Earthwork and Paving (C-12) · Lesson 4 of 6

Aggregate Base: Tons to Order, Lifts, and Grade Tolerance

"Aggregate Base: Tons to Order, Lifts, and Grade Tolerance" is lesson 4 of 6 in the Earthwork and Paving (C-12) Learning Hub. It opens with "Designed in Compacted Yards, Bought by the Ton" and works through 5 short steps, then a worked example you can check yourself against.

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Steps in this lesson

  1. Designed in Compacted Yards, Bought by the Ton
  2. Volume First, Then Weight
  3. Lift Thickness Rule (Caltrans Section 26-1.03D)
  4. Compaction and Grade Tolerance (Section 26-1.03E)
  5. Over-Building Is Expensive

The worked example in the course applies this lesson to a realistic job in 6 steps, from "Convert thickness to feet" through "Cubic yards".

What you'll be able to do

  • Explain the main idea of "Aggregate Base: Tons to Order, Lifts, and Grade Tolerance" in plain language you can use on the exam.
  • Apply this step with confidence: "Lift Thickness Rule (Caltrans Section 26-1.03D)".
  • Apply this step with confidence: "Compaction and Grade Tolerance (Section 26-1.03E)".
  • Apply this step with confidence: "Over-Building Is Expensive".
  • Test yourself on the worked example and the quick-check quiz inside the classroom.
Aggregate Base: Tons, Lifts, and ToleranceBASE SECTION UNDER THE PAVINGLot 150 ft x 60 ft, 8 in compacted baseLIFT 2 - 4 in (0.33 ft)compact to 95% RCLIFT 1 - 4 in (0.33 ft)compact to 95% RCCompacted subgradeRed dashes = top of grade, within 0.05 ftEach lift must stay at or under 0.50 ftORDER TONS FROM COMPACTED YARDSArea = 150 x 60 = 9,000 sq ftVolume = 9,000 x 0.667 ft = 6,000 cu ft6,000 / 27 = 222.2 compacted cu ydTons = 222.2 x 2.1 = 467 tonsCOST OF 0.05 FT OVER-BUILD9,000 x 0.05 = 450 cu ft = 16.7 cu yd16.7 x 2.1 = 35 tons of extra rock2.1 tons per cu yd is an examplefigure - use your supplier ticket weightsOrder about 467 tons of Class 2 aggregate baseTwo 4-inch lifts, each at least 95% relative compactionFinish within 0.05 ft of grade - the extra 0.05 ft alone is 35 tonsSource: 2025 Caltrans Std. Specs 26-1.03D (lifts) and 26-1.03E (95% RC, 0.05 ft tolerance)CC
The diagram for this lesson, exactly as it appears in the Learning Hub.

The first steps of this lesson

Step 1: Designed in Compacted Yards, Bought by the Ton

The plans give the aggregate base (AB) as a thickness - for example 8 inches of Class 2 aggregate base - measured after compaction. The quarry sells by the ton and each truck leaves with a weight ticket. Your job is to convert a compacted volume into tons, using a tons-per-cubic-yard figure for the material. This lesson uses 2.1 tons per compacted cubic yard as a labeled example value; the CSLB C-12 study guide's own sample question hands you a figure in the problem (1.5 tons per cubic yard), and on a job the supplier's weight tickets rule.

Step 2: Volume First, Then Weight

Compacted cubic yards = area (sq ft) x thickness (ft) / 27. Convert inches to feet before multiplying: 8 inches is 8 / 12 = 0.667 ft. Then tons = cubic yards x tons per cubic yard. Round the order up to whole truckloads, because the last partial load still costs a delivery. If AB is paid by weight on a Caltrans job, the Engineer deducts the weight of water in excess of the optimum moisture content plus 1 percent (2025 Caltrans Standard Specifications section 26-1.04), so very wet loads do not pay by the ton.

The remaining 3 steps, the worked example and the quiz are in the course. This is a preview. The full lesson, with the step-by-step explanations, a worked example and a quick-check quiz, is inside the classroom.

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