Temporary Seals and Standards

SANRAL Workshop

15 August 2011 G van Zyl

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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

• 9,5 Single seal (N1/14, N8/8)

No Cover Spray

Cover Spray

1 year 60% heavies

Examples

• 9,5 Cape Seal (N1/14)

Examples

• Microsurfacing (N8/8)

• Benefits

• Sensitivities

Examples

• Half-width (Inverted 6,7 + 13,2)

Require much more binder than normal double seal

6,7 stone must settle

inverted seal

Towards Sealing in Winter

• Winter embargo period

• Based on risks and poor performance

-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

Temperature variance

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

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

Nominal

size (mm)

SANRAL Manual 10

Target

Minimum

ALD

19,0

13,2

9,5

12

8

5

10,8

7.4

5.3

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

End