C-8 Concrete exam questions, with answers
10 practice questions for the CSLB Concrete trade exam, each with the answer, a plain explanation and the source it rests on.
These are not real exam questions. CSLB does not release its test questions or answer keys, and nobody else has them. We write our own questions from the C-8 outline and the codes, standards and references CSLB lists for the exam. Each answer names its source so you can check it.
The C-8 exam has 5 sections. The questions below are grouped by section, with the share of the exam each one carries. Read the question, pick an answer, then open “Show the answer”. The other questions of the free test, scored section by section, are in the free 25-question C-8 test.
Planning and Estimating · 28% of the exam
Planning concrete projects; estimating concrete projects.
1. You have worked out the plan volume of a large slab from the drawings. According to NRMCA CIP 31, how much extra concrete should you normally order to cover contingencies?
- About 15% to 20% more than the plan estimate
- About 4% to 10% more than the plan estimate
- About 1% to 2% more than the plan estimate
- About 25% to 30% more than the plan estimate
Show the answer
Answer: B. CIP 31 says the quantity ordered should be 4% to 10% more than the estimate from plan dimensions, to cover contingencies such as slightly thicker sections or form movement. A 1% to 2% allowance leaves almost no margin, while 15% or more means paying for excess concrete, which the sheet says to avoid.
2. An equipment pad behind a warehouse is 30 ft by 36 ft and 6 in thick. How many cubic yards of concrete does it take, before any waste allowance? (27 cu ft = 1 cu yd)
- 20.0 cu yd
- 24.0 cu yd
- 40.0 cu yd
- 60.0 cu yd
Show the answer
Answer: A. 30 x 36 x (6/12) = 540 cu ft, and 540 / 27 = 20.0 cu yd. 24.0 comes from treating 6 in as 0.6 ft, 40.0 from using a 1-ft thickness, and 60.0 from dividing by 9 instead of 27.
Source: NIST HB 44 (2026) App. C, Units of Volume (27 cu ft = 1 cu yd)
Pre-placement Preparation · 27% of the exam
Demolition, grading and excavating; layout and forming; installing drains and moisture barriers; installing reinforcement and embedded items.
3. Before a patio pour, your crew finds a few soft, soggy patches in the graded subgrade. According to NRMCA CIP 14, what condition should the subgrade be in when the concrete arrives?
- Freshly loosened on top so the concrete can bond into it
- Uniformly compacted, sloped for drainage, with no wet spots
- Flooded with water so it cannot absorb any mix water
- Compacted only along the edges where the forms are staked
Show the answer
Answer: B. CIP 14 says all subgrade excavation and compaction should be complete before delivery, and the subgrade should be compacted uniformly and sloped as needed for drainage, avoiding wet spots. Loosened soil gives uneven support, standing water makes the wet spots the sheet warns about, and compacting only the edges leaves the middle soft.
4. A laborer spraying DUOGARD II release agent on wall forms leaves drips and pools of agent along the bottom. What does the W. R. Meadows data sheet say about this?
- Apply a thin film and brush out the runs and puddles
- Leave the puddles, since extra agent releases cleaner
- Let the puddles soak in overnight before the pour
- Dilute the agent with water so it spreads more evenly
Show the answer
Answer: A. The DUOGARD II data sheet says a thin film should be applied and runs or puddles need to be brushed out; it also says not to over-apply and not to dilute the product. Leaving or soaking in the puddles is the over-application the sheet warns against, and thinning it with water goes against the 'do not dilute' instruction.
Source: W. R. Meadows DUOGARD II data sheet, Application and Precautions
Placing and Finishing · 17% of the exam
Placing concrete; applying finishes; curing and testing.
5. A laborer starts pulling concrete across a driveway form with a garden rake. According to NRMCA CIP 14, why should he switch tools?
- Raking concrete sideways causes segregation
- Raking concrete sideways speeds up its set
- Raking concrete sideways cools it too fast
- Raking concrete sideways traps too much air
Show the answer
Answer: A. CIP 14 says never to use a garden rake or tined tool to move concrete horizontally because it causes segregation; spread it with a short-handled, square-ended shovel or a come-along instead. Raking does not trap extra air, speed the set or chill the concrete; the problem is the paste and stone separating.
6. Your crew has just broom-finished a new sidewalk late in the day. According to NRMCA CIP 14, when should curing begin?
- After the forms are stripped, a day or two later
- Once the surface has turned light gray and dry
- The next morning, once the surface is hard
- As soon as all the finishing is completed
Show the answer
Answer: D. CIP 14 says to cure the concrete as soon as all finishing is completed, to give the cement proper conditions for hydration; curing is essential for the strength and durability of the surface. Waiting overnight, until stripping, or until the surface dries out lets the surface lose the moisture it needs.
Post-placement Tasks · 7% of the exam
Applying stains and sealers; stripping forms; repairing, grouting and caulking concrete.
7. Your crew plans to roll QUIKRETE Acrylic Concrete Cure & Seal on a patio this afternoon. Under which forecast does the data sheet say not to apply it?
- Wind, light fog or temps below 40°F within 12 hours
- Rain, heavy dew or temps below 32°F within 6 hours
- Rain, heavy dew or temps below 50°F within 24 hours
- Sun, low humidity or temps above 70°F within 24 hours
Show the answer
Answer: C. The Cure & Seal data sheet says not to apply it if rain, heavy dew or temperatures below 50°F are expected within 24 hours. The 32°F, 6-hour and 40°F, 12-hour versions are weaker than the sheet's limits, and sunny, dry, warm weather is not a listed reason to hold off.
Source: QUIKRETE Acrylic Concrete Cure & Seal data sheet, Application
8. Your crew has just packed QUIKRETE Non-Shrink Precision Grout under a steel column base plate. What curing does the grout's data sheet call for?
- A damp cure of at least 3 days, to keep it non-shrink and strong
- A damp cure of at least 12 hours, then let it air dry
- No curing, since a non-shrink grout cannot shrink
- Heat lamps for 24 hours to drive the moisture out
Show the answer
Answer: A. The spec data sheet says a damp cure of at least 3 days is needed to control the grout's non-shrink characteristics and keep its strength. Twelve hours is too short, 'non-shrink' does not mean it needs no curing, and drying it with heat works against curing.
Safety · 21% of the exam
Employee safety; job site safety.
9. A laborer wet-cuts a slab with an electric handheld saw fed by a garden hose. Besides the water control, what does OSHA's silica fact sheet for handheld power saws say to use for the electric tools?
- A dry-cutting blade whenever the cord gets wet
- Extra-long cords so the plug stays away from the hose
- Double-insulated tools in place of any GFCI protection
- GFCIs and watertight, sealable electrical connectors
Show the answer
Answer: D. The fact sheet says that where water is used to control dust, electrical safety is a particular concern, so ground-fault circuit interrupters (GFCIs) and watertight, sealable connectors should be used for electric tools. Long cords and double insulation do not replace GFCIs, and switching to dry cutting gives up the dust control Table 1 relies on.
10. Your backhoe is digging a footing trench and piling the spoil alongside. Under Cal/OSHA §1541, where must the spoil be kept if no retaining device is used?
- At least 5 feet back from the edge of the excavation
- At least 2 feet back from the edge of the excavation
- At least 1 foot back from the edge of the excavation
- Anywhere along the edge, if the pile is under 2 feet high
Show the answer
Answer: B. §1541(j)(2) protects workers from materials that could fall or roll into an excavation by keeping them at least 2 feet from the edge, or by using retaining devices that stop them. 1 foot is too close, 5 feet is not the rule, and a low pile right at the edge can still roll in.
Source: 8 CCR §1541(j)(2), Cal. Code Regs. Title 8, §1541 Excavations, General Requirements
Where to go from here
How the license works, from experience to fees: how to get a C-8 license. Everything about the course: the C-8 exam page.
Questions from our free C-8 test, written from CSLB License Examination Study Guide, Concrete (C-8), form 13E-8 (01-2026), for examinations scheduled on or after March 1, 2026. CSLB notes that the percentages are approximate. Reviewed 14 October 2026. Study guidance only; we are not affiliated with CSLB or PSI.