Lightly Surfaced Roads

Dan Wegman, PE Braun Intertec Corporation 2019RIC04 | November 2019 Acknowledgements

TAP Members • John Brunkhorst (Chair), McLeod County • Jim Olson, Becker County • Thomas Johnson-Kaiser, MnDOT • Ken Skorseth, Formerly SD LTAP • Joel Ulring, MnDOT State Aid • Brad Wentz, ND State University • Tom Wood, WSB and Associates, Inc • Darrick Anderson, Cass County • Bruce Hasbargen, Beltrami County • Joe Triplett, Chisago County • Charles Jahren, Iowa State University • Paul Nolan, MnDOT Developed by: Renae Kuehl, SRF Consulting Group Dan Wegman, Braun Intertec Mohammad Sabouri, Braun Intertec This training represents the results of research conducted by the authors and does not necessarily represent the views or policies of the Minnesota Local Road Research Board, the Minnesota Department of Transportation, or SRF Consulting Group, Inc. This training does not contain a standard or specified technique. The authors, the Minnesota Local Road Research Board, the Minnesota Department of Transportation, and SRF Consulting Group, Inc. do not endorse products or manufacturers. Any trade or manufacturers’ names that may appear herein do so solely because they are considered essential to this training. Course Objectives

• Understand Lightly Surface Road (LSR) concept • Understand the advantages and disadvantages of LSR’s • Know the LSR applications • Understand keys to a successful LSR • Be familiar with some LSR failures and ways to avoid them • Understand the LSR treatment options • Be familiar with some online selection tools Course Outline

1. Introduction to Lightly Surfaced Roads (LSR) 2. Key to a successful LSR a. Strong base and subgrade b. Good Drainage 3. Examples of LSR failures 4. LSR Treatment Options Introduction to Lightly Surfaced Roads (LSR) Lightly Surfaced Roads

• A thin surface treatment of liquid asphalt covered with an aggregate that has an applied thickness of about 1.5-inch or less • “Improved Gravel Road”

Photo obtained from: www.dot.state.mn.us Unpaved Roads

Characteristics of Gravel Roads: • High maintenance cost • Dust • Lower riding comfort • Noise • Frequent blade maintenance needed Paved Roads

Bituminous-Surfaced Road Characteristics (for low volume roads): • High riding comfort • High construction cost • HMA • Thick flexible or rigid pavement system • Pavement thickness required: 3.0-Inch or more What is a Lightly Surfaced Road?

Paved Road

Lightly Surfaced Road

Gravel Road Lightly Surfaced Roads – Advantages

• Improved surface condition (waterproof/skid) • Reduction of maintenance cost • Conservation of gravel • Eliminates dust • No wash boarding • Reduction of vehicle operating cost • Increased riding comfort • Significantly lower construction costs compared to paved roads • Better user satisfaction compared to gravel Lightly Surfaced Roads – Disadvantages

• Not providing additional structural strength - Strength must be provided by underlying base • Timely maintenance is required • More frequent repairs • More susceptible to damage by heavy vehicles and equipment than traditional pavements • Load restrictions during certain times of year may be required • Consequences of heavy vehicle damage is greater • Lack of competitive bid because not many qualified contractors have experience building LSRs LSR Application

Where to use? Where NOT to use? • Very low volume roads – • Roads with heavy less than 400 ADT vehicles • Roads with limited heavy • Areas susceptible vehicles to flooding • Existing gravel roads • Poor base strength with a strong base and good drainage • Use selection tools Surface Selection Tool Pavement Preservation and Recycling Alliance Maintenance Considerations

• Maintain the road and ditches to the proper shape • Proper crown • Proper ditching (+ditch clearing) • Timely maintenance and application is critical • Maintain road surface condition

Improper ditch clearing Communication

• Educating public on what LSRs are is important • Performance that can be expected • Maintenance activities required • Lightly surfaced roads have the same alignment/look/feel as a traditional paved road - Drivers may drive faster than on a gravel road. Keys to a Successful Lightly Surfaced Road Lightly Surfaced Road Requirements for Success • Strong base and subgrade • LWD, DCP, Proof Roll (also called test roll) • Good drainage • Crown, shoulder, edge maintenance, roadside ditches • Good construction practices • Good traffic load assessment Base Strength Enhancement

Virgin aggregate or RAP may be added to • Increase depth of finished structural layer • Improve gradation • Address cleanliness, fines (P200) & material quality

Add rock CBR and R-value Correlation AASHTO 1993 R-value Correlation Strong Base and Subgrade

• LSRs are constructed over an aggregate base course • Since LSRs do not add structural capacity to the roadway, the base/subbase must be designed to support the anticipated traffic loading • Subgrade and base materials should be compacted and graded to provide a stable working surface prior to LSR placement • Need a dry/well drained subgrade Strong Base and Subgrade

Result of weak and thin base and poor shoulder drainage Definitions

Soil - Sediments or other unconsolidated accumulations of solid particles produced by physical & chemical disintegration of rock - may contain organic matter

Granular Base - Unbound granular material Sand Equivalent Test - Clay content as % of Clay fine aggregate portion of material (finer than 4.75 mm) Base and Material Assessment

• Structure evaluations • Drainage • Distresses Portable FWD • Proof rolling prior to application of LSR

Dynamic Cone Penetrometer (DCP) Preparation Before LSR is Critical

• Correct any drainage issues • Make sure the base strength is adequate for the anticipated traffic • Construct cross slope at 3% • Established centerline • Shape and compact surface Drainage

When water finds its way underneath roads, the roadway foundation will gradually weaken, causing the surface pavement to eventually fail. Good Surface Drainage Poor Surface Drainage Poor Surface Drainage Poor Drainage Factors

• Traffic loads • Climatic factors of rainfall and temperature (freezing and thawing) • Ground water • Roadway geometry • Pavement/Subgrade type and condition Poor Drainage Factors (Cont'd)

• Design Features - Adequate Crown • Engineers estimate that 90% of roads problems are due to poor drainage/excess water Drainage: Sources of moisture in pavement systems Drainage: Snow Melt Drainage: Snow Melt Drainage: Snow Melt/Plugged Culvert Drainage: Solutions

• Divert — Interceptor ditches slope away from the roadway and are located between the road and higher ground along the road • Drain — Creating a crown in the road so it is higher along the centerline than at the edges encourages water to flow off the road Drainage: Solutions

For gravel surfaces the crown should be 1/2" higher per foot of width (4% cross slope)

Ideal cross section for good drainage Drainage: Solutions

• Road surface must be relatively water tight • Road shoulders also must be sloped away from the road to continue carrying the flow away • Dispose — A ditch system carries water away from the road structure. Ditches should be at least one foot lower than the bottom of the gravel road layer that drains the roadway. Examples of LSR Failures

• Potholes • Base failure • Rutting • Mismatch of materials • Insufficient subgrade support • Localized subcut correction • Lack of proper maintenance • Lack of crown • Heavy traffic • Snow and Ice Impacts • Construction – application rates Example of LSR Failure: Edge Break Example of LSR Failure: Flushing and Corrugation Example of LSR Failure: Surface Delamination Example of LSR Failure: Pothole Example of LSR Failure: Base Failure Example of LSR Failure: Rutting Example of LSR Failure: Mismatched Materials

TAP to provide images – Does Braun have any? Example of LSR Failure: Insufficient Subgrade Support Example of LSR Failure: Localized Subcut Correction Localized Failures Subcut correction Example of LSR Failure: Lack of Proper Maintenance (not fog sealed)

TAP to provide images – Does Braun have any? Example of LSR Failure: Lack of Proper Maintenance Example of LSR Failure: Lack of Crown Example of LSR Failure: Shoulder Aggregate Erosion Example of LSR Failure: Heavy Traffic and Excess Deflections Example of LSR Failure: Snow Plow Damage Plow can pull surface off due to “bare pavement” policy Example of LSR Failure: Construction and Application Rates or Cure Time Ways to Avoid Failures

• Base and subgrade enhancement (FDR, geogrids, etc.) • Base Stabilization (Materials) • Improve base and subgrade drainage • Wise selection of materials - making sure they are compatible and that they have the required engineering properties. • Quality/Quantity control during construction • Good maintenance at regular intervals • Proper design for consideration of traffic loading over design life of the treatment • Build a test strip • Talk to others that have tried various treatments Lightly Surfaced Road Treatment Options LSR Treatment Options

• Otta Seal • Double Chip Seal • Prime and Seal Otta Seal Otta Seal Otta Seal

• An Otta Seal is an asphalt surface treatment constructed by placing a graded aggregate on top of a thick application of relatively soft bituminous binding agent • Minnesota has used emulsified asphalt exclusively (HFMS-2s) • Traffic Range: Very Low to High (AADT < 2000) • In MN common practice is to do two lifts Otta Seal: Single vs. Double Otta Seal: Disadvantages

• The need for experienced people to do maintenance • Grade cannot exceed 8% for single lift (12% for double) • Must be applied at above 50°F • Need for specialized equipment and experienced personal if not completed by an experienced contractor • Higher cost then other options due to need for more material • Constructability can be more difficult Otta Seal: General Design Guidance

Source: Pavement Interactive Otta Seal: Alternating Grading Envelopes

Source: Pavement Interactive Otta Seal: Grading Envelopes with Strength Requirements Otta Seal: Binder Application Rates Otta Seal: Aggregate Application Rates Otta Seal: Example of Iowa Aggregate Application Rates

Source: “Evaluation of Otta Seal Surfacing for Low-Volume Roads in Iowa” Report Otta Seal: Example of Iowa Binder Application Rates

Source: “Evaluation of Otta Seal Surfacing for Low-Volume Roads in Iowa” Report Otta Seal: Gradation Table

* Gradation table was developed for workability (focus on optimal moisture content) through trial and error experience in Becker County. Each agency will have to do the same process locally. Otta Seal: Maintenance

• Maintenance interventions are not required to the extent necessary with conventional seals. • Recommend applying a Chip Seal 1-2 years after installation • Resealing frequency: 9 to 15 years (it is about 7 years for chip seal) • The repair and resealing of any localized surface defects are like any other sprayed type of sealing. Otta Seal: Construction Otta Seal: Proper Construction Sequence Maintain Tight Equipment Spread Otta Seal: Good Work with Spreader Otta Seal: Proper Construction Sequence Otta Seal: Conduct Test Strip

Conduct 500 test strip to check application rates Otta Seal: Truck Paths

Good example of trucks staggering their paths as they back towards the spreader. Otta Seal: Successful Project

Perfect Application Rates Otta Seal: Good Performance

The road has performed well for over 10 years with no need for repair. Otta Seal: Good Performance Otta Seal: Distresses and Failures

• Too heavy traffic resulting in rutting and shoving in curves • Larger mat of material and more binder Otta Seal: Distress and Failure

Loose aggregate on surface Otta Seal: Distress and Failure

Frost Boil Otta Seal: Poor Construction

Centerline overlap of excess materials Otta Seal: Poor Construction

Poorly graded aggregate or too much material (too many fines) Otta Seal: Poor Construction

• Bleeding • Excess Binder

Currently this roadway is fine, but problems may arise if the situation worsens Double Chip Seal/ Prime and Seal Chip Seal

• Process of covering a gravel road with a layer of liquid asphalt then embedding a layer of small rocks • Usually CRS-2P or CRS-2 is used (CSS- 1h at lower temperature). Chip Seal

• What about high float emulsion? • When priming of the base is done, it is sometimes called “prime and seal” • Fog seals are typically added to lock in aggregate Prime and Seal

• Application of an asphalt cutback or emulsified asphalt to a gravel road • Compared to cut back asphalt primes, emulsion primes are more environmentally friendly Prime and Seal/Chip Seal Seal Coat Reference

http://www.dot.state.mn.us/materials/researchsealcoat.html Chip Seal Cover Aggregate

• Should be clean and dust free • Uniform in size and hard for a tight, durable surface able to withstand the abuse of snow plows and vehicles • Fog seals help lock aggerates in place • In Minnesota, the gradation of seal coat aggregate is referred to as either FA-1, 2 1/2 or 3 (FA = Fine Aggregate) • The larger the number, the larger the aggregate. • By far, the most commonly used sizes are FA-2 and FA-3 • An FA-2 consists mainly of particles smaller than 1/4 inch • An FA-3 consists mainly of the chips smaller than 3/8 inch MnDOT Example: Chip Seal Cover Aggregate

Source: MnDOT Specification MnDOT Example: Chip Seal Cover Aggregate

Source: MnDOT Specification Chip Seal: Cover Aggregate Chip Seal: Cover Aggregate Chip Seal: Equipment

Equipment required for chip seal construction includes: • Power Broom • Asphalt Distributor • Chip Spreader • Pneumatic Tired Rollers (1-3) • Haul Trucks • Front End Loader • Asphalt Tanker • Miscellaneous Hand Tools Chip Seal: Procedure

1. Level and pre-wet gravel Chip Seal: Procedure

2. Priming with Penetrating Emulsion Prime (PEP) Chip Seal: Procedure

2. Priming with Penetrating Emulsion Prime (PEP) Chip Seal: Procedure

3. Applying aggregate Chip Seal: Procedure

3. A uniform application of aggregate Chip Seal: Procedure

4. Rolling Chip Seal

The use of pneumatic tire rollers is required; steel rollers will crush the aggregate! Chip Seal: Procedure

5. Sweeping extra chips off roadway Chip Seal: Distress and Failure Chip Seal: Distress and Failure Base Treatment: Shingles RAP Add Rock SFDR What to do if you have a weak base

• Base Modification Options • RAP • Shingles • Add Rock

• Base Stabilization Option • Stabilized Full Depth Reclamation (SFDR) • Cement • Foamed asphalt • Emulsion Base & Material Assessment

Structural Evaluation of Base • Structure evaluations Portable • Drainage FWD • Distresses • Proof rolling prior to application of LSR

Dynamic Cone Penetrometer (DCP) Shingles : Benefits

• Re-use of a valuable resource • Reduce chlorides from dust control • Reduce grading of gravel surfaced roadways and shoulders • Reduction in re-graveling • Less corrugation • Less float (less loose rock on road) • Seem to shed water better • Less dust observed • Environmental savings: • Divert shingle waste from land fills • Protect water from chlorides • Less fugitive dust • Cost effective alternate to other dust control methods Shingles

200,000+ tons of Tear Off Waste Shingle (TOSS) per year produced in MN Shingles: Recommended Grind Size

Recommended grind size: ½ inch minus grind Cost ⅓ less that #4 minus grind Shingles: Improve Quality Test Section Jackson County

Jackson Co. Goals • Limit Corrugation • Less Blading What was done • 1 to 1 blend by volume (=35% by weight) Shingles: Performance in Jackson County

Comments from interviews with Jackson County Personnel • Blade operator wants rest of pile on his roads • Less corrugation • Less float • Seem to shed water better • Less dust observed Shingles: Dust Control Test Section Goodhue County

Goodhue County •Biggest issue is dust control •Use crush limestone for surfacing gravel What was done • Blend TOSS at rate of 1 to 1 by volume for top ½ inch Shingles - Performance in Goodhue County Comments from interviews from Goodhue County Personnel • TOSS made road look dirty • Did observe less dust Shingles Shingles Shingles Reclaimed Asphalt Pavement (RAP)

• RAP can be utilized as an effective material on gravel roads: • Dust reduction • Maintenance cost reduction • Performance and durability improvement RAP

• The amount of floating aggregate decreases as the RAP% increases • RAP can be used to improve gradation of materials that lack large particle sizes • Rutting and wash boarding can develop if the material is mixed with is poorly graded aggregate and if the base is soft Add Rock

• The dozer attachment allows this operator to push a load of rocks into a frost boil with the grader • Without this attachment, a loader would likely have to be brought to the job Stabilized Full Depth Reclamation (SFDR) with Lime or Cement Modification Agents

• Various chloride compounds

• CaCl2 and MgCl2 • Binds fines and aggregates to reduce dust • Undesirable for plants and animals Can be carried by surface water

• Enzymatic stabilizers: • Degradable catalyst that improves bonding of the soil particles • Less problematic for nearby plants Stabilization Agents

• Lime: • Improves the strength of the road base or subbase. • Usually used for clay soils.

• Portland Cement: • Provides greater strengthening. • Can be applied to a wider range of soil types. Stabilization Agents

• Fly Ash: • Much less expensive than cement • Often used to substitute a certain percentage of cement or lime to lower the material costs

• Emulsion: • A mixture of asphalt binder, water, and an emulsifier • When “breaks” the asphalt binder separates from the water and sticks to the aggregate materials • Does not require heat SFDR with Cement Cement is usually spread in a controlled manner by a spreader truck SFDR with Cement Mixing is performed by the reclaimer SFDR with Cement Mixing is performed by the reclaimer SFDR with Cement Pad foot rollers are used to provide initial compaction SFDR with Cement A motor grader is used to finish the grade. SFDR with Cement Final product Base Stabilization

Strength gain should be in a range that provides increased strength and stability without creating a rigid brittle blend that can induce cracking of the overlying pavement surface. Prime and Seal Coat after SFDR with Cement Seal Coat after SFDR with Cement Seal Coat after SFDR with Cement Stabilized Full Depth Reclamation (SFDR) with Emulsion SFDR with Emulsion Emulsion is injected and mixed using a reclaimer SFDR with Emulsion Pad foot rollers are used to provide initial compaction SFDR with Emulsion Pneumatic rollers are used to complete the operation SFDR with Emulsion Final product Non-LSR Options

• Dust Control • Proprietary Products Dust Control: Material Management

While calcium chloride (CaCl2) and magnesium chloride (MgCl2) are the most common choices, many other products are used as well. Dust Control: Material Management

• MgCl2: • Has a residual effect that reduces the rate of application needed after the first year • Reduces need for blading • potential vehicle corrosion, vegetation damage and the tendency to run off when the road is saturated with water. • CaCl2: • can also be corrosive and can cause gravel loss during the winter if applied in late fall Additional Tools

• Unpaved Road Website - Helps pick the gradation for a lightly surface road www.ucprc.ucdavis.edu/unpavedroad

• Unpaved Road Chemical Treatment Selection Tool – helps select the right chemical for dust control www.ucprc.ucdavis.edu/dustcontrol Proprietary Product

• Several proprietary products are also available to enhance gravel road performances • Manufacturers recommendations should be followed Example Project: MNROAD LSR – Chip Seal/SFDR (Emulsion) Emulsion Injection Example Project: MNROAD LSR – Lightly Surfaced Methods Cell 28 Example Project: MNROAD LSR – Lightly Surfaced Methods Cell 28 Selection Tools NDSU Surface Selection Tool

• https://dotsc.ugpti.ndsu.nodak.edu/SurfaceSelection/ Local Road Surface Selection Tool Instructions Local Road Surface selection tool instructions Local Road Surface Selection Tool Instructions Local Road Surface Selection Tool Instructions Local Road Surface Selection Tool Instructions Local Road Surface Selection Tool Instructions Local Road Surface Selection Tool Instructions Local Road Surface Selection Tool Instructions Local Road Surface Selection Tool Instructions Analysis Summary Analysis Summary

LSR

LSR Surface Selection Tool Pavement Preservation and Recycling Alliance Pavement Preservation and Recycling Alliance Pavement Preservation and Recycling Alliance