| dc.description.abstract | The inclusion of increased reclaimed asphalt pavement (RAP) quantities in the production of
asphalt mixtures for low volume roads represents an environmental solution that manages to
reduce waste and demand of fossil derivate products, and at the same time provides an
opportunity for local agencies to optimize roadway construction and maintenance budgets.
The objective of this research project was to develop guidance regarding the methodology for
the performance assessment of asphalt mixtures with elevated contents of RAP (i.e. 60% to
100%) and define their suitability to perform as surface layers of pavements for low volume
roads (i.e. less than 750 vehicles per day). Performance was evaluated for eight hot and ten cold
recycled mixtures in relation to common pavement distresses including moisture susceptibility,
rutting resistance, intermediate temperature cracking, durability and stiffness by modified
Lottman, Hamburg Wheel Track Test (HWTT), Semicircular Bending Beam (SCB) test,
Cantabro abrasion loss test and Resilient Modulus (Mvr), respectively. Compacted specimens
were fabricated with RAP contents of 60, 80 and 100% employing two sources of RAP,
limestone and granite virgin aggregates and two types of recycling agents per recycling
methodology (hot and cold). One organic-based agent and one petroleum-based agent were
selected for the hot recycling methodology and emulsified and foamed asphalt were selected for
the cold recycling methodology.
The performance results demonstrated that the evaluation of rutting and moisture
susceptibility through HWTT and Modified Lottman, respectively, is likely too severe for high
RAP mixtures. With few exceptions, all the recycled mixtures displayed accelerated rutting.
However, hot recycled and cold recycled mixtures with emulsion exhibited capacity to perform
as surface layers for low volume roads according to current standards based on requirements of
tensile strength and moisture susceptibility. Cold recycled mixtures with foamed asphalt did not
meet any distress threshold evaluated. Hot recycled mixtures including recycling agents
exhibited improved cracking resistance in the SCB test, reduction in Mr and most of the cold
recycled mixtures presented poor durability. Varied influence on the mixtures performance was
observed for RAP content and recycling agent/additive type depending on factors such as virgin
aggregate type, RAP source and recycling methodology. The inclusion of cracking resistance and
durability thresholds in the design process of recycled mixtures was found effective at detecting
better performing mixtures. In order to improve the assessment of rutting, it is recommended to
investigate the use of dry tests such as asphalt pavement analyzer (APA). Likewise, further
investigation is recommended with regard to the inclusion of active fillers (i.e., Portland cement
or hydrated lime) to improve tensile strength and durability performance of cold recycled
mixtures. | en |
