2003 - International - TRL Manual for Labour Based Bituminous Surfacings

This manual is a guide to the construction of new bituminous surfacings on unpaved low trafficked roads in tropical countries using labour-based methods. It is aimed at local government officials and their staff, and smallscale contractors who are responsible for carrying out the work employing mainly local labour.

To achieve the desired results it is essential that works supervisors be trained by means of short training courses and field trials to deliver the required standard of workmanship. This manual can also be used to assist with this training. Labour-based construction of bituminous surfacings can be very effective providing there is good roadside drainage and the underlying road surface is sufficiently stable and the workmanship is to a good standard. It is therefore stressed that the preparation of the existing road and materials used must meet the particular country and ministry design specifications before any sealing work is undertaken.

Road construction in rural areas is increasingly being focused on provision of access and poverty alleviation. When access is treated as a priority, it is likely that there will be an increased use of spot improvement techniques. The decision to surface a road with a bituminous seal may be made because the existing gravel pavement requires too much maintenance or because suitable regravelling materials are scarce and in some cases sealing roads, which carry traffic as low as 30 vpd, may be justified. The upgrading of short sections of road for which the use of conventional large road construction equipment is prohibitively expensive make the methods described here most suitable.

The techniques described in this manual, use low cost plant that can either be manufactured locally or be bought or hired by small local contractors. However, there are situations where traffic levels will be at the limit of the ‘low-volume’ category and in these cases the use of bitumen heating and spraying tanks if appropriate, should be used. Any additional equipment that may be required should be relatively cheap and within the range of the capital investment expected by small-scale contractors.