ABSTRACT
Because of the nature of pavements, it is often not feasible to use the best possible materials in their construction. This chapter discusses ways of enhancing sub-standard materials with processes broadly called soil stabilisation. Lime and cement stabilisation are remarkable but quite different processes to mortar-making in that the addition of a very small percentage of lime or cement to some soils can have a major overall impact. This is particularly useful with clays which are inherently unstable and very moisture sensitive. The remarkable improvements stem from the fact the material particles are surface reactive, with many free surface ions which preferentially link to clay particles. This binds the particles and prevents water ions from causing adverse effects. The process reduces the moisture susceptibility and increases the shear and bearing strength of the material. As it works at a particle level, it is only effective if the additive can be thoroughly mixed into pulverised soil. The first field use of cement stabilisation was in South Carolina in 1932. In situ stabilisation is a mobile process in which a purpose-designed machine is used to break up the existing pavement, add the stabilisation material to the broken pavement, mix the materials together and then compact and level the mixture. Granular, thermal and mechanical stabilisation are also used.
