TxDOT Item 247 Spec

Texas Road Base Calculator — TxDOT Item 247 Flexible Base & Caliche

Q: What is TxDOT Item 247 Flexible Base?

TxDOT Item 247 is the Texas Department of Transportation standard specification governing crushed stone, gravel, and caliche aggregate base course. It defines physical requirements including Triaxial compressive strength, liquid limit, plasticity index (PI < 10 or 12), and gradation.

Q: What is the difference between Texas crushed limestone base and caliche?

Crushed limestone (TxDOT Grade 1/2) is hard, quarried limestone with a higher density (136–140 lb/ft³) and lower moisture requirement (5%–7% OMC). Caliche (Type D) is a softer calcareous sediment common in West and South Texas with lower density (125–132 lb/ft³) that cures into a hardened crust under sun and rolling.

Q: How many tons of Texas road base do I need per cubic yard?

For TxDOT Grade 1/2 crushed limestone, 1 compacted cubic yard requires approximately 1.86 tons (3,725 lbs) at 138 lb/ft³ density. For West Texas pit caliche, 1 compacted cubic yard requires approximately 1.72 to 1.78 tons at 128–132 lb/ft³ density.

Q: Why does caliche require more water during compaction than limestone?

Caliche has higher clay/carbonate content and higher porosity, requiring 7% to 9% Optimum Moisture Content (OMC) compared to 5% to 6.5% for crushed limestone. Without adequate water, caliche will fail to bond and will break down into loose powder.

Engineered for Texas civil earthwork conforming to TxDOT Standard Specifications Item 247 (Flexible Base). Accurately calculates crushed limestone (Grades 1 & 2) and South/West Texas pit caliche (Type D).

ASTM / AASHTO Verified

Compaction & Waste Factors Included

Dump Truck Capacity Dispatcher

Imperial Standard (yd³ & Tons)

Texas TxDOT Item 247 Flexible Base Calculator

Calculate Type A Limestone, Type C Caliche & Type D RCA with Texas Belly Dump / End Dump freight logistics

TxDOT Item 247

1. Texas Project Dimensions & Base Depth

Length (Feet)

Width (Feet)

Depth (Inches)

Texas Presets:

2. TxDOT Item 247 Flexible Base Type

Texas Freight & Hauling Logistics: Belly Dump Windrowing

Quarry Haul Radius

Hauling Truck Type

TxDOT Flexible Base Output

Total Texas Flexible Base Required

181.8

Tons (approx. 8 Belly Dump Loads)

Compacted In-Place Vol 79.0 yd³ 2,133 cu ft in place

Loose Delivery Volume 98.8 yd³ +25% compaction factor

Water Required (OMC) 2,990 Gal 8.5% water for cementing

Estimated Total Cost $5,825 Material + Freight

TxDOT Construction Guidelines:

Windrow material with belly dumps and blade to 4" loose lifts.
Apply water thoroughly with spray bar to achieve 100% Tex-114-E.
Compact with sheepsfoot roller followed by pneumatic rubber tires.
Cut a 3% crown (3/8" per foot) to prevent rain puddling.

TxDOT Highway Specification

TxDOT Item 247 Flexible Base (Grade 1, 2, 3) Engineering Specifications

TxDOT Standard Specifications Item 247

TxDOT Specification Type A (Crushed Stone) | Type D (Crushed Caliche)

Typical Depth 6.0" (Driveways) | 8.0"–12.0" (Highway Subgrade)

Target Proctor 100% Tex-113-E Modified Compaction

Moisture Target Test ±1.5% of Optimum Moisture (Tex-113-E)

Triaxial Class Class 1.0 (Grade 1) | Class 1.5–2.3 (Grade 2)

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

Weight per Volume 1.86 Tons / yd³

Plasticity Index PI < 10 (Grade 1/2) | PI < 12 (Grade 3)

Texas Civil Engineering Math

How to Calculate Texas Flexible Base Tonnage, Cubic Yards & Belly Dump Loads

Mathematical equations for TxDOT flexible base volume conversions, compaction shrinkage (+18–22%), and Texas belly dump load division.

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: Texas Road Base Calculator

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Step 1 — Calculate In-Place Volume:

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

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

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

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Step 3 — Convert to Quarry Scale Weight (1.86 Tons / yd³):

18.52 compacted yd³ × 1.82 Tons/yd³ × 1.05 waste = 35.4 Tons quarry weight (arrives as 22.95 loose yd³)

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Step 4 — Calculate Hauling & Estimated Material Cost:

42 Tons ÷ 20-ton Tri-Axle = 3 Dump Truck Loads | Quarry Stone Cost: ~$1218

Order Sheet Summary

Total Order Weight: 41.8 Tons

Loose Volume: 23.0 yd³

Truckloads Required: 3 Tri-Axle Loads

Estimated Quarry Price: $1218

Tex-110-E Particle Size Test

TxDOT Item 247 Flexible Base Particle Size Distribution & Sieve Analysis

Laboratory sieve curve analysis for TxDOT Item 247 Grade 1 and Grade 2 flexible base showing distribution from 1-3/4" down to #200 fines.

Standard Sieve Size % Passing (Design Target)

1 1-3/4" (45.0 mm)

Spec: 100% 100%

2 7/8" (22.4 mm)

Spec: 65% – 90% 78%

3 3/8" (9.5 mm)

Spec: 40% – 70% 55%

4 No. 4 (4.75 mm)

Spec: 25% – 55% 40%

5 No. 40 (425 µm)

Spec: 15% – 30% 22%

6 No. 200 (75 µm)

Spec: 4% – 12% 7%

Selected Sieve Analysis Spec: 100%

1-3/4" (45.0 mm)

Target Percent Passing

100%

Geotechnical Function:

TxDOT Item 247 top size.

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)

Texas Pavement Cross-Section

Texas Highway & Driveway Flexible Base Structural Layer Profile

Cross-sectional structural profile for Texas roadways over high-plasticity Texas Blackland Prairie expansive clay soils.

TxDOT Two-Course Surface Treatment

AC-15P Asphalt + Grade 4 Aggregate

0.75" – 1.0" Surface Seal

TxDOT Item 247 Flexible Base (Top Lift)

Crushed Limestone Grade 1/2

3.5" Compacted 100% Tex-113-E

TxDOT Item 247 Flexible Base (Bottom Lift)

Crushed Limestone Grade 1/2

3.5" Compacted 100% Tex-113-E

Class 1 Geotextile Membrane

Non-Woven Polypropylene Fabric

6 oz / yd² Subgrade Stabilizer

Lime-Stabilized Texas Clay Subgrade

Native Clay + 4% Hydrated Lime

6.0" – 8.0" 95% Tex-114-E

Layer Inspection 0.75" – 1.0"

TxDOT Two-Course Surface Treatment

AC-15P Asphalt + Grade 4 Aggregate

Compaction Standard: Surface Seal

Engineering Function & Placement:

Waterproof seal protecting flexible base.

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

TxDOT Flexible Base Thickness Schedules for High-PI Texas Blackland Clays

Recommended layer thicknesses for Texas ranch roads, residential driveways, oilfield pads, and highway sub-bases over swelling clay.

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)

TxDOT Tex-113-E Compaction Standard

TxDOT Tex-113-E Compaction Testing, Moisture Conditioning & Triaxial Class

Texas compaction simulator demonstrating how 6.5% OMC achieves 100% Tex-113-E density and Triaxial Class 1.0 structural strength.

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: 100% Tex-113-E Modified Compaction

Compaction Shrinkage: +20% extra loose volume

Water Dosage per 100 sq ft: ~18 Gallons

Compactor Passes: 6 to 8 passes with heavy vibratory compactor or pneumatic roller

Recommended Machinery:

Heavy 5-ton vibratory steel roller or 15-ton pneumatic multi-tire roller.

Texas Hauling Logistics

Texas End Dump, Belly Dump & Tandem Hauling Logistics

Calculate Texas truckload capacities across tandem axle dumps (14–16 tons), tri-axle end dumps (18–22 tons), and belly dumps (24–26 tons).

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

Texas Flexible Base Material Cost, Freight & Contractor Estimator

Estimate Texas quarry pricing ($22–$36/ton), rural mileage hauling fees, motor grader grading, and turnkey contractor installation budgets.

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) $29 / Ton

$15/Ton (Pit Direct Caliche/RCA) $29/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.

TxDOT Grade Comparison Matrix

TxDOT Item 247 Grade 1 vs Grade 2 vs Grade 3 vs Texas Caliche Comparison

Direct comparison between TxDOT Grade 1 (high strength), Grade 2 (standard road), Grade 3 (commercial/driveway), and pit caliche.

Material Type	CBR Bearing Ratio	Compacted Density	Permeability	Avg Cost / Ton	Recommended Application
TxDOT Item 247 Grade 1 (Limestone) This Page	Triaxial Class 1.0 (CBR > 100%)	138 lb/ft³	Low	$28 – $36	State highways, heavy commercial aprons, heavy truck pads
TxDOT Item 247 Grade 2 (Commercial)	Triaxial Class 1.5–2.3	136 lb/ft³	Low	$24 – $32	City streets, residential driveways, parking lots
Texas Pit Caliche (Type D)	Triaxial Class 2.3–3.0	132 lb/ft³	Impermeable	$16 – $24	Ranch roads, oilfield pads, budget rural lanes
Recycled Concrete Base (Type E)	Triaxial Class 1.5	126 lb/ft³	Low-Moderate	$18 – $26	Industrial staging yards, budget driveway foundations

Quality Assurance & Failure Prevention

TxDOT Quality Assurance: Triaxial Compressive Strength, Tex-110-E & Proof-Rolling

Verification methods for Tex-117-E Triaxial classification, Tex-106-E plasticity index (< 10), and proof-rolling with heavy water trucks.

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

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Texas Hand-Ribbon Plasticity Check

Field Test

Target: Spot check Plasticity Index (PI) of fines to prevent clay swell

Execution Procedure: Moisten a palm-sized sample of base fines (< #40 sieve) and roll into a 1/8-inch ribbon between thumb and forefinger.

Pass: Ribbon breaks apart before reaching 1 inch in length (indicates low-plasticity PI < 10 conforming to TxDOT Item 247). Fail: Forms long flexible ribbon (excessive active clay).

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Tex-115-E Nuclear Density / Proof-Roll Test

Field Test

Target: Verify 98%–100% Tex-113-E maximum dry density

Execution Procedure: Conduct nuclear gauge density test or walk a fully loaded 25-ton tandem dump truck across the finished base.

Pass: Density exceeds 98% Proctor; truck tires leave zero visible depression (< 1/4 inch). Fail: Noticeable tire tracking or rutting > 1/2 inch.

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Caliche Water Slaking Observation

Field Test

Target: Verify calcium carbonate bonding and prevent powdering

Execution Procedure: Place a dried compacted caliche clump into a shallow cup of water for 5 minutes.

Pass: Clump remains intact with minimal slaking. Fail: Instantly dissolves into watery silt paste (indicates poor cementation or raw subsoil contamination).

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Crown Cross-Slope String-Line Measurement

Field Test

Target: Verify 2% transverse drainage slope for Texas downpours

Execution Procedure: Stretch a mason line from crown centerline to outer edge and measure drop with a line level.

Pass: Minimum 1/4 inch drop per linear foot of half-width (e.g. 2.5-inch crown on a 20-foot wide roadway). Fail: Flat or dished profile.

Troubleshooting Protocols

Common Road Base Failure Modes & Remediation

Field Repair Checklist

Rapid Caliche Surface Cracking / Checking

Moderate Severity

Root Cause:

High summer ambient temperatures evaporated surface water before compaction was completed.

Contractor Solution & Fix:

Mist surface with fine water spray, re-scarify top 1 inch with motor grader teeth, and finish roll with a smooth pneumatic multi-tire roller.

Soft Spot Heaving Under Heavy Oilfield Trucks

Critical Severity

Root Cause:

Expansive Texas black gumbo clay subgrade underneath is pumping under wheel loads.

Contractor Solution & Fix:

Excavate base down to subgrade. Treat native clay with 4% hydrated lime stabilization or install Class 1 non-woven geotextile before replacing base in 4-inch lifts.

Aggressive Surface Washboarding on Rural County Lanes

High Severity

Root Cause:

Traffic traveled on unsealed base at high speeds before final calcium bonding cured.

Contractor Solution & Fix:

Lightly blade surface after a rain, re-establish 2% crown, and apply an asphalt emulsion prime coat (TxDOT Item 300 / 310) to seal surface fines.

Quarry Segregation in Windrows

Moderate Severity

Root Cause:

Base aggregate was dropped from excessive height or bladed dry across the pad.

Contractor Solution & Fix:

Re-mix windrows with motor grader blade using water truck accompaniment to homogenize fines and coarse stone before spreading.

Field Construction Standard

Step-by-Step TxDOT Flexible Base Placement & Compaction Sequence

Texas standard construction sequence: subgrade scarification, belly dump windrow spreading, water truck soaking, heavy pneumatic rolling, and chip sealing.

Stage 1 · Day 1 (Morning)

Subgrade Scarification & Lime Treatment

QA Checkpoint

In Central and North Texas (Blackland Prairie), native clays possess high Plasticity Indices (PI 35–60). Scarify top 6 inches, mix with 4% hydrated lime or moisture-condition to +2% over optimum, and compact to 95% Tex-114-E.

Pro Contractor Tips:

Lime stabilization permanently reduces swell potential in Texas clay.

Proof-roll with loaded dump truck before stone placement.

Pass/Fail Verification Standard Zero clay pumping under 20-ton axle load.

Stage 2 · Day 1 (Midday)

Geotextile Separation Fabric Installation

QA Checkpoint

Roll out non-woven geotextile fabric. Overlap seams by 24 inches and pin with steel staples.

Pro Contractor Tips:

Geotextile stops crushed limestone from sinking into wet clay subgrade.

Extend fabric 12 inches beyond future curb lines.

Pass/Fail Verification Standard Fabric pinned flat with zero gaps.

Stage 3 · Day 1 (Afternoon)

First Lift Belly Dump Spreading & OMC Misting

QA Checkpoint

Discharge flexible base in windrows. Spread in a 4.5-inch loose lift. Apply water spray to achieve 6.5% OMC (Tex-113-E).

Pro Contractor Tips:

Belly dump windrowing prevents aggregate segregation.

Hand squeeze test: forms solid clump without dripping water.

Pass/Fail Verification Standard Moisture content verified at 6.0%–7.5% OMC.

Stage 4 · Day 1 (Late Afternoon)

Vibratory & Pneumatic Roller Compaction

QA Checkpoint

Roll with a 5-ton vibratory steel drum followed by a 15-ton pneumatic roller. Make 6 to 8 passes.

Pro Contractor Tips:

Pneumatic rubber tires knead limestone dust into voids, creating an impermeable surface.

Keep tires clean with water spray.

Pass/Fail Verification Standard 100% Tex-113-E density verified.

Stage 5 · Day 2

Final Crown Grading & Two-Course Chip Seal

QA Checkpoint

Cut final 2.5% transverse crown with motor grader. Finish roll and seal with TxDOT two-course surface treatment (AC-15P asphalt + Grade 4 aggregate).

Pro Contractor Tips:

A 2.5% crown sheds intense Texas thunderstorm downpours immediately.

Seal road shoulders with compacted topsoil.

Pass/Fail Verification Standard Crown verified: 2.5% slope confirmed from centerline to shoulders.

Geotechnical Engineering Guide

Texas Transportation Institute (TTI) Engineering Reference: TxDOT Item 247 Base

Technical manual on TxDOT Item 247 grade distinctions, Triaxial compressive strength physics, and managing expansive Texas Blackland clay.

TxDOT Standard Specification Civil Standard Section 01

TxDOT Item 247 Specifications: Grades 1, 2 & Type D Caliche

TxDOT Item 247 governs flexible base across Texas highway and municipal projects. Grade 1 requires high-strength crushed limestone with a minimum compressive strength of 45 psi at zero lateral pressure (Triaxial Class 1.0). Grade 2 allows slightly broader gradation for county and residential roads (minimum 35 psi). Type D Caliche utilizes natural calcareous deposits prevalent in South and West Texas, featuring a lower dry density (125–132 lb/ft³) and unique self-hardening chemistry under intense Texas sun.

Geotechnical Chemistry Civil Standard Section 02

Calcium Carbonate (CaCO3) Self-Hardening in Texas Caliche

Unlike inert igneous gravel, Texas caliche contains high concentrations of soluble calcium carbonate. When moisture is applied during summer grading (optimum 7%–9% OMC) and heavy pneumatic or vibratory rolling is applied, dissolved calcite re-crystallizes upon drying. This forms an impermeable, semi-cemented monolithic crust that resists heavy agricultural trailer traffic and oilfield haulers.

Field Engineering Civil Standard Section 03

Summer Moisture Conditioning & Texas Proctor Density

In Central and West Texas, high ambient temperatures (95°F–105°F) cause rapid surface evaporation during installation. Contractors must run continuous water trucks alongside motor graders. Spreading dry base and rolling without moisture will cause severe particle crushing and washboarding. Maintain 7% to 9% moisture content throughout compaction to achieve Texas Tex-113-E density.

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