Performance evaluation of nano-material stabilized pond ash as subbase layer material for roadway pavement

Abstract

The power capacity of India is heavily coal based. In the session 2021–22 the overall country’s coal production has been 777.31 million tons, with 8.55% positive growth. However, the Indian coal is of lower grade with higher ash content of 24–63%. This results in the generation of 240.27 million tons of Coal Combustion Ash (CCA) during 2021–22. This huge quantity of industrial byproduct mixed with water and stored in ash lagoons in the form of Pond Ash (PA). From this stored ash deposit only 79.18% finds utilization, which by far falls short of the 100% utilization target as strictly recommended by the Ministry of Environment Forest and Climate Change (MoEF & CC). This high volume generation compounded with lower utilization of PA has been consuming about 65,000 acres of valuable land. Moreover the prolonged disposal of PA in ash lagoons causes serious environmental and health hazards. Besides, the extensive use of Conventional Granular Material (CGM) has been alarming, thus necessitating it to be condemned and strict regulations imposed in construction. Emphasis being laid on the utilization of Non-Conventional Granular Materials (NCGM) like CCA. On the basis of the above mentioned circumstances the PA can be converted into a meaningful wealth for the subbase construction of pavement foundation. Therefore, this paper primarily addresses the potential of PA as subbase layer material for roadway pavement foundation. This study utilizes virgin PA as well as in partial replacement of CGM 10%-100% by weight, being stabilized with lime 0%-14% by weight and Nano-Material (NM) 1:1:150–1:1:400 by dosage as a subbase material for the foundation of pavement. Experimental work was carried out in stages to determine the chemical composition of PA, Lime and NM, characterize the PA samples by FTIR and FESEM followed by understanding the behavior of PA with and without any addition of additives as stabilizers. The c and φ ranges 0.88–40.02 kg/cm2 and 32°-53° The soaked CBR is of 19% to as high as 79% for optimum stabilized PA mix. Terrasil and Zycobond whose pH showed alkalinity, were used as nanomaterial, which provided little to zero permeability for the mix. Slake durability test provided medium to high to very high durability for the optimum mix. A comparative analysis was performed to determine the optimum mix providing the best stability. Light Falling weight Deflectometer (LFWD) showed satisfactory deflection. The values obtained satisfied the Ministry of Road Transport and Highways (MoRTH), Government of India.