In on the conventional materials results in

In
asphaltic concrete, asphalt is a material used to construct the surface layer
of flexible pavement. It is a mixture of conventional materials such
aggregates, binder and filler is used for constructing and maintaining all
roads and parking lots among others. While the aggregate contributes resistance
to support traffic loads, the asphalt binder contributes viscous-elastic
behaviour to help with the adhesion of aggregate particles. However, large
dependency on the conventional materials results in high and increasing cost of these
materials that has greatly hindered the development of road pavement facilities
in developing countries like Nigeria.

Several research efforts into alternative materials for
sustainable development is on-going; in the research carried
out by Shubham et al (2017) on the
evaluation of modified bituminous concrete mix developed using rubber and
plastic waste materials; the 
experimental results demonstrate that partial substitution of bitumen
with waste plastic results up to 16% increment in strength whereas with rubber
material, about 50% increment in strength was observed as compared to the
conventional mix (CM).

            Accordingly,
Olutaiwo and Owolabi (2015) carried out an investigative studies on the effects
of partial replacement of coarse aggregate with graded palm kernel shells in
asphalt binder course at varying percentages of PKS content rates by weight of
total coarse aggregate size of 4- 8mm. Marshall tests conducted established
that PKS was a viable agricultural waste product that could be used as coarse
aggregate at a specific percentage in the production of asphaltic binder
courses for light to medium trafficked roads. Also, Ndoke (2006) investigated
the potential of palm kernel shells as coarse aggregate in road binder course
with concentration on strength of the asphalt as dictated by the Marshall
Stability and flow values. In the study, he inferred that palm kernel shells
could be utilized to replace coarse aggregate up to 10% for heavy traffic roads
and 100% replacement was possible for light traffic roads in rural areas. In
the research carried out by Mohammed
et al., 2014), a paper on the
preliminary assessment of some properties of asphaltic concrete, with partial
replacement of fine aggregate (sand) with crushed palm kernel shell was presented.
Their findings informed the conclusion that their preliminary investigations
have clearly shown that replacement of some proportions of fine aggregate
(sand) with crushed palm kernel shells has the capacity of affecting positively
some properties of asphaltic concrete.

            In the research work of Oyedepo and Oluwajana (2014), and Adewale et al.,(2015), the
properties of bitumen modified with used tyre were investigated. Basic tests like
penetration, softening point, viscosity, flash and fire point and ductility
test were done by using shredded waste tyre which varied from 0% to 20% by
weight of 60/70 penetration grade bitumen at 1600C using dry mix
method. Penetration value decreased with addition of 20% tyre while significant
increase in softening point, viscosity, flash and fire point were obtained with
the corresponding values of 80.9oC, 250.96 sec and 189/280.120C
respectively were obtained. Furthermore, Oyedepo et al (2015) carried out
investigation on the usefulness of palm kernel shell as partial replacement for
aggregate in asphaltic concrete, crushed palm kernel shell (CPKS) and PKS were
added at 20, 40, 50, 60 and 80% by weight of total aggregates to replace the
fine and coarse aggregates in asphaltic concrete partially. It was also deduced
that modifying
bituminous materials can bring real benefits to highway maintenance and
construction, regarding better and durable roads and savings in total road design
life Mangesh et al (2012).

            In the research by Suched and Thanakorn (2016) on laboratory
investigation of the performances of cement and fly ash modified asphalt
concrete mixtures; results show that cement and/or fly ash were advantageous
in terms of improved strength, stiffness and protection against stripping of
asphalt mixture. The findings also show that the strength, stiffness and
moisture susceptibility performances of the asphalt concrete mixtures enhanced
by filler are similar to the performance of the polymer modified asphalt
mixture.

            The
impacts of modifying bituminous concrete with crumb rubber and waste shredded
thermo-plastics was investigated by Harish and Shirakumar (2013); significant increases
in properties like Marshall stability, retained stability, indirect tensile
strength were observed in comparison with traditional
mix. In the research by Dahunsi et al
(2013) on the utilisation of shredded pure water sachets (PWS) to modify
bitumen at various percentages weight of bitumen, they discovered increases in
viscosity decreasing penetration with subsequent increase in PWS while, the
values of the softening point increased with respect to increase in PWS. Fattuhi
and Clark (1996) reported that the use of crumb tyre particles as the partial
replacement for sand in the concrete has better performance at various
serviceability levels as compared to the full or complete replacement of sand
in the concrete with the crumb tyre particles. The sand in the concrete along
with the crumb tyre particles are imparting better shear capacity, fire
resistance and resistance to spalling due to various environmental hazards
like, fire, rainwater and collective segregation in concrete.

            It is reported that New Zealand
produces around 3 million waste tyres per year, with estimates varying from 2.2
to 4 million waste tyres per year (Sweet 2004). However, Sweet also reported
that this number is expected to increase from an increase in vehicle fleet
numbers, importing of used tyres and the reducing numbers of tyres retreaded. According
to Ebewele & Ozong (1990), an estimated 5 million scrap tyre from truck,
cars and motorcycles existed in Nigeria in 1983; with an annual generation rate
of 15%, each year about 700-850 thousand scrap tyres are added to the waste
stream, this was projected to about 15 million scrap tyre by Aisien, et al (2002). Thus, this paper carries
out laboratory
investigation of using non-conventional material in hot-mix asphalt for road
pavement which will bring benefits to highway maintenance and
rehabilitation, and improved pavement performance.