| The use of jet aircrafts has created serious deterioration of concrete runways and parking aprons. In this study, micromechanical damage models and thermal fatigue models are proposed for airfield concrete pavement under transient high temperature loading due to vectored thrust engines.; First, a one-dimensional thermo-micromechanical damage model is proposed. The temperature field is assumed to be independent of the stress field. We consider various strains, such as the purely elastic strain, the stable crack-induced strain, the unstable crack-induced strain, the void-induced strain, the vapor pressure-induced strain, the thermal expansion strain, and the dry shrinkage strain. Based on the strain analysis, a three-dimensional constitutive relation is derived for concrete under high temperature loading. In addition to the constitutive relations, three types of failure mechanisms are also discussed. As a demonstration, a general one-dimensional problem is numerically simulated. Both normal-weight aggregate concrete and light-weight aggregate concrete are considered. The parametric study of the concrete leads to the optimum design of the concrete pavement.; Second, one-dimensional coupled governing equations of heat and mass transfer in concrete pavement are derived. The magnitude of pore pressures and the loss of moisture caused by heating of concrete are considered. High pore pressures make some contributions to the damage of concrete pavement. Moisture migration and water permeability are also investigated. An explicit finite difference scheme is employed to calculate the temperature and pore pressure distributions.; Third, the coupled axisymmetric governing equations of heat and mass transfer in concrete are derived. The pore pressures of water vapor, gas and air are used as the driving forces that govern the moisture transfer, gas transfer and air transfer in concrete. The state equations of water, gas and air are described. The permeability of water in concrete is treated as a function of temperature and pore pressure.; Finally, a general literature review of fatigue models is presented. These include the phenomenological fatigue models and mechanical fatigue models. Fatigue models of Portland cement concrete by several authors are reviewed and compared in detail. The thermal fatigue models of PCC are constructed. The thermal fatigue lives of airfield concrete are predicted. |
