s1_reflectivity of the louisiana chip seal pavement_ltc2013

7/29/2019 S1_Reflectivity of the Louisiana Chip Seal Pavement_LTC2013

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LOUISIANA DOTDSTRIPING STANDARDS


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TYPES OF PAVEMENT MARKINGS

Paint 90 Mil Thermoplastic 40 Mil Thermoplastic Preformed Thermoplastic Tape Plural Components (currently being tested). All Of The Above Contain Glass Beads For

Retroreflectivity.


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PAINT

Water-based paint is used for our district maintenanceoperations.

La DOTD currently uses the third generation high-buildpaint with type 3 beads.

This durable paint helps us get better life; in some casesyou can stripe roads ever other year.

Using the type 3 beads give us better wet recovery; thetype 1 beads will not give any wet recovery.

This paint is applied at a thickness of 22 to 25 mils. On a good application, you should get approx. readings of

250 mcd for white and 175 mcd for yellow.


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90 MIL THERMOPLASTIC Thermoplastic is heated between 400 to 425 and

extruded onto the pavement surface. (No spray applicationis allowed.)

Thermoplastics have a long service life, good visibility, and

good retroreflectivity. We use type 4 glass beads for the first drop and type 1 glassbeads for the second drop. The type 4 glass beads give wetrecovery.

Our specs call for initial readings of 375 for white and 250

for yellow; we have gotten readings of up to 700 for whiteand 400 in yellow. Thermoplastic has short track time. (30 seconds) Its cost is mid-range.


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40 mil thermoplastic

Thermoplastic is heated to 400 and sprayedonto the pavement surface.

Our only use of 40 mil is in some chip sealapplications.

Will talk about striping on chip seal roads laterin the presentation.


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Preformed thermoplastic Easy to apply requires only one person and a gas flame

torch. Precise and consistent line and symbol definition due to

off-site factory manufacture.

Available in precut lines, rolls, numbers, letters, symbolsand multi-colored designs. Surface can be returned to use within minutes. Permanent as good as conventional liquid-applied

thermoplastic. Long lasting. Preformed thermo includes glass beads for high visibility.


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Tape

Pre-formed tape has excellent visibility andretroreflectivity. This is due to off-site factorymanufacture under highly-controlledconditions.

Retroreflectivity readings can exceed 1000mcd.

Lasts 7-8 years. But is higher in cost.


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Glass BeadsLA DOTD Requirements

Paint: Type 3 glass beads. Thermo: A double drop system, first drop is

type 4 glass beads and the second drop iseither type 1 or at the contractors discretion.

Tape: Uses a type 1 glass bead, but it is usuallya high-index bead and could have somecluster beads also.


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Types of Reflection


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Performance / Visibility

Daytime:We depend on diffuse reflection

and color contrast to see pavementmarking during the day.Nighttime:

We depend on retroreflection tosee pavement markings at night.


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30-meter geometry

30-meter viewing distance


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Glass Bead Embedment

High Embedment, Poor

Low Embedment, Poor

60% Embedment, Good


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Effects of Water


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Bead embedment


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Perfect bead embedment in thermo


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Under bead embedment in thermo


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Beads lost due to under embedmentin thermo


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Over bead embedment


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Over bead embedment in paint


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Not enough beads


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Chip seal applications

Chip seal striping is difficult, and methods arestill being evaluated.

The main problem is the rough surface causedby the large rock that is used.

The striping material doesnt have enoughsurface to hold on to.


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Paint Application on Chip Seal


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90 Mil Thermo on Chip SealTraveling in direction striped


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90 Mil Thermo on Chip SealTraveling opposite direction striped


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40 Mil Spray on Chip Seal


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Test Project Using 1.9 and 1.6 Beads onChip Seal in District 05

Material was installed on 8-15-2012. Monitored every 3 months for the first year and then

every 6 months thereafter. Monitoring will show how the 1.9 and 1.6 beads hold

up. The 1.9 bead has a higher index but is said to be a

softer bead. The 1.6 bead has a lower index than the 1.9 but

higher than the 1.5 and is said to be harder. Both beads are the same size as the AASHTO type 1.


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Thermo vs. Paint

40 Mile Thermo Paint Application


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Photo of 1.6 bead in paint after 6months


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Test Results40 Mil Thermo Retro Readings

1.9 Bead Initial white 687 6 Months white 370 Initial Yellow 328 6 Months Yellow 207

1.6 Bead Initial white N/A 6 Months white N/A Initial Yellow N/A 6 Months Yellow N/A


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Test Results PaintRetro Readings

1.9 Bead Paint Initial white 1462 6 Months white 771 Initial Yellow 781 6 Months Yellow 372

1.6 Bead Paint Initial white 635 6 Months white 503 Initial Yellow 446 6 Months Yellow 420


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The most commonly used bead is the ASSHTOType I bead. This Bead has a refractive index

of 1.5. The average readings at 6 months foryellow have been around 96 mcd. LA DOTD districts use the ASSHTO type 3

beads. The average readings at 6 months foryellow have been around 129 mcd.

Q i ?


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Questions?

s1_reflectivity of the louisiana chip seal pavement_ltc2013

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