ASPHALT OVERLAYS PART II OF THE ASPHALT PAVEMENT

ASPHALT OVERLAYS PART II OF THE ASPHALT PAVEMENT DESIGN GUIDE FOR LOW-VOLUME ROADS AND PARKING LOTS Jayson Jordan, PE Technical Director jjordan@scasphalt. org Brad Putman, Ph. D Associate Professor Glenn Department of Civil Engineering putman@clemson. edu

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ASPHALT PAVEMENT DESIGN GUIDE FOR LOW-VOLUME ROADS AND PARKING LOTS “Together we know more” A resource…here to help www. scasphalt. org http: //www. scasphalt. org/scapa-asphalt-pavement-design-guide. html

ASPHALT PAVEMENT DESIGN GUIDE FOR LOW-VOLUME ROADS AND PARKING LOTS

PHASE 1 -DESIGN GUIDE SEMINARS § § § Columbia Greenville Rock Hill Charleston Myrtle Beach Florence

CONTENTS OF THE DESIGN GUIDE § Introduction § Design Considerations Input & external review provided by South Carolina engineers: § Pavement Materials § Thickness Design § Asphalt Pavement Construction § Asphalt Pavement Glossary § References § SCAPA Contractor Member Directory

CONTENTS OF THE NEW DESIGN GUIDE § New Pavements – – – Introduction Design Considerations Pavement Materials Thickness Design Construction § Overlays – – – Introduction Pavement Evaluation Type of Overlay Thickness Design Construction § Asphalt Pavement Glossary § Asphalt Pavement Distresses § SCAPA Contractor Member Directory

OVERLAY GUIDE OBJECTIVES Users should know how to: – Design a new pavement structure (from Part I). – Evaluate pavement condition & existing structure. – Determine why the overlay is needed. – Determine thickness of an asphalt overlay. – Explain how asphalt overlays are constructed.

Part 1 ASPHALT PAVEMENT DESIGN OVERVIEW

TYPICAL ASPHALT PAVEMENT SECTION Asphalt Base Course (Full-Depth Asphalt) Aggregate Base Course Asphalt Surface Course Asphalt Intermediate Course Asphalt Base Course Aggregate Base Course Subgrade

ASPHALT PAVEMENT LOADING Load Contact Stress (so) = Tire Pressure so Asphalt si = Stress at Subgrade

Bleeding Pothole Raveling Shoving Rutting Cracking Fatigue HOW DO ASPHALT PAVEMENTS FAIL

Part 1 DESIGN CONSIDERATIONS

DESIGN CONSIDERATIONS [TRAFFIC]

DESIGN CONSIDERATIONS [TRAFFIC] Class 1 Class 2 Class 3 Class 4 (≤ 50 cars/day) (≤ 5 trucks/day) (≤ 65 trucks/day) (≤ 200 trucks/day) § Driveways § Play areas § Parking lots (≤ 50 stalls) § Seasonal recreation roads § Residential streets § Collector streets § Parking lots (> 50 § Industrial lots, truck stalls) § Bus driveways & loading zones § Major arterial streets § Local business streets § Local industrial streets § Major service drives or entrances

DESIGN CONSIDERATIONS [SUBGRADE] Any structure is only as good as the foundation upon which it is built.

DESIGN CONSIDERATIONS [SUBGRADE] Poor Medium Good § Become soft and plastic when wet. § Clays and fine silts − ≥ 50% passing No. 200 § Coarse silts and sandy loams − Deep frost penetration − High water table § Retain a moderate degree of firmness under adverse moisture conditions. § Loams, silty sands, and sandy-gravels containing moderate amounts of clays and fine silts. § Retain a substantial amount of their loadsupporting capacity when wet. § Clean sands, sandgravels, and those free of detrimental amounts of plastic fines. − ≤ 10% passing No. 200 § Relatively unaffected by moisture or frost. § Typical Properties CBR < 6 LL > 40 PI > 10 GI > 4 § Typical Properties CBR: 6 – 9 LL: 25 – 40 PI: 6 – 10 GI: 2 – 4 § Typical Properties CBR ≥ 10 LL < 25 PI < 6 GI < 2

THICKNESS DESIGN e r Mo t h g i R e n O n a h T r e w s n A

THICKNESS DESIGN Medium Subgrade = =

D) NONE OF THE ABOVE

Part 2 ASPHALT OVERLAY DESIGN OVERVIEW

CONTENTS OF THE OVERLAY GUIDE § Introduction § Pavement Evaluation § Type of Overlay § Overlay Thickness Design § Overlay Construction § References

TYPICAL ASPHALT PAVEMENT SECTION Asphalt Base Course (Full-Depth Asphalt) Aggregate Base Course Asphalt Overlay Asphalt Surface Course Asphalt Intermediate Course Asphalt Base Course Aggregate Base Course Subgrade

EXISTING PAVEMENT CONDITION

EXISTING PAVEMENT EVALUATION § Condition assessment – – Visual evaluation Distress type, density, severity Good, fair, or poor condition Depth of cracking § Pavement Evaluation Guide – Field manual – Reference photos

DISTRESS IDENTIFICATION GUIDE

EXISTING PAVEMENT [CRACKING] A Little or no fatigue cracking and/or only low severity transverse cracking B < 10% low-severity fatigue cracking and/or < 5% moderate and high-severity transverse, longitudinal, or block cracking C D F > 10% low-severity fatigue cracking and/or < 10% moderate and high-severity fatigue cracking and/or 5 -10% moderate and high-severity transverse, longitudinal, or block cracking > 10% moderate-severity fatigue cracking and/or < 10% high-severity fatigue cracking and/or > 10% moderate and high-severity transverse, longitudinal, or block cracking > 10% high-severity fatigue cracking and/or > 10% high-severity transverse, longitudinal, or block cracking

EXISTING PAVEMENT [RUTTING] A Little or no rutting B < ¼ inch rut depth C ¼ to ½ inch rut depth D ½ to 1 inch rut depth F >1 inch rut depth

EXISTING PAVEMENT EVALUATION § Existing Pavement Structure – Need to know the existing pavement structure – Take cores or refer to construction history – How deep are the cracks & are they top-down or fulldepth?

TYPE OF OVERLAY

WHAT TYPE OF OVERLAY? § Preservation (Thin Lift) Overlay – Good condition with minor distress – Goal: Maintain good condition & seal the surface § Structural Overlay – Good to fair condition – Goal: Increase the structural capacity of pavement § Reconstruction – Poor condition – Goal: Rebuild the pavement structure

WHAT TYPE OF OVERLAY? Overlay Function Preservation Pavement Condition Grade Traffic Compared to Initial Design Cracking Rutting A, B Decrease or No Change A, B Increase B, C, D A, B, C Increase or No Change D, F A, B, C, D, F Structural Reconstruction Any A, B, C D, F

OVERLAY DESIGN

OVERLAY THICKNESS DESIGN § We need to know: – Traffic (Class 1, 2, 3, 4) – Subgrade quality (Good, Medium, Poor) – Existing pavement structure – Condition of existing pavement structure • Good • Fair • Poor Preservation Rehabilitation

OVERLAY THICKNESS DESIGN § Overlay thickness based on: – Effective structural value of existing pavement • Based on existing pavement layers & subgrade • Mill or not to mill? • Adjusted based on pavement condition – Required structural value • Based on traffic – Overlay Thickness Need = Required – Effective

OVERLAY THICKNESS DESIGN so si

OVERLAY THICKNESS DESIGN so so si si

OVERLAY THICKNESS DESIGN Required Structural Number Traffic Class Subgrade Category Poor Medium Good 1 2. 12 1. 92 1. 73 2 2. 67 2. 44 2. 22 3 3. 75 3. 46 3. 19 4 4. 12 3. 81 3. 52

THICKNESS DESIGN

OVERLAY THICKNESS DESIGN Surface Condition Layer Coefficients Pavement Material Asphalt Stabilized Aggregate (a. A) Base (a. SB) 0. 35 – 0. 40 0. 25 – 0. 35 0. 20 – 0. 30 0. 14 – 0. 20 0. 08 – 0. 15 Cracking Grade A B C D F Pumping or fines contamination? N Y (a. GAB) 0. 20 – 0. 25 0. 15 – 0. 20 0. 10 – 0. 20 0. 08 – 0. 15 0. 10 – 0. 15 0. 00 – 0. 10

PAVEMENT MATERIALS § Asphalt Surface Course

ASPHALT OVERLAY CONSTRUCTION

OVERLAY CONSTRUCTION § Will milling be done? § Tend to distresses – Leveling course to fill ruts – Crack seal – Full depth patching & subgrade repair where needed § Surface preparation & tack coat § Proper placement & compaction practices

WRAP-UP

WRAP-UP § Design Considerations § Existing Pavement Condition § Overlay Thickness Design § Asphalt Overlay Construction

MOVING FORWARD: RELEASE AUGUST 2016 How You Can Help: • Seminars across state • Contact Information: • Consultant Engineers • County Engineers • Municipal Engineers

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