Flexible road pavement performance and maintenance studies
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The prosperity of any nation depends to a large extent on the effectiveness and efficiency of its communication system. The economic significance of road construction and maintenance cannot therefore be overemphasized. The objective of this research work was to evaluate parameters of structural and functional performance/serviceability of road pavements by conducting field tests (elastic deflection and radius of curvature of deflection profile) and condition surveys (rideability, cracking, rutting and surface roughness). The usefulness of these parameters in estimating maintenance requirements was tested. In addition, Finite Element Method (FEM) was used to theoretically analyse the structural integrity of the road pavements that were tested in the field and both field and FEM compared. Before the above work was done, the highway maintenance system operational in Kenya was studied, and the findings are given as a complete work in Chapter 2. Upon the analyses of condition survey data, an index equation was established which indicated that rideability is affected more by the extent of rutting than by either cracking or roughness. The equation was found practical and could be used to determine the serviceability of the road section using objective measurement of surface defects. A method developed from first principles to determine the radius of curvature of deflection profile was found practical and the values of radii compared well with those determined using the analytical method of the Ministry of Public Works (MoPW). The philosophy of the criterion proposed by Leger and Autret (1972) for evaluating structural condition from deflection measurements was found applicable but the limits require adjustment to suit local road environment. FEM predicted well the maximum deflection and the deflection profile of pavements consisting of non-viscoelastic bases and asphalt concrete surfaces. The elastic moduli of pavement materials given by MoPW were found practical. The institutional capacity of the highway maintenance organisation in Kenya was found inadequate. Further, funds allocated to road maintenance were found to have below requirements in the recent years.