Sub base improvements by stabilization techniques using waste materials

Abstract

Improvements of rural roads are active socio-economic passageways to a high quality of life for most of the Srilankan people living in rural areas. The fund allocated for low volume road project is limited, thus it is important to use existing resources for economic advantages. Also, adverse environmental impact can be reduced. Roads are designed for low-volume traffic and are constructed of local soils containing high percentages of fines and high indices of plasticity. These type of soils may not have certain properties pertinent for the sub base in the construction of flexible pavement in rural roads. Thus, it is necessary to modify or stabilize this kind of soil to make it suitable for construction. The soil modification process can be effectively used to meet the challenges of sustainability of the environment, to minimize the adverse effect of industrial wastes such as plastic, glass, paddy husks, etc. Wastes are multiplying day by day leading to diverse environmental concerns. On the account, the disposal of those wastes without causing any environment hazards is a real challenge. Therefore, using plastic waste, glass waste & paddy husk ash stabilizing agents is an economical utilization since there are demand and shortage of well graded soil for sub-base. This research involves a comprehensive study on the feasible use of the waste products for soil stabilization for the sub-base material in the North Central Province I-Road Project in Sri Lanka. A series of field and laboratory tests were carried out for collected sub-base materials to identify the deficiency of sub base material properties. CIDA specification for the roads was referred and confirmed to the specification for the road projects in Sri Lanka. The specification says that Liquid Limit should be less than 40 (LL<40) and Plasticity Index should be lesser than 15 (PI<15). Three different borrow pits Sub-base materials from Polonnaruwa area were stabilized with different percentage of paddy husk ash, plastic waste and glass waste with weight-based mix proportions. But the experimental study of two sub base borrow pits samples such as Mahadamana source and Sooriyaweva source demonstrated that with a 8% and 10% of optimum paddy husk ash. At the same time, the two composite samples from Mahadamana source and Sooriyaweva source were reduced the Liquid Limit by 20%, 26% and reduced the Plastic Index by 26%, 36 % accordingly. Similarly, California Bearing Ratio of the Mahadamana and Sooriyaweva composite samples were improved by 10% and 14.7% respectively. Finally, it was concluded that the stabilized composite soil can be used for the construction of flexible pavement in rural areas with low volume traffic.