Austroads Spec

Australia Road Base Calculator — 20mm DGB & Crushed Rock Tonnes

Q: What is 20mm Road Base in Australia?

20mm Road Base (also known as DGB20 or Dense Graded Base 20mm) is the standard Australian crushed rock aggregate used for driveways, council roads, and building pads. It contains sharp crushed rock ranging from 20mm down to fine quarry dust that compacts into an immovable pavement.

Q: How many tonnes of road base are in 1 cubic metre?

One cubic metre (1 m³) of compacted in-place 20mm road base weighs approximately 2.20 tonnes (2,200 kg). In its loose, uncompacted state on a tipper truck bed, it weighs approximately 1.80 tonnes per cubic metre.

Q: How thick should a road base driveway be in Australia?

For standard residential driveways carrying cars and 4WDs, a 100mm to 150mm compacted base is standard. For rural driveways carrying horse floats, boat trailers, or farm trucks, install a 150mm to 200mm base laid in two lifts.

Q: What is the difference between an Australian Body Truck and a Truck & Dog?

A Body Truck is a rigid single-chassis tipper truck that carries 10 to 12 tonnes (approx. 5–6 m³). A Truck & Dog is a body truck towing a multi-axle dog trailer that carries 28 to 33 tonnes (approx. 14–16.5 m³), offering much lower freight costs on larger projects.

Calculate Australian standard 20mm and 40mm Dense Graded Road Base (DGB20 / DGB40) cubic metres (m³), compacted tonnes, and Body Truck / Truck & Dog delivery loads per Austroads and State Road Authority guidelines.

ASTM / AASHTO Verified

Compaction & Waste Factors Included

Dump Truck Capacity Dispatcher

Metric Standard (m³ & Tonnes)

Australian Road Base Calculator (20mm / 40mm DGB)

Calculate compacted m³, metric tonnes (t), and Body Truck / Truck & Dog tipper loads under AS 1289 & RMS 3051

AS 1289 / RMS 3051

1. Australian Metric Dimensions & Depth

Length (Metres)

Width (Metres)

Depth (mm)

Project Presets:

2. Road Base Specification (Australian Standard)

Tipper Truck Dispatcher: Australian Bulk Logistics

Truck Configuration

Material Price (AUD/tonne)

Metric Civil Engineering Outputs

Total Metric Tonnes (t) to Order

47.5

Metric Tonnes (approx. 2 Truck & Dog loads)

Compacted In-Place Vol 18.0 m³ 120 m² area @ 150mm

Loose Delivery Volume 21.6 m³ +20% compaction factor

Transverse Cross-Fall 1:33 (3.0%) 120mm crown height

Estimated Total Cost $2,720 AUD Materials + Delivery

Australian Construction Rules:

Lay in maximum 100mm compacted lifts.
Moisture-condition to 6.5% OMC (AS 1289.5.2.1).
Compact to 98% MMDD with twin-drum vibratory roller.
Provide minimum 3% cross-fall for stormwater drainage.

Australian Civil Standard

Australian Road Base Technical Data Sheet (RMS 3051, MRTS05 & VicRoads 812)

Austroads / AS 1289 / RMS 3051

Metric Bulk Density 2.20 t/m³ (2,200 kg/m³ Compacted)

Loose Metric Density 1.80 t/m³ (1,800 kg/m³ Loose Tipper Weight)

Sieve Gradation 20mm (DGB20) or 40mm (DGB40) Minus

Compaction Factor +18% to +22%

Optimum Moisture (OMC) 5.5% – 7.5% by Weight

CBR Bearing Ratio 80% – 100% (High Australian Bearing)

Governing Standard RMS 3051 / TMR MRTS05 / VicRoads 812 / AS 1289

Max Lift Thickness 100mm to 125mm Maximum per Pass

Permeability Low (Impermeable when vibrated)

Linear Shrinkage < 3.5% (TMR MRTS05 Spec)

Metric Civil Math

How to Calculate Australian 20mm DGB Tonnes, Cubic Metres & Tipper Loads

Mathematical formulas for converting square metres and depth in millimetres into solid m³, applying +18% compaction shrinkage, and converting to tonnes (2.20 t/m³).

1 Surface Area

Area Geometry

Area = Length (m) × Width (m)

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 (m³) = Area × (Depth_mm ÷ 1000)

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

Tonnes = Vol (m³) × 2.20 t/m³ × 1.05

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: 100 m² Driveway at 150 mm Compacted Depth

Target Material: Australia Road Base Calculator

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Step 1 — Calculate In-Place Volume:

100 m² × 0.15 m depth = 15.0 m³ compacted volume

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

15.0 m³ × 1.20 (shrinkage) × 1.05 (waste) = 18.6 m³ gross loose material

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Step 3 — Convert to Quarry Scale Weight (2.20 t/m³):

15.0 compacted m³ × 2.20 tonnes/m³ × 1.05 waste = 34.7 Tonnes quarry weight (arrives as 18.6 loose m³)

✓

Step 4 — Calculate Hauling & Estimated Material Cost:

41 Tonnes ÷ 12 t Body Truck = 4 Delivery Loads | Estimated Material Cost: ~$1968 AUD

Order Sheet Summary

Total Order Weight: 41.0 Tonnes

Loose Volume: 18.6 m³

Truckloads Required: 4 Body Truck Loads

Estimated Quarry Price: $1968 AUD

AS 1141.11 Particle Analysis

Australian DGB20 / DGB40 Particle Size Distribution & AS 1141 Gradation

Laboratory grain-size distribution analysis for Australian 20mm Dense Graded Base (DGB20) manufactured from hard basalt, granite, or hornfels rock.

Standard Sieve Size % Passing (Design Target)

1 26.5 mm

Spec: 100% 100%

2 19.0 mm

Spec: 95% – 100% 98%

3 13.2 mm

Spec: 70% – 85% 78%

4 4.75 mm

Spec: 35% – 55% 45%

5 0.425 mm

Spec: 12% – 28% 20%

6 0.075 mm

Spec: 4% – 11% 7%

Selected Sieve Analysis Spec: 100%

26.5 mm

Target Percent Passing

100%

Geotechnical Function:

Maximum oversize 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.

Road Base Calculator Standards & Editorial Desk

Standards-Based

All mathematical models, dry densities, and lift schedules published on Road Base Calculator are derived directly from published civil engineering standards: AASHTO M147, ASTM C33 / D2940, ASTM D698 / D1557, and state DOT specifications. Read our Methodology and our Editorial & Review Policy. Have a quarry test report or correction? Submit a correction.

• AASHTO M147 Compliant • ASTM C136 Sieve Analysis • ASTM D698 / D1557 Proctor Compaction • State DOT Calibrated (TxDOT, Caltrans, VDOT, CDOT)

Austroads Pavement Profile

Austroads Pavement Cross-Section: Base Course, Sub-base & Subgrade Profile

Cross-sectional structural profile showing bitumen spray seal, 150mm 20mm DGB base course, Bidim non-woven geofabric, and reactive clay subgrade.

Two-Coat Bitumen Spray Seal / Asphalt

C170 Bitumen + 14mm/7mm Aggregate

25 – 40mm Wearing Surface

20mm Road Base Course (DGB20 Top Lift)

20mm Crushed Basalt / Granite DGB

75mm Compacted 98% MMDD (AS 1289.5.2.1)

20mm Road Base Course (DGB20 Bottom Lift)

20mm Crushed Basalt / Granite DGB

75mm Compacted 95% MMDD (AS 1289.5.2.1)

Non-Woven Geofabric (Bidim A14/A19)

Non-Woven Polypropylene Geotextile

140–200 g/m² Subgrade Stabilizer

Prepared Native Subgrade

Compacted Native Soil / Clay

150mm Proof-Rolled 95% Standard Compaction

Layer Inspection 25 – 40mm

Two-Coat Bitumen Spray Seal / Asphalt

C170 Bitumen + 14mm/7mm Aggregate

Compaction Standard: Wearing Surface

Engineering Function & Placement:

Waterproof seal protecting road base from tropical rain.

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

Austroads Road Base Depth Recommendations for Reactive Black Soil & Driveways

Recommended layer thicknesses: 100mm for paths, 150mm for residential driveways, 200mm for rural farm tracks, and 250mm+ for heavy transport pads.

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	75 – 100 mm	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	100 – 150 mm	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)	150 mm	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	200 – 250 mm	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	125 – 150 mm	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	250 – 350 mm	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)

AS 1289.5.2.1 Compaction Lab

AS 1289 Maximum Dry Density (MMDD), OMC & Roller Compaction Guide

Australian compaction simulator demonstrating how 6.5% OMC moisture achieves 98% Modified Maximum Dry Density (MMDD) under heavy twin-drum vibratory 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) 6.5% OMC (Optimum)

2% (Too Dry / Friction) 6.5% (Optimum Peak) 12% (Over-Saturated / Pumping)

Compaction Result: Optimal 98% Proctor

At 6.5% 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: 98% Modified Maximum Dry Density (MMDD AS 1289.5.2.1)

Compaction Shrinkage: +20% extra loose volume

Water Dosage per 100 sq ft: ~20 Gallons

Compactor Passes: 6 passes with 2-to-5 tonne vibratory roller

Recommended Machinery:

2-to-5 tonne twin-drum vibratory steel roller or 35+ kN reversible plate compactor.

Australian Hauling Logistics

Australian Tipper Truck Logistics: Body Trucks vs. Truck & Dog Deliveries

Calculate tipper truck deliveries across Australian Body Trucks (10–12 tonnes / 5–6 m³), Truck & Dog combinations (28–33 tonnes / 14–16.5 m³), and Semi Tippers.

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

Australian Road Base Cost Simulator: Quarry Rates (AUD/Tonne) & Contractor Quotes

Estimate Australian quarry direct rates ($35–$60 AUD/tonne), local tipper delivery charges, roller hire, and professional 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) $48 / Ton

$15/Ton (Pit Direct Caliche/RCA) $48/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.

Australian Material Matrix

Australian 20mm DGB vs 40mm Sub-base vs Recycled Crushed Concrete Matrix

Compare 20mm Dense Graded Base (DGB20), 40mm Sub-base (DGB40), Recycled Crushed Concrete (DGB Recycled), and Decomposed Granite (DG).

Material Type	CBR Bearing Ratio	Compacted Density	Permeability	Avg Cost / Ton	Recommended Application
Road Base 20mm (DGB20) This Page	80% – 100%	2.20 t/m³	Low (Dense)	$42 – $55 AUD	Driveways, council roads, parking lots, concrete/paver sub-base
Road Base 40mm (DGB40)	90% – 110%	2.25 t/m³	Low	$38 – $48 AUD	Heavy haul roads, deep sub-base, rural farm tracks
Crushed Concrete (Recycled DGB)	85% – 105%	2.05 t/m³	Low-Moderate	$28 – $38 AUD	Sustainable commercial sub-base, hardstands, budget drives
Decomposed Granite (DG)	40% – 60%	1.95 t/m³	Moderate	$65 – $95 AUD	Garden pathways, walking tracks, decorative driveways

Quality Assurance & Failure Prevention

Australian Field QA: AS 1289 Compaction Testing, Proof-Rolling & 3% Cross-Fall

Verification methods for AS 1289 dry density, proof-rolling with loaded tipper trucks, and establishing a 3% (1:33) cross-fall for tropical downpours.

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 Australian Road Base Driveway & Pad Construction Sequence

Complete Australian installation sequence: reactive clay subgrade excavation, Bidim geofabric placement, 100mm lift spreading, roller compaction, and two-coat bitumen seal.

Stage 1 · Day 1 (Morning)

Excavation & Proof-Rolling Reactive Clay Subgrade

QA Checkpoint

In Australia, native soils frequently contain reactive black soils or expansive clay (CBR 2%–3%). Excavate to design depth (typically 200mm to allow 150mm base + 50mm surface). Proof-roll with loaded tipper truck to identify soft heaving zones.

Pro Contractor Tips:

Never place road base directly on dry, cracked reactive clay; moisture-condition first.

Over-excavate 150mm wider on both sides for edge support.

Pass/Fail Verification Standard Proof-roll passes show zero subgrade pumping.

Stage 2 · Day 1 (Midday)

Non-Woven Geofabric (Bidim) Placement

QA Checkpoint

Roll out non-woven geotextile fabric (such as Bidim A14/A19) across the excavated subgrade. Overlap seams by 500mm.

Pro Contractor Tips:

Geofabric prevents heavy basalt stone from punching into wet clay subgrade.

Pin securely against wind.

Pass/Fail Verification Standard Fabric is flat and pinned.

Stage 3 · Day 1 (Afternoon)

First 100mm Loose Lift & Moisture Conditioning

QA Checkpoint

Spread first 100mm loose lift of 20mm DGB with bobcat or grader. Apply water spray to achieve Optimum Moisture Content (6.5% OMC according to AS 1289.5.2.1).

Pro Contractor Tips:

Australian sun dries stone quickly; mist continuously during spreading.

Hand squeeze test: forms solid clump without dripping.

Pass/Fail Verification Standard Moisture verified at 5.5%–7.5%.

Stage 4 · Day 1 (Late Afternoon)

Vibratory Roller Compaction

QA Checkpoint

Roll with a 2-to-5 tonne twin-drum vibratory roller or 35+ kN reversible plate compactor. Complete 6 passes.

Pro Contractor Tips:

Roll from low edge upward toward the crown.

Keep roller drums wet.

Pass/Fail Verification Standard 98% Modified Maximum Dry Density (MMDD) achieved.

Stage 5 · Day 2

Second Lift, 3% Cross-Fall & Bitumen Spray Seal

QA Checkpoint

Spread second lift to finished grade. Establish a prominent 3% (1:33) cross-fall to shed torrential downpours. Perform final static roll and apply two-coat bitumen seal or asphalt.

Pro Contractor Tips:

A 3% cross-fall is mandatory under Australian council guidelines to prevent ponding.

Seal outer shoulders with topsoil.

Pass/Fail Verification Standard Cross-fall verified: 30mm fall per metre width.

Geotechnical Engineering Guide

Austroads Engineering Manual: Unbound Flexible Pavements (DGB20 & DGB40)

Technical manual on Australian state specifications (RMS 3051, TMR MRTS05, VicRoads 812), managing reactive black soil clays, and moisture-density physics.

Australian Standards Civil Standard Section 01

Australian Specifications: DGB20 vs. RMS 3051 vs. TMR MRTS05 vs. VicRoads 812

In Australia, civil road base is designated as Dense Graded Base (DGB) or Dense Graded Sub-base (DGS) manufactured from hard basalt, granite, or hornfels rock. Each state road authority establishes strict technical standards: Transport for NSW (TfNSW) RMS 3051 specifies DGB20 as heavily bound or unbound structural road base with strict particle size limits from 20mm down to 75µm fines; Queensland Department of Transport and Main Roads (TMR) MRTS05 governs Type 2.1 to 2.5 road base based on strict California Bearing Ratio (CBR > 80%) and linear shrinkage limits (< 3.5%); VicRoads Section 812 regulates Class 2 and Class 3 Crushed Rock for Victorian highways. All materials must be tested in accordance with Australian Standard AS 1289.

TfNSW 3051 Engineering Standards Civil Standard Section 02

DGB20 vs. DGB40 Density, Compacted Tonnes per m³ & Proof Rolling

In New South Wales, Queensland, and Victoria, 20mm Dense Graded Base (DGB20) has an average compacted dry density of 2.25 to 2.35 tonnes per cubic metre (t/m³), while uncompacted loose material weighs approximately 1.85 to 1.95 t/m³ (an 18% compaction shrinkage factor). 40mm Dense Graded Base (DGB40) or Dense Graded Subbase (DGS40) is utilized for heavy haulage roadbeds with an in-place compacted density of 2.30 to 2.40 t/m³. Under Australian Standard AS 1289 and TfNSW 3051, road base acceptance requires proof rolling with a heavy tri-axle tipper (gross mass >= 20 tonnes) without visible subgrade deflection, rutting, or pumping.

Specialized Hubs