CSLB C-8 Concrete (Trade Exam) — All Questions
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68 questions
Proof-rolling reveals a soft, rutting area in a slab subgrade. What should be done?
- a.Replace it with compacted fill.✓
- b.Pour thicker concrete over it.
- c.Leave it; the slab will bridge it.
- d.Cover it with plastic sheeting.
A uniform foundation matters more than a strong one, and there should be no hard or soft spots. A soft area left in place becomes a crack line; it is removed or reworked and recompacted.IMCP Manual for Concrete Pavement, 2nd ed. (FHWA/CP Tech Center, 2019)
Expansive clay under a planned slab has dried out badly during a delay. Why is that a concern?
- a.Dry clay makes the slab cure faster.
- b.Dry clay is always Type A soil.
- c.Later swelling can lift the slab.✓
- d.Dry clay has no effect on slabs.
The IMCP manual notes expansive soils cause trouble when compacted too dry or allowed to dry out before paving; later wetting makes them swell unevenly. Moisture conditioning per the soils report addresses it.IMCP Manual for Concrete Pavement, 2nd ed. (FHWA/CP Tech Center, 2019)
A dry, semi-porous subgrade will receive a footing. What does the federal guide specification say to do?
- a.Flood it to 2 inches deep.
- b.Cover it with dry cement.
- c.Leave it dry for better bond.
- d.Sprinkle it to eliminate suction.✓
The specification says to sprinkle a semi-porous, dry subgrade to eliminate suction when concrete is deposited, or seal it with the specified vapor retarder. Flooding leaves standing water, which must be removed.UFGS 03 30 00 Cast-in-Place Concrete (Chg 10, Aug 2025)
Under the 811 law, how wide is the tolerance zone around an operator's field marking?
- a.5 feet on each side
- b.12 inches on each side
- c.24 inches on each side✓
- d.36 inches total
Government Code §4216 defines the tolerance zone as 24 inches on each side of the operator's field marking; inside it, the excavator uses hand tools to find the exact location first.Cal. Gov. Code §§4216–4216.9
A footing will be dug 6 ft from a high-priority gas transmission line. What must happen first?
- a.Nothing extra; hand dig only
- b.An onsite meeting✓
- c.A Cal/OSHA permit for the line
- d.A second 811 ticket
When excavation is proposed within 10 feet of a high-priority installation, the operator sets up an onsite meeting, and the excavator may not begin until it is completed.Cal. Gov. Code §§4216–4216.9
For the 811 notice period, which of these counts as a working day?
- a.A non-holiday Wednesday✓
- b.A state holiday
- c.A Sunday afternoon
- d.A Saturday morning
A working day is a weekday, Monday through Friday, 7:00 a.m. to 5:00 p.m., excluding federal and state holidays. Weekends and holidays do not count toward the two working days.Cal. Gov. Code §§4216–4216.9
What must every operator on the ticket provide before the legal excavation start time?
- a.A copy of its insurance
- b.A crew to dig by hand
- c.A written excavation permit
- d.An electronic positive response✓
Every operator must supply an electronic positive response through the regional notification center before the legal start date and time, and the excavator may not begin until all listed operators have done so.Cal. Gov. Code §§4216–4216.9
When may an excavation have vertical sides with no protective system, whatever its depth?
- a.When it is entirely in stable rock✓
- b.When it is dug in dry clay
- c.When workers wear hard hats
- d.When it will be open one day
Title 8 §1541.1 exempts excavations made entirely in stable rock. Dry clay can still cave, and short duration or PPE does not replace a protective system.Cal. Code Regs. tit. 8, §1541.1
An 8-ft-deep excavation in Type A soil will be sloped. How far back must each side lay back from the bottom edge?
- a.8 feet
- b.12 feet
- c.6 feet✓
- d.4 feet
Type A soil is sloped no steeper than 3/4 horizontal to 1 vertical for excavations under 20 ft: 0.75 × 8 = 6 ft. Eight feet is a 1:1 Type B slope and 12 ft is the 1½:1 Type C slope.Cal. Code Regs. tit. 8, §1541.1, App. B
A 6-ft excavation is near an old landfill where hazardous gases could be present. What is required before entry?
- a.Only post a warning sign.
- b.Only limit entry to 15 minutes.
- c.Only open the trench wider.
- d.Test the atmosphere first.✓
Where oxygen deficiency (under 19.5%) or a hazardous atmosphere could reasonably exist, the atmosphere must be tested before employees enter excavations greater than 4 ft deep.Cal. Code Regs. tit. 8, §1541
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A worker must enter a deep bell-bottom pier hole. What does Title 8 require?
- a.Only a hard hat and gloves
- b.A harness with an attended lifeline✓
- c.A second worker in the hole
- d.A ladder within 50 feet
Employees entering bell-bottom pier holes must wear a harness with a lifeline, separate from any material line, individually attended at all times.Cal. Code Regs. tit. 8, §1541
Why are layout lines often carried on batter boards set back from the corners?
- a.To mark the property line.
- b.To hold the forms plumb.
- c.To make the corners square.
- d.So the lines survive excavation.✓
Stakes on the exact corners are dug out with the footing; batter boards set outside the work hold the string lines so they can be removed for digging and restored to the same marks.Field layout practice; Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 2 (control stakes)
A rectangular form layout measures 36 ft and 40 ft on its two diagonals. What does that tell you?
- a.Only the sides are wrong.
- b.The slab is 38 ft long.
- c.The layout is square.
- d.The layout is not square.✓
A true rectangle has equal diagonals; unequal diagonals mean the layout is a parallelogram and a corner is out of square.Field layout practice (rectangle geometry)
What is the job of the kickers on a wall form?
- a.To bevel the top edge
- b.To hold the rebar off the form
- c.Brace it plumb to the ground✓
- d.To tie the two faces together
Kickers are diagonal braces between the form and the ground or a stable platform that keep vertical forms plumb. Ties hold the faces together and chamfers bevel edges.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 3
After a snap tie is tensioned with its wedge, what keeps the wedge from loosening during the pour?
- a.It is nailed to the form.✓
- b.It is left loose to flex.
- c.It is taped to the waler.
- d.It is welded to the tie.
Caltrans notes that once the tie is tensioned, the tie wedge is nailed to the form so it will not move and loosen during concrete placement.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 3
A wall will be poured on a cold morning. How does the low concrete temperature affect form pressure?
- a.Pressure rises only if it is air-entrained.
- b.Pressure rises, as it stays fluid longer.✓
- c.Temperature has no effect.
- d.Pressure falls, as it sets faster.
At low temperatures concrete stays fluid longer, so a greater height acts as fluid and lateral pressure is higher; forms for cold-weather pours must account for it.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 3
Form release agent is being sprayed next to yesterday's wall at a construction joint. What must it not touch?
- a.The form ties
- b.The plywood edges
- c.The hardened joint surface✓
- d.The inside of the new forms
Release agent must not contact reinforcement or hardened concrete against which fresh concrete will be placed, because it prevents bond at the joint.UFGS 03 30 00 Cast-in-Place Concrete (Chg 10, Aug 2025)
A falsework span is short and low, but a traffic lane will pass beneath it. Who must sign the design?
- a.The foreman
- b.A registered civil engineer✓
- c.The building inspector
- d.The rebar supplier
Title 8 §1717 requires calculations and drawings signed by a California registered civil engineer when provisions are made for vehicular or railroad traffic through falsework, regardless of height or span.Cal. Code Regs. tit. 8, §1717
Shoring will support a 4-inch elevated slab without carts. What minimum design load applies?
- a.70 pounds per square foot
- b.120 pounds per square foot
- c.100 pounds per square foot✓
- d.50 pounds per square foot
Concrete weight (150 × 0.333 = 50 psf) plus 20 psf is 70 psf, but the total may not be less than 100 psf, so 100 psf governs.Cal. Code Regs. tit. 8, §1717
How should vapor retarder sheets be laid out under a slab?
- a.With gaps so water can drain
- b.In the widest sheets practicable✓
- c.Only under the slab edges
- d.In narrow strips for easy handling
The federal specification calls for the greatest widths and lengths practicable to eliminate joints, with laps as specified. Gaps and strips defeat the retarder.UFGS 03 30 00 Cast-in-Place Concrete (Chg 10, Aug 2025)
What does filter fabric around a drain rock envelope do?
- a.Adds strength to the slab
- b.Keeps fines out✓
- c.Replaces the need for pipe
- d.Makes the pipe waterproof
Filter fabric keeps fines from migrating into the drain rock and clogging it; Caltrans requires it installed per the manufacturer's instructions where drains are used.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 6
A perforated subdrain is being laid. What slope should the pipe have?
- a.A low point in the middle
- b.A continuous fall to the outlet✓
- c.An uphill run to the outlet
- d.Dead level for its whole length
A drain must carry water to its outlet, so it needs continuous fall; a level pipe or a low spot holds water instead of removing it.IMCP Manual for Concrete Pavement, 2nd ed. (FHWA/CP Tech Center, 2019)
On a Caltrans job, the plans do not state the clear cover for a formed retaining wall. What cover does Caltrans describe as typical?
- a.2 inches minimum✓
- b.3/4 inch minimum
- c.No cover is needed
- d.6 inches minimum
Caltrans states clear cover is typically 2 inches minimum unless specified otherwise, with more for cast-in-drilled-hole piles (3 in) and severe environments. Three-quarters of an inch is an interior-slab value in other specifications.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 4
On a Caltrans job, which bar supports are generally not allowed?
- a.Ferrous metal chairs
- b.Precast mortar blocks
- c.Wood, plastic or aluminum✓
- d.Dobies with tie wire
Caltrans' specification does not allow aluminum, plastic or wood spacers and supports (with a CIDH exception); precast mortar blocks (dobies) and ferrous metal chairs are acceptable.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 4
What tie wire do ironworkers usually use to fasten rebar intersections?
- a.Welding rod
- b.About 22 gauge
- c.About 8 gauge
- d.About 16.5 gauge✓
Caltrans notes ironworkers usually use 16.5-gauge tie wire at intersections; enough intersections are tied to keep the steel stable, and crossing bars are not tack welded.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 4
Two bars are lap-spliced in a wall. How must the lapped bars be placed?
- a.Bent at 90 degrees
- b.Welded end to end
- c.Spaced 6 inches apart
- d.In contact and tied✓
Caltrans states lapped sections must be in contact and securely tied, with at least 2 inches clear to adjacent reinforcement or splices.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 4
A pipe sleeve passes through a slab form. What does the federal specification say about the sleeve before the pour?
- a.Leave it open for air to escape.
- b.Fill it with removable material.✓
- c.Cut it off after the pour.
- d.Fill it with grout.
The specification says to temporarily fill voids in sleeves with readily removable material to keep concrete out, and to secure the sleeve against displacement.UFGS 03 30 00 Cast-in-Place Concrete (Chg 10, Aug 2025)
Why are steel drum rollers not recommended for proof-rolling a prepared subgrade?
- a.They are too light to find any weak spot at all
- b.They leave the grade too smooth for good slab bonding
- c.They tend to crush buried pipes and conduits in the grade
- d.They can bridge soft spots without movement✓
Proof-rolling uses a heavy, pneumatic-tired vehicle because a rigid steel drum can bridge soft spots without rutting. Weight is not the issue, buried pipes are not the stated concern, and surface smoothness is unrelated to proof-rolling.IMCP Manual for Concrete Pavement, 2nd ed. (FHWA/CP Tech Center, 2019)
For long-term slab and pavement performance, which subgrade quality is described as more important than strength?
- a.A smooth, hand-troweled surface
- b.Uniformity, with no hard or soft spots✓
- c.Maximum stiffness at the highest cost
- d.A high percentage of clay particles
The guidance is that a uniform foundation matters more than a strong one, with no hard or soft spots. Stiffness alone does not fix nonuniform support, a smooth surface is not a performance measure, and clay content does not give uniformity.IMCP Manual for Concrete Pavement, 2nd ed. (FHWA/CP Tech Center, 2019)
A crew wants to place a slab on a subgrade that has not thawed. What does Caltrans say?
- a.Allowed if an accelerator is added to the mix
- b.Allowed if warm concrete is delivered to the pour
- c.Expressly prohibited on frozen subgrade✓
- d.Allowed if the slab is thicker than 6 inches
The specification explicitly prohibits placing concrete on frozen or ice-coated ground or subgrade. Warm concrete, an accelerator, and extra thickness do not remove the problem of thawing, settling support.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 5
A large amount of water has collected at the bottom of a footing excavation before the pour. Where does Caltrans suggest the pump be placed?
- a.Beside the truck, with dry cement spread on the water
- b.At the middle of the footing, with the bottom left level
- c.In a corner, with the excavation bottom sloped toward it✓
- d.Nowhere, since the incoming concrete displaces the water
Standing water must be removed, and sloping the bottom to a corner lets the sump collect it for the pump. Pumping from the middle leaves water pooled around the edges, concrete does not safely displace water, and dry cement on water makes a weak, contaminated base.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 5
Under the federal guide specification, what must be done before slabs on ground are built?
- a.The next floor's reinforcing must be delivered to the site
- b.Buried pipe and conduit work must be done and approved✓
- c.The footing forms must be fully stripped and cleaned out
- d.The vapor retarder must be allowed to cure for seven days
Underground work on pipes and conduits is completed and approved first, since it is buried under the slab. A vapor retarder does not cure, next-floor steel is unrelated, and footing forms are not tied to the slab sequence.UFGS 03 30 00 Cast-in-Place Concrete (Chg 10, Aug 2025)
Which of these is exempt from the state 811 notification requirement?
- a.A non-contractor homeowner doing permit-free work on a principal residence✓
- b.A rental company whose signed rental agreement lacks the required clause
- c.A licensed contractor digging only a shallow trench for a patio slab
- d.A subcontractor digging footings under a general contractor's ticket
A private owner who is not a licensed contractor and does work on a principal residence that needs no excavation permit is exempt. Every contractor or subcontractor excavating at a jobsite needs its own ticket, a licensed contractor is not exempt because the trench is shallow, and a rental company is exempt only if its signed rental agreement carries the required provision.2026 CSLB Law Book (Underground Service Alert)
How far from the edge of an excavation must excavated material and equipment be kept, at minimum?
- a.10 feet
- b.5 feet
- c.6 inches
- d.2 feet✓
Title 8 requires spoil and equipment to be kept at least 2 feet from the edge. 6 inches is too close to prevent loading the wall, while 5 and 10 feet are not the stated minimum.Cal. Code Regs. tit. 8, §1541
Who must make the daily inspections of excavations, adjacent areas and protective systems?
- a.Any laborer working nearby
- b.The utility operator
- c.The ready-mix driver
- d.A competent person✓
Daily inspections are the competent person's job, someone able to identify hazards and authorized to correct them. The operator marks lines, a driver does not inspect trenches, and a laborer may lack the training and authority.Cal. Code Regs. tit. 8, §1541
Below what oxygen percentage is an atmosphere in an excavation considered oxygen deficient?
- a.19.5 percent✓
- b.10 percent
- c.21 percent
- d.16 percent
Title 8 treats atmospheres with less than 19.5 percent oxygen as deficient. 10 and 16 percent are far below the trigger and would let workers enter too late, while 21 percent is ordinary air.Cal. Code Regs. tit. 8, §1541
Water is steadily accumulating in a footing trench. Under Title 8, may employees work in it?
- a.Yes, provided the water looks clear and has no odor
- b.Yes, provided everyone on the crew wears rubber boots
- c.Yes, as long as the water is less than 12 inches deep
- d.Not without adequate precautions against water hazards✓
Employees may not work in excavations with accumulated or accumulating water without adequate precautions. Shallow depth, boots, and clear water do not remove the cave-in and drowning hazards.Cal. Code Regs. tit. 8, §1541
A backhoe is swinging a bucket of spoil over the edge of a trench. Where may employees stand?
- a.Under it, if they wear hard hats
- b.Under it, if the operator waves them in
- c.Never underneath the load✓
- d.Under it, if the load is small
No employee may be underneath loads handled by lifting or digging equipment. A hard hat, a signal, and a small load do not make the position safe.Cal. Code Regs. tit. 8, §1541
A trench will run along a sidewalk. May the sidewalk be undermined?
- a.Yes, because concrete flatwork can bridge any trench
- b.Yes, whenever the trench is shallower than 5 feet
- c.Not unless a support system or other protection is used✓
- d.Yes, whenever the sidewalk contains reinforcing steel
Sidewalks, pavements and appurtenant structures must not be undermined unless support or other protection prevents collapse. Slabs do not reliably span a void, trench depth under 5 feet is not an exception, and rebar does not carry a slab over open ground.Cal. Code Regs. tit. 8, §1541
A 6-ft-deep excavation in Type B soil will be sloped under Appendix B. How far back must each side lay back horizontally from the bottom edge?
- a.4.5 feet
- b.9 feet
- c.12 feet
- d.6 feet✓
Type B soil is sloped at 1:1 (45 degrees), so 6 ft deep means 6 ft back. 4.5 ft is the 3/4:1 slope for Type A, 9 ft is the 1 1/2:1 slope for Type C, and 12 ft would be a 2:1 slope that the table does not use.Cal. Code Regs. tit. 8, §1541.1, App. B
In Title 8, which description fits a trench?
- a.An open excavation that is wider across than it is deep
- b.A narrow cut deeper than wide, at most 15 ft at the bottom✓
- c.Any hole that was dug only with hand tools and a shovel
- d.Any open excavation more than 4 feet deep, however wide
A trench is generally deeper than it is wide, and its width measured at the bottom is not greater than 15 ft. A depth of 4 feet is a different threshold, an excavation wider than deep is not a trench, and the digging method is irrelevant.Cal. Code Regs. tit. 8, §1540
On a Caltrans job, how should the survey's control stakes be checked?
- a.Check only the stake at the first footing to be formed
- b.Spot-check the stakes at each location rather than resurvey✓
- c.Redo the entire survey from scratch before forms go up
- d.Accept them without checking, since the engineer set them
Control stakes carry location and elevation for all the work, so each location is spot-checked rather than the survey being recreated. Trusting them blind or checking just one risks building off a wrong stake, and a full re-survey is not needed.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 2
Which part of a forming system touches the concrete and gives it its surface texture?
- a.The wall studs
- b.The sheathing✓
- c.The horizontal walers
- d.The diagonal kickers
Sheathing is the form material in direct contact with the concrete, so it carries its texture. Studs back the sheathing, walers support the studs, and kickers are diagonal braces that keep forms plumb.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 3
Why are form studs spaced as they are?
- a.To give the snap ties something to hook onto
- b.To let the panels be stripped and reused
- c.To keep the whole wall form standing plumb
- d.To limit how far the sheathing bows between them✓
Studs are spaced to limit how far the sheathing bows between them under the concrete's pressure. Ties resist spreading, kickers keep forms plumb, and reuse depends on materials and handling, not stud spacing.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 3
What is the smallest triangular fillet Caltrans requires on exposed sharp edges of formed concrete?
- a.1/2 by 1/2 inch
- b.1 1/2 by 1 1/2 inch
- c.1/4 by 1/4 inch
- d.3/4 by 3/4 inch✓
Exposed edges get fillets not less than 3/4 by 3/4 inch to produce smooth, straight chamfers. 1/4 and 1/2 inch are below the minimum, and 1 1/2 inch is larger than required.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 3
Which method of holding forms in position is not permitted on a Caltrans job?
- a.He-bolt form ties
- b.Twisted wire loops✓
- c.Taper ties with rods
- d.Snap ties with wedges
Twisted wire loops are not permitted for holding forms. Snap ties, he-bolts and taper ties are all recognized tensile form ties that prevent the forms from spreading.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 3
Wood spreaders keep the faces of a wall form the correct distance apart. What must happen to them?
- a.They are cut off flush after the forms are stripped
- b.They are oiled and then left in place as sleeves
- c.They stay in the wall as extra permanent ties
- d.They must be pulled out during the pour✓
Wood spreaders cannot stay in the concrete and must come out as concrete rises. Leaving them, cutting them flush later, or treating them as sleeves all leave wood embedded in the wall.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 3
Why must forms be mortar-tight?
- a.A sealed form keeps the panels from floating up
- b.Standing water is needed in the form for curing
- c.Leaking grout means more finishing afterward✓
- d.It keeps the form ties from rusting in the wall
Grout leakage from forms that are not mortar tight increases the finishing required and can leave defects such as rock pockets. Curing water, floating panels, and tie rust are not the reason for tight joints.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 3
What do clean-out openings in formwork allow?
- a.Pumping water out of the form after the pour
- b.Inspection and debris removal✓
- c.Releasing air that the vibrator has trapped
- d.Placing concrete from the bottom of the form up
Clean-out openings let the crew inspect and remove debris before concrete goes in. They are not pump ports or placing points, and trapped air is dealt with by vibration, not by these openings.UFGS 03 30 00 Cast-in-Place Concrete (Chg 10, Aug 2025)
Under the federal guide specification, when are adjustments to formwork not allowed?
- a.After release agent has been applied to the forms
- b.After the first truck arrives at the site
- c.After the rebar has been inspected and accepted
- d.After the concrete has reached initial setting✓
Formwork must not be adjusted once concrete has reached initial setting, because it would disturb the setting concrete. Inspected rebar, a truck's arrival, and release agent do not set that limit.UFGS 03 30 00 Cast-in-Place Concrete (Chg 10, Aug 2025)