Mechanical performance of cold mix asphalt containing cup lump rubber as a sustainable bio-modifier

The road construction industry aims to contribute to the protection of already compromised environment.Cold mix asphalt(CMA)is a measure initiated by the road industry to protect the environment and preserve energy.Despite having additional benefits,CMA has attracted little attention due to its inferior performance.CMA's performance is enhanced using a sustainable binder bio-modifier,natural cup lump rubber(CLR)is one of them.This study evaluated the tensile properties,rutting,moisture susceptibility,and adhesion properties of CLR-modified CMA(CMA-CR).The tensile property was enhanced by 26%due to CLR modification.CMA-CR had excellent rutting resistance of less than 2 mm rut depth at 10,000 load cycles,showing 70%improvement compared with conventional CMA.Moisture susceptibility evaluation indicated that CMA-CR had tensile strength ratio(TSR)value of 104%,satisfying the minimum 80%requirement of AASHTO T283.It also retained more than 96%bitumen coating.The moisture damage resistance was improved by 12%and 10%in terms of TSR and stripping,respectively.The durability results revealed that the CMA-CR mixture prevented higher mass loss,representing 14%improvement compared with conventional CMA.

Testing and assessing the performance of a new warm mix asphalt with SMC

Warm mix asphalt （WMA} is a new technology which asphalt mix is produced and placed at normal temperature. It has advantages including low cost, environmentally friendly, haul-convenience, and so on. WMA has been widely tested and applied in the USA in the last decade, but it has just started in China. Recently, a new WMA using a new plastic- macromolecule-normal temperature additive, which was called ＂SMC＂ by the production company, was introduced as asphalt modifier. Based on discussing the strength forming process of this new WMA with SMC, a series of laboratory tests, including Marshall stability test （MST）, boiling test （BT）, modified immersion Marshall test （MIMT）, freeze-thaw split- ring test （FTST）, rutting test （RT）, low-temperature bending test （LTBT）, and abrasion loss test （ALT）, were conducted in this study to assess the performance of this WMA and the capability of applying it on low volume roads in China. SMC modified asphalt mixed under normal temperature is used in testing samples. It was found that this WMA product exhibited merits on its strength, which was about 6.7 kN bigger than the requirement of 5.0 kN in the JTG F40-2004, on high-temperature stability, which is about 1100 times/ram greater than the requirement of 600-1000 times/mm in the ）TG F40-2004, and on its storage stability. Based on these indicators, it is recommended that this product could be used for low volume low class roads construction. However, due to the relatively lower water resistance and low-temperature cracking resistance, this product is suggested to be applied first in the areas with warm weather and little rainfall. In order to improve the perfor- mance of this WMA with SMC, further research on this SMC asphalt modifier should be continued.