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

1

2018-01-23

Problem

Concept:

Soft asphalt

Double Otta Seal

Experimental research

Results

Conclusions

OUTLINE

2

PROBLEM

In Lithuania 33 % of national significance roads are gravel roads

3

TYPICAL SOLUTIONS

Chemical dust suppressants

4

TYPICAL SOLUTIONS

Asphalt pavement

5

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

6

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)

7

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

8

Base coursepreparation

Soft asphaltlaying

Compaction Aggregatespreading

Finalcompaction

ALTERNATIVE SOLUTIONS

9

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)

10

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

11

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

12

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

13

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

14

EXPERIMENTAL RESEARCH

Qualitative visual assessment of defects

Soft asphalt in spring and summer

Double Otta Seal in spring and autumn

15

QUALITATIVE VISUAL ASSESSMENT OF DEFECTS

SOFT ASPHALT

16

Longitudinal cracking

Transverse cracking

Potholes

Ravelling

Seals

Bleeding

QUALITATIVE VISUAL ASSESSMENT OF DEFECTS

DOUBLE OTTA SEAL

17

Longitudinal cracking

Transverse cracking

Fatting up, bleeding

Tracking

Scabbing

Tearing

Longitudinal joint crack

Corrugation

Streaking

18

RESULTS

INTERNATIONAL ROUGHNESS INDEX

QUALITATIVE VISUAL ASSESSMENT OF DEFECTS

SOFT ASPHALT

19

62.98%

13.90% 6.77%

87.23%

SEALED LONGITUDINAL CRACKS

Road no. 2430 in summer 2017

20

QUALITATIVE VISUAL ASSESSMENT OF DEFECTS

SOFT ASPHALT

21

100%

98%

33%

98%

98%

QUALITATIVE VISUAL ASSESSMENT OF DEFECTS

SOFT ASPHALT

22

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

24

QUALITATIVE VISUAL ASSESSMENT OF DEFECTS

DOUBLE OTTA SEAL

25

QUALITATIVE VISUAL ASSESSMENT OF DEFECTS

DOUBLE OTTA SEAL

26

QUALITATIVE VISUAL ASSESSMENT OF DEFECTS

DOUBLE OTTA SEAL

27

Autumn 2013

Scabbing

Spring 2014

Sealed scabbing

QUALITATIVE VISUAL ASSESSMENT OF DEFECTS

DOUBLE OTTA SEAL

28

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.

32

https://www.youtube.com/watch?v=8Na1yzJBppY

33