Effect of Different Types of Filler Materials on Characteristics of Hot-Mix- Asphalt Concrete
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Date
2007-02
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Addis Ababa University
Abstract
Various studies have shown that the properties of mineral fillers have
significant effect on the performance of asphalt concrete pavements.
This study was intended to investigate the effect of different types of mineral
fillers in hot-mix-asphalt performance. The mineral fillers, with different
percentages by total weight of the mixture, used in the study were crushed
stone, volcanic-cinder, and limestone passing 0.075mm sieve.
Using the different types and contents of the mineral fillers, a number of trial
mixes have been prepared using the Marshal Mix design procedure to arrive
at asphalt concrete mixtures that fulfill the Marshal criteria. The effects of
each mineral filler type on Marshal Properties of the asphalt mixtures at
their respective optimum asphalt content were evaluated and possible basis
for such difference in properties was discussed.
Using the different mineral fillers at their respective optimum asphalt
content, specimens were prepared to investigate moisture susceptibility of
asphalt mixtures. The Marshal Immersion test method was adopted to
determine the moisture effect of mixtures.
The test results show that all mineral fillers do have an effect on various
mixture properties. Mixtures prepared with volcanic-cinder require higher
asphalt content to fulfill all the Marshal requirements. This makes these
mixtures more costly from practical point of view. Higher stability values
were however, obtained by mixes with volcanic-cinder as compared to
limestone and crushed stone fillers. Moreover, higher retained stability
values are obtained by mixes prepared with limestone and volcanic–cinder as
compared to the widely used crushed stone. The dynamic moduli values,
estimated using the formula developed by the Asphalt Institute, were higher
for mixtures prepared with limestone fillers and crushed stone as compared
to volcanic-cinder at higher filler contents starting from 5% in the mixture.
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From the study, similar trend of mixture properties, particularly Marshal
properties, were observed for mixes made with limestone and crushed stone
fillers as compared to that of volcanic-cinder. This indicates that limestone
can be used as a substitute for the widely used crushed stone where
available. This, of course, requires further investigation that better simulates
the field condition. On the other hand, inconsistent mixture properties were
observed from mixes made with volcanic-cinder. This also entails further
investigation if it is deemed to be used as filler materials in asphalt concrete.
Generally, different characteristics of bituminous mixtures were observed by
varying the fillers in the mixture by type and content. This indicates that,
mineral fillers are recognized as an important ingredient in the mixture
property. From the test results obtained, there is a common trend in
obtaining different mixture properties with varying filler content, which
shows, there exists optimum filler content that best mix performance could
be achieved.
The results of this research work is hoped to be used as the basis for further
investigation on the effects of mineral fillers and improve asphalt concrete
mixtures as well as find alternative materials.
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Keywords
Asphalt ;Concrete