EFFECTS OF THE BUILT-IN CONSTRUCTION GRADIENT AND ENVIRONMENTAL CONDITIONS ON JOINTED PLAIN CONCRETE PAVEMENTS

摘要

Slab curvature, which represents the response of concrete pavement to environmental loads, influences the location and magnitude of critical slab stresses and affects long-term pavement performance. The purpose of this study was to measure the changes in temperature and moisture profiles in a newly constructed concrete pavement, to determine the deformed shape of the slabs and the resulting stress and identify the relative contributions of built-in and transient environmental effects over time. To do this, an instrumented jointed plain concrete pavement (JPCP) was monitored over a two-year period.The built-in construction gradient is a major factor contributing to slab curvature and stress. Therefore, first, static strain and pressure gage data used to establish the built-in gradient and zero stress temperature.Slab curvature was predicted using measurements of temperature and moisture conditions in the slab and computed using static strain and pavement surface profile measurements. It was found that the additional restraint provided by the dowel and tie bars does not appear to significantly reduce slab curvature resulting from daily temperature fluctuations or from reversible drying shrinkage. It does have a substantial effect on reducing slab curvature due to long-term drying shrinkage. It was also found that the slab curvature is predominantly curled upward (99 percent of the time), resulting in top-down fatigue cracking, while it is traditionally assumed that fatigue cracking in concrete pavements initiates at the bottom.Finite element models were developed to study the effect of various environmental conditions and slab restraints on the development of stress in the slabs. The models were validated based on measured strain data. It was found that the effect of moisture has the most significant effect on stress in the slabs. The measured curvature in the restrained slab (tie and dowel bars) is over 50 percent lower when compared to the unrestrained (no tie or dowel bars) slab. This reduction in deformation resulted in a critical stress that was 20 to 22 percent larger for the restrained slab compared to the unrestrained slab.