Research On Material Design Method Of Full Depth Asphalt Pavement Based On Layer Function Requirements

Full-depth pavement as a kind of pavement structure with asphalt mixture directly laid on the roadbed can better avoid the occurrence of early diseases such as reflective cracks and structural ruts compared with the semi-rigid basic highgrade pavement built in China in the early stage,and is easy to maintain and maintain in the later stage,and prolongates the service life of the pavement.Full-depth asphalt pavement is paved with asphalt mixtures of different grade and types and different maximum nominal particle sizes,which reduces the pavement thickness and provides greater possibility for the functional design and combination of materials of each layer.In addition,with the construction of expressways in the early 20 th century entering the phase of reconstruct ion and expansion,it is inevitable to produce a large number of waste pavement materials.The stacking of these construction wastes is not only pollution to the environment,but also a waste of storage.In this context,in view of the asphalt pavement surface layer exposed aging problem caused by environment mixture,under the vehicle load recompacted irrecoverable deformation of the surface accumulation in the rutted,and close to the subgrade material caused by the tensile stress fatigue cracking problem again and again,this study attempts to these diseases are put forward based on the structure layers of a solution and design method,In the middle layer,the old road milling material is applied to form a full-thickness recycled asphalt pavement with excellent road performance and durability and economic and practical value.In view of the asphalt pavement surface layer is exposed to the environment is easy ageing effect by environment,anti-aging agent was prepared in the laboratory,with asphalt after aging of asphalt mucilage effect test,the result proved that high temperature performance,the anti-aging agent can keep the recovery rate R and non-recovery creep compliance Jnr of asphalt mortar at the level of non-aging after short-term aging;In terms of low temperature performance,it can delay performance degradation of 50% of stiffness modulus S and m value.In order to facilitate the subsequent application of test road paving,the preparation process of anti-aging agent was optimized.The pavement performance of the mixture was verified based on the grading design of the test road.The results showed that the addition of anti-aging agent increased the flexibility of the mixture,delayed the modulus increase caused by long-term aging,and improved the high and low temperature performance and water stability of the mixture.The recycled asphalt mixture is used to improve the modulus of middle surface layer and solve the rutting problem.The grade optimization of RAP content of 20%,35% and 45% was carried out to obtain the best oil-stone ratio in Marshall design method.Based on the dynamic modulus test of uniaxial compression,the variation of Asphalt to rock ratio with dynamic modulus was investigated under different content of Reclaimed As phalt Pavement,different temperature and loading frequency.The main curve of dynamic modulus was plotted with 20℃ as reference temperature.The results of dynamic modulus test at 20℃ and 10 Hz were fitted,and the dynamic modulus was considered as one of the factors to determine the optimum asphalt stone ratio.A rutting resistan t material design method was proposed,which improved the dynamic stability of the mixture by 8%～15% without affecting other basic properties.The lower layer under the action of repeated tensile stress,accumulated to a certain extent will produce fatigue cracking,cracks from bottom to top seriously damage the pavement structure.The volume parameters of AC-13 gradation mixture were determined by Marshall test,and the optimum asp halt-stone ratio was calculated.Based on the four-point bending fatigue life test,the mixture oilstone ratio changed with the fatigue life,and the fatigue equation of the mixture was further constructed in the log-log coordinate.Based on the fitting results of the fatigue equation parameter K,the fatigue life was taken as one of the factors to determine the optimal oil-stone ratio,and the design method of anti-fatigue materials was proposed.Finally,based on the material design results of anti-aging surface layer,antirutting middle surface layer and anti-fatigue bottom layer,relying on the reconstruction and expansion project of Beijing-Taibei Expressway,a fullthickness factory heat regeneration test road was paved in Zaozhuang,Shandong Province.The temperature sensor data recorded the phenomenon that the peak value of the internal temperature of the pavement at different depths in winter weakened and moved later with the increase of the depth,while the strain sensor data proved that the addition of anti-aging agent had no effect on the internal stress of the pavement structure.In the calculation of the economic benefit of the whole life span of the test road,the cost of materials,construction and maintenance can be saved about 1.26 million yuan/km,which has considerable economic value.