Improving Clay of Intermediate Plasticity for Rural Road Sub-Grades – A Case Study

Many regions of the world are affected by soils with poor engineering properties. This has significant influence on infrastructure development of the region. Design and construction of civil engineering structures on such soils has always been a challenging task for engineers. Stabilization has been recommended and used to overcome the weakness of these soils and making the condition appropriate for construction of structures or laying of the roads. This paper presents a systematic experimental investigation undertaken to explore the possibility of using stabilizing materials for improving the engineering properties of soil of type clay with intermediate plasticity. Effectiveness of commonly used stabilizing materials viz. cement, lime, and fly ash is investigated. Further, using the CBR values of the soil obtained for different quantity of stabilizing material, the sub-grade of pavement for rural roads was designed following the guidelines recommended by Indian Road Congress. Cost estimation per km of sub-grade for rural road pavement is done for all the designed sub-grades. Cost analysis for sub-grades of rural road pavement shows that 2% cement is the most economical option for improvement of properties of such clays. However, combination of (4% lime & 4% fly ash) as stabilizing agent is more attractive because, without any noticeable increase in the cost, it also helps in protecting environment by (i) enabling significant disposal of fly ash, a non-decomposable waste material and (ii) reduction in cement consumption and in turn reduction in emission of harmful gases, which are released during cement production.