| Summary: | Conventional Hot Mix Asphalt (HMA) has been the primary material used in
pavement in past decades. Recently, compared to conventional HMA, Warm Mix
Asphalt (WMA) has shown great potential and offers benefits not given by HMA,
since the WMA can be produced at lower temperatures without affecting pavement
performance. Since WMA additives can reduce the binder viscosity, the production
and compaction temperatures can be lowered, compared to conventional HMA. One
of the additives used to produce WMA is a type of wax named RH-WMA. In this
thesis, the rheological properties of a conventional a virgin PG64 asphalt binder with
and without RH-WMA at different aging conditions were investigated. The overall
rheological binder tests results indicated that RH-WMA content had significant effects
on the rheological parameters of asphalt binders in terms of viscosity, G*/sin δ and
G*sin δ. Image analysis technique was used to classify the adhesive failure by using
impact test. The impact test was conducted on a newly fabricated mould and the effects
of aging conditions and test temperatures of asphalt binder incorporating RH-WMA
were investigated. The analysis results showed that short-term aging and long-term
aging of asphalt binder increased the percentage of adhesion failure. The construction
temperature (mixing and compaction) was reduced by the addition of RH-WMA
additive due to viscosity reduction. However, the reduction of mixing temperatures
may prevent moisture from being completely evaporated from the aggregate and thus,
effect the asphalt binder bond, making the mixture more susceptible to stripping. Two
anti-stripping additives, namely hydrated lime and Pavement Modifier (PMD) were
used to reduce the destructive effects of moisture. Effects of RH-WMA content,
production and testing temperatures on mixture performance were investigated in
terms of indirect tensile strength, resilient modulus and creep stiffness. The result
indicates that both ITS and MR decreased as the RH-WMA content increased at the
respective test and mixing temperatures. The effects of incomplete drying of
aggregates on the mechanical properties of asphalt mixtures were clearly evident in
this thesis. Therefore, the use of fully dried aggregates was important in ensuring
satisfactory mix performance. Mixes prepared with 3% RH-WMA and compacted at
125°C° exhibit the best performance compare with HMA. Specimen incorporating
PMD filler improved resistance to stripping compared to mixes with hydrated lime
filler regardless of compaction temperature. The test results also indicated that aging
improved the moisture resistance of WMA.
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