EXPERIMENTAL STUDY OF BITUMINOUS MIXES USING NATURAL FIBRE

Abstract

Generally a bituminous mixture is a mixture of coarse aggregate, fine aggregate, filler and binder. A Hot Mix
Asphalt is a bituminous mixture where all constituents are mixed, placed and compacted at high temperature. HMA can
be Dense Graded mixes (DGM) known as Bituminous Concrete (BC) or gap graded known as Stone Matrix Asphalt
(SMA). SMA requires stabilizing additives composed of cellulose fibbers, mineral fibres or polymers to prevent drain
down of the mix. In the present study, an attempt has been made to study the effects of use of a naturally and locally
available fibre called SISAL fibre is used as stabilizer in SMA and as an additive in BC. For preparation of the mixes
aggregate gradation has been taken as per MORTH specification, binder content has been varied regularly from 4% to
7% and fibre content varied from 0% to maximum 0.5% of total mix. As a part of preliminary study, fly ash has been
found to result satisfactory Marshall Properties and hence has been used for mixes in subsequent works. Using Marshall
Procedure Optimum Fibre Content (OFC) for both BC and SMA mixes was found to be 0.3%. Similarly Optimum Binder
Content (OBC) for BC and SMA were found to be 5% and 5.2% respectively. Then the BC and SMA mixes prepared at
OBC and OFC are subjected to different performance tests like Drain down test, Static Indirect Tensile Strength Test and
Static Creep Test to evaluate the effects of fibre addition on mix performance. It is concluded that addition of sisal fibre
improve the mix properties like Marshall Stability, Drain down characteristics and indirect tensile strength in case of
both BC and SMA mixes. Ii is observed that SMA is better than BC in respect of indirect tensile strength and creep
characteristics.