FLY ASH/ LIME- FLY ASH/ LIME AS FILLER IN BITUMINOUS MIXES- A COMPARATIVE STUDY

Abstract

It is well known that addition of mineral fillers enhances the physical properties and field performance, of the bituminous mixes. Fly ash, hydrated lime satisfies the requirements of specifications for the mineral fillers. Fly ash is a waste product of thermal power plants which is causing environmental pollution, can be used as cost effective filler in bituminous mixes. Commonly available hydrated lime does not meet the gradation requirement and processing is required in the powder mills to bring it to the desired gradation. However, hydrated lime has been successfully used as filler to improve the performance of bituminous mixes, especially as an anti stripping agent. The strength and deformation characteristics play an important role in design of the bituminous mixes but the field performance of the mixes is the ultimate goal of the designer. The use of fly ash/ lime- fly ash/ lime as filler in bituminous mixes needs to be evaluated based on these parameters. This dissertation report compares the effect of using fly ash/ lime- fly ash/ lime as filler in bituminous mixes with the help of laboratory investigations. The Marshall stability and flow values have been determined to evaluate the strength and deformation characteristics. To evaluate the field performance, indirect tensile strength, tensile strength ratio, retained stability and permanent deformation etc. have been determined through various tests. It has been observed that Marshall properties of mixes with fly ash are on lower side as compared to lime- fly ash and lime mixes but generally meet the specification requirements. The indirect tensile strength increases with the increase in the fly ash content and it is higher than that of the mixes with other fillers which is an indicator of improved resistance against low temperature cracking and fatigue cracking. Tensile Strength Ratio (TSR ) and retained stability have increased with the increase in fly ash content, indicating improved resistance to moisture resistance. However, permanent deformation has increased with the increase in fly ash content indicating a decrease in rutting potential. The cost of optimized mixes with lime- fly ash is 14 to 19% higher than fly ash mixes. Whereas the cost of optimized mix with lime is 25 to 36% higher than fly ash mixes. A 5% content of fly ash can be optimally utilized as filler in the bituminous mixes.