EXPERIMENTAL STUDY ON THE EARLY-AGE STRESS BEHAVIOR OF CEMENT CONCRETE PAVEMENT

To understand the behavior and characteristics of the early-age stress of cement concrete pavement, field monitoring tests were carried out at the early age of slabs constructed under typical environmental conditions in Fujian such as high temperature in summer, low temperature in winter and constant temperature in tunnel. Non-stress strain of temperature and humidity was removed by a nonstress cylinder device. Based on the strain histories and considering the creep relaxation, the stress state and histories at typical positions of the slabs were obtained by a step-by-step numerical method. The early-age temperature field and curling deformation were monitored. The relationship between early-age stress, temperature and curling was compared. The results show that the early-age stress of pavement has three stages, namely, compressive stress, tensile stress and stress fluctuating cycle. Stress relaxation stage exists in the initial stage of stress fluctuating cycle. Active factors effecting the early-age stress include hydration heat release, environmental temperature, curling deformation and gravity, and their combined action. The effect of hydration heat is significant in the preliminary stage, while the effect of temperature curling is significant in the later stages. Passive factors effecting the early-age stress include the early-age concrete behavior, structural constraints and boundary conditions. The early-age stress and the curling of pavement constructed in summer are higher than that constructed in winter. Under the condition of stable temperature in tunnel, there is a concave built-in curling in the slab with the corners being always upward due to humidity shrinkage. The existence of stress fluctuation and relaxation process in the early age causes the stress in the initial service period to be different from the stress in later service period. It is necessary to avoid the initial adverse conditions that may be inconsistent with the design state.