PROGRAMMABLE CALCULATORS IN THE ASSESSMENT OF OVERLAYS AND MAINTENANCE STATISTICS --PROCEEDINGS OF THE FIFTH INTERNATIONAL CONFERENCE ON THE STRUCTURAL DESIGN OF ASPHALT PAVEMENTS HELD DEFLT UNIVERSITY OF TECHNOLOGY, AUGUST 23-26 1982. VOL 1 AND 2. -- NETHERLANDS

A technique for assessing the serviceability of an existing pavement and predicting its future life under specified traffic loading and seasonal conditions has been developed. It is based on a simplified form of multi-layer elastic theory which can be incorporated in programs for the larger programmable pocket calculators. This program will handle structures having up to four layers consisting of one bituminous layer, two unbound granular layers and a subgrade. The properties of the material in the existing pavement are determined from non-destructive measurements of surface deflection using a falling weight deflectometer or some similar instrument which measures deflection at the centre of the loaded area and at various distances from it. A method is given for converting the moduli of bituminous materials determined at one temperature and time of loading to values appropriate to other temperatures and times of loading. The overlay program gives the residual life, in years, of each of the granular layers in a pavement and of the subgrade. It will also provide the residual life of each of these layers after the application of a bituminous overlay of stated thickness and modulus to the pavement structure. Different values of moduli can be assigned to the various layers according to the seasons of the year being considered. A pavement management program has been developed to determine the effect of applying an overlay on the total life of the pavement or to compare the benefits of applying one of a number of alternative maintenance procedures such as overlaying and surface dressing. The extension of life resulting from the application of each maintenance procedure considered is determined and, if the costs of each are known, the raio of functional benefit to cost is evaluated. The most effective maintenance strategy for a given road network within a stated cost budget can be found by applying the pavement management program to the individual road sections making up the complete network.(a) for the covering abstract of the conference see IRRD 815640.