Prediction Models For Reflection Cracking Of Asphalt Ultra-thin Overlay And Experimental Analysis

Direct overlay Asphalt surface on the old cement concrete pavement is a commonly usedpavement rehabilitation measure. But due to the presence of the joints or cracks over oldconcrete pavement, reflective crackings at temperatures and loads is the main reason thatleads to the damaged in asphalt overlay, the appearance of reflective crackings and otherdiseases reduces the driving comfort and safety. How to delay or prevention asphalt overlaylayer reflection cracks production and propagation is a major challenge facing the roadengineering. On the basis of previous studies, this article continue to systematic study of theproduce mechanism and prevention measures of asphalt overlay reflective crackings, and toexplore the ability of anti-reflective asphalt cracks on the basis of experimental studies onlaboratory analysis.In this paper, the basic theory of fracture mechanics and finite element analysis are usedto analysis the stress intensity factor at the crack tip of asphalt overlay, and it mainly studiesthe extent of the stress intensity factor when thickness of asphalt overlay, asphalt overlay layermodulus, fracture propagation length, axle load size, cooling rate and so on, changing in thelimited range.The article analyzed the production mechanism and propagation law of reflectioncrackings of asphalt overlay layer, summarized the measures that can delay or prevention ofreflective cracking, proposed active control model and passive control mode, and control thereflection cracks should emphasis on active control, passive control measures can be asupplement.Learn a kind of Asphalt Mixture CAM (Crack Attenuating Mixtures) which is R&D byTexas Transportation Institute, this paper starts the research from asphalt mixture performanceimprovement areas to study the ability to resistant reflective crackings. By a tensile testfixture designed by ourselves testing tensile directly in the MTS testing machine, studyCAM-type neoprene modified asphalt mixture properties and tensile fatigue and therelationship of asphalt content and neoprene modifier.The results showed that asphalt mixturewhich has mixed neoprene modifier, tensile cracking stress cycles increased about14%than conventional asphalt mix. This suggests CAM-type neoprene modified asphalt Mixture withmixing neoprene modifier has good crack resistance, this experiment also shows that directtensile test fixture design our own can be a good test on the MTS testing machine.Finally, relying on the reconstruction project XingNing G205, paving asphalt CAM andNovaChip ultra-thin wearing course test section, then describes the construction process ofCAM-type neoprene modified asphalt Overlay and NovaChip ultra-thin wearing course.Through long-term tracking test to verify the CAM type chloroprene rubber modified asphaltmixture and NovaChip ultra-thin wearing layer resistance capacity of reflection cracking.