A Study on Improvement in Engineering Properties of Dense Grade Bituminous Mixes with Coal Ash by Using Natural Fiber

Abstract

Coal-based thermal power plants have been a major source of power generation in India. The prime waste products of a coal thermal power plant are fly ash and bottom ash. Heavy dumping of these waste products causes fatal environment pollution to air, water, and land, besides impairing human health. This research work is done to explore the optimum use of ash, namely bottom ash (as fine aggregate) and fly ash (as mineral filler) along with natural fiber (such as sisal fiber) used to improvise the engineering properties of bituminous paving mixes. For national interest, these waste products that are available easily and abundantly can be used economically for bituminous paving applications which ultimately help in saving the natural aggregate resources of the nation. In the present study, dense graded bituminous mix specimens were prepared using natural aggregates as coarse aggregates, bottom ash as fine aggregates, fly ash as filler and sisal fiber as additive. The grading of aggregates was chosen for dense graded bituminous macadam (DBM) mixes with nominal maximum aggregates size (NMAS) of 26.5 mm as per MORTH (2013). To strengthen the mix, slow setting emulsion (SS1) coated sisal fiber was added in varying percentages such as 0%, 0.25%, 0.5%, 0.75%, and 1% by weight of the mix, with different length variations such as 0 mm, 5 mm, 10 mm, 15 mm and 20 mm. At the initial stage of the research, specimens were prepared with two types of paving bitumen i.e. VG-30 and VG-10.The initial trials resulted better Marshall characteristics with VG-30 bitumen and hence was considered for subsequent studies. The most suitable composition (such as optimum bitumen content and optimum fiber content including the optimum length of fiber of the mix) was selected based on the results of the Marshal tests. Marshall stability as high as 15 kN was obtained with optimum bitumen content of 5.6% and optimum fiber content of 0.5% with optimum fiber length of 10 mm. Further, for justifying the performances of the paving mix, tests such as indirect tensile strength (ITS) test and moisture susceptibility test in form of retained stability test and tensile strength ratio (TSR) of bituminous mixes were also conducted. It was finally observed that the paving mixes formed with bottom ash as part of fine aggregate and fly ash as filler, stabilized with natural sisal fiber duly coated with SS-1 emulsion were not only satisfactory, but also yielded much improved engineering properties. From the above it is observed that waste materials such as coal ash and locally available natural fiber such as sisal fiber can together be used in an appropriate way for bituminous paving mixes. Thus, this may not only help to find a new way of construction of bituminous pavement, but may also help evading the problems such as huge space required for dumping and environmental pollution.