Soil stabilisation, using cement and lime, has been widely used throughout the world for over 40 years. However, recently there has been a loss of confidence in the chemical stabilisation process in parts of Southern Africa. Some studies have indicated that road failures could be attributed partly to the degradation of the stabilising agents and their cemented products through the process known as carbonation. As a result, some countries in the region have discontinued the use of chemical stabilisation in road projects. Conversely, there are also many examples within Southern Africa where the use of chemical stabilisation has been very successful, even on roads that have received little maintenance. This conflicting evidence has resulted in considerable uncertainty about the continued use of stabilisation as an option for road projects.
Against this background, a project was undertaken to investigate the performance of a variety of chemically stabilised roadbases to assess their performance over time.
This report contains a description of the basic principles of chemical stabilisation, followed by a description of the problem of carbonation. The methodology adopted by the study is put forward and the results are given. The findings of the research, including those on the impact of carbonation on the performance of stabilised roadbases, are discussed. A detailed discussion is also provided on the question of the impact of stabilisation on road strength.