Abstract:
Now a day, the scarcity of conventional filler material needs a quick solution in the production
of hot mix asphalt. Hence, this study investigated the suitability of volcanic ash as an alternative
filler material in hot mix asphalt. The study used purposive method of sampling materials. An
experimental research method was used to investigate the partial replacement of volcanic ash in
hot mix asphalt based on Marshall Mix design method. Marshall Specimens were prepared with
bitumen content of 4 to 6% at 0.5% increments using crushed stone dust as a control mix. Forty
five Marshall Specimens were prepared to determine optimum bitumen content. This optimum
bitumen content was used to prepare Marshall Specimen with replacement of volcanic ash from
10 to 100% at 10% increments. Thirty three specimens were prepared to evaluate the effects of
volcanic ash on Marshall Properties of hot mix asphalt. Marshall Immersion test method was
used to determine tensile strength ratio of both filler to evaluate Moisture susceptibility of the
mix.
The plastic index and specific gravity of volcanic ash are 0.92% and 2.44 respectively. The
chemical composition analysis indicated the volcanic ash can be classified as class – N
pozzolana. All the mixes prepared with 5.15% optimum bitumen content at different proportions
of volcanic ash met Marshall Criteria for asphalt concrete wearing course. Maximum stability of
11.38 kN was obtained at full replacement of volcanic ash. Marshall Immersion test resulted,
tensile strength ratio of 82 and 98% for mix with crushed stone dust and fully replaced volcanic
ash respectively. This result showed higher moisture resistance of volcanic ash than crushed
stone dust filler in hot mix asphalt.
This study concluded, all the mixes with different proportions of volcanic ash had no significant
effect on performance or volumetric properties of hot mix asphalt. Hence, volcanic ash can be
used for hot mix asphalt pavement either fully replacing or in combination with crushed stone
dust filler. Further study on hot mix asphalt with different bitumen contents and grades,
performance test (rutting) and economic analysis are recommended.
