The Volumetric Properties Of Water-foaming Warm Recycled Reclaimed Asphalt Pavement(RAP)

Highway pavement is mainly paved by asphalt mixtures in our country. Traditionalhot mix asphalt (HMA) is mixed and compacted at high temperature, consuming largeamount of energy and emitting a large amount of toxic fumes that pollute the environment.In addition, many highway pavements in China is about to be resurfacing, which willproduce huge waste asphalt mixtures. How to deal with these waste materials is becomingan important problem. Water injection foaming technology (one warm-asphalt-mixtechnology) can be applied to recycling of reclaimed asphalt pavement (RAP) and generatefoaming warm recycled RAP. This is a new and green technology solving this problem.In this research, volumetric properties of the foaming warm recycled RAP werestudied though Marshall mixtures design at reduced mixing and compaction temperatures.Focuses were made on how the quality of RAP will affect the volumetric propertiesincluding the%RAP added, the size of RAP particles and the blending effect as well.Selected properties of the design foaming warm recycled RAP were validated. Waterfoaming asphalt was produced by the foamer made in Road Engineering Research Center,Suzhou University of Science and Technology. Some conclusions were drawn as follows:1) As the water content increased, foamed asphalt expansion ratio increased, but hehalf-life reduced. A water content of1.5%is the most suitable for asphalt foaming. Afoamed asphalt from a base asphalt (no modified asphalt) and a modified asphalt weretested and found that the penetration increased by5.9%and4.5%, respectively, the softenpoint reduced by5.7%and5.8%, respectively. DSR test indicated that foamed asphalt’sviscosity and elasticity are reduced.2) Marshall design based on orthogonal proportion method concluded that the mostsuitable mix design factor combination is75double-sided blows,1.5%foaming watercontent,4.9%of asphalt content, and150℃of compaction temperature (10℃is reducedcompared with hot mix).3) Using Superpave Gyrator Compaction (SGC) design, it was found that the bestcompaction temperature is near the145℃, compared with hot mix, a reduction of15℃.In addition, warm-mix asphalt mixture is easier to be compacted at the early stage.4) When the dosage of RAP added is same, the mixtures with coarse RAP (CRAP)had the largest void ratio and vice verse. With a higher%RAP, the mixture’s void ratio increased.5) With the addition of RAP, the mixtures’ anti-rutting performance was improved, thewater damage resistance was reduced. When the fine RAP was added, the water damageresistance performed the worst.