Research On Design And Application Of Recycled Asphalt Mixture

Recycling reclaimed asphalt pavement (RAP) is more and more important because of the energy crisis and the pressure of environment. Hot in plant recycling technology was implemented to produce recycled asphalt mixture in this paper. The related properties of recycled asphalt mixture were also investigated.Full scale investigations were conducted on reclaimed asphalt pavement using chemical composition analysis and rheological property analysis of aged asphalt binder, physical properties analysis and gradation variability analysis of recycled aggregates. Experimental results show that aged asphalt binder harden, which have dramatically increase of relative absorption peak areas of carbonyl compounds and sulfoxides compounds, decrease of relative absorption peak areas of aromatic functional groups in FT-IR spectra compared with virgin asphalt. The rheological behaviors of recycled asphalt investigated using DSR show significant high complex modulus and low phase angle, which presents elastic-like behaviors compared with virgin asphalt.The aggregates in recycled asphalt materials show relatively high percent of flat and elongated particles in course aggregates. Statistical analysis indicates that percent passing 0.075mm shows significant coefficient of variation, which is also considered the most important factors of variability of total recycled aggregates.The Newtonian liquid properties of asphalt binder were recovered by the increase of virgin asphalt binder concentration, which indicated that aged asphalt binder in RAP can be rejuvenated by virgin asphalt binder. Rheological properties of recovered asphalt binder could be changed into lower complex modulus and higher phase angle.Based on Marshall mix design methodology, mixtures of identical composition, containing 20wt%, 30wt% and 50wt% recycled asphalt pavement with different rejuvenators containing SBS modified asphalt, liquid anti-stripping agent and recycling agent, were produced certain conditions and were all tested in more detail for volumetric properties and moisture sensitivity and rutting resistance behaviors. The results indicated that the recycling agent has advantages of improving the volumetric properties of recycled asphalt mixtures. Recycled asphalt mixtures containing either SBS modified asphalt or liquid anti-stripping agent show remarkable improvement in moisture sensitivity and rutting resistance compared to original mixtures on certain conditions. In addition, recycled asphalt mixture and conventional asphalt mixture show similar performances on low temperature cracking resistance and fatigue resistance properties.Quality control mechanisms of recycled asphalt mixture were investigated based on temperature storage stability test, infrared thermal imaging test and gradation variability test. Experimental results show that a series of experiments should be conducted to confirm the temperature characterizes of recycled asphalt mixture. Infrared thermal monitoring indicates that temperature differentials can be observed because of the different temperature of the components of recycled asphalt mixture. In addition, percentage passing 0.075mm in gradation of aggregates shows significant influences on properties of recycled asphalt mixture.