Field Investigation on Complete Replacement of Granular Subbase with Flyash and Blast Furnace Slag in Flexible Pavement

Abstract

With rapid industrial and transportation-related infrastructural growth in India, the problems of environmentally injurious metal slags, flyash open dumps and depleting natural aggregate resources are ever-increasing. The focal point of this research is to substantiate the bulk utilization of fly ash and granulated blast furnace slag (GBFS) as a replacement for a granular subbase (GSB) in flexible pavement. Based on detailed laboratory study and finite element analyses, optimal combinations of two waste mixes, i.e., fly ash + 5% lime (FL) and 80% fly ash + 20% GBFS (FG) were chosen. 7 test sections (each 3.5 m wide and 50 m long) with different thicknesses of waste mix subbase (200, 300 & 400 mm) layers were constructed. To compare the field performance and service life of waste mix test sections with conventional control section with GSB, structural and functional evaluation is carried out employing a falling weight deflectometer (FWD) and Bump Integrator for two years. The results showed that this technology could save up to 4200 tons of natural aggregates per lane per km of highway construction, with an overall cost saving of 4% to 10%.