INTERPRETATION OF BITUMINOUS MIXES WITH MODIFIED BINDERS

Abstract

This report shows research carried out to investigate the effect of mixing process on polypropylene (PP)
modified bitumen mixed with well graded fine and coarse aggregates to form modified bituminous concrete mix. There
are two mode of mixing, namely dry and wet with different concentration of polymer polypropylene was used with 60/70
pen bitumen, to evaluate the bituminous concrete mix properties. Five percentages of polymer varying from 1% - 5% by
the weight of bitumen was used in this study. There are three mixes namely control mix, wet mix and dry mix, were
prepared. Engineering properties thus obtained at the calculated optimum bitumen content revealed that wet mixing
process is advantageous in comparison to dry mixing as it increases the stiffness of the mixture with the increase in
polymer content in the bitumen. The stiffness value for wet mix increases with the increase in polymer content which is
advantageous in terms of rutting. 1% of PP dry mix also shows improved stiffness, with the air void content limited to
5.8%. The flow behavior of dry mix does not indicate any major difference with the increase in polymer content revealing
that polymer acting as an aggregate only without affecting the viscosity of the binder in the mix. Polypropylene when
interact with 60 pen base bitumen, it enhances its performance characteristics which were brought about by altered
rheological properties of the modified bitumen.