CSLB C-8 Concrete (Trade Exam) — All Questions
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68 questions
Under Title 8, when may form release oil be applied to horizontal formwork?
- a.After all of the reinforcing steel is tied
- b.Before any nailing starts, to protect the lumber
- c.After the carpentry on the form is finished✓
- d.At any time, if workers wear slip-resistant boots
Oil is not applied to horizontal forms until the carpentry is finished, so workers are not walking and nailing on slick surfaces. Oiling before nailing creates that hazard, tying steel is not the trigger, and boots do not replace the rule.Cal. Code Regs. tit. 8, §1713
A rectangular layout is 24 ft by 32 ft. If it is square, how long should each diagonal measure?
- a.45 feet
- b.40 feet✓
- c.56 feet
- d.28 feet
The diagonal is √(24² + 32²) = √1,600 = 40 ft, and equal diagonals show the corners are square. 56 adds the two sides, 28 averages them, and 45 is not the result of the right-triangle relationship.Field layout practice (right-triangle check)
A benchmark is 98.40 ft. The backsight reading on it is 3.25 ft, and the rod then reads 6.10 ft on a grade stake. What is the elevation at the stake?
- a.95.55 feet✓
- b.89.05 feet
- c.92.30 feet
- d.107.75 feet
Instrument height = 98.40 + 3.25 = 101.65 ft; stake elevation = 101.65 − 6.10 = 95.55 ft. 107.75 adds the second reading, 92.30 ignores the backsight, and 89.05 subtracts both readings from the benchmark.Field layout practice (differential leveling)
The federal guide specification lists polyethylene vapor retarder sheeting (ASTM E1745) with what minimum thickness as its base option?
- a.10 mil✓
- b.30 mil
- c.3 mil
- d.6 mil
The specification lists a minimum of 10 mil, with 15 mil as a heavier alternative. 3 and 6 mil are thinner than that base option (6 mil appears in a local Los Angeles note, not this specification), and 30 mil is not the stated minimum.UFGS 03 30 00 Cast-in-Place Concrete (Chg 10, Aug 2025)
What can water trapped inside a pavement structure lead to?
- a.Subgrade pumping and weaker subgrade and base✓
- b.Higher air content in the delivered mix
- c.Faster early strength gain in the slab above
- d.Less drying shrinkage cracking in the slab
Trapped water leads to subgrade pumping and reduced subgrade and base strength, which is why drainage is designed in. Water does not speed strength gain, change air content, or reduce cracking.IMCP Manual for Concrete Pavement, 2nd ed. (FHWA/CP Tech Center, 2019)
Cement-treated permeable base is being placed over slotted pipe drains. What must be prevented?
- a.Water entering the slotted pipe
- b.Cement paste plugging the drain openings✓
- c.Any compaction of the base layer
- d.Contact between the base and the subgrade
Cement paste must not plug the drain openings, since that would defeat the drain. Water entering the pipe is its job, the base is compacted as specified, and contact with the subgrade is normal.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 6
What should a waterstop form in each joint where it is installed?
- a.A rigid expansion plate
- b.A rough bond breaker
- c.An open drainage gap
- d.A continuous diaphragm✓
Waterstops are installed to form a continuous diaphragm across the joint, which is why splices are kept to a minimum. A bond breaker, open gap, or rigid plate would not block water.UFGS 03 30 00 Cast-in-Place Concrete (Chg 10, Aug 2025)
In designing drainage for a pavement, why are grade lines set high and side ditches made deep where possible?
- a.To reduce the quantity of concrete in the pavement
- b.To speed up the strength gain of the slab concrete
- c.To let the engineers make the base layer thinner
- d.To lengthen the gap from water table to subgrade✓
A higher grade and deeper ditches lengthen the distance from the water table to the prepared subgrade, keeping it drier. The base is not made thinner, curing speed is unaffected, and concrete quantity is not the aim.IMCP Manual for Concrete Pavement, 2nd ed. (FHWA/CP Tech Center, 2019)
Under the Los Angeles general notes for single-family dwellings, what must a concrete floor slab on grade be placed on?
- a.A 4-inch fill of coarse aggregate or a moisture barrier✓
- b.Bare compacted native soil with no fill or membrane
- c.A 12-inch bed of fine sand with no membrane under it
- d.A 2-inch bed of damp sand with no membrane at all
The note calls for a 4-inch fill of coarse aggregate or a moisture barrier membrane under floor slabs on grade. A thin sand bed, bare soil, and a deep bed of fine sand are not what the note says.LADBS Information Bulletin P/GI 2026-022 (general notes, single-family dwelling)
What lap length does Caltrans use for uncoated Grade 60 #9, #10 and #11 bars?
- a.45 times the bar diameter
- b.100 times the bar diameter
- c.30 times the bar diameter
- d.60 times the bar diameter✓
Nos. 9, 10 and 11 bars lap at 60 diameters, while #8 and smaller lap at 45. 30 diameters is too short, and 100 is longer than any rule given.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 4
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Which reinforcement may not be lap spliced under Caltrans guidance?
- a.Small #3 and #4 bars in walls
- b.Any bars placed in a footing
- c.#14 and #18 bars, and all hoops✓
- d.Any bars larger than a #6 bar
Lap splicing is not allowed for #14 and #18 bars or for any hoops. Small bars are routinely lapped, footing bars can be lapped, and bars above #6 (up to #11) are lapped by the diameter rules.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 4
On reinforcing drawings, what does the clear distance between bars measure?
- a.The distance from the center of a bar to the form face
- b.The distance from center to center of adjacent bars
- c.The gap between the outer surfaces of two adjacent bars✓
- d.The length of a bar measured between its end bends
Clear distance is surface to surface, unlike center-to-center spacing, which measures between bar centers. Center-to-form measures something else, and bar length between bends is a detailing dimension.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 4
What are the "dobies" used under rebar on Caltrans jobs?
- a.Aluminum clips on the form
- b.Wood blocks cut to size
- c.Precast mortar blocks✓
- d.Plastic wheel-type chairs
Dobies are precast mortar blocks and are the most common spacer. Caltrans does not allow aluminum, plastic, or wood spacers and supports.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 4
How can an inspector check that reinforcement is tied firmly enough to stay in position?
- a.Try to move it out of position by hand✓
- b.Weigh a sample of the tied bars
- c.Pull each tie wire with pliers
- d.Count the tie wires per square foot
Not every intersection needs a tie, but the bars must stay put, and a hand check shows whether they do. Counting ties, weighing bars, and pulling wires do not test whether the mat holds position.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 4
What kind of tie wire goes on bars that carry a factory-applied protective coating?
- a.Galvanized wire, to prevent rust
- b.Epoxy-coated or plastic-coated wire✓
- c.Bare black wire, for the best bond
- d.Copper wire, for conductivity
Epoxy-coated bars are tied with non-conductive wire such as epoxy-coated or plastic-coated wire. Bare or galvanized wire can damage the coating or set up corrosion, and conductivity is something to avoid, not seek.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 4
Under the federal guide specification, which condition is cause to reject reinforcing bars?
- a.A grade mark rolled into the bar's surface
- b.Bends or kinks not shown on the drawings✓
- c.Ends that were cut square at the mill
- d.Bars that arrive bundled and tied with wire
Bars with bends or kinks not on the drawings or approved shop drawings are rejected, as are bars with reduced cross section. A grade mark, delivery bundles, and square-cut ends are normal.UFGS 03 30 00 Cast-in-Place Concrete (Chg 10, Aug 2025)
What is an example of a benchmark inspection of reinforcement?
- a.Measuring the cover after the concrete is placed
- b.Checking the lower mat before the upper mat starts✓
- c.Reading the grade stamp on a bar at the mill
- d.Counting the bar bundles as they arrive on site
A benchmark inspection happens at a stage after which the work is covered or built over, such as the lower mat before the upper mat. Counting bundles is delivery checking, a mill stamp is a material check, and cover after the pour is too late.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 4
Under the federal specification's cover table, what cover applies to #8 bars exposed to weather or ground but not cast against it?
- a.2 inches✓
- b.3/4 inch
- c.1 1/2 inches
- d.3 inches
The table gives 2 inches for bars #6 through #18 exposed to weather or ground. 3/4 inch is for interior surfaces, 1 1/2 inches is for #5 and smaller, and 3 inches is for concrete cast against and permanently in contact with ground.UFGS 03 30 00 Cast-in-Place Concrete (Chg 10, Aug 2025)