Load Deflection Evaluation on Concrete Pavements

Abstract

The sampling of time histories from falling weight deflectometer testing allows for plotting load-deflection curves. These curves reflect non-elastic properties. As linear-elastic models often are used for the backcalculation of pavement layer moduli, the curves provide information on the quality of the evaluation. Previous studies have shown that the influence of asphalt concrete visco-elasticity has a large influence of the shape of the curve, as the area enveloped is greater at e.g. higher temperatures. Also there is a difference between asphalt and Portland cement concrete when the unbound materials and subgrade conditions are similar. However, other predicaments influence the shape of the curve too. Either water or air moving in open materials will affect the deflection during the test. This effect is often seen while testing on unbound materials during construction. Further, inertia is playing a part in the dynamic behavior. While evaluating the dynamics it is not given which underlying effect is dominating the shape. However, it is a good guess that less area enveloped would mean less attenuation of energy added to the system. This is viable information as there is a need to design and construct pavements that keeps the rolling resistance to a minimum. Comparing asphalt with concrete pavements will reveal the visco-elastic effects, but within cement concrete pavements there is also some variability observed. The present paper presents some of the findings with a discussion on how to assess the various parameters. E.g. the effect of curling shows up as a larger area being enveloped. By continued research these findings lead a way to finding a model capable of describing the load-deflection envelope entirely, so that sustainable pavements could be refined for high volume roads and air fields as well.