Good roads provide an economic lifeline for remote areas, allowing the transportation of goods and also enabling people to access services such as education and health. The clear link between poor access and poverty is established.
In rural parts of Cambodia and Vietnam road conditions are generally poor, with ruts and gaping potholes slowing down and damaging vehicles, and raising transport costs. New ways of using cheap local materials are smoothing out these roads, allowing access for South-east Asia’s cross-country traffic.
Laterite, along with other forms of naturally occurring gravel, was until recently relatively cheap and available in many locations. It provided an intermediate solution between a basic earth road construction and the more sturdy, but costly, bituminous or paved road. It was therefore widely adopted as a surfacing material for low-cost rural roads. However, laterite and other gravels are becoming increasingly scarce, and they have practical limitations – traffic loads and levels must not be too high, gradients must not be too steep, and extreme weather such as tropical monsoons will wash away the material; in the dry season dust is a significant hazard and there is further loss of the surface material.
All roads need regular maintenance because otherwise, once the surfaces are eroded, rural communities become cut off, slowing down their economic and social development. Proper maintenance in developing countries is unfortunately difficult to achieve for a range of reasons.
The scale of this problem is huge; for instance, in Cambodia it is estimated that there are 28,000 kilometres (km) of rural roads, most of which are unsurfaced. In Vietnam the total road network is approximately 210,000 km, but only about 15 per cent is considered to be in good condition. The cost of fully rehabilitating and maintaining these roads to gravel standard would be prohibitive, especially as natural gravel is becoming an increasingly scarce resource. The transportation of gravel in heavy trucks over ever-greater distances is itself a factor in the deterioration of roads.
A project run by Intech Associates and supported by TRL Ltd, with financial support from the UK Department for International Development (DFID) and the World Bank, is looking at the effectiveness of alternative materials, such as bamboo, stone, cement and brick, to make roads in Cambodia and Vietnam. The use of local resources and machinery makes the roads more affordable, and provides a useful income for local enterprises and communities.
The project takes a realistic approach to road design, taking into account local conditions and the road environment, traffic characteristics and loading, maintenance, resources, technical and implementation options, environmental and whole life cost considerations.
“In essence what we are trying to do is develop road construction and surfacing techniques that governments and communities can afford, that have low maintenance so they will be possible to maintain and also to create local job opportunities,” says Rob Petts from Intech Associates.
Although surfacing materials other than laterite and gravel may have a higher initial cost, they have proved to be more durable and therefore more cost effective over the whole life cycle of the road. Improvement options ranged from the low-cost ‘hardening’ of earth roads where these were used only by non-motorised transport or motorcycles, up to paving which could cope with heavily loaded trucks.
Bamboo can be used to reinforce a concrete road surface. It is a native plant in many parts of Asia and, laid as a lattice within the concrete, has proved as effective as imported steel in reinforcing these roads. The strong straight structure of mature bamboo splints enables them to function like thin binding steel rods, preventing shrinkage cracks as the concrete road surface dries out after casting.
The best results are obtained from bamboo that is mature, about four years old, with straight, thick stems. It should be cut and allowed to dry and season for up to six weeks before use. Then the bamboo should be split into splints, no more than 25 mm wide. The cured splints are placed in a reinforcing lattice framework within the concrete. The road itself should have well designed drainage, with a slight surface camber (1 cm drop in every 50 cm) to allow rainwater run-off to the side, to ensure longevity. The concrete when mixed must not be too wet (like soup) as this inevitably causes cracking as it dries out. This is a common fault with concrete roads built by communities or inexperienced contractors. Engineers usually ask for a standard “slump test” to be carried out which ensures that neither too much, nor too little water is present in the freshly mixed concrete.
Although using bamboo-reinforced concrete means construction takes longer and has higher initial costs, the advantages are considerable:
- It has an estimated life span of 40 years or more.
- There is minimum maintenance.
- Its use requires only simple equipment – a small roller, concrete mixer and vibrator.
- It is a good use of local resources, especially labour and materials.
- It produces a dust-free, easy-to-clean surface.
- It has tolerance to flooding.
The use of local stone for the road base requires a means of breaking the stone into pieces small enough to use. In Cambodia women gain a valuable income as they are employed to break the stone by hand. Depending on the quantity of stone they break, these women can earn up to 85p ($1.50) per day – equivalent to a man’s earnings in these rural areas.
Depending on the size of the stone, a layer is bedded on a thin layer of sand and gravel, for example 10-15 cm stones are hand picked and placed in a 2-3 cm thick sand/gravel layer, tightly packed and wedged into place; then smaller stone chippings are hand rammed into the joints and remaining gaps filled with sand.
“In this country where labour is abundant and cheap you know that US$1 a day wage is attractive for many rural people. This is an ideal local resource. Most of the investment will go to the local economy and generate direct employment as well as indirect benefits.”
Heng Kackada, Cambodia manager from Intech Associates
Southern Vietnam has a thriving brickmaking industry and very few hard stone deposits for road building. Clay is available locally and the small local brick kilns make use of rice husk as a renewable energy source to fire the bricks. These traditional bricks are emerging as ideal material for road building. The bricks are as strong and regular as factory-made products, generally 10 cm x 20 cm in area and 7-10 cm thick. They are laid by hand on a thin, 3-5 cm, sand bed over a prepared and compacted road base. The joints are filled with sand-cement mortar and the surface is then lightly compacted.
Whatever the road surface construction, all traffic causes wear and tear, so action needs to taken to ensure road sustainability. One of the most damaging transport issues is the overloading of vehicles – the increasing weight of trucks causes damage to the road surface and leads to bridge collapses. Now width restricters on selected rural roads are stopping the large lorries of 2.5 metres wide, and these barriers are helping to preserve the road surface.
Regular maintenance also prolongs the life of the existing gravel and earth roads. The gravel roads are built with a camber to assist rainwater run-off, but over a period of time the traffic and rain tend to flatten the surface, and potholes start to appear. Carrying out repair work to re-shape the roads every two to three months increases their longevity.
Development Technology Workshop (DTW) has developed a low-cost prototype road grader that can be used to repair road surfaces. The design focuses on making the grader as robust and easily reparable as possible. It has no mechanical gearing or hydraulics, and all labour and parts are Cambodian apart from a steering column that is made from recycled light truck parts from Japan. Using just a small tractor, the grader can be towed to its workplace. As this grader is less than a third of the price of other graders, it reduces the cost of maintaining rural roads.
The initial trial phase of this project in Cambodia and Vietnam has come to an end. The technical results are still being assessed and documented for website and other distribution, but the results so far have been very encouraging. Not only are the roads in better condition, but also income is being generated by local construction enterprises that are in place to provide the long-term maintenance services that the roads require.
Local people confirm the impact of the project, saying that they now have improved access to healthcare, information and education. Improvements in road links have resulted in investment along the roads. Young people are able to find work in the industrial zones because of better links to the district roads and main highways, and local people are enjoying shorter journey times to markets because of improved community roads.
The Governments of Cambodia and Vietnam are eager to mainstream these new approaches. They are already being incorporated in new World Bank and Asia Development Bank projects worth over £60 million ($100 million).
Hands On would like to thank the Intech-TRL teams for help in putting together this case study.
From Road Surfacing Problems to Mainstreaming New Techniques in National Standards: Rural Road Research in Vietnam. Robert Petts, Dr Jasper Cook, Pham Gia Tuan, Bach The Dzung, World Road Association, Sustainable Access and Local Resource Solutions Seminar, Cambodia, November 2005
The Performance of Low-Volume Unsealed Rural Roads in Vietnam, Dr J.R.Cook, Robert Petts, Dr Doan Minh Tam, World Road Association, Sustainable Access and Local Resource Solutions Seminar, Cambodia, November 2005
LCS Working Paper No. 1 – Rationale for the compilation of international guidelines for low-cost sustainable road surfacing. R. Petts, 2002
LCS Working Paper No. 7 (Part 3) – Bamboo Reinforced Concrete Pavement Road Construction in Cambodia (draft). M. Azam, S. Al-Fayadh, F. Gleeson, R. Petts, 2002
LCS Working Paper No. 12 – Paving the Way for Rural Development and Poverty Reduction. Dr C. Gourley, A. Greening, Dr D. Jones, R. Petts, 2002
LCS Working Paper No. 19 – Evaluation of Mark 2 Cambodia Light Grader. R. Petts, 2004
Low-cost, Labour-based Paved Roads for Poor Communities (LCS). Theme: T2 – Reduce the costs of construction, rehabilitation, and maintenance of road infrastructure to help reduce vehicle operation costs.
Intech Associates –TRL Regional Office
Donor and Supporting Organisations
Development Technology Workshop (DTW) www.dtw.org.kh
Department for International Development (DFID) www.dfid.gov.uk
World Bank www.worldbank.org
CNCTP – Cambodia
Ministry of Transport Vietnam mt.gov.vn/en/
Global Transport Knowledge Partnership www.gtkp.com
DFID Transport Links www.transport-links.org
Planning Rural Roads www.ruralroads.org