SCI/IAT/IHT Seminar Cases for and against hot mix road surfacings

Transcription

1 SCI/IAT/IHT Seminar Cases for and against hot mix road surfacings Overview, Insert the including title of your less common presentation options here Presented Presented by by Dr Name Cliff Here Nicholls Senior Job Title Academy - Date Fellow 15 Oct. 2009

2 Table of contents 1 Material types 2 Similarities 3 Differences 4 Porous asphalt 5 Mastic asphalt 6 Conclusions Page 2

3 Material Types Mixtures defined by standards BS 594 and BS 4987 replaced by BS EN Page 3

4 Material Types BS EN Asphalt concrete (AC) - Includes macadams, Marshall asphalt and EME2 BS EN Asphalt concrete for very thin layers (BBTM) BS EN Soft asphalt (SA) BS EN Hot rolled asphalt (HRA) BS EN Stone mastic asphalt (SMA) BS EN Mastic asphalt (MA) BS EN Porous asphalt (PA) pren Ultra-thin layer asphalt concrete (UTLAC) Page 4

5 Table of contents Material types Similarities Differences Porous asphalt Mastic asphalt Conclusions Page 5

6 Similarities All made from the same component materials Different proportions - Aggregate gradings - Binder contents How different are the gradings? BS EN overall envelope for target gradings - 10 mm size for comparison

7 Asphalt concrete AC 10 gradings Poportion passing (%) AC Sieve Size (mm) Page 7

8 AC 10 and BBTM 10 gradings Poportion passing (%) AC10 BBTM10A BBTM10B BBTM10C BBTM10D Sieve Size (mm) Page 8

9 AC 10 and BBTM 10 gradings Poportion passing (%) AC10 BBTM Sieve Size (mm) Page 9

10 AC 10, BBTM 10 and SMA 10 gradings Poportion passing (%) AC10 BBTM10 SMA Sieve Size (mm) Page 10

11 AC 10, BBTM 10, SMA 10 and MA 10 gradings Poportion passing (%) AC10 BBTM10 SMA10 MA Sieve Size (mm) Page 11

12 AC 10, BBTM 10, SMA 10 and PA 10 gradings Poportion passing (%) AC10 BBTM10 SMA10 PA Sieve Size (mm) Page 12

13 AC 10, BBTM 10, SMA 10, PA 10 and HRA gradings Poportion passing (%) AC10 BBTM10 SMA10 PA10 HRA15/10F Sieve Size (mm) Page 13

14 AC 10, BBTM 10, SMA 10, PA 10 and HRA gradings Poportion passing (%) AC10 BBTM10 SMA10 PA10 HRA30/10F Sieve Size (mm) Page 14

15 AC 10, BBTM 10, SMA 10, PA 10 and HRA gradings Poportion passing (%) AC10 BBTM10 SMA10 PA10 HRA0/10F Sieve Size (mm) Page 15

16 AC 10, BBTM 10, SMA 10, PA 10 and HRA gradings Poportion passing (%) AC10 BBTM10 SMA10 PA10 HRA55/10F Sieve Size (mm) Page 16

17 AC 10, BBTM 10, SMA 10, PA 10 and HRA gradings Poportion passing (%) AC10 BBTM10 SMA10 PA10 HRA55/10C Sieve Size (mm) Page 17

18 AC 10, BBTM 10, SMA 10 or PA 10 grading Poportion passing (%) AC10 or BBTM10 or SMA10 or PA10? Sieve Size (mm) Page 18

19 Similarities Grading envelopes overlap What is the common mixture like? Do not know, but expect: - Relatively open macadam, thin surfacing or SMA - Relatively impermeable PA Mixture types relatively arbitrary classifications

20 Table of contents Material types Similarities Differences Porous asphalt Mastic asphalt Conclusions Page 20

21 Properties Required of Surfacings The envelopes do have differences Effect on properties of surfacings? (taken from TRL Report TRL250) Suitability for re-profiling Deformation resistance Resistance to cracking Spray reduction Noise reduction Skid resistance Texture depth Durability Quality of ride Initial cost Speed of construction Sustainability Page 21

22 Performance of Surfacings (1) Material Re-profiling Deformation Cracking Hot rolled asphalt ( ) Porous asphalt Macadam Mastic asphalt Stone mastic asphalt Thin surf. (26-39 mm) Thin surf. (18-25 mm) Thin surf. (< 18 mm) Page 22

23 Performance of Surfacings (2) Material Spray Noise Skid Hot rolled asphalt Porous asphalt Macadam Mastic asphalt Stone mastic asphalt Thin surf. (26-39 mm) Thin surf. (18-25 mm) Thin surf. (< 18 mm) Page 23

24 Performance of Surfacings (3) Material Texture Durability Ride Hot rolled asphalt Porous asphalt Macadam Mastic asphalt Stone mastic asphalt Thin surf. (26-39 mm) Thin surf. (18-25 mm) Thin surf. (< 18 mm) Page 24

25 Performance of Surfacings (4) Material Cost Speed Hot rolled asphalt Porous asphalt Macadam Mastic asphalt Stone mastic asphalt Thin surf. (26-39 mm) Thin surf. (18-25 mm) Thin surf. (< 18 mm) Page 25

26 Differences Some properties also dependant on aggregate size No mixture is best for all properties No mixture is worst for all properties Engineering judgement for each situation Horses for courses Overall durability - Wild variations with workmanship - Workmanship in design, manufacture and laying - To UK specifications Page 26

27 Expected Service Life of Different Surfacings Type Category Expected Life Thin surfacing BBTM 11 to 15 years SMA 10 to 16 years Ultra-thin 8 to 11 years Multiple surface dressing 4 to 8 years Micro-surfacing 2 to 6 years Hot rolled asphalt High & medium stability 14 to 24 years Low stability 8 to 13 years Asphalt concrete DBM 10 to 16 years Open graded macadam 6 to 10 years Marshall asphalt 15 to 25 years Porous asphalt 7 to 10 years

28 Table of contents Material types Similarities Differences Porous asphalt Mastic asphalt Conclusions Page 28

29 Porous asphalt - Concept

30 Porous asphalt - History PSA developed friction course for airfields 1950s First TRL road trial 1967 Pervious macadam incorporated into BS HA 50/93 issued 1993 Porous asphalt incorporated into SHW 1994 Still in SHW but not preferred material Page 30

31 UK trials of porous asphalt 20 Number of Trials mm Unmodified 20 mm Modified 16 & 14 mm Unmodified 14 & 16 mm Modified 10 mm Unmodified 10 mm Modified Page 31

32 Service life of porous asphalt 100% Proportion of servicable sections 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Ultimate life Spray-reducing life Life (years) Page 32

33 Identification of failure Failure can be sudden Literally There one day, gone the next Identify potential Estimate for paving grade binders Polymer-modified binders different slope Predicted recovered penetration (0.1 mm) /60 pen 70/100 pen 160/220 pen Brittle failure Time from laying (years) Page 33

34 Advantages of porous asphalt Less traffic noise in both dry and wet conditions Less splash and spray in wet conditions Reduced possibility of aquaplaning Reduced surface glare Reduced rolling resistance Page 34

35 Disadvantages of porous asphalt Reduced structural strength Requires positive edge drainage details Requires extra lighting Requires tighter tolerances Care needed to ensure no barriers within mat Tendency for the pores to clog Maintenance operations limited to avoid creating dams Winter maintenance regimes need adjustment Concerns over durability High cost Page 35

36 Uses for porous asphalt High prestige sites Sites not needing long durability Sites with spray problems Sites where excessive surface water with heavy rainfall Not necessary for sites with noise problems Therefore uses will be limited but there are still some uses Page 36

37 Table of contents Material types Similarities Differences Porous asphalt Mastic asphalt Conclusions Page 37

38 Mastic asphalt Basic components: - Stiff binder - Aggregate in powdered or finely crushed form - High binder content Heated and mixed together to form a pudding or porridge-like product Capable of being poured and trowelled or screeded out to level Poured asphalt Two sub-categories Page 38

39 Mastic asphalt Mastic asphalt - Voidless with the consistency of a pudding - Screeded by hand - Used in UK, France and Mediterranean Gussasphalt - Relies on a graded aggregate structure - Flows into place, albeit assisted by compaction - Laid by machine - Germany, Northern Europe and Scandinavian countries Page 39

40 Mastic asphalt Good waterproofing Primary uses: - Tunnels - Concrete bridge decks - Steel bridge decks - Footpaths - Flat roofs Page 40

41 Table of contents Material types Similarities Differences Porous asphalt Mastic asphalt Conclusions Page 41

42 Conclusions Mixture types are relatively arbitrary But are still useful No mixture is best for all properties No mixture is worst for all properties Engineering judgement for each situation Appropriate choice is important But care and attention (workmanship) can be as important Page 42

43 Asphalt Surfacings All that there is to know about the details of all asphalt types Page 43

44 Conclusions Porous asphalt - Widely used on airfields - Not widely used on highways - Good for sites with spray problems or where excessive surface water with heavy rainfall - Limited durability Mastic asphalt - Highly impermeable - Several specialist uses - One of the few options for long steel bridge decks - High costs Page 44

45 Do ButYou You Will Have Any To Just Have Questions? Wait! Page 45

46 Thank you SCI/IAT/IHT Seminar Overview, including less common options Presented by Dr Cliff Nicholls Senior Academy Fellow 15 October 2009 Tel: Page 46