CURRENT PRACTICES · Warmer areas –just adhere to temp specs Emulsion sealing –always 2 coats...
Transcript of CURRENT PRACTICES · Warmer areas –just adhere to temp specs Emulsion sealing –always 2 coats...
CURRENT PRACTICES
Gerrie van Zyl
MYCUBE ASSET MANAGEMENTSYSTEMS (PTY) LTDMYCUBE ASSET MANAGEMENTSYSTEMS (PTY) LTD
Acknowledgements
International overview
Local experiences
Winter seal experiments
General embargo during winter USA, Australia, New Zeeland
Central Africa still high use of cutbacks (TRL influence)
However cutters and adhesion agents used by
several contractors (Australia and NZ) Australia prefer primer seals on new roads and single
seals as reseals
NZ prefer racked-in seals due to stone loss
General drive towards emulsions Varying specs on temperatures and humidity
USA limitations - varying
Australia General winter embargos in SRAs
Primer seals with cutters
Cutters with 60/70 grade std
Precoating variations
New Zeeland NZTA – Winter embargo
Using cutters during summer season 1-5% on 130/150 Pen
Temporary holding seals if necessary
Rapid setting low temperature emulsions
High float emulsions
Promote adhesion No/low dust
Precoating/ Wetting agents
Soft binders/ cut-back/ emulsions
Heated aggregate
Tandem sprayer/chipper
Increased binder (50 – 70% of stone height)
Racked-in seals
Additional rolling/ compaction
High road surface temperatures
Observations Low volume roads
Wetting agents and cutters added
Open seal structure
Binder rise
Warmer areas – just adhere to temp specs Emulsion sealing – always 2 coats Cutback of conventional 80/100 pen bitumen Cape seals Grit/ sand/ graded aggregate seals Cut-back binder or emulsion
Proprietary products e.g. Wintergrade BR Microsurfacing
Emulsion seals (Cationic) Suppliers added 2-4% Cutter
Larger window due to road surface temperature
Typical Cape seals and single seals + grit
Conventional cut-back binders MC 3000
Sand/Grit seals, 13+Grit/sand
Worked well on Low volume roads
Cut-back on site for single seals (refer TRH3)
Winter grade modified binders WG Bitumen rubber
WG Polymer Modified (SBR or SBS)
Temperature and Wind chill
Humidity
Rainfall soon after construction
Adhesion development
Precoating Wet vs Dry precoating
Tar based vs Bitumen
Wet aggregate
Traffic
History of up to 12% cutters in 80/100 Pen
3-5% suggested by practitioners
Only in latter half of winter
Not in Cape Seals, Geotexstiles
TG 1- < 5000 elv/day, heavies < 15%, not in high stress areas
Opinions on negative effect on properties of bitumen rubber
Hazard of heating cut-back binders
No heating during transportation
Guidelines for safehandling
19 Sites evaluated Cut-back Bitumen rubber (13.2 Single)
Cut-back Polymer modified (SBS & SBR - 9.5 Single)
19 Cape seals (70/100 or S-E1 precoated)(SC-E1
precoated or Cat 65 fogspray)
Effect of cutters – more rapid ageing ?
19 Sites evaluated continue… 19/6/6 SC-E1/ S-E1(4%LFS) plus anionic or cationic emulsion
fogspray Effect of anionic stable versus cationic spray grade
ANIONIC CATIONIC
19 Sites evaluated continue… Microsurfacing (Rapid setting slurry)
Concerns
9.5 mm Cape Seal (Temp)
SC-E1(t) @ 1.0 l/m2 + M-F slurry @ 200 l/m3
Emulsion seals Emulsion seals (Cat 65 or SC-E1 plus Cat 65)
With and without fogspray
Grit seals Precoated and unprecoated
MC 3000 and Cat 65
Sensitivity to rain
Stone & 1/3 13.2 plus Grit or 13.2 plus 4.75
19 plus 6.7
Risks
Experimental Matrix Seal types
Binder types & combinations
Application rates
Traffic Low
Med
High
Climatic conditions Dry winter
Wet winter
Seal types Binders Application Cover spraySolvents
13 Single
19/9 Double
19/6/6 Split
BR Summer
BR Winter
NCRT
S-E1(SBS)
S-E1(SBS)
SC-E1
S-E1(SBR)
4% HFS
0-4% LFS
None
0.8-1.0 l/m2
50/50 - Undiluted
0-3% LFS
0.8-1.0 l/m2
50/50 - Undiluted
0-3% LFS
0.8-1.0 l/m2
50/50 - Undiluted
0-3% LFS
Low –High
Low –High
Low –High
0-4% LFS
0-3% LFS
13/6, 19/9, 19/6/6,Cape Seals
Stone packing on Cape Seals
Binder distribution e.g. 40/60 with SC-E1and S-E1
Seal at 10(SC-E1),15 and 20oC dependant on LFS
Heavy traffic
Precoating with emulsion