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

A round pad has a 15-ft radius and is 5 in thick. About how much concrete does it take?

• a.About 43.6 cubic yards
• b.About 8.7 cubic yards
• c.About 32.7 cubic yards
• d.About 10.9 cubic yards✓

Area = π × 15² = 706.9 sq ft; × 5/12 ft = 294.5 cu ft; ÷ 27 = 10.9 cu yd. Using the 30-ft diameter as the radius gives 43.6, dividing by 9 gives 32.7, and using 4 in gives 8.7.NIST Handbook 44 (2026), Appendix C

A takeoff comes to 18.6 cubic yards. The supplier sells whole yards and the owner wants a 5% allowance for waste. How many yards should be ordered?

• a.18 cubic yards
• b.21 cubic yards
• c.20 cubic yards✓
• d.19 cubic yards

18.6 × 1.05 = 19.53, which rounds up to 20 because the order must cover the pour. Rounding down to 19 leaves the pour short, 18 ignores the waste allowance, and 21 comes from adding about 10% instead of 5%.NIST Handbook 44 (2026), Appendix C

A 52-cubic-yard pour will arrive in trucks that each carry 8.5 cubic yards. How many truckloads must be ordered?

• a.6 loads
• b.5 loads
• c.8 loads
• d.7 loads✓

52 ÷ 8.5 = 6.1, and the last partial load still needs a truck, so 7 loads. Rounding down to 6 leaves 1 cu yd unplaced, 8 over-orders a whole truck, and 5 divides by 10 cu yd, which is not the truck size.NIST Handbook 44 (2026), Appendix C

A sidewalk is 4 ft wide and 4 in thick. About how many linear feet does one cubic yard of concrete cover?

• a.About 81 linear feet
• b.About 20 linear feet✓
• c.About 27 linear feet
• d.About 6.8 linear feet

The cross-section is 4 ft × 0.333 ft = 1.33 sq ft, so 27 cu ft ÷ 1.33 sq ft = 20.25 linear feet. 81 is the square-foot coverage at 4 in, not a length for a 4-ft-wide walk, 6.8 divides 27 by the width and ignores the thickness, and 27 treats cubic feet as feet.NIST Handbook 44 (2026), Appendix C

Ten square footing pads are each 3 ft on a side and 18 in deep. How much concrete do they need in all?

• a.About 6.7 cubic yards
• b.About 5.0 cubic yards✓
• c.About 3.3 cubic yards
• d.About 15.0 cubic yards

Each pad is 3 × 3 × 1.5 = 13.5 cu ft; × 10 = 135 cu ft; ÷ 27 = 5.0 cu yd. Dividing by 9 gives 15.0, using 12 in of depth gives 3.3, and using 24 in gives 6.7.NIST Handbook 44 (2026), Appendix C

A takeoff shows 1,250 linear feet of #4 bar, which a supplier sheet lists at 0.668 lb per foot. What is the total weight?

• a.About 835 pounds✓
• b.About 1,250 pounds
• c.About 1,871 pounds
• d.About 84 pounds

1,250 ft × 0.668 lb/ft = 835 lb. Dividing by 0.668 gives 1,871, a slipped decimal gives 84, and 1,250 is just the length with no weight conversion.Estimating practice (bar weight from supplier data)

Bars run at 16 in on center across a 20-ft width, with a bar on each edge line. How many bars are needed in that direction?

• a.15
• b.20
• c.16✓
• d.18

20 ft = 240 in; 240 ÷ 16 = 15 spaces; bars = spaces + 1 = 16. Answering 15 counts spaces instead of bars, 18 uses a spacing near 14 in, and 20 assumes one bar per foot.Estimating practice (bar count)

Under the Caltrans rule of 45 bar diameters for uncoated Grade 60 bars of #8 and smaller, what is the minimum lap for a #8 bar?

• a.60 inches
• b.36 inches
• c.24 inches
• d.45 inches✓

A #8 bar is 8/8 = 1.0 in in diameter, so 45 × 1.0 = 45 in. 60 inches applies the 60-diameter rule meant for #9, #10 and #11 bars, while 36 and 24 inches are shorter than the rule allows.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 4

A 40-ft by 60-ft slab is 6 in thick. How many square feet of contact area do its perimeter edge forms need?

• a.50 square feet
• b.100 square feet✓
• c.200 square feet
• d.2,400 square feet

The perimeter is 2 × (40 + 60) = 200 ft; × 0.5 ft of height = 100 sq ft. 200 treats the edge as 1 ft high, 50 uses only half the perimeter, and 2,400 is the slab's top area, not the edge area.Estimating practice (form contact area)

A footing is 100 ft long and 18 in deep and will be formed on both sides. How much form contact area is that, ignoring ends?

• a.600 square feet
• b.300 square feet✓
• c.200 square feet
• d.150 square feet

Each side is 100 × 1.5 = 150 sq ft; two sides = 300 sq ft. 150 forms only one side, 600 uses 3 ft of depth, and 200 uses a 12-in depth on both sides.Estimating practice (form contact area)

Plywood sheets are 4 ft by 8 ft. How many whole sheets are needed to cover 300 square feet of form contact area, with no waste allowance?

• a.38 sheets
• b.9 sheets
• c.75 sheets
• d.10 sheets✓

Each sheet covers 32 sq ft; 300 ÷ 32 = 9.4, so 10 whole sheets are needed. 9 sheets leave part of the area uncovered, 38 divides by 8 and 75 divides by 4, which are single dimensions, not the sheet area.Estimating practice (sheet count)

A crew of 3 finishers each finishes about 150 square feet per hour. About how many hours will they need for 1,800 square feet?

• a.4 hours✓
• b.12 hours
• c.36 hours
• d.6 hours

1,800 ÷ 150 = 12 worker-hours; ÷ 3 finishers = 4 hours on the clock. 12 hours forgets to split the work across the crew, 36 multiplies by crew size instead of dividing, and 6 assumes only two finishers.Estimating practice (labor productivity)

A 6.5-cubic-yard order costs $185 per yard, plus a $90 short-load fee and a $650 pump charge. What is the total?

• a.$2,032.50
• b.$1,852.50
• c.$1,292.50
• d.$1,942.50✓

6.5 × 185 = $1,202.50; + 90 + 650 = $1,942.50. $1,852.50 leaves out the short-load fee, $1,292.50 leaves out the pump charge, and $2,032.50 counts the short-load fee twice.Estimating practice (cost takeoff)

A 24-ft by 30-ft pad needs a 6-in compacted base. About how many cubic yards of base is that?

• a.About 26.7 cubic yards
• b.About 40.0 cubic yards
• c.About 13.3 cubic yards✓
• d.About 8.9 cubic yards

24 × 30 = 720 sq ft; × 0.5 ft = 360 cu ft; ÷ 27 = 13.3 cu yd. Dividing by 9 gives 40.0, using 4 in gives 8.9, and using 12 in gives 26.7.NIST Handbook 44 (2026), Appendix C

A takeoff gives 4.5 cubic yards of concrete. How many cubic feet is that?

• a.121.5 cubic feet✓
• b.13.5 cubic feet
• c.40.5 cubic feet
• d.0.17 cubic feet

One cubic yard is 27 cu ft exactly, so 4.5 × 27 = 121.5 cu ft. 13.5 multiplies by 3 (feet in a yard), 40.5 multiplies by 9 (sq ft in a sq yd), and 0.17 divides instead of multiplying.NIST Handbook 44 (2026), Appendix C

A grading plan shows 2.5 acres of disturbed soil. How many square feet is that?

• a.1,089,000 square feet
• b.108,900 square feet✓
• c.87,120 square feet
• d.17,424 square feet

One acre is exactly 43,560 sq ft, so 2.5 × 43,560 = 108,900. 87,120 is only two acres, 17,424 divides by 2.5 instead of multiplying, and 1,089,000 slips a decimal place.NIST Handbook 44 (2026), Appendix C

A pump places concrete at 100 cubic yards per hour, a rate Caltrans calls easily attainable. About how long does an 85-cubic-yard pour take at that rate?

• a.3 hours 24 minutes
• b.8 hours 30 minutes
• c.85 minutes
• d.51 minutes✓

85 ÷ 100 = 0.85 hr, which is 51 minutes. 85 minutes treats yards per hour as yards per minute, 3 h 24 min uses the 25 cu yd per hour crane-and-bucket rate, and 8 h 30 min uses 10 cu yd per hour.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 5

A wall is 8 in thick, 4 ft high and 50 ft long. About how much concrete does it hold?

• a.About 3.7 cubic yards
• b.About 7.4 cubic yards
• c.About 4.9 cubic yards✓
• d.About 14.8 cubic yards

8 in = 0.667 ft; 0.667 × 4 × 50 = 133.3 cu ft; ÷ 27 = 4.9 cu yd. Dividing by 9 gives 14.8, using 6 in gives 3.7, and using 12 in gives 7.4.NIST Handbook 44 (2026), Appendix C

On a public job the rebar factor is 180 pounds per cubic yard. About how much steel belongs with a 25-cubic-yard element?

• a.2.25 tons✓
• b.0.14 tons
• c.4.5 tons
• d.22.5 tons

25 × 180 = 4,500 lb; ÷ 2,000 lb per ton = 2.25 tons. 4.5 divides by 1,000 as if it were a metric ton, 0.14 divides cubic yards by the factor, and 22.5 slips a decimal place.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 2

Eight round columns are each 16 in in diameter and 9 ft tall. About how much concrete do they take in all?

• a.About 11.2 cubic yards
• b.About 2.1 cubic yards
• c.About 3.7 cubic yards✓
• d.About 14.9 cubic yards

Radius = 8 in = 0.667 ft; area = π × 0.667² = 1.396 sq ft; × 9 ft = 12.57 cu ft each; × 8 = 100.5 cu ft; ÷ 27 = 3.7 cu yd. Using the 16-in diameter as the radius gives 14.9, dividing by 9 gives 11.2, and using a 12-in diameter gives 2.1.NIST Handbook 44 (2026), Appendix C