Research On Anti-crack Evaluation And Improvement Measures Of Semi-rigid Base Based On Pavement Performance Requirements

According to investigation, semi-rigid base asphalt pavement play an important role, about 75%, in express highways in China. However, there are sill exist many questions for semi-rigid base asphalt pavement, mainly presented as pavement cracking. But up to now, effective method has not been found to prevent cracks growing in semi-rigid base asphalt pavement. Hence, based on present investigation, thoroughly studied has been taken for cement-stabilized and lime- fly-ash- stabilized materials, such as anti-cracking mixture design method, microcosmic shrinkage mechanism, crack prediction, construction technology, quality control and so on. The main achievements are as follows:(1) Research on anti-cracking evaluation index for semi-rigid base.In order to improving the anti-cracking performance for semi-rigid base, anti-cracking mixture design method of it is put forward considering aggregate gradation, binder species, binder dosage and so on. According to the road construction material served in construction zone, systematic study are done from the aspects of mixture design, mechanical properties, crack resistance, anti-erosion property and fatigue characteristics, etc...(2) Analysis on constriction mechanism and research on anti-cracking evaluation index for semi-rigid base material.Well mix proportion base material, with appropriate fly ash or expansion agent, have good pavement performance, such as higher early strength, small contraction coefficient, better anti-cracking performance, well-distributed nature and so on. The rationality and applicability for anti-cracking mixture design method of semi-rigid base material is verified. The anti-crack evaluation index is recommended as the control index during the mixture design.(3) Analysis on temperature stress of asphalt typical pavement structure for semi-rigid base.Formula for shrinkage stress of semi-rigid base is derived. Influencing factors of the maximum shrinkage stress is analyzed, and the cracking law for semi-rigid base is proved. Temperature contraction cracks for semi-rigid base is predicted, and the approximate formula for the width and space between two Temperature contraction cracks is put forward.(4) Prediction on temperature constriction cracks for semi-rigid base.A uniformly forced calculation model for long plate based on elastic foundations is set up with the method of elasticity theory. Approximate formula of crack space and width for semi-rigid base, caused by thermal stress, is derived and calculated. (5) Study on construction technology of semi-rigid base for cement-stabilized materials and test roadAccording to the construction condition of semi-rigid base for expressway in Hebe Province, systematically research on construction technology and construction quality control standard of semi-rigid base for cement-stabilized materials are carried out. Then, construction technology and construction quality control points and standard of semi-rigid base are put forward.