Effect of Filler Composition on the Performance of Asphaltic Concrete Mixture

Fillers can be used as additive material in bituminous mixtures to minimize distress,
such as permanent deformation and fatigue on highway pavements. Fillers with
different physical and chemical properties have been found to improve the
performance of pavement. However, the exact relationship of specific filler property
on the resulting properties of the bituminous mixture has not been clearly defined by
previous studies.
This study looks at the effect of the physical and chemical properties of filler on the
performance of bituminous paving mixtures by correlating the filler properties to
permanent deformation and fatigue characteristic of mixture. Three types of filler
namely ordinary Portland cement (OPC), quarry dust and fly ash were combined with
two types of bitumen i.e. penetration grade 50-60 and 80-100. Each filler was mixed
with each bitumen type at filler to bitumen ratios of 0.75, 1.0 and 1.25 by weight,
respectively. Hence, a total of 18 mixtures were prepared.
The properties of the prepared bituminous mixture along with optimum bitumen
content (OBC) were determined by using Marshall test. The OBC was then used to
prepare the specimens for performance test. The performance test includes permanent
deformation test using creep and wheel tracking tests, and beam fatigue test to
determine fatigue characteristic.
The test results show that a spherical particle reduces the percentage of voids and
OBC of the mixture, thus improving the performance of the bituminous pavement.
Irregular particles were found to increase the consistency of filler-bitumen system and
the stability and stiffness of bituminous mixture by its interlocking mechanism. The
content of silica and alumina in fillers were found to affect the quality of bituminous
pavement by increasing the hardness of the mix and hence the pavement becomes
more resistant to permanent deformation. However, increased hardness causes the
pavement to brittle faster, therefore, fatigue cracking can occur in early pavement life.
The combination of bitumen penetration grade 80-100 mixed with cement in the
filler-bitumen ratio 1.0 (80/cmt/1.0) shows the superiority in term of fatigue, whilst
the combination of bitumen penetration grade 50-60 mixed with fly ash in the fillerbitumen
ratio 1.25 (50/fa/1.25) was the most superior in term of permanent
deformation.