Hammer a stake with the ticket number at each corner
• c.Spray each utility color along the planned trench
• d.Leave it unmarked until the operators arrive

The excavator clearly marks the boundaries of the work area, usually with white paint, and operators then mark their lines inside those boundaries. Ticket stakes are not the standard marking, operators need the boundary to know where to mark, and the utility colors are the operators' marks, not the excavator's.2026 CSLB Contractors License Law & Reference Book (Underground Service Alert)

What is the maximum fine for knowingly and willfully violating the state 811 excavation law?

• a.$10,000
• b.$1,000
• c.$50,000✓
• d.$100,000

A knowing and willful violation carries a fine not to exceed $50,000. $10,000 is the cap for a negligent violation, and $1,000 and $100,000 are not the stated amounts.2026 CSLB Contractors License Law & Reference Book (Gov. Code §§4216–4216.9)

After discovering or causing damage to a buried line, within what time must the excavator notify the regional notification center?

• a.7 calendar days
• b.48 hours✓
• c.72 hours
• d.24 hours

An excavator must notify the regional notification center within 48 hours of discovering or causing damage. 24 and 72 hours are not the stated period, and 7 days is far too long.2026 CSLB Contractors License Law & Reference Book (Underground Service Alert)

A job disturbs 0.6 acre, but it is one phase of a larger common plan that disturbs 4 acres in total. What does the State Water Board require?

• a.No coverage, because this phase alone is under one acre
• b.Coverage depends on the site draining straight to a creek or river
• c.Coverage depends on whether it rains while the work is under way
• d.Coverage is still required, because the full project exceeds one acre✓

Projects under one acre are still covered when they are part of a larger common plan of development that disturbs one acre or more in total. Counting only this phase ignores the common plan, and neither rain timing nor a creek is the test.State Water Resources Control Board, Construction Stormwater Program

A massive foundation must keep heat low while it hardens. Which portland cement type is designed for low heat of hydration?

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

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

An ASTM C494 water-reducing admixture (Type A) is added to a mix. About how much does it cut the mixing water while holding the slump?

• a.1% to 2%
• b.40% to 50%
• c.5% to 10%✓
• d.12% to 30%

A normal water reducer lowers water content by about 5% to 10% at the same slump. 12% to 30% is the high-range water reducer, and 1% to 2% and 40% to 50% are not figures given for either.IMCP Manual for Concrete Pavement, 2nd ed. (FHWA/CP Tech Center, 2019)

Why does a slab usually need reinforcing steel, given how concrete behaves?

• a.Only about one-tenth as strong in tension as in compression✓
• b.It is about half as strong in tension as in compression
• c.Its compressive strength falls sharply as it cures over time
• d.Steel is needed only to give the slab enough dead weight

Concrete is strong in compression and weak in tension, about one-tenth as strong, so steel carries the tension. Its compressive strength rises with curing rather than falling, a one-half ratio overstates its tensile strength, and steel is not added for weight.IMCP Manual for Concrete Pavement, 2nd ed. (FHWA/CP Tech Center, 2019)

Under the City of Los Angeles general notes for a single-family dwelling, how deep must footings be below natural and finished grade?

• a.At least 24 inches for exterior and 18 inches for interior footings✓
• b.At least 18 inches for exterior and 24 inches for interior footings
• c.At least 12 inches for both exterior and interior footings
• d.At least 36 inches for exterior and 30 inches for interior footings

The notes set not less than 24 inches for exterior footings and 18 inches for interior footings. Reversing them, using a flat 12 inches, and using 36 and 30 inches do not match the stated minimums.LADBS Information Bulletin P/GI 2026-022 (general notes, single-family dwelling)

The same Los Angeles general notes say adverse soil conditions found during construction may call for what?

• a.A change of cement type at the plant
• b.A new 811 ticket for the site
• c.A second stormwater permit
• d.A soils investigation report✓

If adverse soil conditions are encountered, a soils investigation report may be required. A new 811 ticket concerns utilities, a second stormwater permit concerns runoff, and the cement type does not address bearing soil.LADBS Information Bulletin P/GI 2026-022 (general notes, single-family dwelling)

The Los Angeles general notes cite the California Green Building Standards Code for construction and demolition waste. What share of nonhazardous waste must be recycled or salvaged?

• a.At least 25 percent
• b.At least 95 percent
• c.At least 65 percent✓
• d.At least 50 percent

A minimum of 65 percent of nonhazardous construction and demolition waste must be recycled or salvaged. 25 and 50 percent fall short of the stated minimum, and 95 percent is more than the requirement.LADBS Information Bulletin P/GI 2026-022 (general notes, single-family dwelling)

What must be on a Cal/OSHA excavation permit for it to be valid?

• a.The soil type and the lay-back angle to be used
• b.The county parcel number of the project site
• c.The excavator's 811 ticket identification number✓
• d.A signature from each affected utility operator

A permit is not valid without the Underground Service Alert (811) identification number. Soil type and lay-back angle, a parcel number, and operator signatures are not what validates it.2026 CSLB Contractors License Law & Reference Book (excavation permit note)

An L-shaped slab is made of a 40 ft by 24 ft section plus a 16 ft by 12 ft wing, all 4 in thick. About how much concrete does it hold?

• a.About 21.3 cubic yards
• b.About 14.2 cubic yards✓
• c.About 11.9 cubic yards
• d.About 42.7 cubic yards

Total area is 960 + 192 = 1152 sq ft; × 0.333 ft = 384 cu ft; ÷ 27 = 14.2 cu yd. Leaving out the wing gives 11.9, dividing by 9 instead of 27 gives 42.7, and using 6 in gives 21.3.NIST Handbook 44 (2026), Appendix C

A stoop is 4 ft by 6 ft and 6 in thick. About how much concrete does it hold?

• a.About 0.2 cubic yard
• b.About 0.9 cubic yard
• c.About 1.3 cubic yards
• d.About 0.4 cubic yard✓

4 × 6 = 24 sq ft; × 0.5 ft = 12 cu ft; ÷ 27 = 0.44 cu yd. Dividing by 9 gives 1.3, using 12 in of thickness gives 0.9, and using 3 in gives 0.2.NIST Handbook 44 (2026), Appendix C