excellent and cheap roads have been built in many parts of africa using stabilised soil for the base and surface- dressings for the running surface. the most commonly used stabilising agent is cement, but some countries have employed lime stabilisation to great advantage. bituminous stabilisation is not widely used but is important in several countries that border the sahara. the strength criteria that are commonly used to specify stabilised soil in africa were developed empirically in temperate climates may not always be valid for use in the tropics. one of the most successful large-scale applications of soil stabilisation in africa is in zambia where locally developed cbr criteria are used to specify lime-stabilised gravels. research is being carried out at the transport and road research laboratory into the physical properties of stabilised soil with the object of enabling the cracking of stabilised soil pavements which is sometimes a problem, to be better controlled. improved strength criteria based on tensile strength are also being sought. it is concluded that stabilised soil will continue to play a major role in the development of highways in africa. (a) this report was prepared as a contribution to the second african highway conference organised by the international road federation in rabat, morocco, april 1972.

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