Abstract: Laboratory trial results of mixing crumb rubber produced from discarded tires with 60/70 pen grade Kuwaiti bitumen are presented on this paper. PG grading and multiple stress creep recovery tests were conducted on Kuwaiti bitumen blended with 15% and 18% crumb rubber at temperatures ranging from 40 to 70 °C. The results from elastic recovery and non-recoverable creep presented optimum performance at 18% rubber content. The optimum rubberized-bitumen mix was next transformed into a pelletized form (PelletPave®), and was used as a partial replacement to the conventional bitumen in the manufacture of continuously graded hot mix asphalts at a number of binder contents. The trialed PelletPave® contents were at 2.5%, 3.0%, and 3.5% by mass of asphalt mix. In this investigation, it was not possible to utilize the results of standard Marshall method of mix design (i.e. volumetric, stability and flow tests) and subsequently additional assessment of mix compactability was carried out using gyratory compactor in order to determine the optimum PelletPave® and total binder contents.
Abstract: The main objective of this paper is to evaluate the use of plastic waste as a low cost asphalt binder modifier. For this purpose Marshall mix design procedure was used. Marshall mix design procedure seeks to select the Optimum Binder Content (OBC) to be added to a specific aggregate blend resulting in a mixture that satisfies the desired properties of strength and durability. In order to evaluate the plastic waste modified (PWM) asphalt mixtures, the OBC for the conventional asphalt mix was first identified, and then different percentages of crushed plastic waste by weight of the identified OBC were tested. Marshall test results for the modified asphalt mixtures were analyzed to find the optimum PWM content. Finally, the static indirect tensile strength (IDT) was determined for all mixtures using the splitting tensile test. It was found that PWM content of 7.43% by weight of OBC is recommended as the optimum PWM content needed for enhancing the performance of asphalt mixtures. It enhanced stability by 42.56%, flow by 89.91% and strength by 13.54%. This would lead to a more durable pavement by improving the pavement resistance to fatigue cracking and rutting.
Abstract: Asphalt concrete pavements have a short life cycle,
failing mainly due to temperature changes, traffic loading and ageing.
Modified asphalt mixtures provide the technology to produce a
bituminous binder with improved viscoelastic properties, which
remain in balance over a wider temperature range and loading
conditions. In this research, 60/70 penetration grade asphalt binder
was modified by adding 2, 4, 6, 8 and 10 percent by weight of asphalt
binder following the wet process and the mineral aggregate was
modified by adding 1, 2, 3, 4 and 5 percent crumb rubber by volume
of the mineral aggregate following the dry process. The LDPE
modified asphalt binder rheological properties were evaluated. The
laboratory results showed an increase in viscosity, softening point
and stiffness of the binder. The modified asphalt was then used in
preparing asphalt mixtures by Marshall Mix design procedure. The
Marshall Stability values for mixes containing 2% crumb rubber and
4% LDPE were found to be 30% higher than the conventional asphalt
concrete mix.
Abstract: Steel slag is a by-product of the steel industry and can
be used potentially as aggregate in the asphalt mixture. This study
evaluates the use of Steel Slag Aggregates (SSA) as a substitute for
natural aggregates in the production of hot mix asphalt (HMA) for
road construction. Based on intensive laboratory testing program, the
characteristic properties of SSA were assessed to determine its
suitability to be used in HMA. Four different percentages (0, 50, 75,
and 100%) of SSA were used, and the proposed mix designs for
HMA were conducted in accordance with Marshall mix design. The
experiment results revealed that the addition of SSA has a significant
improvement on the properties of HMA. An increase in density and
stability and a reduction in flow and air voids values were clearly
observed in specimens prepared with 100% SSA. It is concluded that
the steel slag can be considered reasonable alternative source of
aggregate for concrete asphalt mixture production.