pavement & material design,tanzania

7/24/2019 Pavement & Material Design,Tanzania

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Cut back slope

Shoulder breakpoint

Shoulder Shoulder

Embankment side slope

Carriageway

Roadway

Open side drain

Centre

line

Lane Lane

Original ground level

Finished road level

Pavement layers

Improvedsubgrade layers

Cutting

In-situ subgrade Fill

Formation level

Subgrade

Roadbed

Asphalt concrete surfacing Surface treated pavementsWearing course

Binder course (if required)

SurfacingSurfacing

SubgradeSubgrade

Surfacing

Gravel roads

Gravel wearing course

Structural layer (improved subgrade, if required)

Subgrade


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Project appraisal

Environment

Pavement Design-

New Roads

Cross Section,Shoulders and Drainage

Traffic

Subgrade

Problem Soils

Pavement Materials

DESIGNELEMENTS

PavementRehabilitation

BituminousSurfacings

Gravel RoadsSTRUCTURAL

DESIGN

Comparison of alternatives andselection of design

Refinement of design, if required

Ch

Ch


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Project appraisal

Pavement Design-

New Roads


Traffic

Subgrade

Problem Soils

Pavement Materials

DE

SIGN

ELEMENTS




DESIGN



Ch

Ch


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Project appraisal

Environment

Pavement Design-

New Roads

Traffic

Subgrade

Problem Soils

Pavement Materials

DESIGNELEMENTS




DESIGN



Ch

Ch


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75 mm

Water Pervious materialBase

course

Subbase

Granularbase course

Subbase

Water


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General requirementmin 0,5 m

Cuttings - general requirementmin 1,0 m

Cuttings - lime modified subgrademin 0,5 m

Pavement

Formationlevel

Pavement

Formationlevel

Pavement

Formationlevel


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Project appraisal

Environment

Pavement Design-New Roads


Subgrade

Problem Soils

Pavement Materials

DESIGNELEMENTS




DESIGN



Ch

Ch


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tonnes load

kPa

load per area

contact pressure

loads t1 t2 t3 t4.......tn


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Pavement serviceability

Project construction, the

pavement beingcompleted in parts.

Completed

pavementon

theentire

project

Terminal valueof serviceability

(nore

seal)

Res

eal

Reseal

Pavement

rehablitation

Design Period

Traffic count

for each

direction

Chapter 4.2.1

Axle load survey

for each

direction

Chapter 4.2.2

Proportion of

E80 made up

from axles

heavier than 13t

Chapter 4.2.4

Vehicle

equivalency

factor

Chapter 4.2.3

Proportion of

E80 made up

from axles

heavier than13tChapter 4.2.4

Vehicle

equivalency

factorChapter 4.2.3

Classify

as'heavy' or not

Chapter 4.2.4

Apply

traffic growth

Chapter 4.2.5

and lane

distribution

Chapter 4.2.6

Include

construction

traffic

Chapter 4.2.7

Classify into

Traffic Load Class

Chapter 4.3Socio -economicstudies

Design trafficloading


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Project appraisal

Environment

Pavement Design-

New Roads

Traffic

Subgrade

Problem Soils

Pavement Materials

DESIGNELEMENTS


BituminousSurfacing


DESIGN



Ch

Ch


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Original ground level

Finished road level

Pavement layers

Design depth

Other roads

Paved trunk roads


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Sitereconnaissance

Compilation

of input data

Demarcation ofhomogenoussections

Min 3 CBRtests per uniform

section

Cut ?Use lowestCBR value

:CBRdesignClassify

S3, S7, S15

Design improved

subgrade as

required

Min 5 CBRtests per uniform

section

Specialassessmentof thesection

Plot valuesin ascendingorder

Determine 90%-ile valueat the 0.1 X (n-1) pointon the curve

Yes

Yes

YesNo

No


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0

2

4

6

8

10

12

14

16

1 2 3 4 5 6 7 8 9Test

CBR(%)

n = 9 tests

d = 0.1 x (n-1)

= 0.8

d=0.8

Example

CBR data68999

11121214

90% -ile7.6

CBRdesign8%

CBR values plottedin ascending order

1

10

100

88

90

92

94

96

98

100

102

104

% of MDD

CBR4dayssoaked

(%)


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Subgrade Density for

class Wet or moderate determinationclimatic zones of CBRdesign

4 days soaked value Tested at OMC 4 days soaked value [% of MDD]

S15 Min 15 Min 15 Min 7 95 BS-HeavyS7 7 - 14 7 - 14 3 - 14 93 BS-HeavyS3 3 - 6 3 - 6 2 - 6 100 BS-Light

Soaked and OMC refer to standard 4 days soaking and the optimum moisture content determined inaccordance with tests CML1.9 and CML 1.11. Climatic zones are shown in/Figure 2.1/.

BS-Light compaction effort is used on poor in-situ soils and deep in-situ soils rather than BS-Heavy due to itsbetter correspondence with the actual effect from compaction equipment under conditions with poor support

for compaction. The referred laboratory test methods are CML 1.9 and 1.11.

Problem soils: Special treatment is required./Chapter 6/

CBRdesign [%]

Dry climatic zones(both requirements shall be met)


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sub grad e l ayers C ompa cted l ayer

Formation level (150 +150 mm) thickness (max 1m)

Roadbed or previous fill layer

Dump rock - cross section

Max 2/3 of compactedlayer thickness

dMAX

*) Material requirements for improved subgrade layers, including limits for maximum compacted layerthickness are given inTable 5.5.

G15G15

300mm

150mm

G15

150mm

150mm

150mm

G15

G7

requirement or dry climate Moderate Wet

General General requirements

S3S7Heavy traffic classes (-H)

WetModerate climateor dry

G15

S15

Subgrade classes

G7

300mm 300mm

150mmG7

G7

300mm 300mm

Heavy traffic

classes (-H)

none

none

none none

G15

Improvedsubgrade

layertobeconstructed

Lowerlayer*)

Upperlayer*)

CBR [%], wet or moderate

climatic zones 1)

CBR [%], dry climatic zones 1) Min 15 at OMC Min 7 at OMC 1.9 and

(both requirements shall be met) Min 7 after 4 days soaking Min 3 after 4 days soaking 1.7

CBR-swell [%] 2) Max 1.5 Max 2.0

PI [%] Max 25 Max 30 1.2 and 1.3

Max particle size, dMAX 2/3 of layer thickness 2/3 of layer thickness 1,7

Compacted layer thickness [mm] Max 250 Max 250

1) Climatic zones are shown in /Figure 2.1/. CBR values shall be assesed at density as given in Table 5.3.

Soaked and OMC refer to standard 4 days soaking and the optimum moisture content determined in

accordance with tests CML test methods 1.9 and 1.11

2) CBR-Swell is measured at 100% BS-Heavy compaction effort.

Min 15 after 4 days soaking Min 7 after 4 days soaking


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Depth

150mm

Scarify & compact

Future formation level


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Project appraisal

Environment

Pavement Design-

New Roads


Traffic

Subgrade

Pavement Materials

DESIGNELEMENTS




DESIGN



Ch

Ch


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Routine investigations

Expansive

Extended investigations

Expansive?

In-depth studyDesign and constructionmeasures for expansive soils

Normaldesign

Severe consequencesto the construction

economy?

No

No

No

Yes

Yes

Perhaps

Cross section

Outer zones having large seasonalvariations in moisture content

Expansive soils

Seasonal

movement

Seasonal

movement


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min. 6 m (4 m)

side drainembankment


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Freely draining material

Pavement layers

Fill and improved subgrade Side-fill

Expansive soil

1:6 or flatter

1:2

Freely draining materialPavement layers

Fill and improved subgrade

Side-fill

Expansive soil excavated 0.6 m

deep and replaced with fill

Freely draining materialPavement layers

Fill and improved subgrade Side-fill

Temporary stockpile of

Embankments 2 m or higher

Embankments less than 2 m in hight

excavated expansive soilto be used for side-fill

>2 m

Max. the width of the surfacing

excavated expansive soilto be used for side-fill

Temporary stockpile of

< 2 m

1:4 or flatter

1:2

1:6 or flatter

1:2

Expansive soil excavated 0.6 m deep and replaced with fill


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cross section

A thin bituminous sealgets pushed up by thecrystallisation forcesand blistering occurs,having a diametre of5 to 10 cm initially, Crystallisation of

subsequently developing soluble salts under

into a pothole. the bituminous seal.

Soluble salts migrate towards thesurface within granular layers

See detail


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Project appraisal

Environment

Pavement Design-New Roads


Traffic

Subgrade

Problem SoilsDESIGNELEMENTS




DESIGN



Ch

Ch


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Material CML test properties method

Wet or moderate climatic zones: min 80after 4 days soak Wet or moderate climatic zones: min 60after 4 days soakCBR [%] Dry climatic zones (both requirements shall be met): Dry climatic zones (both requirements shall be met):

at 98% MDD of min 80at OMC of BS-Heavy min 60at OMC of BS-Heavy 1.7 and

BS-Heavy min 60after 4 days soaking min 45after 4 days soaking 1.11

General Coral rock, calcrete or General Coral rock, calcrete or

Atterberg requirements other calcified materials requirements other calcified materials

limits 1) Wet or Dry Wet Dry or Wet Dry or Wet Dry or

moderate climate climate moderate climate moderate climate moderate

maxLL [%] 30 40 35 45 35 45 40 45 1.2

maxPI [%] 8 14 10 16 10 16 12 18 1.3maxLS [%] 4 7 5 8 5 8 6 9 1.4

Grading, sieve

sizes [mm]

63

37.5 Grading requirements:

20 - dMAXshall be maximum 2/3 of the compacted layer thickness

5 - Grading Modulus (GM*)

): min2.0 2 *) 0.425 GM = [ 300 - (% passing 2mm) - (% passing 0.425mm) - (% passing 0.075mm) ] / 100

0.075

Particle TFVdry : min80 kN TFVdry : min50 kN

strength TFVsoaked : min60% of TFVdry TFVsoaked : min60% of TFVdry

Soluble salts Where the gravel is used under a surface treatment, soluble salt content is assessed in accordance with /7-11/.

Field density

CBR - swell [%]max 0.5 max 1.0

measured at BS-Heavy compaction measured at BS-Heavy compaction

30 - 65

1) It is emphasised that the Atterberg limits shall be measured according to CML test methods 1.2, 1.3 and 1.4. These methods follow BS procuders and

Nominal value: min 98% of MDD, BS-Heavy

utilise BS equipment. Other laboratory test procedures are likely to give results that are not comparable with the given material requirements.

1.7

2.7

10 - 30

20 - 50

Material class

5 - 15

100

80 - 100

60 - 95

Grading envelope, G80

[% passing]

G80 G60

(no envelope for G60, coral rock, calcrete or other calcified materials)


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Material CML test

propertiesmethod

Wet or moderate climatic zones: min 45after 4 days soak Wet or moderate climatic zones: min 25after 4 days soak

CBR [%] Dry climatic zones (both requirements shall be met): Dry climatic zones (both requirements shall be met):

at 95% MDD of min 45at OMC of BS-Heavy min 25at OMC of BS-Heavy 1.7 andBS-Heavy min 25after 4 days soaking min 15after 4 days soaking 1.11

General Coral rock, calcrete or General Coral rock, calcrete or

Atterberg requirements other calcified materials requirements other calcified materials

limits 1) Wet or Dry Wet Dry or Wet or Dry Wet Dry ormoderate climate climate moderate moderate climate climate moderate

maxLL [%] 40 45 45 50 45 50 45 55 1.2

maxPI [%] 14 18 16 20 16 20 18 24 1.3 maxLS [%] 7 9 8 10 8 10 9 12 1.4

Grading *)

Modulus (GM) *) GM = [ 300 - (% passing 2mm) - (% passing 0.425mm) - (% passing 0.075mm) ] / 100

Particle size dMAXshall be maximum 2/3 of the compacted layer thickness

Soluble salts Where the gravel is used under a surface treatment, soluble salt content is assessed in accordance with /7-11/.

Field density

BS equipment. Other laboratory test procedures are likely to give results that are not comparable with the given material requirements.

Nominal value: min 95% of MDD, BS-Heavy

G45 G25

1) It is emphasised that Atterberg limits shall be measured according to CML test methods 1.2, 1.3 and 1.4. These methods follow BS procuders and utilise

1.7

Material class

min1.5 min1.2

CBR - swell [%]max 0.5 max 1.0

measured at BS-Heavy compactionmeasured at BS-Heavy compaction


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Material CML test properties method

Material source

maxLL [%]1) 1.2

maxLS [%]1) 1.4

Grading, sieve

sizes [mm] Coarse Type Fine Type Coarse Type Fine Type

50 100

37.5 100 90 - 100 100

28 87 - 97 100 75 - 95 90 - 100

20 75 - 90 87 - 97 60 - 90 65 - 95

10 52 - 68 62 - 77 40 - 75 40 - 70

5 38 - 55 44 - 62 29 - 60 29 - 52

2 23 - 40 27 - 45 20 - 45 20 - 40

1,18 18 - 33 22 - 38 17 - 40 15 - 33

0,425 11 - 24 13 - 27 12 - 31 10 - 24

0,075 4 - 12 5 - 12 5 - 15 4 - 12 Aggregate strength

Soluble salt content For aggregate used under a surface treatment, soluble salt content is assessed in accordance with /7-11/.

Field density requirements

4

of MDD BS-Heavy

Nominal value: min 100%

Material class

CRR

[% passing][% passing]

CRS

335

Nominal value: min 88%

30

1) It is emphasised that Atterberg limits shall be measured according to CML test methods 1.2, 1.3 and 1.4. These methods follow BS procuders and utilise

BS equipment. Other laboratory test procedures are likely to give results that are not comparable with the given material requirements.

2.7

1.7

TFVdry: min110 kN

TFVsoaked : min75% of TFVdry TFVsoaked : min60% of TFVdry

of Aggregate Density

Crushed rock. Shall be made by crushing and

screening of fresh quarried rock or clean, un-weathered

boulders of minimum 0.3 m diameter. All particles shall

be crushed, no soil fines allowed.

Crushed stone. Made by crushing and screening of

blasted rock, stones, boulders and oversize from natural

gravel. Min 50% by mass of particles larger than 5 mm

shall have at least one crushed face. Max 30% of

material passing 5 mm can be soil fines.


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Material CML test properties C2 C1 CM method

Earthworks quality soils/gravel

minUCS [MPa] 2,0 1,0 0,5 1.21

ICL - test 1.22

max PI after stabilisation [%]1)

8 8 8 1.2 and 1.3

Before stabilisation:

min CBRsoaked [%] at 95% MDD of BS-Heavy

max PI [%]1) 20 25 35 1.2 and 1.3

min 1.5 min 1.2 -

Particle size, dMAX

Aggregate strength TFVdry : min 50 kN - - 2.7

Field density Nominal value: min 97% of MDD BS-Heavy

Grading modulus*)

Nominal quality of source material - with requirements as given here

1)

It is emphasised that Atterberg limits shall be measured according to CML test methods 1.2, 1.3 and 1.4. These methods follow BS procuders and utilise BS equipment. Other laboratory test procedures are likely to give results that are not comparable with the given material requirements.

1.11

1.7

The content of organic matter should not exceed 0.5% - 1% - 2% for C2 - C1 - CM materials respectively.

Source material

Material class

d MAXto be max 2/3 of compacted layer thickness

Stabiliser content [ % design ] shall be minimum the initial consumption of lime (ICL) value

*) GM = [ 300 - (% passing 2mm) - (% passing 0.425mm) - (% passing 0.075mm) ] / 100

30 -20

Subbase quality soils/gravel


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curing membrane

cemented base course

Loose - 50 mm -granular layer tobe kept wet.

cemented subbase


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Material properties DBM 40 DBM 30

CMLtestmethod

Dense bitumen macadam Dense bitumen macadam

Max nominal size 40 mm 30 mm

Grading, sievesizes [mm] % passing % passing

50 100 -

37.5 95 - 100 100 28 70 - 95 90 - 100

20 - 70 - 95

14 56 - 76 58 - 82

10 53 - 70 52 - 73

5 39 - 56 40 - 56 1.7

2 24 - 40 24 - 40

1,18 19 - 35 19 - 35

0,425 9 - 25 9 - 25

0,300 7 - 21 7 - 21

0,075 2 - 9 2 - 9

3.22

Type of bitumen

Aggregate strength

Layer thickness 80 - 200 mm 60 - 150 mm

Bitumen content nominally 4.0% nominally 4.5%

60/70 or 40/50 penetration grade

Material class

TFV soaked : min 75% of TFV dry TFV dry : min 110 kN

2.7


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Material LAMBS CML test properties Large aggregate mix for base course method

Aggregates shall be made by crushing of fresh rockor clean, large boulders with a diametre >0.3 m.

min 37.5

max 50

Shape of the grading min 0.4 *)

curve, n-value max 0.7

Aggregate TFVsoaked 24hrs: min 75% of TFVdry

strength TFVdry : min 110 kN

Aggregate LS [%] max 2 1.4

Filler content, pass. 0.075 mm [%] 5 - 8 1.7

Traffic TLC 20 and TLC 50: 40/50 pen. grade

Traffic TLC 1 to TLC 10: 60/70 pen. grade

Bitumen content [%] 3.5 to 4.5 to be determined in the mix design 3.22

Mix design Shall be carried out in accordance with Ref/7- 4/

min 1.5 x ( dMAX), preferably 2 x ( dMAX)80 - 200 mm compacted thickness

3.5

Aggregate type

Bitumen grade

Layer thickness

2.7

Max particle size, dMAX [mm]

1.7

Water absorption [%] max 3 3.13


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Material CMLtestmethod properties PM 80 PM 60 PM 30

Max nominal size [mm] 80 60 30

125 100 50

The layer thickness of the penetration macadam should correspond with theaggregate fraction in order to obtain stability of the layer.

Bitumen spray rate [l/m2]

*)3 - 4 3 - 4 2 - 3

3.5 Bitumen type 80/100 or 60/70 penetration grade

Aggregate strength TFVsoaked : min 75% of TFVdry TFV dry : min 110 kN 2.7

Grading, sieve Main fraction sizes [mm] % passing % passing % passing

100 100 - -

75 75 - 100 100 -63 - 80 - 100 -

50 0 - 50 0 - 50 -37,5 0 - 25 0 - 25 100 2.3

28 0 - 5 0 - 5 80 - 10020 - - 0 - 50

14 - - 0 - 2510 0 - 5

Flakiness Index - - 35

Grading, sieve Key stone *)

sizes [mm] % passing % passing % passing

50 100 - -37,5 85 - 100 100 -

28 0 - 50 85 - 100 -20 0 - 25 0 - 50 100

14 0 - 5 0 - 25 85 - 100 2.3

10 - 0 - 5 0 - 55

6.3 - - 0 - 25 5 - - 0 - 10

Flakiness Index - 35 35

Material class

Layer thickness [mm]

*) Requirements for alternative use of a bituminous mix instead of key stone are set out in the text.

2.4

2.4


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Material Material class

propertiesFBMIX

CML test

Foamed bitumen mix method

Aggregate source Natural gravel or crushed material, free from lumps of clay or other deleterious matter.

PI [%]1) max 14 before admixture of bitumen 1.2 and 1.3

CBRsoaked [%] min 30 before admixture of bitumen, tested at 95 % MDD of BS-heavy 1.11

Aggregate TFVsoaked: min 75% of TFVdry

strength Traffic TLC 3 and TLC 10: TFVdry : min 110 kN

Traffic TLC 1 and lower: TFVdry: min 80 kN

Grading, sievesizes [mm] % passing

37,5 10028 80 - 10020 60 - 9510 42 - 785 30 - 652 20 - 50

0,425 10 - 300,075 5 - 15

E-Modulus [MPa] min 1600, measured by indirect tensile strength, tested at 29oC 3.21

Marshall stability [N] min 6000 tested at 40oC

Marshall flow [mm] 2 - 4

Moisture content at min: mix design moisture less 1.5% points

the time of laying [%] max: mix design moisture plus 0.5% points

Type of bitumen 80/100 or 150/200 penetration grade 3.5

Adhesion agents Approved adhesion agents shall be admixed at min 0.5% by weight of bitumen

Bitumen content Consumption, residual bitumen: 80 to 100 litres per m3of compacted material 3.22

Field density min 96% of Marshall dry density

1) It is emphasised that Atterberg limits shall be measured according to CML test methods 1.2, 1.3 and 1.4. These methods follow

BS procuders and utilise BS equipment. Other laboratory test procedures are likely to give results that are not comparable with the given material requirements.

1.1

2.7

1.7

3.18


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MaterialMaterial class

CML test

properties BEMIXmethod

Bitumen emulsion mix

Aggregate source Natural gravel or crushed material, free from lumps of clay or other deleterious matter.

PI [%]1) max 8 before admixture of bitumen 1.2 and 1.3

CBRsoaked [%] min 30 before admixture of bitumen, tested at 95 % MDD of BS-heavy 1.11

Aggregate TFVsoaked : min 75% of TFVdry

strength Traffic TLC 3: TFV dry : min 110 kN

Traffic TLC 1 and lower: TFVdry : min 80 kN

Grading, sievesizes [mm] % passing

37,5 10028 80 - 10020 60 - 9510 35 - 705 25 - 502 18 - 35

0,425 10 - 250,075 5 - 8

E-Modulus [MPa] min 1200, measured by indirect tensile strength, tested at 29oC 3.21

Marshall stability [N] min 4500 tested at 40oC

Marshall flow [mm] 2 - 4

Moisture content at min: mix design moisture less 1.5% points

the time of laying [%] max: mix design moisture plus 0.5% points

Type of base bitumen 80/100 or 150/200 penetration grade 3.5

Bitumen content Consumption, residual bitumen: 80 to 100 litres per m3of compacted material 3.22

Field density min 96% of Marshall dry density

1)It is emphasised that Atterberg limits shall be measured according to CML test methods 1.2, 1.3 and 1.4. These methods follow

BS procuders and utilise BS equipment. Other laboratory test procedures are likely to give results that are not comparable with the given material requirements.

1.1

2.7

1.7

3.18


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Project appraisal

Environment


Traffic

Subgrade

Problem Soils

Pavement Materials

DESIGNELEMENTS




DESIGN



Ch

Ch


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granular

granular

time and traffic

riding quality

rut depth

cracking

granular

cemented

traffic

deformation

deflection

curvature

post-cracked phasepre-cracked influenceof waterphase


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bituminous mix

granular or cemented

time and traffic

riding quality

rut depth

cracking

cemented

cemented (preferred)

time and traffic

riding quality

rut depth

cracking

penetration macadam

granular or cemented

time and traffic

riding quality

deformation

cracking


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< 0.2 0.2 - 0.5 0.5 - 1.0 1 - 3 3 - 10 10 - 20 20 - 50

G45

150mm

Basecourse

150mm

G80

150mm

G25

150mm

Subgrade

C1G45

CBR >15%

G45

150mm

Subbase

1)

C1

200mm

ST

AC

ST

TLC 20 TLC 50

GranularBase course type:

AC50mm

applicable)

TLC 10TLC 02 TLC 05

2)

CRR

200mm

G60 G80

150mm

(not applicable)

150mm

AC50mm

100mm

CRRCRR

asbelow

CRS

150mm

150mm

150mm

asbelow

200mm

+150mm

150mm

C2200mm

CM

For the heavy Traffic Load


General requirements

below

as

as

below


asbelow

asbelow

asbelow


Classes (TLC 05-Hto TLC 20-H) (notCRS

(not

applicable)

below

ST

CRS

125mm

ST ST

asbelow

as

Heavy Traffic Load Classes (-H) apply for


loaded to above13 tonnes.

Surfacing

Classes (TLC 05-Hto TLC 20-H)

Traffic Load Classes (million E80) E80 >0.2 million under conditions where

TLC 3

Material requirements:

Climatic zones: layers or base course:/Chapter 7/ Dry / Moderate

Bituminous surfacings:/Chapter 10/-

more than 50% of E80 comes from axles

-

- Granular or cemented materials for subbase

TLC 1

- Surface treatments, carriageway:

- Shoulders: /Chapter 10.7/

Traffic:- Traffic Load Classes, including the heavy ( -H)

classes: /Chapter 4/ Subgrade design:

- Design for CBR less than 15%: /Chapter 5/


/Chapter 10.2 to 10.4/

Asphalt concrete: /Chapter 10.8/

- Material standards of improved subgrade layers: /Chapter 5/

Surfacing design:

/Figure 2.1/


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< 0.2 0.2 - 0.5 0.5 - 1.0 1 - 3 3 - 10 10 - 20 20 - 50

200mm

- Surface treatments, carriageway:



Surfacing

Basecourse

E80 >0.2 million under conditions where

150mm

G45

150mm

G80

200mm

150mm

CRS

below

loaded to above13 tonnes.

below below



ST

G80

Subgrade

AC

AC

AC50mm

100mm

150mm

CRS

150mm

G45

asbelow

150mm

Subbase

1)

C2

G25

CBR >15%

200mm

CM

200mm

asbelow

C1

CRR

150mm

150mm

as

below

+150mm

as

CM C1

as

asbelow

125mm

CRR

150mm

CRS

STST

TLC 50

50mm

100mm

AC

AC

TLC 20

50mm

CRR

below



as150mm

CRR

ST

150mm





(not

applicable)

(not

applicable)

(not

applicable)as

Base course type:

layers:/Chapter 5/

Surfacing design:

TLC 02 TLC 05 TLC 1 TLC 3

Traffic Load Classes (million E80) more than 50% of E80 comes from axles

TLC 10

Bituminous surfacings:/Chapter 10/ Wet-

/Chapter 10.2 to 10.4/- Shoulders: /Chapter 10.7/- Asphalt concrete: /Chapter 10.8/

Material requirements:- Granular or cemented materials for subbase Climatic zones:

layers or base course:/Chapter 7/

GranularSubgrade design:

- Design for CBR less than 15%: /Chapter 5/- Material standards of improved subgrade

Traffic:

- Traffic Load Classes, including the heavy (-H)lasses: /Chapter 4/

/Figure 2.1/


96/185

< 0.2 0.2 - 0.5 0.5 - 1.0 1 - 3 3 - 10 10 - 20 20 - 50

150mm150mm

Subgrade

Subbase

1)


(not

applicable)

CM

CBR >15%

G45G45

G45 C1

C1150mm

200mmC1



G25


Basecourse

Surfacing


+150mm

CM

150mm150mm

CM

150mm

+125mm

AC100mm

ST STST

50mmAC

below AC

C1 C2C1

50mm

asbelow

as

as

150mm 150mmGeneral requirements

below belowClasses (TLC 05-Hto TLC 20-H)

ST

150mm 150mm 150mm 150mm

CM

ST

(not

applicable)

as

below

as

200mm

C1

125mm

as

below

For the heavy Traffic LoadClasses (TLC 05-Hto TLC 20-H)

asbelow(not

applicable)

below

as

below

as

below

C2 C2

as

Traffic:

- Traffic Load Classes, including the heavy ( -H) classes: /Chapter 4/

TLC 50

Subgrade design:- Design for CBR less than 15%: /Chapter 5/- Material standards of improved subgrade

layers: /Chapter 5/

Surfacing design:

Cemented

TLC 10 TLC 20

- Surface treatments, carriageway:/Chapter 10.2 to 10.4/

E80 >0.2 million under conditions where more than 50% of E80 comes from axles loaded to above13 tonnes.


- Asphalt concrete: /Chapter 10.8/

- Bituminous surfacings:/Chapter 10/

- Granular or cemented materials for subbase Material requirements:

layers or base course:/Chapter 7/

- Shoulders: /Chapter 10.7/

Base course type:


Traffic Load Classes (million E80)

AllClimatic zones:

/Figure 2.1/


97/185

< 0.2 0.2 - 0.5 0.5 - 1.0 1 - 3 3 - 10 10 - 20 20 - 50

150mm

FBMIX

DBM 30

DBM 40

DBM 30

FBMIX FBMIX

CM

CM

CM

150mm

200mm200mm

G45G45G45

60mm

DBM 40

DBM 30

BEMIX BEMIX BEMIX BEMIX

DBM 30

FBMIX

ST ST

125mm+

125mm

LAMBS LAMBS LAMBS

80mm

ACAC50mm

200mm175mm

LAMBS

DBM 40

50mm

STST

TLC 20 TLC 50TLC 10

100mm125mm

Subbase1)

200mm

150mm

Subgrade

G45G45

CBR > 15%

150mm

this pavement type.

DBM 30

ST

Alternative material types: FBMIX

Basecourse

S

urfacing

LAMBS

DBM 40 DBM 40


Traffic Load Classes(million E80)No special pavement design alternatives are required for the heavy Traffic LoadClasses (TLC 05-Hto TLC 50-H )for

All

Base course type:

layers: /Chapter 5/

Surfacing design:-

Climatic zones:

- Bituminous base course: /Chapter 7/

Bituminous

mix- Asphalt concrete: /Chapter 10.8/

Surface treatments, carriageway: /Chapter 10.2 to 10.4/-


Traffic:- Traffic Load Classes:/Chapter 4/

Subgrade design:

Shoulders: /Chapter 10.7/


- Granular or cemented materials for subbase layers:/Chapter 7/

- Bituminous surfacings: /Chapter 10/ /Figure 2.1/


98/185

< 0.2 0.2 - 0.5 0.5 - 1.0 1 - 3 3 - 10 10 - 20 20 - 50

TLC 02 TLC 05 TLC 1 TLC 3 TLC 10 TLC 20

150mm125mm

+

150mm

+

125mm

50mm

PM60

50mm

100mm125mm

PM80

CMCM CMCM

C1150mm200mm

150mm

50mm

PM30Basecourse

PM80

AC50mm

STST

100mm

AC

PM30 PM60

G45

150mm

G45

150mm

ST

CBR > 15%

C1

Subgrade

Subbase

1)

CM

125mm 125mm

Surfacing

Traffic Load Classes(million E80)

TLC 50

are required for the heavy Traffic LoadClasses (TLC 05-Hto TLC 50-H)forthis pavement type.

No special pavement design alternatives

PM80

AC100mm100mm

AC

Penetration

Traffic:

Subgrade design:

layers: /Chapter 5/

- Traffic Load Classes:/Chapter 4/

Shoulders:/Chapter 10.7/- Asphalt concrete:/Chapter 10.8/-


Macadam

Base course type:

AllClimatic zones:- Bituminous surfacings: /Chapter 10/

- Penetration Macadam: /Chapter 7/

Surfacing design:- Surface treatments, carriageway: /Chapter 10.2 to 10.4/


- Granular or cemented materials for subbase layers:/Chapter 7/

/Figure 2.1/


99/185


100/185

Project appraisal

Environment

Pavement Design-

New Roads


Traffic

Subgrade

Problem Soils

Pavement Materials

DESIGNELEMENTS



DESIGN



Ch

Ch


101/185


102/185

Carry out desk study

Start Carry out initial assessment ofpavement condition

Establish homogenous sections

based on initial assessment ofpavement condition

Carry out structural surveys asrequired based on the detailedcondition survey

Carry out detailed condition surveyif required in accordance with/Fig. 9.2/

Assess each homogenous sectionaccording to/Fig 9.2/

Re-assess demarcation intohomogenous sections based on allavailable data

Carry out pavement rehabilitationdesign for each homogenoussection

Combine sections with similarrehabilitation measures intopractical lengths for construction


103/185

YES NO

NO YES

NO

YES

NO

YES

Any possibilitiesof salvaging the

pavement ?

Determine

subgrade CBR/Chapter 5/

Design full pavement

reconstruction without anyfurther investigation of the

section./Chapter 9.3.3/

Carry out detailed condition

surveys: - rutting

- roughness - surface defects

/Chapter 9.1.4/

Start

Determine the need forstructural surveys:

- DCP

- deflection - sampling (lab. testing)

/Chapter 9.1.4/

Traffic

projection/Chapter 9.1.2/

Recommend correctivemeasures. Further

investigation of the section isnormally not necessary.

Section withno distress ?

Section with

only localiseddistress ?

Section withonly surface

defects ?

Establish the cause of thelocalised distress, if necessarycarry out additional fieldtesting.

Traffic

projection/Chapter

9.1.2/


104/185


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107/185

RUTTING: SOUND WARNING or SEVERE WARNING or SEVERE

CRACKING: WARNING or SEVERE SEVERE SOUND or WARNING

If rutting is due to shoving in the asphalt:carry out special investigations.

Cons ider whether full reconstruc tion Cons ider whether full reconstruc tionapplies/Chapter 9.3.3/ applies/Chapter 9.3.3/

NO

YES

NO

YES

Structural number method/Chapter 9.2.2/, or (for confirmation) Maximum deflection method /Chapter 9.2.1/

Mechanistic method /Chapter 9.2.3/

Select appropriate rehabilitation option /Chapter 9.3/ and consider options to prevent reflective cracking if applicable /Chapter 9.4/

Major mode of distress

Rehabilitation design method

Design traffic loading is less than

10 million E80?

Good correlation rutting / deflection, orroughness / deflection?


108/185


109/185

YES

NO

YES

NO

Establish homogenous

sections. (The CUSUM

method in /Appendix A8.3/may be used).

Measure and calculate design

deflection for each

homogenous section.

Determine expected pavement

life (total E80)

/Fig. 9.5/

Maximum deflection methoddoes not apply.

Past E80 larger

than expected

pavement life?

Calculate residual capacity:= expected capacity - past E80

Residual life

larger than

design traffic

loading?

No strengthening is required

based on the maximum

deflection method.

Determine target deflection.

/Fig. 9.5 or /Fig. 9.6/

Determine requiredstrengthening, SNdiff

/Fig. 9.7/

Select overlay alternative as

appropriate.

/Table 9.9/

Determine traffic loading:

- past E80

- future E80 (design traffic loading)


110/185


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112/185

TLC 05 TLC 1 TLC 3 TLC 10 TLC 20

Critical condition. 90%confidence in achieving life

167

154

142

129

116

103

90

77

64

51

39

2613

0.2 0.3 0.5 1.0 1.5 2.0 3.0 5.0 10 15 20 30

Equivalent standard axles, E80 [ x 106 ]

De

flection

[mm

x10

2]

0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

0.8

0.6

0.4

0.2

0.50

0.80

1.60

2.20

Targetdeflection[mm]

Design deflection, measured [ mm ]

Structuralnumber,SNdiff

1.20


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117/185

*) Asphalt concrete Bituminous mix Penetration Granular baseoverlay for base course 1) macadam 2) course 3)

< 0.50

Only TLC 10 or lower




CRR 200 mm

Bit. 100 mm

ACPM 60 100 mm

100 mmPM 60

80 mm

ST

PM 80

80 mm

125 mm

ST

50 mm

ST

2,25

2,00

Bit.

ST

AC Bit.

50 mm50 mmPM 30

Apply a surface treatment or do nothing depending on site conditions.

CRR

ST

150 mm

ST

PM 30 50 mm

100 mmBit. 80 mm

ST

AC 60 mm

AC

PM 60

alternatively:

alternatively:

alternatively:

alternatively:

alternatively:

alternatively:

alternatively:

PM 80

ST

AC 100 mm

PM 60

50 mm

100 mm

125 mmPM 80

ST

140 mmBit.

AC

50 mm

50 mm

ST

100 mm

Bit.

AC60 mm

50 mm

AC 50 mm

PM 80 125 mm

ST

AC

200 mm

AC 50 mm

AC 50 mm

125 mm

50 mm

CRR 150 mm

CRR

ST

200 mm

AC

0,50

CRR

ST

PM 30 50 mm

1,00

1,25

1,50

120 mm

ST

*) Select the nearest of the given values for SN diffSN diff

0,75

Overlay alternatives

AC 40 mm

AC

PM 30 50 mm

1,75

AC 50 mm

PM 60 100 mmBit.

PM 60 100 mmAC 120 mm2 mm

100 mm

PM 60Bit. 100 mm

AC

130 mm

50 mm

ST

PM 60


118/185


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121/185

Project appraisal

Environment

Pavement Design-

New Roads


Traffic

Subgrade

Problem Soils

Pavement Materials

DESIGNELEMENTS



DESIGN



Ch

Ch


122/185

Asphalt Concrete *)

Double Surface Dressing

Double Otta Seal

Single Otta Seal with a Sand Cover Seal

Single Surface Dressing with a Sand Cover Seal

Double Sand Seal

32 11 125 640 1

Years

Type of surfacing 13 147 8 9 10


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130/185

MaterialCML test

properties method AADT>100: TFVsoaked: min. 75% of TFVdry For AADT100: TFVdry: min. 110 kN For AADT


131/185

Sieve sizes Coarse grading1)

Medium grading1)

CML test

[mm] [% passing] [% passing] method

20 100 100

14 60 - 82 68 - 94

10 36 - 58 44 - 73

5 10 - 30 19 - 42 1.7

2 0 - 8 3 - 18

1,18 0 - 5 1 - 14

0,425 0 - 2 0 - 6

0,075 0 - 1 0 - 2

1)These grading envelopes are given for the the purpose of proper design of the seal and are not material requirements for aggregate.

AADT at the time Type of bitumen of construction

The grading should be

altered for this application

150/200 normally

MC3000 in cold weather

80/100 penetration grade bitumen shall not be used in Otta Seal unless softened or cut back to meet the above requirements.

Softening to make 150/200: 3% - 5% softener is mixed with 95% - 97% 80/100 pen. grade bitumen. Softener can be apurpose-made petroleum destillate, alternatively engine oil, old or new.

The cutback bitumen grades can be made by blending 150/200 pen. grade bitumen on site using the following proportions:

MC3000: 5% - 8% kerosine mixed with 92% - 95% 150/200 pen. grade bitumen

MC800: 15% - 18% kerosine mixed with 82% - 85% 150/200 pen. grade bitumen

If the cutback grades are made directly from 80/100 pen. grade bitumen, then an additional 3% - points kerosine shall be used.

Diesel shall not be used for cutting back to MC grades. Circulation in the tank shall be carried out at least 1 hour after mixing.

Proper safety procedures shall be adhered to in the case cutting back on site is being done.

Type of Otta Seal

2nd layer 1,5 1,6 1,7 AADT


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Material CML test properties AC 20 AC 14 AC 10 method

Primarily b inder course. Wearing course in areas with Wearing course, but only under

Notes - use of the different Wearing course in severely normal traffic loading. conditions with moderate

mix types loaded areas Chapter 10.8.2. traffic loading.

Preferably to be surface dressed

when used as wearing course.

Layer thickness [mm] Compacted 50 - 80 Compacted 40 - 60 Compacted 30 - 40

Aggregate properties

3.13

Aggregate strength TFVsoaked : min 75% of TFVdryTFVdry : min 110 kN

2.7

The filler shall be hydrated lime, Portland cement, limestone dust or other suitable types proven to

1.7

% passing 0.075 mm: 70 - 100 %, all material shall pass the 0.600 mm sieve size

Grading, sieve sizes

[mm]

28 100

20 80 - 100 100

14 60 - 80 85 - 100 100

10 50 - 70 72 - 94 85 - 100

5 36 - 56 52 - 72 55 - 72

2,36 28 - 44 37 - 55 38 - 57 1.7

1,18 20 - 34 26 - 41 27 - 42

0,600 15 - 27 16 - 28 18 - 32

0,300 10 - 20 12 - 20 13 - 23

0,150 5 - 13 8 - 15 9 - 16

0,075 2 - 6 4 - 10 4 - 10

Bitumen type

Normal loading conditions: 60/70 or 40/50 penetration grade Severely loaded areas: Chapter 10.8.2 40/50 penetration grade, or modified binders

3.5

Marshall (2x75 blow)

mix requirements

Severely loaded areas: min 9000 Chapter 10.8.2

Traf fic TLC 20 and TLC 50: min 8000 max 18000

Traffic TLC 10 and TLC 3: min 7000 max 15000

Traffic TLC 1 and lower: min 4000 max 10000

Flow [mm] min 2 max 4 3.18

Air voids [%] min 3 max 6

Voids in Mineral Aggregate [%] min 14 for AC 20 min 15 for AC 14 min 16 for AC 10

Refusal lab. compaction Air voids shall be min. 3% after refusal lab. compaction for severely loaded areas Chapter 10.8.2.

Indirect tensile strength [kPa] min 800 tested at 25oC

3.20

3.21 Imersion index [%] min 75

Water absorption [%]

provided materials are carefully selected. Addition of a separate type of fines is normally needed.

[ % passing ]

give acceptable results in AC mixes under the prevailing conditions.

max 2

Stability [N]

Requirements for the filler

Mix type

Coarse aggregates shall be made of crushed fresh rock or stones. Fine aggregate, passing the

and free from soft or unsound particles, clay or other deleterious matter. Coral rock can be used

5 mm sieve, can be a material such as sand, gravel or crushed stone. All aggregate shall be durable Types of aggregate


139/185

Nominal mix CML testmethod proportions

AC 20 AC 14 AC 10 Aggregate [%] 95 94,5 94 Bitumen [%] 5 5,5 6

3.18

Normal loading conditions: 60/70 or 40/50 penetration grade

Severely loaded areas: 40/50 penetration grade or modified binders3.5

Asphalt Concrete

Type of bitumen


140/185


141/185

Project appraisal

Environment

Pavement Design-

New Roads


Traffic

Subgrade

Problem Soils

Pavement Materials

DESIGNELEMENTS



STRUCTURAL

DESIGN



Ch

Ch


142/185


143/185


144/185

Erodible materials

0 10

200

100

0

20

Good

Ravels and corrugates

30

Ravels

Slippery

270

40

Good, but may be dusty

ShrinkageProduct,SP

Grading Coefficient, GC

500

400

300

400

120

16 34


145/185

Moderate or dry Wet climatic zones climatic zones

1) Classification S15, S7 and S3 and requirements for G7 materials are given:/Chapter 5 Subgrade/.

Subgrade classes1)

GW

100mm

150mm200mm

S3S15 orS7

100mm

GW

( none )G7

subgrade

layer

Gravelwearingcourse

Improved

100mm

GW

G7

1) Classificationsubgrade classes S3, S7 and G15 and requirements for G7 and G15 materials are given:/Chapter 5 Subgrade/.2) Maximum 50% heavy vehicles is assumed. Heavy vehicles are those having an un-laden weight of more than

3 tonnes, or buses with a seating capacity of 40 or more: /Chapter 4 Traffic/.

S7 1)

G71)150 G7 1)G7 1)

150 GW

G15 1)

300150 G71)

150 G151)

GW

100 mmGWGW

G15 1)

Dry / Moderate Dry / Moderate Dry / ModerateWet

G151)100

GWGW150

Wet

GW 150

G71) 200

GW 150

G151) 200G151) 200

AADT 2)

S15 1) GW GW

< 20 20 - 100 100 - 300

150 mm

150 mm 150 mm 150 mm

150 mm

150 mm150 mm

S3 1)

climatic zones

150

GW

300

Wetclimatic zones climatic zones climatic zones climatic zones climatic zones

G7 1)

150150

GW

mm

mm mm

mm

mm

mm


146/185


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CML test method,reference number

Tests on Soils and Gravels1.1 Moisture Content BS1377:Part 2:19901.2 Liquid Limit (Cone Penetrometer) BS1377:Part 2:19901.3 Plastic Limit & Plasticity Index BS1377:Part 2:1990

1.4 Linear Shrinkage BS1377:Part 2:1990

1.5 Particle Density Determination - Pyknometer BS1377:Part 2:19901.6 Bulk Density for undisturbed samples BS1377:Part 2:19901.7 Particle Size Distribution - Wet sieving BS1377:Part 2:19901.8 Particle Size Distribution - Hydrometer Method BS1377:Part 2:19901.9 Compaction Test - BS Light and BS Heavy BS1377:Part 4:19901.10 CBR Test - One point method BS1377:Part 4:1990

BS1377:Part 4:1990 andTMH1:method A8:1986

1.12 Consolidation Test - Oedometer BS1377:Part 5:19901.13 Triaxial Test BS1377:Part 7:19901.14 Shear Box Test BS1377:Part 7:19901.15 Permeability Test - Constant Head BS1377:Part 5:1990

BS1377:Part 3:1990 and

NPRA 014 test 14.445

1.17 Crumb Test BS1377:Part 5:19901.18 pH Value (pH meter) BS1377:Part 3:1990

TMH1:method A14:1986 and

BS1924:Part 2:1990

TMH1:method A14:1986 and

BS1924:Part 2:19901.21 UCS of Stabilised Materials TMH1:method A14:1986

1.22 Initial Consumption of Lime - ICL BS1924:Part 2:1990

Tests on Aggregates and Concrete

2.1 Moisture Content of Aggregates BS812:Part 109:19902.2 Relative Density and Water Absorption BS812:Part 2:1975

2.3 Sieve Tests on Aggregates BS812:Part 103.1:19852.4 Flakiness Index (FI) and Average Least Dimension (ALD) BS812:Section 105.1:19892.5 Elongation Index BS812:Section 105.2:19902.6 Aggregate Crushing Value (ACV) BS812:Part 110:19902.7 Ten Percent Fines Value (TFV) BS812:Part 111:19902.8 Aggregate Impact Value (AIV) BS812:Part 112:19902.9 Los Angeles Abrasion Test (LAA) ASTM C535-89

2.10 Sodium Soundness Test (SSS) ASTM C88-902.11 Slump Test BS1881:Part 102:19832.12 Making of Concrete Test Cubes BS1881:Part 108:19832.13 Concrete Cube Strength BS1881:Part 116:1983

Tests on Asphalt and Bituminous Materials3.1 Pre-conditioning of Bitumen Samples Prior to Mixing or Tes ting NPRA 014 test 14.5113.2 Density of Bituminous Binders ASTM D70-973.3 Flash and Fire Point by Cleveland Open Cup ASTM D92-90

3.4 Thin-Film Oven Test (TFOT) ASTM D1754-873.5 Penetration of Bituminous Materials ASTM D5-86

3.6 Softening Point Test ASTM D36-70

3.7 Ductility ASTM D113-863.8 Viscosi ty Determination using the Brookfield Thermosel Apparatus ASTM D4402-913.9 Density and Water Absorption of Aggregates Retrieved on a 4.75 mm Sieve ASTM C127-883.10 Density and Water Absorption of Aggregates Passing the 4.75 mm Sieve ASTM C128-883.11 Calibration of Glass Pycnometers (0.5-1 litre) NPRA 014 test 14.59223.12 Mixing of Test Specimens; Hot Bituminous Mixes NPRA 014 test 14.5532

Determination of Maximum Theoretical Density of Asphalt Mixes

and Absorption of Binder into Aggregates3.14 Bulk Density of Saturated Surface Dry Asphalt Mix Samples ASTM D2726-963.15 Bulk Density of Paraffin-Coated Asphalt Mix Samples ASTM D1188-893.16 Bulk Density of Asphalt Mix Samples, Calliper Measurements NPRA 014 test 14.56223.17 Calculation of Void Content in Bituminous Mixes ASTM D3203 and AASHTO pp19-933.18 Marshall Test ASTM D1559-893.19 Marshall Mix Design ASTM D1559-89

3.20 Refusal Density Mix Design TRL Overseas Road Note 31, app. D:19903.21 Indirect Tensile Strength Test ASTM D3967 and NPRA 014 test 14.5543.22 Determination of Binder Content and Aggregate Grading by Extraction ASTM D2172-88, method B3.23 Effect of Water on Bituminous Coated Aggregates, Boiling Test ASTM D3625-96

ASTM D2041-95 and D4469-85

Reference to test methods

CBR Test - Three point method1.11

Preparation of Stabilised Samples for UCS1.19

Compaction Test - Stabilised Materials1.20

Organic Content - Ignition Loss Method1.16

Name of test

3.13


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172/185

CBR data

3

4 90%-ile

5 3,4

5 CBR DESIGN6 3 %

0

1

2

3

4

5

6

7

1 2 3 4 5

Test

CBR(%)

d=0.4

n = 5 testsd = 0.1 x (n-1)

= 0.4


1 2 3

Subgrade class

G15

150mm

G15

150mm

G15Upper layer

Lower layer

Section

S3 S7 S7

not required

150mm

G7

150mm


CBR data

68

9

9

9

11 90%-ile12 7,6

12 CBR DESIGN14 8 % 0

2

4

6

8

10

12

14

16

1 2 3 4 5 6 7 8 9

Test

CBR(%)

d=0.8

n = 9 testsd = 0.1 x (n-1)

= 0.8


173/185

B C

Chainage Rutting Difference CUSUM

measured from average (Accumulated[Km] [mm] (A- B) values of C )

1 14 -1,2 -1,2

2 13 -0,2 -1,4

3 15 -2,2 -3,6

4 14 -1,2 -4,85 13 -0,2 -5,0

6 14 -1,2 -6,2

7 7 5,8 -0,4

8 9 3,8 3,4

9 8 4,8 8,2

10 13 -0,2 8,0

11 15 -2,2 5,8

12 18 -5,2 0,6

13 14 -1,2 -0,6

14 16 -3,2 -3,8

15 14 -1,2 -5,0

16 14 -1,2 -6,2

17 15 -2,2 -8,4

18 18 -5,2 -13,6

19 14 -1,2 -14,8

20 15 -2,2 -17,0

21 9 3,8 -13,222 10 2,8 -10,4

23 9 3,8 -6,6

24 12 0,8 -5,8

25 9 3,8 -2,0

26 11 1,8 -0,2

Average: A = 12,8

Homogenous sections

-20

-15

-10

-5

0

5

10

0 2 4 6 8 10 12 14 16 18 20 22 24 26

Chainage

CUSUM

Plotting of CUSUM against Chainage

Interpretation of data:

A change of slope indicates change of conditions along

the data. Four distinct homogenous sections can be seenin the above chart.


174/185


175/185

Existing pavement: Material coefficients:/Table 9.4/

t1= 60 mm Asphalt concrete, severely cracked a1= 0.18

t2= 180 mm Natural gravel, PI = 10, CBR = 40% a = 0.10

t2= 150 mm Natural gravel, PI = 15, CBR = 15% a = 0.08

CBR = 8%

Calculations: /Chapter 9.2.2/

SNexist = (a1xt1) / 25.4 = (0.18 x60) / 25.4 = 0.43

Old AC a1= 0.18 t1=60mm

SNrequired = 2.35 /Table 9.5/ for TLC 10 and CBR=40

CBR = 40% a2 = 0.10 t2= 180mm

SNexist = [(a1xt1)+(a2xt2) ] / 25.4 = [(0.18 x60)+(0.10 x180)] / 25.4 = 1.33

SNdiff = SNrequired - SNexist = 2.75 - 1.33 = 1.42

SNrequired= 2.75 /Table 9.5/ for TLC 10 and CBR=15

CBR = 15% a3 = 0.08 t3 = 150mm

SNexist= [(a1xt1)+(a2 xt2)+(a3 xt3)] / 25.4 = [(0.18 x60)+(0.10 x180)+(0.08 x150)] / 25.4 = 1.61

SNdiff = SNrequired - SNexist = 3.30 - 1.61 = 1.69SNrequired = 3.30 /Table 9.5/for TLC 10 and CBR=8

CBR = 8%

SNdiff = SNrequired - SNexist = 2.35 - 043 =1.92 (highest, i.e. critical)


176/185

AC 50 mm

PM 80 125 mm

Asphalt concrete Bituminous mix Penetration Granular baseoverlay for base course macadam course

3 )1 ) 2 )

Overlay alternatives

SNdiff The nearest value for SNdiff has been selected.

2,00

AC 50 mm

PM 80 125 mm

Alternatively:ST

AC 50 mm

Bit. 100 mm PM 60

AC 50 mm

PM 60 100 mmCRR 00 mm

100 mm


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New base course and surfacing to be selected in compliance with

Exitsing AC reprocessed, or removed, depending on chosen method.

Existing base course (and subbase) reprocessed to subbasein the new pavement.

/Chapter 8.3.2/depending on achieved quality of the new subbase.

Existing base course (and subbase)

Reprocessed AC

New base course

New surfacing


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pavement & material design,tanzania

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