5 YEARS EXPERIENCE IN USING OTTA SEAL AND SOFT ASPHALT FOR GRAVEL ROADS IMPROVEMENT

Transcription

1 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

2 OUTLINE Problem Concept: Soft asphalt Double Otta Seal Experimental research Results Conclusions 2

3 PROBLEM In Lithuania 33 % of national significance roads are gravel roads 3

4 TYPICAL SOLUTIONS Chemical dust suppressants 4

5 TYPICAL SOLUTIONS Asphalt pavement Asphalt pavement (AC 16 PD) Unbound base course from crushed stone Frost resistant layer Subgrade 1) When ESAL ) Depends on class of frost resistance of soil 5

6 ALTERNATIVE SOLUTIONS Soft asphalt Surface course from soft asphalt Unbound base course from crushed stone +29% Existing gravel pavement (can be partly new layer) Subgrade 6

7 SOFT ASPHALT IDENTIFICATION (EN ) SA No identification or reference b D Grading designation d or o Binder Type A, B, C, S Soft asphalt The maximum aggregate size, mm No identification surface course b base course d dense graded aggregate o open graded aggregate Examples: SA 16-d-V6000 type C SA b 16-d-V12000 type S 7

8 SOFT ASPHALT CONSTRUCTION Base course preparation Soft asphalt laying Compaction Aggregate spreading Final compaction 8

9 ALTERNATIVE SOLUTIONS Surface dressing (Double Otta Seal) Double Otta seal Unbound base course of crushed stone +44% Existing gravel pavement (can be partly new layer) Subgrade 9

10 SURFACE DRESSING IDENTIFICATION (BASED ON TECHNICAL REQUIREMENTS) Type D BE VPA single surface dressing Bitumen emulsion DPA double surface dressing EDPA double surface dressing in stages The maximum aggregate size, mm Examples: VPA16BE DPA1611BE EDPA1616BE 10

11 SURFACE DRESSING CONSTRUCTION Base course preparation Binder spraying Aggregate spreading Compaction (rolling) 11

12 APPLICATION CONDITIONS Soft asphalt: ESALs < ESALs (asphalt base course is required) Bearing capacity of the subgrade 45 MPa Bearing capacity of the unbound base course 120 MPa Otta Seal: ESALs Bearing capacity of the subgrade 45 MPa Bearing capacity of the unbound base course 120 MPa 12

13 EXPERIMENTAL RESEARCH Criterions for trial sections: Number of freeze-thaw cycles AADT ESAL Frost depth 5 sections with soft asphalt 13 sections with double Otta seal 13

14 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

15 EXPERIMENTAL RESEARCH Qualitative visual assessment of defects Soft asphalt in spring and summer Double Otta Seal in spring and autumn 15

16 QUALITATIVE VISUAL ASSESSMENT OF DEFECTS SOFT ASPHALT Longitudinal cracking Transverse cracking Potholes Ravelling Seals Bleeding 16

17 Streaking QUALITATIVE VISUAL ASSESSMENT OF DEFECTS DOUBLE OTTA SEAL Longitudinal cracking Transverse cracking Fatting up, bleeding Tracking Scabbing Tearing Longitudinal joint crack Corrugation 17

18 RESULTS INTERNATIONAL ROUGHNESS INDEX 18

19 QUALITATIVE VISUAL ASSESSMENT OF DEFECTS SOFT ASPHALT 62.98% 13.90% 6.77% 87.23% 19

20 SEALED LONGITUDINAL CRACKS Road no in summer

21 QUALITATIVE VISUAL ASSESSMENT OF DEFECTS SOFT ASPHALT 33% 98% 98% 98% 100% 21

22 QUALITATIVE VISUAL ASSESSMENT OF DEFECTS SOFT ASPHALT Bleeding Potholes <0.5% Ravelling Seals 22

23 QUALITATIVE VISUAL ASSESSMENT OF DEFECTS SOFT ASPHALT (AFTER 5 YEARS) Road no Road no Road no

24 QUALITATIVE VISUAL ASSESSMENT OF DEFECTS DOUBLE OTTA SEAL 24

25 QUALITATIVE VISUAL ASSESSMENT OF DEFECTS DOUBLE OTTA SEAL 25

26 QUALITATIVE VISUAL ASSESSMENT OF DEFECTS DOUBLE OTTA SEAL 26

27 QUALITATIVE VISUAL ASSESSMENT OF DEFECTS DOUBLE OTTA SEAL Autumn 2013 Scabbing Spring 2014 Sealed scabbing 27

28 QUALITATIVE VISUAL ASSESSMENT OF DEFECTS DOUBLE OTTA SEAL 28

29 QUALITATIVE VISUAL ASSESSMENT OF DEFECTS DOUBLE OTTA SEAL (AFTER 5 YEARS) Road no Road no Road no

30 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

31 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 31 and double Otta Seal, respectively.

32 CONCLUSIONS Critical factor for road sections covered with double Otta Seal is incomplete construction and maintenance of constructed road sections. During construction phase light moistening should be applied on the base before bitumen emulsion spreading. Two-stage construction of first and second layer of double Otta Seal is strictly recommended; the second one should be applied not less than after four weeks of road exploitation and maintenance of emerged defects in first layer. The trial emulsion and aggregate spreading and compaction rolling are strictly recommended for Otta Seal technology in order to verify the emulsion and aggregate application rates and a sufficient number 32 of roller passes.

33 33