Research Of Sress Absorbed Layer

The asphalt overlay layer on existing concrete pavement is one of the major rehailitationways. Because the existing concrete pavement can't bear shearing stress and tensile stress atjoint or crack, on which asphalt overlay is liable to be damaged and induced reflection crack bycyclic temperature stress and wheel loads. With the time going, the reflective cracking keeps onexpanding for cyclic traffic and environment loads. So pavement performance and smoothnessare decreased.On the basis of investigation of Tongsan highway's performance, this dissertationanalyzes thmain reasons of pavements failures, such as ruputure, cracking, and mud-pumping inexisting cement concrete pavement, and puts forward the processing measures and composition design. At the same time, this dissertation also analyzes the bending stress on the bottom of each of layers with different loads based on the elastic layered system theory, obtaining the result that absorbed layer is the most adverse layer in the overlay structures. Furthermore, the mixing ratio of absorbed layer material was carried out by combinating volumn method of Superpave theory with Mashell design method. As a result, the optimumasphalt amount is 8.99ï¼…, and the percentage of voids is 3.1ï¼…, the bigest theory density is2.383g/cm~3.In order to confirm the feasibility and usability of stress absorbed layer mixture ratio, thisdissertation carried out an examination to pavement performance, such as stability in hightemperature, crack resistance in lower temperature, water erosion characteristic and fatiguecharacteristic from material testing. From this examination, the absorbed layer material notonly has great strength in anti-freezing and thawing ability by the freezing and thawing test, itscracking strength ratio has achieved the value of 89.8ï¼…, which is greatly more than the demandof 85ï¼…. Therefore, it is confirmed that the absorbed layer material has big superiority in theanti-water erosion, and that this layer has also the greatly superiority to delay or to suppressthe reflection crack in existing cement concrete pavement surface. Consequently, this will be akind of important measure in asphalt overlay layer for existing cement concrete pavement.