GUIDANCE NOTE ON
TYPES AND DESIGN OF
SURFACE DRESSING
ROAD
SURFACE DRESSING ASSOCIATION
GUIDANCE NOTE ON
TYPES AND DESIGN OF
SURFACE DRESSING
Consultant
Director and Secretary
John Baxter
Little Horkesley
Essex CO6 4BS
Ó
Copyright RSDA 1993
First
Published
Revised 2001
Second
Revision 2004
reproduced without the written permission of the Road Surface Dressing Association
No part of this document
may be
R S D A
Types and Design of Surface Dressing Guidance Note 2004
INDEX
|
|
|
Page No |
|
1 |
Introduction |
1 |
|
2 |
Types
of Dressing |
1 |
|
3 |
Design
of Dressing |
2 |
|
4 |
Training |
4 |
ROAD
SURFACE DRESSING ASSOCIATION
GUIDANCE NOTE ON TYPES &
DESIGN OF SURFACE DRESSINGS
1
Introduction
1.1
There are 5
basic types of surface dressings plus a range of "proprietary"
dressings such as high friction systems and multiple layer dressings.
1.2
Advice on the
parameters used in the design of dressings is given in the Design Guide for
Surface Dressing by J C Nichols, which is known as TRL Road Note 39 5th edition. The Road Note is available from the
Transport Research Laboratory at Crowthorne,
1.3
This RSDA
Guidance Note is not intended to reproduce the information in Road Note 39, but
to draw attention to important information on types of dressings and their
design. It also references the relevant sections to help the designer when
using the Note.
1.4
The design
parameters that should be considered are:
·
type of
dressing
·
type and
spread rate of binder
·
type, size and spread rate of the aggregate/s to be used.
1.5
Each type of
dressings has different characteristics.
Care needs to be taken to select the type of dressing which is
appropriate for the site to be dressed.
1.6
It is also
important that the dressing is designed to give maximum performance under the
site operating conditions. This will
ensure that maximum life is gained from the work.
2
Types of Dressing
2.1
The basic
types of dressings are:
|
·
single
surface dressing |
- one layer of binder and one layer
of chippings |
|
·
racked-in
surface dressing |
- one layer of binder and two
layers of chippings with the larger size placed in the bottom layer followed
by the smaller chippings to lock the larger chippings in position |
|
·
double
surface dressing |
- two
layers of chippings (the larger size in the bottom layer) and two
applications of binder, the second one being placed between the layers of
chippings |
|
·
inverted
double dressing |
- as above for double dressing with the layers of larger and
smaller chippings reversed. |
|
·
|
-
a layer of
chippings laid on the road surface prior to
the application of a single surface dressing. |
2.2
Reference
should be made to Section 2 in Road Note 39 for full descriptions and the
advantages of each of these various types.
2.3
There are also
many different "proprietary" surface dressings which are specifically
designed for particular circumstances.
3
Design of Dressings
3.1
As previously
stated, surface dressings should be designed in order to give maximum
performance under the expected working conditions on the site.
3.2
The design
process is fully set out in Road Note 39 and includes determining the
following: (the relevant Road Note Sections are given against each factor.)
|
·
Latitude in
the hardness category highway layout
(gradients/bends/junctions) surface condition |
Sections 4.1 & 4.2 --:-- --:-- --:-- |
|
·
materials to
be used
type, size, psv & shape of chippings
type of binder type of dressing size(s) of aggregate(s) |
Sections 4.3, 4.4 & 4.5 Section 7.1 Sections 2, 5 & 6 |
|
·
rate of
spread of chippings |
Section 6.3 |
|
·
rate of
spread of binder |
Sections 7.2, 7.3 & 7.4 |
3.3
A summary of
the Tables to be used with their relevant page numbers is set out at Fig 1
to this note.
Figure 1
FLOW CHART FOR USE WITH
THE FIFTH EDITION OF ROAD NOTE 39
SITE DETAILS, CHOICE OF DRESSING AND CHIPPING SIZE
|
TASK |
TABLE OR FIGURE |
PAGE |
|
|
Traffic Category |
T6.2.4 |
17 |
|
|
Total Traffic |
From Client |
|
|
|
Traffic Speed |
From Client |
|
|
|
Geographical Zone |
F 6.2.1 |
15 |
|
|
Road Hardness |
F 6.2.3 |
16 |
|
|
Road Altitude |
Maps/Site Visit or Client |
|
|
|
Minimum Radius of Bends |
Maps/Site Visit or Client |
|
|
|
Road Condition |
Site Visit or Client |
|
|
|
Type of Dressing |
F 7.3a or b |
24 or 25 |
|
|
Type of Binder |
Guidance from RN 39 Client / Contractor choice |
|
|
|
PSV of Chippings required |
F 6.3.1 |
19 |
|
|
Size of Chippings |
|
|
|
|
|
single |
F 8.2.1.1 |
28 |
|
|
racked and double |
F 8.2.2.1 |
29 |
|
Stage 1 |
|
|
|
|
|
single or second layer of inverted double
dressing racked dressing double dressings and sandwich dressings |
T 9.2.3a T 9.2.3b T 9.2.3c,d or e |
33 34 35 |
|
|
|||
|
|
|||
|
Stage 2 |
|
|
|
|
|
Flakiness index & grading of chippings |
Laboratory report |
|
|
|
Binder rate of spread |
T 9.2.4 |
35 |
|
Stage 3 |
|
|
|
|
|
Adjustment factors |
T 9.2.5a |
36 |
|
|
Target rate of spread 1/m2 |
T 9.2.5b |
37 |
4. Training
4.1 The Road Surface Dressing Association (RSDA)
runs several courses each year covering all aspects of surface dressing,
including tuition on the design process outlined in this Guidance Note.
4.2 Details
of these courses, together with dates and locations, can be obtained from:
Consultant
Director & Secretary
Road
Surface Dressing Association
Little
Horkesley
Tel: 01206 274052
Fax: 01206 274053
E-mail: enquiries@rsda-gb.co.uk
Or visit the RSDA website at:
4.3 A video or DVD "Making Britain’s Roads
Safer", which sets out the design procedure, is also available from the
RSDA at the address above.
REFERENCES
1
Road Note 39 5th
Edition
Transport Research Laboratory
Crowthorne House
Nine Mile Ride
Wokingham
RG40 3GA
Tel: 01344 773131
R S D A PUBLICATIONS
Pocket Guide based on R N 39
Operators’ Guide to the Safe use of Surface
Dressing Sprayers