OGFC & SMA Use in Georgia

Will Rogers

Technical Director

Georgia Asphalt Pavement Association

SMA & OGFC in Georgia

• Background

• SMA: Aggregate Requirements

• SMA: Design

• OGFC: Design

• Open-Graded Mix Comparison

• Open-Graded Mix: Current Policy

• Interesting Project

• SMA Family Feud

Background

• (Almost) All HMA Interstates in GA are SMA + Open-Graded Mix

– I-185 FM Columbus, GA to I-85 is 12.5mm SP + OGFC

• Open-Graded Mixes

– Began using w/o Polymers (Pop Corn Mix)

– Added Polymers after PG Grading System

– Began Using Permeable European Mix (PEM)

– Went Back to OGFC gradation

Background

• SMA:

– Started Using after NAPA/FHWA Scanning Tour of Europe in Mid/Late ‘90’s.

– Typically use 12.5mm SMA, but have used 19mm and 9.5mm NMAS

– Mineral Filler: Marble Dust -> Fly Ash -> ?

– Not Typically a Wearing Surface

SMA Aggregate Requirements

General Aggregate Requirements

General Aggregate Requirements

• Producing SMA Stone to Meet GDOT’s F&A Requirements…– VERY Difficult

– Few Quarries Could Meet Spec

– Quarry had to Shut Down All Other Production

– Generated Massive Amounts of Waste

– Stone was VERY Expensive

– Long Hauls

• Most Quarries HMA Stone Meets F&A According to AASHTO Caliper

General Aggregate Requirements

General Aggregate Requirements

• Before Notice to Contractors (402-3600):

– 2013: $107.02 per TN

– 2014: $99.12 per TN

– 2015: $127.95 per TN

• After Notice to Contractors (402-3600):

– 2016: $83.95 per TN

– 2017: $127.35 per TN

SMA Design

• Compactive Effort

– 35 Gyration OR 50 Blow Marshall

• RAP: Max 15%

• Apply COAC

• Fiber Stabilizers

– Mineral Fibers OR

– Cellulose Fibers

• Mineral Filler (QPL 81)

• PG 76-22

Mineral Filler Requirements

SMA Design

• Mineral Fillers

– Fly Ash**

– Marble Dust

– Carmeuse was Working on a Product from their Lime Production

SMA: I-520 in Augusta

SMA: I-520 in Augusta

SMA: I-520 in Augusta

SMA & OGFC in Georgia

• Background

• SMA: Aggregate Requirements

• SMA: Design

• OGFC: Design

• Open-Graded Mix Comparison

• Open-Graded Mix: Current Policy

• Interesting Project

• SMA Family Feud

OGFC: Design

OGFC: Design

• All Open-Graded Mixes Designed by GDOT per GDT 1141. Surface Capacity Method (KC Factor)

2. Modified Marshall Method (Stability & Flow)

3. Pyrex Bowl Method (Visual)

– Average AC Contents from 3 Methods• Modify by Field Experience if Needed

– Boil Test

• In Reality: #3 + Cantabro (typ. 15-19%, 20% Max)

Open-Graded Mix Comparison

OGFC

• Finer

• Less Void Space

• Easier to Clog

• Placed 0.75” Thick

• More Durable

PEM

• Coarser

• More Void Space

• Harder to Clog

• Placed 1.25” Thick

• Susceptible to Truck Rim Cuts

• Susceptible to Freezing Water

Open-Graded Mix Comparison

SCDOT

• Tack Application (Emulsion)– 0.05 – 0.15 Gal/SY

– (Residual): 0.0325 – 0.0975

– Min. 0.10 Gal/SY per Best Practices Document

• Placed on: Surface A

GDOT

• Tack Application (PG)– 0.06 – 0.08 Gal/SY

• Placed on: SMA*

Open-Graded Mixes: Current Policy

• PEM Has Been Removed from Active Use

• OGFC Being Placed @ 100 lbs/SY

• OGFC Occasionally Being Further Fined Up to Enhance Performance

Interesting Projects: I-95 in Camden County

• GDOT Covered CRCP in 1998-1999

• 19mm SMA + 12.5mm SMA + 90 lbs/SY OGFC

• Micro-Mill & Inlay let in December 2017

Interesting Project: I-95 in Camden County

Interesting Project: I-95 in Camden County

Interesting Project: I-95 in Camden County

SMA Family Feud

• 6 GA Contractors Surveyed on Headaches & Tips for SMA

• 4 Contractors Responded

SMA Family Feud: Headaches (4)

(3) #7 Stone Consistency

(3) Mineral Filler

(3) Sticky / Build-Up, Poor Flow

(2) Release Agent

SMA Family Feud: Tips & Tricks (3)

(2) Keep Rollers Tight to Paver

(3) TEMPERATURE! – Screed, Plant, Rolling

(2) Aggregate! – Mult. Bins, Partner w/ Supplier

Contractor 1• Consistency of aggregate is a MUST• Use mult. Bins for aggregates to blend consistency back

into the gradation blend• Coarser material works better (esp. the #7’s)• More material does better (coarse #7’s allow for the use of

89’s)• Hotter the better:

– Handling Issues– Locking down the MTV– Shadowing/Hot Lapping– Compaction

• Back Roller 150 – 180F. It will be a factor in compaction• In cooler temps, keep Breakdown Roller close to screed.

Hotter temps., may back off.

Contractor 1

• Consider Mineral Filler Source– Higher Density Fly Ash (Need higher % of mineral filler due

to compaction issues)

– Lower Density Fly Ash (Can replace some with rock dust)

– Marble Dust (need higher % due to compaction issues)

• Need depth for Compaction (Issues @ 1.5” & Below. 2” yields much better results)

• Finer Designs tend to be Easier:– Work with & Manage

– Improved Permeability in Lab & Field

Contractor 2

• Dealing w/ Fly Ash. The supply & hauling logistics & storage issues w/o finding a Storage Pig to Rent

• Aggregate Supply

– Variability!

• Boy Scout Motto: “BE PREPARED”

Contractor 3

• Doesn’t come out of the Trucks into the Paver very well

• Need a Clean-Out Area near Laydown Operations for Trucks

• Not Using Release Agent Correctly

• Plant Temps Must be Higher than Normal HMA

• Heated Screed on Paver to Help with Laydown

• Keeping Rollers up Tight with Laydown to get better Compaction & Rideability

Contractor 4

• Sensitivity to Temp. Becomes stiff quickly.

• Can’t Use Rubber Tire Roller

• Sticky & Often Build-Up in Trucks & on Tools

• Require Continuous Operation & Head of Material

• Ash & Lime Require 2 Silos for Fillers

• VERY Consistent #7 Stone

• Feed MTV Slowly when Steel is Cool

• 2 Breakdowns in Cooler Weather

Contractor 4

• Partner w/ Agg. Supplier

• Increase Release Agent: 5:1 from 15:1

• Set Screed Strike-Off higher or will Build Up & Tear Mat

• No More Hand Work than NECESSARY

• Don’t Run Buggy Low

• Fine Mastic can Build Up & Break Loose -> Fatty Blemishes in Mat

Questions?