Caltrans Section 26

Class 2 Road Base Calculator — Caltrans Spec Aggregate

Q: What is Caltrans Class 2 Road Base?

Class 2 Aggregate Base is a Department of Transportation certified crushed rock specification defined in Caltrans Section 26. It features strict 3/4" or 1-1/2" gradation, high shear resistance (R-value > 78), and a mandatory Sand Equivalent of 30+ to prevent clay contamination.

Q: How much does a yard of Class 2 base weigh in tons?

One cubic yard of compacted in-place Class 2 Road Base weighs approximately 1.86 tons (3,725 lbs) at standard 138 lb/ft³ density. When ordering loose material from a California quarry, estimate 1.60 tons per loose cubic yard.

Q: Can I use recycled crushed concrete as Class 2 base in California?

Yes! Caltrans Section 26 explicitly permits Recycled Class 2 Aggregate Base made from crushed reclaimed asphalt concrete (RAP) and portland cement concrete (PCC), provided it meets the required grading, R-value, and Sand Equivalent (SE > 25) standards.

Caltrans Class 2 Aggregate Base (Section 26) is the gold standard structural road base across California, engineered with mandatory Sand Equivalent (SE 30+) and Resistance Value (R-value 78+) metrics.

ASTM / AASHTO Verified

Compaction & Waste Factors Included

Dump Truck Capacity Dispatcher

Imperial Standard (yd³ & Tons)

Class 2 Road Base Calculator — Caltrans Spec Aggregate

Precision volume, tonnage, compaction shrinkage & dump truck dispatcher

Caltrans Section 26

1. Excavation Area & Compacted Depth

Length (ft)

Width (ft)

Compacted Depth (in)

Project Presets:

2. Compaction Shrinkage (%)

3. Grading & Waste Buffer (%)

Geotechnical Material Density: 135 lb/ft³ (1.82 Tons/yd³)

Compacted Dry Density (lb/ft³)

Material Price ($/Ton)

Material Estimation Output

Total Weight to Order (incl. buffers)

25.1

Tons (approx. 1.3 Tri-Axle Loads)

Compacted In-Place Vol 11.1 yd³ 300 cu ft in place

Loose Delivery Volume 13.8 yd³ +24% combined buffer

Lift Schedule 2 Lifts (3.8" ea) 7.5" total loose spread

Material Subtotal $778.00 Excl. freight & taxes

Engineering Recommendation:

For a 6.0" compacted Class 2 Road Base Calculator base, spread in 2 separate loose lifts of 3.8". Mist with water to achieve optimum compaction before running a 3,000+ lb plate compactor.

Caltrans Highway Standard

Caltrans Class 2 Aggregate Base (Section 26) Engineering Data Sheet

Caltrans Standard Specs Section 26

Compacted Dry Density 138 lb/ft³ (2,210 kg/m³)

Weight per Volume 1.86 Tons / yd³

Sieve Gradation 3/4" (19mm) or 1-1/2" (37.5mm) Caltrans AB

Compaction Factor +18% to +22%

Optimum Moisture (OMC) 6.0% – 8.0% by Weight

CBR Bearing Ratio 85% – 105% (R-Value 78+)

Governing Standard Caltrans Standard Specifications Section 26

Max Lift Thickness 3" to 4" Maximum per Pass

Sand Equivalent (SE) SE > 30 Minimum (CTM 217)

Resistance Value (R-Value) R > 78 Minimum (CTM 301)

Durability Index Durability > 35 (CTM 229)

Fractured Face Ratio 90% with 1+ fractured face, 50% with 2+

Civil Engineering Math

How to Calculate Caltrans Class 2 AB Tonnage, Loose Volume & Truckloads

Mathematical formulas for Caltrans Class 2 AB volume conversions, compaction factors (+18–22%), and California Super Dump loads.

1 Surface Area

Area Geometry

Area = Length (ft) × Width (ft)

Determine the square footprint of your driveway, patio, slab, or pad. For curved shapes, break the area into offset rectangles.

2 In-Place Volume

Compact Volume

Vol (yd³) = (Area × Depth_in ÷ 12) ÷ 27

Convert design depth to volumetric units. This represents the final solid in-place compacted volume required after rolling.

3 Compaction Loss

Gross Loose Volume

Loose Vol = Compact Vol × (1 + 20%)

Quarries sell aggregate in its loose, aerated state. Adding 20% accounts for void compression under mechanical vibration.

4 Weight & Ordering

Quarry Tonnage

Tons = Vol (yd³) × 1.82 × 1.05 Waste

Convert volume to bulk weight using dense-graded stone density, adding 5% for site grading tolerance and edge bevel waste.

Real-World Numerical Example

Worked Calculation: 1,000 sq ft Driveway at 6" Compacted Depth

Target Material: Class 2 Road Base Calculator

✓

Step 1 — Calculate In-Place Volume:

1,000 sq ft × (6 ÷ 12 ft) = 500 cu ft ÷ 27 = 18.52 cubic yards

✓

Step 2 — Apply +20% Compaction & +5% Waste:

18.52 yd³ × 1.20 (shrinkage) × 1.05 (waste) = 22.95 loose cubic yards

✓

Step 3 — Multiply by Quarry Bulk Density (1.86 Tons / yd³):

18.52 compacted yd³ × 1.24 combined factor × 1.82 Tons/yd³ = 41.8 Tons total order weight

✓

Step 4 — Calculate Hauling & Estimated Material Cost:

42 Tons ÷ 20-ton Tri-Axle = 3 Dump Truck Loads | Quarry Stone Cost: ~$1596

Order Sheet Summary

Total Order Weight: 41.8 Tons

Loose Volume: 23.0 yd³

Truckloads Required: 3 Tri-Axle Loads

Estimated Quarry Price: $1596

CTM 202 / Caltrans Sieve Standard

Caltrans Section 26 3/4" & 1-1/2" AB Sieve Gradation Inspector

Grain-size distribution testing showing percentage passing standard sieves for Caltrans Class 2 AB with strict limits on plastic fines.

Standard Sieve Size % Passing (Design Target)

1 1" (25.0 mm)

Spec: 100% 100%

2 3/4" (19.0 mm)

Spec: 90% – 100% 95%

3 3/8" (9.5 mm)

Spec: 50% – 70% 60%

4 No. 4 (4.75 mm)

Spec: 35% – 55% 45%

5 No. 30 (600 µm)

Spec: 12% – 25% 18%

6 No. 200 (75 µm)

Spec: 3% – 9% 6%

Selected Sieve Analysis Spec: 100%

1" (25.0 mm)

Target Percent Passing

100%

Geotechnical Function:

Caltrans 3/4" Class 2 top control sieve.

Dense-Grading Principle: Continuous particle distribution from top size to sub-75µm fines locks stone voids, reducing empty space from 35% to <12% under vibration.

Civil Estimating & Geotechnical Engineering Review

Peer-Verified

Formulas, density conversions, and lift recommendations are modeled after AASHTO M147 (Materials for Aggregate and Soil-Aggregate Subbase) and ASTM C33/D2922 standards. Reviewed by licensed civil engineers and heavy highway earthwork estimators.

• AASHTO M147 Compliant • ASTM C136 Sieve Analysis • ASTM D698 / D1557 Proctor Compaction

Pavement Structural Section

Caltrans Highway & Parking Lot Structural Layer Cross-Section

Structural layer profile from Rubberized HMA wearing surface down through Class 2 AB base lifts and California adobe clay subgrade.

Caltrans RHMA / HMA Surface

Rubberized Hot Mix Asphalt (Type A/G)

2.0" – 4.0" Pavement Layer

Class 2 AB Top Lift

Caltrans 3/4" Class 2 Base

3.0" Compacted 95% Relative Compaction (CTM 216)

Class 2 AB Bottom Lift

Caltrans 3/4" Class 2 Base

3.0" Compacted 95% Relative Compaction (CTM 216)

Caltrans Class B Geotextile

Non-Woven Polypropylene Fabric

5.5 oz / yd² Section 88 Spec

Prepared California Subgrade

Proof-Rolled Native Soil / Adobe Clay

6.0" Compacted 95% CTM 216 Compaction

Layer Inspection 2.0" – 4.0"

Caltrans RHMA / HMA Surface

Rubberized Hot Mix Asphalt (Type A/G)

Compaction Standard: Pavement Layer

Engineering Function & Placement:

Flexible surface layer designed for high California traffic volumes.

Subgrade Rule: Never place aggregate over uncompacted or organic subsoil. Proof-roll native soil with a loaded dump truck before laying the geotextile separation membrane.

Structural Depth Schedules

Caltrans Class 2 Base Thickness Schedules for Expansive Adobe Clay Soils

Recommended layer thicknesses for California driveways, parking structures, and public works roads over expansive clay subgrades.

Structural Depth & Lift Schedule by Use Case

Recommended compacted thickness and placement lift sequences

AASHTO / ICPI Guidelines

Project Application	Recommended Depth	Lift Sequence	Target Compaction	Engineering Note
Pedestrian Walkways & Garden Paths	3.0 – 4.0 inches	1 Lift (3–4" loose)	95% Standard Proctor	Edge restraints recommended to prevent foot-traffic gravel scatter. Geotextile optional on firm soil.
Paver Patio & Outdoor Living Slabs	4.0 – 6.0 inches	1–2 Lifts (3" compacted each)	98% Modified Proctor	Top with 1.0 inch of ASTM C33 concrete bedding sand. Screed flat without compacting sand prior to paver placement.
Light Residential Driveways (Cars & SUVs)	6.0 inches	2 Lifts (3" compacted each)	98% Modified Proctor	Crown driveway 1/4" per foot from center to edges. Install 4–6 oz non-woven geotextile over clay subgrades.
Heavy Vehicle, RV & Boat Storage Pads	8.0 – 10.0 inches	3 Lifts (3" compacted each)	100% Modified Proctor	Over-excavate pad footprint 12 inches beyond parked tire footprint for lateral edge confinement.
Shed, Pole Barn & Equipment Foundations	5.0 – 6.0 inches	2 Lifts (3" compacted each)	98% Modified Proctor	Extend gravel pad 12–18 inches beyond shed drip edge to capture roof runoff without foundation erosion.
Commercial Parking Lots & Highway Sub-Base	10.0 – 14.0 inches	3–4 Lifts (3–4" compacted each)	100% AASHTO T180	Requires proof-roll QA testing with loaded dump truck (20-ton axle) and nuclear density gauge verification.

Geotechnical Subgrade Rule

Subgrade Soil Adjustments & Geotextile Requirements

ASTM D1883 Subgrade Evaluation

CBR > 15%

Dense Gravel / Coarse Sand Subgrade

Base Depth Mod: Standard design depth (0" added)

Geotextile: Optional / Not Required

CBR 6% – 10%

Firm Silt / Sandy Loam Subgrade

Base Depth Mod: +1.0 to +2.0 inches extra base

Geotextile: Recommended (4 oz Fabric)

CBR 2% – 4%

Expansive Clay / Black Cotton Soil

Base Depth Mod: +2.0 to +4.0 inches extra base

Geotextile: Mandatory (6 oz Non-Woven Geotextile)

CBR < 2%

Wet Saturated / Organic Muck Subgrade

Base Depth Mod: +4.0" to +6.0" Base + 4" Surge Stone

Geotextile: Mandatory (Class 1 Geotextile + Biaxial Geogrid)

CTM 216 Relative Compaction

Caltrans Test Method CTM 216 Relative Compaction & Moisture Lab

California field compaction simulator demonstrating how 7.0% OMC achieves the mandatory 95% Relative Compaction under vibratory steel rollers.

1. Loose Lift Thickness (Inches) 4.0" Loose Lift

2.0" (Hand Tamper) 4.0" (Max Plate Compactor) 6.0" (Small Roller) 8.0" (Heavy 5-Ton Roller)

2. Moisture Content (% by Dry Weight) 7% OMC (Optimum)

2% (Too Dry / Friction) 7% (Optimum Peak) 12% (Over-Saturated / Pumping)

Compaction Result: Optimal 98% Proctor

At 7% moisture and 4.0" loose lift, stone dust particles lubricate under vibration, packing completely into rock voids without excess pore water pressure.

Field Compaction Parameters

Target Proctor Density: 95% Relative Compaction (Caltrans Test Method CTM 216)

Compaction Shrinkage: +20% extra loose volume

Water Dosage per 100 sq ft: ~19 Gallons

Compactor Passes: 5 to 7 passes with vibratory steel drum

Recommended Machinery:

Heavy vibratory tandem roller (3-5 ton) or 4,000+ lb plate compactor.

Commercial Hauling Logistics

California Super Dump & End Dump Delivery Fleet Dispatcher

Calculate deliveries using California-standard Super Dumps (19–25 tons payload) and transfer trucks with strict bridge weight compliance.

Selected Vehicle Specification

Tri-Axle Commercial Dump Truck

Most economical rate per ton (Contractor standard)

Payload Weight 18–22 Tons

Payload Volume 11–13.5 yd³

Clear Gate Width 12 ft Min

Overhead Wire Clear 24 ft Raised

Site Access Rule: A loaded tri-axle weighs ~65,000 lbs (32.5 tons gross). Ensure driveway culverts and bridges are rated for this axle weight before scheduling delivery.

Delivery Site Checklist:

Check overhead tree branches and power/phone wires.

Mark septic tanks, leach fields, and sprinkler heads.

Never dump on a cross-slope >8% (dump bed tip-over risk).

Have driver tailgate-spread stone in a thin pass to save shovel time.

Budget & Labor Estimator

California Class 2 AB Material Pricing, Freight & Contractor Budget Simulator

Estimate California quarry rates ($28–$48/ton), metro freight delivery charges, compactor rentals, and licensed contractor installation costs.

1. Total Project Area (Square Feet) 1,000 sq ft

100 sq ft (Walkway) 600 sq ft (2-Car Pad) 1,200 sq ft (Driveway) 10,000 sq ft (Acre Lane)

2. Material Quarry Price ($ / Ton) $38 / Ton

$15/Ton (Pit Direct Caliche/RCA) $38/Ton (Avg Crusher Run) $75/Ton (Imported Granite)

Equipment & Hauling Options:

Delivery Fee (per truckload)

Equipment Rental

DIY vs Contractor Cost Comparison

DIY Total Cost (Materials + Rental + Delivery)

$1,444

~$1.44 per square foot

Contractor Turnkey Cost (Excavation + Install + Base)

$5,500

~$5.50 per square foot ($4.50 – $7.50 / sq ft range)

DIY Labor Savings: You save approximately $4,056 in contractor excavation and installation labor on this project.

Material Selection Matrix

Caltrans Class 2 AB vs. Class 4 Base & Recycled Aggregate Matrix

Comparison of Caltrans 3/4" Class 2 AB, 1-1/2" Class 2 AB, Class 4 Base, and Crushed Recycled AB (RAP/RCA).

Material Type	CBR Bearing Ratio	Compacted Density	Permeability	Avg Cost / Ton	Recommended Application
Caltrans 3/4" Class 2 AB This Page	90% – 105%	138 lb/ft³	Low (Dense)	$34 – $46	California DOT roads, driveways, commercial parking, city streets
Caltrans 1-1/2" Class 2 AB	95% – 115%	142 lb/ft³	Low	$30 – $40	Heavy industrial yards, deep sub-base, semi-truck loading bays
Class 4 Aggregate Base	50% – 70%	130 lb/ft³	Moderate	$24 – $32	Low-volume temporary access roads, sub-base fill
Crushed Recycled AB	85% – 100%	126 lb/ft³	Low-Moderate	$20 – $28	Sustainable LEED projects, budget driveway foundations

Quality Assurance & Failure Prevention

Caltrans QA Protocol: Sand Equivalent (SE 30+), R-Value & Proof-Rolling

Verification methods for California Test 217 (Sand Equivalent) and California Test 301 (R-Value 78+) to prevent pavement failure.

4 Contractor Field Tests to Verify Density (Without Nuclear Gauge)

💧

Hand-Squeeze Moisture Test

Field Test

Target: Verify Optimum Moisture Content (OMC) before rolling

Execution Procedure: Grab a handful of spread base material and squeeze tightly in a closed fist. Open your hand.

Pass: Aggregate forms a dense, solid clump with zero crumbling and leaves palm damp without dripping liquid. Fail: Crumbles to dust (too dry) or oozes watery mud (too wet).

🚛

Proof-Roll Axle Deflection Test

Field Test

Target: Identify weak subgrade pockets and verify base rigidity

Execution Procedure: Drive a fully loaded tandem or tri-axle dump truck (minimum 10-ton axle weight) at walking speed over the completed base.

Pass: Surface deflection is under 3/8 inch (10mm) with zero visible wheel rutting. Fail: Tire sinks into rut or adjacent gravel waves/heaves upward.

🥾

Heel-Strike Impact Test

Field Test

Target: Fast spot-check for localized loose compaction pockets

Execution Procedure: Drive the heel of a heavy work boot forcefully down into the compacted surface with full body weight.

Pass: Boot heel produces a sharp, ringing thud with zero visible indentation (< 1/8 inch). Fail: Heel punches into stone or dislodges loose gravel scatter.

🔨

Steel Rebar Penetration Test

Field Test

Target: Check full-depth compaction down to the subgrade layer

Execution Procedure: Attempt to drive a standard 1/2-inch (#4) steel rebar or probe into the compacted base using hand pressure.

Pass: Rebar cannot penetrate deeper than 1/2 inch into the stone matrix without a sledgehammer. Fail: Rebar easily slides into base deeper than 2 inches.

Troubleshooting Protocols

Common Road Base Failure Modes & Remediation

Field Repair Checklist

Soft, Spongy Pumping Under Compactor

Critical Severity

Root Cause:

Over-saturation of aggregate or wet, uncompacted native clay subgrade underneath.

Contractor Solution & Fix:

Stop rolling immediately. Allow surface to dry in the sun for 24–48 hours. If subgrade clay is pumping, excavate 4" deeper, install non-woven geotextile fabric, and place 3" of clean surge rock before re-laying base.

Surface Washboarding, Ravelling & Loose Dust

Moderate Severity

Root Cause:

Aggregate was rolled bone-dry without water lubrication, causing surface particles to shear instead of lock.

Contractor Solution & Fix:

Heavily mist surface with garden hose or water truck spray bar to 6%–7% OMC. Scarify top 2 inches with grader teeth or rake, then make 4–6 overlapping passes with a vibratory plate compactor.

Deep Wheel Rutting in Tire Tracks

High Severity

Root Cause:

Lift thickness was spread too deep (> 4.5" loose), resulting in dense top crust over loose bottom aggregate.

Contractor Solution & Fix:

Excavate rutted section. Re-place material in thin loose lifts not exceeding 3.5 to 4.0 inches per pass, compacting each lift to 98% Proctor before spreading the next.

Edge Blowout & Shoulder Erosion

Moderate Severity

Root Cause:

Lack of lateral confinement or insufficient excavation width along outer driveway margins.

Contractor Solution & Fix:

Always excavate base trench 6 to 12 inches wider than the finished road width. Install compacted soil/crushed stone shoulder berms at a 3:1 slope, or install rigid commercial timber/concrete edge restraints.

Field Construction Standard

Step-by-Step Caltrans Class 2 Aggregate Base Placement & Rolling Sequence

California standard installation procedure: subgrade moisture-conditioning, geotextile layout, lift placement, and 0.05-ft grade trimming.

Stage 1 · Day 1 (Morning)

California Subgrade Preparation & Adobe Clay Treatment

QA Checkpoint

Excavate native soil. In many parts of California (Bay Area, Central Valley, LA Basin), expansive adobe clay expands when wet and contracts when dry. Scarify top 6 inches, moisture-condition to +2% over optimum, and compact to 95% CTM 216.

Pro Contractor Tips:

Never compact expansive clay bone-dry; it will swell dramatically during winter rains.

Use a water truck with spray bar for uniform coverage.

Pass/Fail Verification Standard Relative compaction of 95% verified via California Test 216/231.

Stage 2 · Day 1 (Midday)

Geotextile Separation Placement

QA Checkpoint

Roll out Caltrans Section 88 approved non-woven geotextile. Overlap edges 18 inches and pin securely.

Pro Contractor Tips:

Mandatory over Bay Area bay mud or Central Valley alluvial silt.

Anchor edges in shallow keyway trench.

Pass/Fail Verification Standard Fabric is flat, aligned, and pinned against wind lift.

Stage 3 · Day 1 (Afternoon)

Class 2 AB First Lift Placement

QA Checkpoint

Spread 4-inch loose lift using a motor grader or skid steer. Apply water to bring aggregate to 7.0% OMC. Mix stone with grader blade to prevent segregation of fines from coarse aggregate.

Pro Contractor Tips:

Prevent aggregate segregation: do not push dry stone into long windrows.

Check Sand Equivalent: material must not contain muddy clay balls.

Pass/Fail Verification Standard Moisture and thickness check: Uniform 4-inch loose depth with no stone segregation.

Stage 4 · Day 1 (Late Afternoon)

Vibratory Roller Compaction

QA Checkpoint

Roll with a 3-to-5 ton vibratory steel roller. Execute 5 to 7 passes. The vibratory action forces Sand Equivalent fines into inter-particle voids.

Pro Contractor Tips:

Roll from low side to high side on superelevated slopes.

Maintain consistent roller travel speed under 3 mph.

Pass/Fail Verification Standard 95% CTM 216 relative compaction verified.

Stage 5 · Day 2

Final Lift, Cross-Slope Profiling & Finish Roll

QA Checkpoint

Place final 3-inch compacted lift. Cut final grade with grader blade to ensure exact cross-slope. Finish roll statically to seal the surface.

Pro Contractor Tips:

Caltrans Section 26 requires finished surface tolerance within 0.05 ft of design grade.

Apply asphalt prime coat prior to paving.

Pass/Fail Verification Standard Grade check: Surface within Caltrans 0.05-ft tolerance.

Geotechnical Engineering Guide

California Civil Engineering Manual: Caltrans Section 26 Class 2 Base

Technical manual on Sand Equivalent criteria, R-value lateral resistance, and managing high-PI California adobe soils.

Caltrans Standards Civil Standard Section 01

Caltrans Section 26 Specifications: 3/4" vs. 1-1/2" Class 2 Aggregate Base

Caltrans Standard Specifications Section 26 governs Aggregate Base across California public works and private commercial engineering projects. Caltrans defines two primary gradations: 3/4-inch Maximum and 1-1/2-inch Maximum. 3/4" Class 2 AB is the standard specification for roadway top-base, parking lots, and residential driveways because it finishes smoothly and grades easily around forms and utility vaults. 1-1/2" Class 2 AB is specified for deep structural sub-base sections (8 to 14 inches) under high-speed freeway pavements and heavy container ports, where larger stone diameters deliver superior shear distribution.

California Test Methods Civil Standard Section 02

Sand Equivalent (SE 30+) and Resistance Value (R-Value 78+) Testing

Two strict geotechnical parameters differentiate Caltrans Class 2 base from generic road gravel: Sand Equivalent (California Test 217) and Resistance Value (California Test 301). Sand Equivalent measures the relative proportion of harmful clay-like plastic fines versus beneficial sand dust in the aggregate. Caltrans mandates an SE of not less than 30 (or 25 for recycled base). The R-value measures the base material's resistance to plastic deformation under vertical wheel load while under lateral confinement. Class 2 AB requires an R-value of 78 or higher, ensuring the roadbed will not develop wheel ruts under sustained California freeway freight traffic.

Specialized Hubs