Study On The Mechanism Of Crack Generating Of Cement Concrete Airport Pavement

Cracks appear in concrete pavement in stages from construction to service, and the repairing work is time and money consuming. Accordingly, there is an urgent demand to determinate the cracking mechanisms and the factors that influence the cracking tendency of the concrete pavement.In this paper, the cracking of concrete pavement in stages from construction to service was modeled using the universal finite element analysis software. In construction stage, in the temperature field calculation, both the effects of temperature and age on the rate of cement hydration were in consideration, and the theory of hydration degree was used to offset the defect of conventional cement hydration heat formula. And in the calculation of thermal stress field, both the effects of temperature and age on the strength and modulus of elasticity development of concrete were in consideration and the theory of mature degree was used. Moreover, the methods of relaxation coefficient and equivalent difference in temperature were used in consideration of the effects of creep and shrinkage in integrative stress field calculation. In service stage, the mechanical responds of concrete pavement under static loads and impact loads of aircraft are analysed. Based on these responds, the influence of material parameters to stress and cracking tendency are revealed.This paper simulates the cracking of concrete pavement on the cement stabilized macadam foundation through numerical modeling. Based on the theory of temperature and stress field and elastic half-space foundation, two three-dimensional finite element analysis models of concrete pavement were established. In construction stage, The influence of each factor was discussed by analyzing the greatest principal tensile stress and cracking risk, such as cement hydration heat, content of cement, thickness of concrete slab, casting temperature, ambient temperature, ultimate shrinkage, creep, modulus of elasticity and coefficient of thermal expansion. In service stage, the influence of some main factor was discussed by analyzing the greatest principal tensile stress and cracking risk, such as concrete slab depth, concrete slab modulu, base modulu, foundation rebound modulu and so on. Problem of cavity beneath the cement-concrete slab and its effects was analysed. The content and conclusions of above may provide a reference for design and research of concrete pavement.Finally, the existing shortages of the research were indicated and the research direction in the future was put forward.