Post on 05-Feb-2020
5 YEARS EXPERIENCE IN USING OTTA SEAL AND SOFT
ASPHALT FOR GRAVEL ROADS IMPROVEMENT
PhD. AUDRIUS VAITKUS, PhD. VIKTORAS VOROBJOVAS, PhD. FAUSTINA TUMINIENĖ,
PhD. candidate JUDITA GRŽULYTĖ
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2018-01-23
Problem
Concept:
Soft asphalt
Double Otta Seal
Experimental research
Results
Conclusions
OUTLINE
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PROBLEM
In Lithuania 33 % of national significance roads are gravel roads
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TYPICAL SOLUTIONS
Chemical dust suppressants
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TYPICAL SOLUTIONS
Asphalt pavement
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Asphalt pavement (AC 16 PD)
Unbound base course from crushed stone
Frost resistant layer
1) When ESAL ≤ 500002) Depends on class of frost resistance of soil
Subgrade
ALTERNATIVE SOLUTIONS
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Soft asphalt
Surface course from soft asphalt
Unbound base course from crushed stone
Existing gravel pavement (can be
partly new layer)
Subgrade
+29%
SOFT ASPHALT IDENTIFICATION (EN 13108-3)
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SANo identification
or reference bD
Grading designation
d or oBinder
Type
A, B, C, S
Soft asphalt
No identification – surface course
b – base course
The maximum
aggregate size, mm
d – dense graded aggregate
o – open graded aggregate
Examples: SA 16-d-V6000 type C
SAb 16-d-V12000 type S
SOFT ASPHALT CONSTRUCTION
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Base coursepreparation
Soft asphaltlaying
Compaction Aggregatespreading
Finalcompaction
ALTERNATIVE SOLUTIONS
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Surface dressing (Double Otta Seal)
Double Otta seal
Unbound base course of crushed stone
Existing gravel pavement (can be partly new layer)
Subgrade
+44%
SURFACE DRESSING IDENTIFICATION (BASED ON TECHNICAL
REQUIREMENTS)
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Type D BE
VPA – single surface dressing
DPA – double surface dressing
EDPA – double surface dressing
in stagesThe maximum
aggregate size, mm
Bitumen emulsion
Examples: VPA16BE
DPA1611BE
EDPA1616BE
SURFACE DRESSING CONSTRUCTION
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Base coursepreparation
Binderspraying
Aggregatespreading
Compaction(rolling)
APPLICATION CONDITIONS
Otta Seal:
ESALs ≤ 100 000
Bearing capacity of the
subgrade ≥ 45 MPa
Bearing capacity of the
unbound base course ≥
120 MPa
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Soft asphalt:
ESALs ≤ 100 000
100 000 < ESALs ≤ 300 000
(asphalt base course is
required)
Bearing capacity of the
subgrade ≥ 45 MPa
Bearing capacity of the
unbound base course ≥ 120
MPa
EXPERIMENTAL RESEARCH
Criterions for trial sections:
Number of freeze-thaw cycles
AADT
ESAL
Frost depth
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5 sections with soft asphalt
13 sections with double Otta seal
EXPERIMENTAL RESEARCH
Measurement of roughness
In autumn 2012 by the Road Surface Profilometer Dynatest 5051 RSP
In summer 2013 by the Mobile Road Survey Laboratory RST 28
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EXPERIMENTAL RESEARCH
Qualitative visual assessment of defects
Soft asphalt in spring and summer
Double Otta Seal in spring and autumn
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QUALITATIVE VISUAL ASSESSMENT OF DEFECTS
SOFT ASPHALT
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Longitudinal cracking
Transverse cracking
Potholes
Ravelling
Seals
Bleeding
QUALITATIVE VISUAL ASSESSMENT OF DEFECTS
DOUBLE OTTA SEAL
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Longitudinal cracking
Transverse cracking
Fatting up, bleeding
Tracking
Scabbing
Tearing
Longitudinal joint crack
Corrugation
Streaking
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RESULTS
INTERNATIONAL ROUGHNESS INDEX
QUALITATIVE VISUAL ASSESSMENT OF DEFECTS
SOFT ASPHALT
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62.98%
13.90% 6.77%
87.23%
SEALED LONGITUDINAL CRACKS
Road no. 2430 in summer 2017
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QUALITATIVE VISUAL ASSESSMENT OF DEFECTS
SOFT ASPHALT
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100%
98%
33%
98%
98%
QUALITATIVE VISUAL ASSESSMENT OF DEFECTS
SOFT ASPHALT
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Bleeding
Potholes
Ravelling
Seals
<0.5%
QUALITATIVE VISUAL ASSESSMENT OF DEFECTS
SOFT ASPHALT (AFTER 5 YEARS)
23Road no. 1716 Road no. 4028 Road no. 5235
QUALITATIVE VISUAL ASSESSMENT OF DEFECTS
DOUBLE OTTA SEAL
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QUALITATIVE VISUAL ASSESSMENT OF DEFECTS
DOUBLE OTTA SEAL
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QUALITATIVE VISUAL ASSESSMENT OF DEFECTS
DOUBLE OTTA SEAL
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QUALITATIVE VISUAL ASSESSMENT OF DEFECTS
DOUBLE OTTA SEAL
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Autumn 2013
Scabbing
Spring 2014
Sealed scabbing
QUALITATIVE VISUAL ASSESSMENT OF DEFECTS
DOUBLE OTTA SEAL
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QUALITATIVE VISUAL ASSESSMENT OF DEFECTS
DOUBLE OTTA SEAL (AFTER 5 YEARS)
29Road no. 4118 Road no. 4726 Road no. 5017
CONCLUSIONS
The construction of soft asphalt instead of construction of typical asphalt
concrete pavement results in saving 5.36 mln. EUR/year, while double Otta
Seal saves 7.77 mln. EUR/year.
The pavement condition of rehabilitated low-volume gravel roads after five
years exploitation confirmed the suitability of soft asphalt and double Otta
Seal technologies for the improvement of gravel roads with less than 0.1 m
ESALs for a 20-year period.
All tested road sections met IRI requirement for roads of regional significance
(≤3.5 m/km).
Longitudinal cracks, transverse cracks, and bleeding can be defined as
dominant distresses of road sections with soft asphalt.30
CONCLUSIONS
Fatting-up, bleeding, and tracking and, on some roads, longitudinal
cracks, scabbing, tearing, and longitudinal joint crack can be defined
as dominant distresses of road sections covered with double Otta Seal.
There is not any evidential relationship between the degree of
distresses and AADT, ESALs, or road section location.
Longitudinal cracking is 10 to 25 times severer distress than transverse
cracking depending on technology (soft asphalt or double Otta Seal)
and existing pavement structure composition.
Both technologies are able to self-heal within spring-summer. The
healing effect is higher than 13% and 19% on roads with soft asphalt
and double Otta Seal, respectively. 31
CONCLUSIONS
Critical factor for road sections covered with double Otta Seal isincomplete construction and maintenance of constructed roadsections.
During construction phase light moistening should be applied on the basebefore bitumen emulsion spreading.
Two-stage construction of first and second layer of double Otta Seal isstrictly recommended; the second one should be applied not less thanafter four weeks of road exploitation and maintenance of emergeddefects in first layer.
The trial emulsion and aggregate spreading and compaction rollingare strictly recommended for Otta Seal technology in order to verifythe emulsion and aggregate application rates and a sufficient numberof roller passes.
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