Effects of mixing process on polypropylene modified bituminous concrete mix properties

This paper presents a research conducted to
investigate the effect of mixing process on polypropylene (PP)
modified bitumen mixed with well graded aggregate to form modified
bituminous concrete mix. Two mode of mixing, namely dry and wet
with different concentration of polymer polypropylene was used with
80/100 pen bitumen, to evaluate the bituminous concrete mix
properties. Three percentages of polymer varying from 1-3% by the
weight of bitumen was used in this study. Three mixes namely
control mix, wet mix and dry mix were prepared. Optimum binder
content was calculated considering Marshall Stability, flow, air voids
and Marshall Quotient at different bitumen content varying from 4%
- 6.5% for control, dry and wet mix. 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 bitumen. Stiffness value for wet mix increases with the
increase in polymer content which is beneficial in terms of rutting.
1% PP dry mix also shows enhanced stiffness, with the air void