Evaluating the durability of stabilized conventional granular material with Pond Ash and lime used as subbase course of flexible pavement

Abstract

The backbone of power capacity addition in India has always been the coal-based thermal power generation. The thermal power stations has been fueled by the coal produced in India, which are predominantly low grade with 30–22% ash content. The ever-growing disposal problem of the Pond Ash (PA) generated by these thermal power stations, on account of using the high ash content coal having, granular particle sizes has become a huge issue. The associated environmental hazard is the primary coencern along with the dumping zone, which covers large hectares of land over a prolonged period. On the other hand, a strictly regulated sand mining scenario restricted the progress of the construction activities in the related field. So effective reuse of such industrial waste by replacing the conventional granular material, may overcome the environmental and health hazard, as well as speed up the construction activities. Moreover, the PA will find effective bulk usage. Prior Investigational works have shown improvement in the geotechnical properties of stabilized coal combustion ash. This study involves sand and PA blended in varying proportions from 0% −100% at an increment of 10% by weight of sand, with addition of lime (0%, 1%, 2%, 3%, 4%, 5%, 6%, 7% and 8% by weight of sand) as stabilizer. The un-soaked bearing ratio of sand – PA optimum mix with different lime content was observed. The results indicated a considerable rise in the bearing ratio up to 4% lime content which gradually reduces on further addition. Experimental results showed a maximum CBR of 32.85% for standard compaction un-soaked sample. Sand – PA – Lime samples were further tested for their UCS values after curing them for 7, 14, and 28 days. The results maxed out at 0.8 MPa for 28 days curing at 4% lime content. Slake Durability Indices showed high to medium–high durability value for the optimum mix. Chemical composition of lime and PA along with XRD and FESEM of PA sample was also conducted to characterize the sample. The test outcomes satisfied the MORD and MORTH requirements to use the sand (71%): PA (25%): lime (4%) as suitable subbase material for pavement foundation construction as cost-effective mix proportion.