Temporary Seals and Standards. SANRAL Workshop 15 August 2011 G van Zyl

Transcription

1 Temporary Seals and Standards? SANRAL Workshop 15 August 2011 G van Zyl

2 Scope Temporary seals Deviations Half width construction Temporary winter sealing Towards Winter Seals Appropriate standards

3 Temporary Seals Seal types preferred Sand/ Grit seals Single 6,7; 9,5 Single plus sand/grit - 9,5 or 13,2 Double seals 9,5+4,75 or 13,2 + 6,7 Cape Seals 9,5 or 13,2 Graded seals (Otta Seals)

4 Key aspects Base type, quality and texture Prime recommended At least two binder applications Design Dual direction? Prefer higher binder applications What seal will follow? Texture treatment required?

5 Examples 9,5 Single seal (N1/14, N8/8) No Cover Spray Cover Spray 1 year 60% heavies

6 9,5 Cape Seal (N1/14) Examples

7 Examples Microsurfacing (N8/8) Benefits Sensitivities

8 Examples Half-width (Inverted 6,7 + 13,2) Require much more binder than normal double seal 6,7 stone must settle inverted seal

9 Towards Sealing in Winter Winter embargo period Based on risks and poor performance

10 Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Deg C Minimum Temperature selection of appropriate seal types 7year min Ave 7y min ENGINEERING OUT-OF-THE BOX SOLUTIONS

11 1-Jan Jan Jan Feb Feb Mar Mar-03 9-Apr Apr-03 7-May May-03 4-Jun Jun-03 Degree C Minimum Temperature station Minimum Temperature (Station ) Date ENGINEERING OUT-OF-THE BOX SOLUTIONS

12 Temperature variance

13 Temperature (Celsius) Temperature (Celsius) Towards Sealing in Winter Considerations Winter embargo periods Area specific Temperatures Rainfall Consequential Average Minimum Temperature (Coastal) Average Minimum Temperature (Inland) Durban Cape Town Mosselbaai 10 5 Sutherland Upington Bela Bela 0 PE 0 Bloemfontein -5-5 Jan Feb Ma Ap May June Jul Aug Sept Oct Nov Dec Jan Feb Ma Ap May June Jul Aug Sept Oct Nov Dec Month Month

14 Towards Sealing in Winter Considerations More appropriate surfacing type & Design More binder (20-50%) Split application of binder eg add cover spray Add grit/ coarse sand after breaking of emulsion Double seals or Cape seals Note: Principles More bond strength (surface area) Stronger matrix Less friction on individual stones (smaller top stone)

15 Towards Sealing in Winter Winter grade binders Considerations Conventional versus modified Cutters Type and effects slow evaporation Safety risks Recommended Max 4% paraffinic in Pol Mod Binder Single versus Double seals Risks / Trapping volatiles Excellent experiences with single seals Low traffic versus high traffic volumes - Risk

16 Winter grade binders Current recommendations Up to 12% Cutters conventional (MC 3000) 4% Max in Polymer Modified binders Risk increases if closer to summer Stick to first half of winter Add fogspray (normal Cat 65 SG 60/40 undiluted) Double seals only use WG binder in penetration coat

17 Examples: Winter Seals Single seal (ELVs using SC-E1 tack Precoated and unprecoated stone Cat 65% spray grade 60/40, 70/30 and undiluted Application rates 30% higher than TRH3 Min Do we need a texture treatment before the final seal?

18 Examples: Winter Seals 9,5 mm Cape Seal Using SC-E1 as tack Precoated stone or cover spray 50/50 CAT Dry slurry Min on Wet Track Abrasion Test Tested different emulsion contents Result

19 Example:Double Winter seals 19/6/6 Split Application Double Seal Using Cat 65 SG as Tack (1,5 l/m2) 19 precoated tightly packed 1 st pen Layer Cat 65 at 0.8 l/m2 1 st 6,7mm layer SC-E1 at 1.5 l/m2 Cat 65 Cover spray 60/40 at 1.2 l/m2 Night Temps -10 Deg C

20 Example:Double Winter seals 19/6/6 Split Application Double Seal Using Cat 65 SG as Tack (1,5 l/m2) 19 precoated tightly packed Dry layer S-E1 cut back 4% paraffin at l/m2 Cat 65 Cover spray 60/40 at 1.2 l/m2 Night Temps -3 Deg C

21 STANDARDS

22 Standards & Specifications What is appropriate? Traffic spectrum/ Functional purpose / Safety Increase of relax? Design Simplify, method statements

23 Specs & Standards Seal type (Skid/ noise/ etc) risk Design possible move to method specs Material Binder - K Louw Aggregate

24 Network Distance (km) Traffic Distribution South African Surfaced Rural Road Network > LVSR Average Daily Traffic (ADT) (Both Directions) Possible relaxation No relaxation Stick to AC

25 Aggregate Hardness (Evaluate sources and traffic) Grading and dust content COLTO grade 2 Durability needs attention for seal aggregate Polished stone value could be relaxed for lower volume roads and low risk situations Stone shape ALD Flakiness Elongation?

26 Seal Costs Proportional costs for 13mm Single seal (80/100 Pen Bitumen) Large Far Large Close Average Small Far Aggregate cost Aggregate haul Equip Establishment Construction Binder deliver &apply Binder costs Labour Small Close % of Average 13mm Seal costs

27 Flakiness Aggregate size Grade of Aggregate Grade 1 Grade 2 & 3 19,0 mm nominal size ,2 mm nominal size ,5 mm nominal size ,7 mm nominal size 30 35

28 Nominal size (mm) 19,0 13,2 9,5 SANRAL Manual 10 Target Minimum ALD ,

29 Transverse distribution Emulsions, cutback 5% penetration grade bitumens Homogeneous modified bitumens Nonhomogeneous binders (bitumen rubber) 5% 7% 10%

30 Sieve size (mm) Grade 26,5 mm nominal size 19,0 mm nominal size Percentage passing by mass 13,2 mm nominal size 9,5 mm nominal size 6,7 mm nominal size 4,75 mm nominal size 2,36 mm nominal size 37, , , , Grades 9, * &2 6, ** 0-30* , ** 0-30* , , ** Grade 3 Grading shall comply with the requirements for grades 1 and 2 with the following exceptions: * 0 50 ** 0 10 Fines content: Material passing a 0,425 mm sieve (max) Grade 1 0,5 0,5 0,5 0,5 0,5 1,0 15,0 Grade 2 1,5 1,5 1,5 1,5 2,0 2,5 15,0 Grade 3 N/A N/A 2,0 2,0 3,0 3,5 15,0 Dust content: Material passing a 0,075 mm sieve (max) Grade 1 N/A N/A N/A N/A N/A N/A 2,0 Grade 2 0,5 0,5 0,5 0,5 1,0 1,0 2,0 Grade 3 N/A N/A 1,5 1,5 1,5 1,5 2,0

31 Conclusions Scope for adjustments Need study and appropriate guidelines Do not change for the sake of changing No excuse for poor construction quality

32 End