Evaluation of Pond Ash Mixed with Coir as a Pavement Material

Abstract

With a population of 1.21 billion people according to the 2011 Census, India is putting a lot of strain on its resources. Thermal power facilities in India create massive amounts of coal ash as a waste product. Coal ash production in India is around 225 million metric tons per year, and disposal is a big issue. In India, ash ponds have already taken up more than 65,000 acres of precious land. Coal ash, with or without any admixture, is being utilized in many ways such as filling of low-lying areas, productions of bricks, cement concrete, construction of embankment, etc. It can also be used as a sub-base/subgrade in the pavement construction. The fibrous material may be mixed with coal ash to reinforce and strengthen it. Due to the commercial availability of a variety of synthetic materials at lower prices, the application of reinforcement in enhancing the strength properties of geomaterials has gained popularity. A natural fiber coir has been used in this study as an admixture to pond ash with an expectation of improving the geotechnical characteristics of pond ash. The percentage of coir fiber by dry weight of pond ash is varied from 0–2% at an interval of 0.5% at three different aspect ratio of 50, 100, and 150. The specific gravity of both the materials, i.e., pond ash (2.11) and coir (0.91) was found to be lesser than conventional earth materials. Pond ash is poorly graded and classified as SM as per IS 1948: 1970 with Cu and Cc values of 3.6 and 1.7. Maximum dry density of coal ash, coir fiber mix showed a slight variation, i.e., (9.90–10.30) kN/m3 for aspect ratio 50, (9.96–10.47) kN/m3 for aspect ratio 100, and (10.01–10.28) kN/m3 for aspect ratio 150. Coir being lighter in weight still increases the maximum dry density of the composite mix which shows that the voids in pond ash decrease on addition of coir. Optimum moisture content decreases on addition of coir to pond ash from 40.3 to 34%. The rate of increase of UCS on addition of coir fiber is more up to coir addition of 1%. After further increase in percentage of coir till 2%, the rate of increase of UCS has remained almost constant. Soaked CBR value of PA and PA-CF mix came at 5 mm for all aspect ratios. CBR value for a particular aspect ratio increases with increase in coir content up to 1%, and any further increase in percentage of coir starts to decrease the CBR value. Thus, it can be safely said that for all aspect ratios, the optimum value of soaked CBR is attained at a coir content of 1%.KeywordsPond ashCoirSoaked CBRAdmixture