TRANSPORT and ROAD RESEARCH LABORATORY

Department of the Environment Department of Transport

TRRL SUPPLEMENTARY REPORT 816

BITUMEN PERMITTIVITY AND TEXTURE DEPTH OF ROLLED ASPHALT: AN EXPERIMENT ON MOTORWAY M4

by

M E Daines

Any views expressed in this Report are not necessarily those of the Department of the Environment or of the Department of Transport

Pavement Materials and Construction Division Highways and Structures Department

Transport and Road Research Laboratory Crowthorne, Berkshire

1983

ISSN 0305-1315

Ownership of the Transport Research Laboratory was transferred from the Department of Transport to a subsidiary of the Transport Research Foundation on 1 st April 1996.

This report has been reproduced by permission of the Controller of HMSO. Extracts from the text may be reproduced, except for commercial purposes, provided the source is acknowledged.

Abstract

1.

2.

°

4.

5.

Introduction

Experimental work

2.1 Site

2.2 Traffic

2.3 Rolled asphalt

2.4 Bitumens

2.5 Mixing

2.6 Laying

2.7 Pre-coated chippings

2.8 Rolling

2.9 Climate

2.I0 Surface texture

2.11 Skidding resistance

Future measurements

Acknowledgements

References

CONTENTS

Page

1

1

2

2

2

2

3

3

5

8

8

9

9

10

11

11

11

© CROWN COPYRIGHT 1983 Extracts from the text may be reproduced, except for

commercial purposes, provided the source is acknowledged

BITUMEN PERMITTIVITY AND TEXTURE DEPTH OF ROLLED ASPHALT: AN EXPERIMENT ON MOTORWAY M4

ABSTRACT

During August 1982 a full-scale experiment was begun with the aim of studying the effect of the permittivity of bitumen on the texture depth of heavily-chipped Marshall-designed rolled asphalts. Seven sections of asphalt were laid and, apart from the differences in permittivity, the asphalts were nominally identical. The experimental sections were laid in all three lanes of Motorway M4, Wiltshire. The changes in texture depth and skidding resistance at the three traffic intensities will be monitored for at least 5 years.

1. INTRODUCTION

Prior to 1976 the only binders that were specified for use in roiled asphalt surfacing on Trunk Roads and Motorways

were Trinidad Lake Asphalt/bitumen and pitch/bitumen blends. These binders had proven 'weathering' ability; as

the asphalt mortar was eroded, the applied chippings and coarse aggregate were re-exposed to enable the texture

depth to be maintained, even under heavy traffic. Petroleum bitumens had been excluded because some produced

slippery surfacings. Green 1 showed that the ability of petroleum bitumens to 'weather ' under the combined

effects of ultra-violet light in sunlight, oxidation, rain and oil deposition f rom traffic was related to the permittivity

of the bitumen. Consequently, 50 pen grade petroleum bitumen was included in the Department of Transport

Specification 2 provided its permittivity was at least 2.650 at 25°C. A requirement for a value of 2.630 for 35 pene-

tration grade bitumen was subsequently included in the Specification 3 and both values included in the revised

edition of BS 3690 published in 1982.

1 The experimental basis of this work was the core-transplant technique m which 200 mm diameter cores of

experimental asphalts made with 50 penetration grade bitumens were inserted in an existing trunk road surfacing.

Several parameters were studied at a number of sites and it was found that the absolute level of texture depth that

developed depended on binder content, type of sand and climate. However, the ranking of bitumens was independent

of these variables and depended on their permittivity. Evidence from a subsequent experiment 4 showed that the

weathering rate was independent of the penetration grade, at least in the range 35 to 70 penetration. Because the

presence of pre-coated chippings would, to some extent, hinder the reliable measurement of the development of

texture depth, most o f the previous work was accomplished using unchipped asphalts containing 30 per cent coarse

aggregate.

Since the publication of that work in LR 777 a number of developments have occurred in rolled asphalt

technology. The use of the Marshall Test, a design method to determine the opt imum binder content for rolled

• asphalt has increased, resulting in a reported slight reduction in binder contents generally. Rates of spread of chippings

have also increased and it is now common to apply them at a rate that covers 70 per cent o f the surface and is

sufficient to achieve a minimum texture depth of 1.5 mm. It is also believed that the rate of deposition of oil from

constant loss lubrication systems has reduced as more efficient systems are now being fitted to commercial vehicles.

These changes may affect the contribution 'weathering' plays in the retention of texture depth and when they are

coupled with the possibility that bitumens may in future have to be manufactured from crude oils drawn from new

or alternative sources, it is highly desirable to re-assess the permissible level o f bi tumen permittivity. This paper

describes the initiation of a full-scale experiment to study the changes in texture depth of a typical modern heavily-

chipped rolled asphalt designed by the Marshall Test and made with bitumens covering a range of permittivities.

2. EXPERIMENTAL WORK

Because the primary object of the experiment was to study the effect of bitumen permittivity on the long-term

retention o f texture depth, the only planned variable was the level of permittivity. As far as was practicable, all

other factors were kept constant. A secondary objective, to study the effect of traffic intensity, was introduced

on learning that the experimental asphalts could be laid on all three lanes of a motorway over a length of about

800 m.

The experiment comprised seven sections of rolled asphalt wearing course, laid as 50 mm thick overlays on

the existing wearing course and covering both the main carriageway and hard shoulder. Each section, of approxi-

mately 120 m, was made with a bitumen denoted by its permittivity level. Because all the asphalts laid were of

the same nominal composition, the concept of a control section did not apply; the performance of each section

will be assessed directly in relation to the others. The experimental surfacings were laid during August 1982 and

the details are given below.

2.1 Site

The site was on M4, near Acton Tundlle, on the eastbound carriageway east of Junction 18 between marker

posts 164/8 and 163/9. The asphalts were laid between 21st and 28th August 1982,the agent authority being

Wiltshire County Council. Figure 1 shows the site o f the experiment and Figure 2 shows the layout of the

experimental sections.

2.2 Traffic

A manual traffic count made on Thursday 9th September 1982 yielded the following results.

TABLE 1

M4 Acton Turville: Daily Traffic Flow*

Lane

Nearside

Centre

Offside

commercial vehicles (>1.5 tonnes)

3,676

759

10

Cars

3,647

6,693

1,603

Total vehicles

7,323

7,452

1,613

Total 3 lanes Westbound 4,615 12,909 17,524

* Basis: 6 a.m. - 10 p.m. count X 1.06

2.3 Rolled asphalt

For the experimental surfacings a crushed 14 m m basalt was used as the coarse aggregate, and the time

aggregate was a blend of 2 parts of crushed Cromhall doleritic limestone and one part of Hilton sand. Crushed

limestone was used as added Idler.

The mixture was designed in accordance with Section 3 of BS 594:1973. For the mortar of free aggregate,

filler and binder, the contractors found the op t imum binder content to be 9.8 per cent and with the 30 per cent

o f coarse aggregate specified, a design binder content o f 7.6 per cent. Verification of the procedure by TRRL gave

a design binder content o f 7.0 per cent; this is however, well within the reproducibility of the test.

2

The specified mix (on analysis) was thus:-

Coarse aggregate

Fine aggregate (crushed limestone/sand)

Filler

Binder

30 per cent

53.4 per cent

9.0 per cent

7.6 per cent

2.4 Bitumens

Seven experimental bitumens were used with permittivities ranging from 2.619 to 2.684. The softening points

were similar at about 52°C but penetrations varied from 36 to 68. The range of bitumens was obtained through the

Ref'med Bitumen Association, representing most of the major suppliers in the U.K.

The bitumens were delivered in tanker quantities of about 17 tonnes, usually on the day prior to laying, to

a 40 tonne c~pacity storage tank reserved for the purpose; delivery was planned in decreasing order o f permittivity,

the bitumens being numbered 1 to 7 corresponding with laid section members. Prior to discharge from the tanker

the storage tank was pumped out to as low a level as was practicable; approximately 1.3 tonne remained as a tank-

bottom. This sequence was followed so that the least change in permittivity occurred on mixing in the storage tank.

Bitumen samples were taken from the delivery tanker during or immediately prior to discharge and also from the

storage tank the following morning during mixing of the asphalt. Results of tests on the bitumen are given in Table 2.

TABLE 2

Properties of bitumens

Bitumen

1

2

3

4

5

6

7

Penetration 25°C

DT ST R

68 62 41

44 49 38

49 49 41

48 53 37

50 51 36

50 46 37

36 38 32

Softening Point °C Permittivity 25°C

DT DT

52.5

53.5

51

52

52

51.5

53.5

ST R

52 58.5

53.5 59.5

50.5 54.5

51.5 58

52 56.5

52 57.5

53 57

2.684

2.646

2.659

2.648

2.641

2.626

2.619

ST R

2.684 2.698

2.653 2.730

2.664 2.698

2.651 2.709

2.645 2.681

2.630 2.662

2.622 2.652

DT: sampled from delivery tanker on arrival

ST: sampled from storage tank during mixing

R: bitumen recovered from second lorry load laid on nearside lane

2.5 Mixing

The asphalts were mixed in a new Marini plant, capable of 100 t/h, sited at Cromhall Quarry, about 13 miles

from the road site. The plant was fitted with 200 t total capacity hot storage hoppers. Mixing of experimental

asphalts commenced at about 6 a.m., and 100 tonnes of asphalt were mixed and stored prior to discharge into

delivery lorries. The plant was then switched to providing material for another contract for about 1 hour and

subsequently a further 100 tonnes of experimental asphalt was produced, using up the remainder of the experi-

mental bitumen. The asphalts were mixed at a target temperature of 190°C. Samples were taken from the delivery

3

lorries at the plant for analysis by the Contractor. Their analyses are given in Table 3. From these results, binder

contents varied by up to -+0.5 per cent from the target figure.

TABLE 3

Analysis of asphalt samples taken at mixing plant

Section and Lane

Section 1

Offside

Centre

Nearside

Section 2

Offside

Centre

Nearside

Section 3

Offside

Centre

Nearside

Section 4

Offside

Centre

Nearside

Section 5

Offside

Centre

Nearside

Section 6

Offside

Centre

Nearside

Section 7

Offside

Centre

Nearside

Coarse Aggregate

%

30.9

29.3

32.7

33.0

30.9

27.1

27.9

31.2

34.1

28.1

30.9

29.9

34.5

30.3

32.2

27.7

28.7

28.1

29.9

30.7

29.1

Filler* %

8.4

8.6

8.6

8.4

8.7

9.0

8.9

9.5

9.8

8.9

9.2

9.7

9.8

9.6

9.1

11.2

9.7

10.1

9.1

9.4

10.0

Binder* %

7.6

7.4

7.7

7.7

7.1

7.4

7.3

7.4

7 3

7.6

7.7

7.6

7.7

7.6

7.6

7.2

7.5

7.4

7.9

8.1

7.6

Average 30.3 9.3 7.5

Analysis by ARC at Cromhall Quarry. Bottle method (binder by difference)

The samples were taken from the second lorry load destined for each lane section.

* Adjusted to 30 per cent stone content.

4

2.6 Laying

Laying usually commenced after 8 a.m., starting with the offside lane, laying in the direction of traffic flow.

Approximately three 18 t lorry loads of asphalt were laid per lane-length of about 110 m. The Blaw-Knox paver

laid the asphalt as an overlay, nominally 50 mm thick on the existing wearing course. A number of cracks up to

about I0 mm wide, were generally evident throughout the length of old surfacing; these were not grouted prior to

surfacing. If the adjacent strip was laid immediately following the previous one, the longitudinal joint was painted

with hot bitumen without being first cut-back. I f laying did not follow immediately all joints were cut before

painting. The beginning and end of each section • was cut at about 70 ° to the direction of the traffic at the request

of the Agent Authority, as this was believed to improve the riding quality at the joints. However, this necessitated

hand-laying asphalt at the start of each section, and there has been some fretting in these areas, together with some

10 m or so of poor longitudinal profde.

The temperature of the asphalt was monitored as delivered, when leaving the paver and in the mat when first

roiled; the values recorded are given in Table 4. Samples of asphalt were taken f rom the screws of the paver for

the middle lorry load for each lane length. Analysis results are given in Tables 5 to 7. The thickness of the

uncompacted asphalt mat leaving the paver was monitored by a simple depth gauge. Results are given in Table 8.

TABLE 4

Asphalt temperatures

Asphalt Temperatures (°C)

Delivery Lorry Leaving •Paver (average) Rolling (start) Section Lane

Load 1

1 NS 155 C 163 OS 158

2 NS - C 169 OS 155

3 NSt 160 C 171 OS 160

4 NS 170 C 180 OS 159

5 NS 165 C 169 OS 152

6 NS 180 C 180 OS 168

7 NS 172 C 182 OS 182

Load 2

171 166 160

170 172 * 164

178 166

188 170 167

170 162 160

180 185 172

170 194 180

Load 3

163

168

164 165

189 168 172

165 165 170

181 180 166

185 180

Load 1

140 145 140

130 150

145 150 140

147 162 148

150 150 140

175 170 152

165 175 174

Load 2 Load 3

150 160 160 152 147 145

155 150 165 155

147 152 155 150 145. 155

175 178 156 150 159 160

160 157 153 146 150 160

165 168 172 173 163 153

165 180 176 165 166

Range* * Ave rage

115-150 143 115-152 144 120-140 130

110-130 121 115-160 126 130"145 137

100-140 125 1 1 0 - 1 3 4 125 100-143 124

110-142 125 117-140 130 103-148 119

128-155 142 110-146 131 114-156 136

123-151 135 122-149 136 107-155 134

100-147 130 125-150 136 123-149 138

NS = nearside C = centre OS = offside * Non-experimental 35 pen asphalt laid approximately 4 0 - 6 4 m from start of section. ** The lower values represent the cooler starts and ends of laid loads. t Chipping spreader breakdown. Asphalt hand-chipped from about 1 0 - 2 4 m f rom start of section, and rolled

cool (104°C). 3-hour delay before remainder of mixed asphalt laid. 5

TABLE 5

Analysis of wearing course samples

Nearside Lane

Measured/ Corrected

Constituent 1

Coarse aggregate Measured 32.2 % Corrected 30.0

Fine aggregate Measured 52.4 % Corrected 54.2

Filler % Measured 8.1 Corrected 8.3

Bitumen % Measured 7.3 Corrected 7.5

Notes: 1. 2. 3.

Section

2 3 4 5

23.3 28.9 28.5 31.3 30.0 30.0 30.0 30.0

57.8 53.4 54.0 52.0 53.5 52.5 52.9 53.1

11.1 9.8 9.7 9.2 10.4 9.7 9.5 9.3

7.8 7.9 7.8 7.5 7.1 7.8 7.6 7.6

6 7

27.2 25.9 30.0 30.0

54.4 56.6 52.2 53.3

10.7 9.2 10.4 8.8

7.7 8.3 7.4 7.9

Analysis by DTp Materials Testing Laboratory using sieve-shaker method (dry-sieving basis). Each section comprised three lorry loads: the sample was taken from the second load. Constituents corrected to a coarse aggregate content of 30 per cent.

TABLE 6

Analysis of wearing course samples

Centre Lane

Constituent Measured/ Corrected

Coarse aggregate Measured % Corrected

Fine aggregate Measured % Corrected

Filler % Measured Corrected

Bitumen % Measured Corrected

Notes: 1. 2. 3.

1 2*

25.5 (34.4) 30.0 (30.0)

57.3 (49.9) 53.8 (53.5)

9.2 (8.0) 8.7 (8.4)

8.0 (7.7) 7.5 (8.1)

Section

3 4 5

28.4 27.6 31.0 30.0 30.0 30.0

54.0 55.0 52.2 52.8 53.0 53.4

9.8 9.3 9.2 9.6 9.1 9.1

7.8 8.1 7.6 7.6 7.9 7.5

6 7

26.0 34.2 30.0 30.0

55.3 48.2 52.1 51.6

10.6 10.0 10.2 10.4

8.1 7.6 7.7 8.0

Analysis by DTp Materials Testing Laboratory using sieve-shaker method (dry-sieving basis). Each section comprised three lorry loads; the sample was taken from the second load. Constituents corrected to a coarse aggregate content of 30 per cent.

* Sample was taken from section 2NX.

6

TABLE 7

Analysis of wearing course samples

Offside Lane

Constituent Measured/ Corrected

Coarse aggregate Measured % Corrected

Fine aggregate Measured % Corrected

Filler % Measured Corrected

Bitumen % Measured Corrected

Notes: 1. 2. 3.

1 2

27.3 30.4 30.0 30.0

56.3 53.6 54.2 53.6

9.0 8.4 8.7 8.4

7.4 7.6 7.1 7.6

Section

3 4

31.1 27.2 30.0 30.0

52.1 53.0

55.7 53.5

9.3 9.2 9.4 8.9

7.5 7.9 7.6 7.6

5 6 7

28.6 2 7 9 31.2 30.0 30.0 30.0

53.8 54.2 52.0 52.6 52.5 53.0

9.6 10.2 9.0 9.5 10.0 9.1

8.0 7.7 7.8 7.9 7.5 7.9

Analysis by DTp Materials Testing Laboratory using sieve-shaker method (dry-sieving basis). Each section comprised three lorry-loads; the sample was taken from the second load. Constituents corrected to a coarse aggregate content o f 30 per cent.

T A B L E 8

Tonnages and thicknesses

Section Lane

1 NS C OS

2 NS C OS

3 NSt C OS

4 NS C OS

5 NS C OS

6 NS C OS

7 NS C OS

Average thickness* (ram)

Tonnage ~ ) Nea~ide Centre Offside Overall

of lane of lane of lane

- 57 52 53 54 - 5 2 5 5 5 4 5 4 - 5 5 5 5 5 3 5 4

- 52 49 49 50 43.0 56 52 5 3 54

- RoUed depth 50--52 51

- 61 51 52 54 48.9 54 52 54 53 48.8 51 51 54 52

48.6 57 51 52 53 53.5 52 52 56 53 49.6 56 55 55 55

4 8 3 55 51 51 52 53.1 53 51 52 52 49.3 53 53 52 53

50.3 55 51 52 53 48.9 56 54 56 55 49.6 53 53 53 53

39.7 ** 55-.7 54.9

53 54 56

53 55 55

56 57 54

54 55 55

NS = Nearside C = Centre OS ~- Offside

* Behind paver, before being chipped and compacted. ** 1st part started with load 3 of centre lane; a further part load was used to finish off. t See footnote to Table 4. Load 2 laid too thick for 1st 10 m; raked off and rolled at 125°C.

2.7 Pre-coated chippings

These were 20 m m Craig-yr-Hesg (PSV 6 8 - 7 0 ) applied with a Bristowes spreader. The rate-of-spread was

moni tored with 5 x 300 m m square trays laid across the lane width. Three sets of measurements were made per

lane per section, and the target rate o f spread necessary to achieve 70 per cent coverage of chippings was checked

daily. Results are given in Table 9; the average overall rate of spread was 13.0 kg/m 2 , slightly lower than the target

rate o f spread of 13.8 kg/m 2 .

During the measurement of rate-of-spread, the chippings were not replaced on the 300 mm square test area

coincident with the wheelpath. This provided three unchipped areas of asphalt per lane-section that will enable the

relationship between the retention of texture depth by the chipped asphalt and the development of texture by the

unchipped asphalt, to be studied.

T A B L E 9

Rates of spread of chippings (kg/m 2)

Section Lane

1 2 3 4 5 6 7

Nearside

Centre

Offside

Hard shoulder

12.6

12.5

13.2

11.3

12.8

13.0

13.1

12.7

12.9

14.4

12.0

12.4

13.7

12.7

13.3

13.6

13.1

13.4

14.1

12.8

12.4

11.6

Note: Each value is the mean of 3 groups of at least 5 trays.

Target rate o f spread

Date kg/m 2

20/8/82 13.5 21/8/82 14.0

21/8/82 13.2

23/8/82 13.7

25/8/82 14.0

28/8/82 14.2

Overall average 13.8 kg/m 2 for 70 per cent coverage rate

2.8 Rolling

Target rate of spread 13.8 kg/m 2

Actual overall average 13.0 kg/m 2

ie. actual coverage was 13.0

13.8 - - x 70 per cent = 66 per cent

Rolling was carried out by two 8 - 1 0 tonne tandem rollers and was controlled to achieve, as far as was

practicable, the same rolling conditions for each section and a texture depth of 1.5 ram. Initial rolling was in half

roller-width strips, rolling the but t edge first. The roller was held back until the asphalt mid-layer temperature was

8

140°C or less; because of high delivery temperatures coupled with warm ambient conditions and a 50 mm thick

layer, this sometimes resulted in a long mat being laid before roiling could commence. Final rolling on these

occasions had to be delayed by up to an hour.

2.9 Climate

Weather conditions, including temperature and wind speed, were monitored to provide an estimate of the

time available for compaction. The estimated compaction times given in Table 10 range from 16-21 minutes and

were well in excess of the 10 minutes reckoned to be the lower limit for satisfactory compaction as suggested by

Br0wn 5. It should be noted that the compaction time includes the time between the material being laid and the

application of pre-coated chippings, time that is not available for rolling.

TABLE 10

Weather and estimated times for compaction

Section Date laid Wind km/h

Temp. o C

Weather

Remarks

Estimated time for

compaction* (rain)

1 21/9[82 8 13 Dry and sunny 17.1

2 23/9/82 11 16 Dry, sunny intervals 16.8

3 24/9182 12 13 Gusty, early rain, cloudy and 16.2 heavy rain during laying of nearside lane. Asphalt steam- heaving

4 25/9/82 5 14 High cloud and drying from 17.9 overnight rain

5 26/9/82 10 14 Dry and sunny at site (but 16.7 raining hard at mixing plant)

6 27/9/82 5 14 Wet surface initially but dry 17.9 and sunny later

7 28/9/82 0 - 5 16 Dry and sunny 21.0-18.2

* Predicted time to cool from a mid-layer initial laid temperature of 150°C, to 100°C, for a layer thickness of

50mm.

2.10 Surface texture

After the surfacings had cooled sufficiently, texture depth was determined for each lane in each section.

Ten sand patches at 10 m spacing were measured in the nearside wheelpath and 10 patches at 5 m spacing along

a 50 m diagonal were also determined. The surface texture was monitored along the same two lines with a

prototype portable hand-operated texture meter. Sand-patch results, given in Table 11, show significant differences

in initial texture depths between sections, but it is changes from these values that will be observed. All the work

complied with the requirements of Departmental Standard HD/3/80.

9

TABLE 1 1

Initial surface textures

Sand-patch texture depth: means o f l O tests (mm)

Lane

Hard shoulder

Nearside

Centre

Offside

Position

50 m Diagonal 100 m Wheelpath

50 m Diagonal 100 m Wheelpath

50 m Diagonal

100 m Wheelpath

50 m Diagonal 100 m Wheelpath

* 5 tests near end of section

** Wheelpath on NX 35 pen

1.41 1.75

1.30 1.60

1.49

1.57

2

D

D

1.86 1.80

1.97* (2.00) ** 2.14

1.68 1.60 1.55 1.59

D

1.79 1.49

1.51

1.73

1.78 1.76

Section

3 4

1.87 2.15

1.69

1.73

1.40 1.56

5 6

1.38 1.84 1.71 2.13

1.92 1.54

1.82 1.79

1.68 1.71 1.39 1.74

7

2.07 1.78

1.73

1.85

1.47 1.32

2.11 Skidding resistance

Measurements of sideway-force coefficient, at 50 km/h (SFCs o) were made in the nearside lane a week after

opening to traffic, and also a month later. Results are included in Table 12. No interpretation should be placed on

these early results except that the initial skidding resistance of all the sections is satisfactory.

T A B L E 12

Sideway force coefficient (SFCs o)

Section

NX (old surfacing)

1

2

3

4

5

6

7

NX (new surfacing)

" Sideway force coefficient

3/9/82*

0.59

0.64

0.64

0.63

0.62

0.63

0.61

0.60

0.59

12/11/82"*

' 0.55

0.53

0.54

0.55

0.54

0.55

0.53

0.55

0.54

* After 1 week of traffic

** After 11 weeks of traffic

NX: Non-experimental surfacing up to and after experimental work.

1 0

3. F U T U R E M E A S U R E M E N T S

The following measurements are to be made at 6-monthly intervals, during the Spring and Autumn for at least the next five years.

1) Texture depth by sand-patch and texture meter. 2) Sideway force coefficient at 50 km/h.

3) Rut depths and longitudinal profiles. 4) Visual inspections (annually at Ftrst and then biennially).

It is unlikely that significant conclusions relating to permittivity and texture depth retention will be apparent for some years. Although the sections comprised materials that were nominally the same, except for their binders,

differences in initial texture depths and other properties roay have to be taken into account in interpreting long-

term trends.

4. A C K N O W L E D G E M E N T S

The co-operation and assistance of the following organisations is gratefully acknowledged. The County Surveyor

of Wiltshire and his staff; the Regional Controller ( R & T) South West; and the Refined Bitumen Association.

The laying work was carried out by Amey Roadstone Corporation, Frome, Somerset.

This report was prepared in the Pavement Materials and Construction Division of the Highways and

Structures Department, TRRL. (Division Head: Mr G F Salt).

.

.

.

.

.

5. R E F E R E N C E S

GREEN, E H. An acceptance test for bitumen for rolled asphalt wearing course. Department of the Environ- ment, Department of Transport, TRRL Report LR 777. Crowthorne, 1977 (Transport and Road Research

Laboratory).

DEPARTMENT OF TRANSPORT. Specification for Road and Bridge Works. Amendment to specification

for bitumen binder in rolled asphalt wearing course. Department of Transport Technical Memorandum H1/7Z London, 1977 (Department of Transport).

DEPARTMENT OF TRANSPORT. Specification for Road and Bridge Works. Rolled Asphalt Wearing

Course Departmental Standard HD/2/79, London, 1979 (Department of Transport).

DAINES, M E. The weathering of 35 pen and 70 pen bitumens in rolled asphalt. Department of the Environment, Department of Transport, TRRL Working Paper MM 62. Crowthome, 1980 (unpublished).

BROWN, J.R. The cooling effects of temperature and wind on rolled asphalt surfacings. Department of the Environment, Department of Transport, TRRL Report SR 624, Crowthorne, 1980 (Transport and Road

Research Laboratory).

11

Luckington

Badminton

Old Sodbury

B4040

SITE OF EXPT.

Tormarton

0 I 0

1 2kin ! J

I

1mile

North Wraxall

Fig. 1 Locat ion of pe rm i t t i v i t y experiment on the eastbound carriageway of M4 at Acton Turville

T

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~D

L~

~D

r~

e~ 0

"0

0 .-J

0

X Z

r ~

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ABSTRACT

Bitumen permittivity and texture depth of rolled asphalt: an experiment on motorway M4: M E DAINES: Department of the Environment, Department of Transport, TRRL Supplementary Report 816: Crowthome, 1983 (Transport and Road Research Laboratory). During August 1982 a fuU-scale experiment was begun with the aim of studying the effect of the permittivity of bitumen on the texture depth of heavily-chipped Marshall-designed rolled asphalts. Seven sections of asphalt were laid and, apart from the differences in permittivity, the asphalts were nominally identical. The experimental sections were laid in all three lanes of Motorway M4, Wiltshire. The changes in texture depth and skidding resistance at the three traffic intensities will be monitored for at least 5 years.

ISSN 0305-1315

ABSTRACT

Bitumen permittivity and texture depth of rolled asphalt: an experiment on motorway M4: M E DAINES: Department of the Environment, Department of Transport, TRRL Supplementary Report 816: Crowthorne, 1983 (Transport and Road Research Laboratory). During August 1982 a full-scale experiment was begun with the aim of studying the effect of the permittivity of bitumen on the texture depth of heavily-chipped Marshall-designed rolled asphalts. Seven sections of asphalt were laid and, apart from the differences in permittivity, the asphalts were nominally identical. The experimental sections were laid in all three lanes of Motorway M4, Wiltshire. The changes in texture depth and skidding resistance at the three traffic intensities will be monitored for at least 5 years.

ISSN 0305-1315