Post on 02-Apr-2018
transcript
Scope
• Temporary seals
Deviations
Half –width construction
Temporary winter sealing
• Towards Winter Seals
• Appropriate standards
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)
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 ?
Examples
• Half-width (Inverted 6,7 + 13,2)
Require much more binder than normal double seal
6,7 stone must settle
inverted seal
-4
-2
0
2
4
6
8
10
12
14
Ja
n
Fe
b
Ma
r
Ap
r
Ma
y
Ju
n
Ju
l
Au
g
Se
pt
Oct
No
v
De
c
De
g C
7year min Ave 7y min
Minimum Temperature
… selection of appropriate seal types
ENGINEERING OUT-OF-THE BOX SOLUTIONS
Minimum Temperature (Station 589591)
-5
0
5
10
15
20
25
1-J
an-0
3
15-J
an-0
3
29-J
an-0
3
12-F
eb-0
3
26-F
eb-0
3
12-M
ar-
03
26-M
ar-
03
9-A
pr-
03
23-A
pr-
03
7-M
ay-0
3
21-M
ay-0
3
4-J
un-0
3
18-J
un-0
3
Date
Deg
ree C
Minimum Temperature
ENGINEERING OUT-OF-THE BOX SOLUTIONS
… station 589591
Towards Sealing in Winter
Considerations
• Winter embargo periods – Area specific
Temperatures
Rainfall
Consequential
-5
0
5
10
15
20
25
Jan Feb Ma Ap May June Jul Aug Sept Oct Nov Dec
Te
mp
era
tu
re
(C
els
ius)
Month
Average Minimum Temperature (Coastal)
Durban
Cape Town
Mosselbaai
PE
-5
0
5
10
15
20
25
Jan Feb Ma Ap May June Jul Aug Sept Oct Nov Dec
Te
mp
era
ture
(C
els
ius)
Month
Average Minimum Temperature (Inland)
Sutherland
Upington
Bela Bela
Bloemfontein
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)
Towards Sealing in Winter
Considerations
• Winter grade binders
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
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
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 ?
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
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
1st pen Layer Cat 65 at 0.8 l/m2
1st 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
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 1.3 – 1.5 l/m2
Cat 65 Cover spray 60/40 at 1.2 l/m2
Night Temps -3 Deg C
Standards & Specifications
• What is appropriate?
• Traffic spectrum/ Functional purpose / Safety
• Increase of relax ?
• Design – Simplify, method statements
Specs & Standards
• Seal type (Skid/ noise/ etc) – risk
• Design – possible move to method specs
• Material
Binder - K Louw
Aggregate
0
2000
4000
6000
8000
10000
12000
14000
16000
0-200 200-500 500-1000
1000-2000
2000-4000
4000-6000
6000-10000
10000-20000
20000-50000
50000-100000
>100000
Ne
two
rk D
ista
nce
(km
)
Average Daily Traffic (ADT) (Both Directions)
Traffic DistributionSouth African Surfaced Rural Road Network
LVSR
Possible relaxation
Stick to ACNo relaxation
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 ?
Seal Costs
0 20 40 60 80 100 120 140 160
Small Close
Small Far
Average
Large Close
Large Far
% of Average 13mm Seal costs
Proportional costs for 13mm Single seal (80/100 Pen Bitumen)
Aggregate cost
Aggregate haul
Equip Establishment
Construction
Binder deliver &apply
Binder costs
Labour
Flakiness
Aggregate size Grade of Aggregate
Grade 1 Grade 2 & 3
19,0 mm nominal size 25 30
13,2 mm nominal size 25 30
9,5 mm nominal size 30 35
6,7 mm nominal size 30 35
Transverse distribution
Emulsions,
cutback
5%
penetration
grade bitumens
5%
Homogeneous
modified
bitumens
7%
Non-
homogeneous
binders
(bitumen rubber)
10%
Sieve size (mm) Grade
Percentage passing by mass
26,5 mm
nominal
size
19,0 mm
nominal size
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
37,50
Grades
1&2
100 - - - - - -
26,50 85 - 100 100 - - - - -
19,00 0 - 30 85 - 100 100 - - - -
13,20 0 - 5 0 - 30 85 - 100 100 - - -
9,50 - 0 - 5 0 - 30* 85 - 100 100 - -
6,70 - - 0 - 5** 0 - 30* 85 - 100 100 -
4,75 - - - 0 - 5** 0 - 30* 85 - 100 100
3,35 - - - - - 0 - 30 -
2,36 - - - - 0 - 5** 0 - 5 0 - 100
Grade 3Grading 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
Conclusions
• Scope for adjustments
• Need study and appropriate guidelines
• Do not change for the sake of changing
• No excuse for poor construction quality