Moisture Susceptbility Of Water-foaming Warm Asphalt Containing Reclaimed Asphalt Pavement(RAP)

The water injection foaming warm mix asphalt(WMA) technology is a new regeneration technique for old asphalt pavement, which is different from cold recycling technology and hot recycling technology. In order to provide the understanding of the machniam and practical technology, it refer the scientific theory and engneering experience available and carried out a series of laboratory tests to study the moisture susceptbility of the recycled reclaimed asphalt pavement(RAP) by water injection foaming warm mix asphalt technology.At first, in this study, the asphalt foaming equipment developed independently by Suzhou University of Science and Technology Road Research Centre was used to obtain foaming parameters. Based on the plenty of experiments with the foamed asphalt expansion and half-life being meet standard requirements, the best foaming parameters were obtained: foaming temperature is 320 F, the pressure is 100 bar and water consumption is 1.5%. Second, SUP-19 asphalt mixture was designed in various experimental conditions for an excellent gradation and optimum asphalt content. Third, based on the design result, samples were maded using Marshall method for reeze-thaw splitting testing to evaluate the moisture susceptbility of the recycled(RAP) by water injection foaming warm mix asphalt technology. At the last, Tensile Strength Ratio(TSR) was caculated for the moisture susceptbility of water-foaming warm recycled(RAP).This thesis focused on the influence of the RAP content( 0%, 20%, 30%), the different of screening RAP pretreatment methods, effective asphalt content of RAP, compaction temperature, additives(lime, anti-stripping agent) and other factors on the moisture susceptbility of water-foaming warm recycled(RAP).Based on the results, conclusions can be made as follows, 1)with the increase of RAP content, the mechanical properties of asphalt mixture increased, but TSR decreased; when the RAP content was 30% coarser than 4.75 mm sieve, the higher the percentage, the bigger TSR, i.e, the better the moisture susceptibility; 2)RAP with a service life of 5~8 years, its effective asphalt binder content was decreased to about 70%; 3)to enhancing test temperature appropriately can improve the moisture susceptibility of water-foaming warm recycled(RAP); 4)When adding additives as lime or anti stripping agent to water-foaming warm recycled(RAP). the moisture susceptbility of water-foaming warm recycled(RAP) increased significantly, and the addition of lime(the addition of lime is 1.0% of total mineral aggregate quality) is superior to the effect of adding anti stripping agent(addition quantity is 5‰ of the asphalt total quality).