Application of Bottom Ash with Hydrated Lime in Pavement Subgrade Construction

Abstract

Introduction:: A structurally strong subgrade is always desirable in pavement construction so as to provide a resilient and durable foundation for the subsequent pavement layers for adequate performance under the given traffic load/volume and environmental conditions. Emphasizing the increased awareness for effective waste recycling and demand for a sustainable construction approach, re-utilizing industrial wastes in pavement subgrade construction can be a viable option. Method: Bottom ash (BA) is an incombustible by-product generated in huge quantities from coal combustion in thermal power plants. The potential re-utilization of bottom ash in replacing natural soil in the subgrade construction of pavements will not only limit the extent of disturbance to ecological balance through over-utilization of natural soil but also open an avenue for the reuse of bottom ash. Different natural soil types have varying characteristics, which vary from place to place, and sometimes, this soil may be deficient in some essential properties, which make it unsuitable for pavement construction. Under these challenges, various techniques are employed to improve the geotechnical characteristics of the soil to meet the requirements of the intended purpose. Result: One such common technique is soil stabilization through the use of hydrated lime as a chemical additive. In this study, an effort was made to study the possible use of different percentage replacement of BA (0 to 60% with an increment of 15%) with natural soil with and without hydrated lime (5% by weight of soil-bottom ash mix) for applications in road subgrade. Laboratory investigations were conducted for basic soil characteristics, compaction properties, and strength evaluation through California bearing ratio (CBR) and unconfined compressive strength (UCS) tests. Conclusion: The observed results indicated that the coupled behavior of the bottom ash and hydrated lime treatment has effectively increased the soil's compaction and mechanical strength and its suitability for use in road subgrade construction.