Closed-form and semi-closed form algorithms for backcalculation of concrete pavement parameters

This paper presents the development of a family of closed-form and semiclosed-form backcalculation algorithms for nondestructive evaluation of rigid-pavement layer properties. Using measured surface deflections as input, these closed-form algorithms were developed for a rigid pavement slab supported on one of the following foundations: (i) a Winkler (i.e. liquid) foundation, (ii) an elastic solid foundation, and (iii) a two-layer elastic solid foundation. These closed-form algorithms were next employed to develop semi-closed-form algorithms for nondestructive evaluation of rigid pavements with two slab layers. All the algorithms were developed for execution on personal computers. The formulation of the algorithms and the, corresponding methods of solution are presented. It is also highlighted that the closed-form algorithms can be used to evaluate the quality of measured deflections and to single out erroneous deflection sensor readings.