Application And Research Of Large Stone Asphalt Mixes For Base In Expressway

The reflection crack is one of the main damages of the semi-rigid base asphalt pavements; however, there is no ideal method to solve it still now. Some studies show that increasing the thickness of asphalt layer could alleviate reflection cracks to some extent, but with the rapid growth of traffic load and tire pressure, the rutting problem has become the primary issue of thick asphalt layer once again. Aiming at these problems, a series of studies in domestic and foreign show that the large stone asphalt mixes(LSAM) has the better reflection cracks and rutting resistance at the same time, that is, it will solve the problems above effectively.LSAM as a kind of skeleton-closed type asphalt mixe, it has the advantages of greater friction force and interaction force, better framework stability which relatives to the traditional asphalt mixes. In view of these performances of LSAM, the method of cubage design based on the uniform design experiments is used in designing its target proportioning. According to the LSAM designed above, some performance experiments are preceded. Then the experimental results are as follows:LSAM has the better rutting resistance than the common asphalt mixes;LSAM possesses the better capacity of moisture resistance damage because of its squeezed-dense structure; compared with the semi-rigid base material, LSAM average tensile strength is increased by 52.7%.The article calculates the stresses of pavements which lay flexible bases of large stone asphalt mixes and traditional ones by a calculation of finite element procedure ANSYS. The results of calculation indicate that the former ones are more effective in prevention of reflection crack. Because of the greater volume of coarse aggregate and the larger maximum nominal particle-size, the LSAM-30 thermal conductivity is greater and the temperature shrinkge coefficient is lower as well as the modulus of resilience, so it could reduce the temperature gradient among the structure layers effectively, and then minish the thermal stress. At the same time, the adequate flexibility performance may also absorb the strain energy at the crack of the semi-rigid sub-base well. So it possesses the better reflection crack resistance.With the LSAM is used as flexible base on the Yichang-Changyang test section of the west expressway of Shanghai to Chengdu, the construction techniques and the construct performance of LSAM are studied. By means of detection of construction quality, it is proved that the integer intensity of the LSAM base asphalt pavement is sufficient and the LSAM base has the better compactibility, structural compactability, and so on. Through 5 months'observation of the test section, the pavement is also in good condition from the perspective of reflection cracks. Moreover, its rutting resistance is still waiting for the further observation in a long time.