Abstract:
The use of waste, recycled, and modified materials is a growing trend, particularly in the
construction of roadways, as it not only seeks to be sustainable but also increases the lifespan
of pavements. This can be done by mixing steel slag (SS) with a certain kind of plastic polymer,
known in the industry as low-density polyethylene (LDPE). Pallets made of LDPE, which is
not biodegradable, are used to make plastic bags, and steel slag (SS) is a byproduct of the steel
manufacturing process. Both of these pollutants are harmful to the environment, though using
them to make pavement helps lessen environmental pollution. The use of LDPE as a binder
modifier in two bitumen grades, namely 60-70 and 80-100, is investigated in this study with
3%, 5%, and 7% by weight of bitumen in both grades, and SS was used as a replacement for
coarse aggregate. Prior to creating and testing HMA samples for the modified and unmodified
samples for dynamic modulus and martial mix design, physical characteristics of modified and
unmodified bitumen grades as well as steel slag were studied. The dynamic modulus was
measured at temperatures of 4.4 °C, 21.1 °C, 37.8 °C, and 54.4 °C with frequencies of 0.1 Hz,
0.5 Hz, 1 Hz, 5 Hz, 10 Hz, and 25 Hz. In addition to creating master curves for both bitumen
grades, the dynamic modulus dataset also underwent design of experiment (DOE) and
computational intelligence (CI) analyses. Lastly, damage analysis was performed using
KENPAVE, a mechanistic-empirical tool that calculated design life in terms of percentage
improvement and reduction in damage ratio for each grade and each modifier. Research result
indicates that adding LDPE improves the softening point and penetration grade but reduces the
ductility value because of the stiffness of bitumen, which leads to premature fatigue failure at
higher LDPE contents. In addition, 3% LDPE by weight of bitumen and 3% SS-modified
LDPE show improvements in Marshall Stability and dynamic modulus at all temperature and
frequency ranges; they improve the stability by 13 to 16% in the case of 3% LDPE and by 30
to 32% in the case of 3% SS-LDPE. Moreover, the KENPAVE result of 3% LDPE indicates
the improvement in design life is up to 19% to 25% and reduction in damage ratio up to 15 to
18%, while in the case of 3% SS-LDPE, the improvement in design life is up to 50% to 60%
and reduction in damage ratio up to 25 to 35%. Overall, 3% LDPE and 3% SS-LDPE modified
HMA in both bitumen grades 60-70 and 80-100 shows best results.
