However, sometimes a pair of desirable properties may show conflicting trends with the variation of a constituent of the mix. The composition of a pavement material is finalized through appropriate mix design, so that the desirable levels of various engineering properties of the material are achieved. The engineering properties of a pavement material depends on the relative composition of its constituents. These materials show complex response when subjected to load, temperature and moisture variations. While there are design considerations involved in a pavement from the geometric, functional and drainage aspects, the structural design indicates estimation of appropriate thicknesses of the pavement layers.ĭifferent kinds of materials are used to construct individual layers of a pavement structure. Thus, this pamphlet and its companions are critically important to anyone who designs flexible pavements.An asphalt pavement is made up of multiple layers, namely subgrade, sub-base, base, surfacing and wearing course. Furthermore, although the procedures are specifically developed for use with the 1993 AASHTO Guide, their use will give agencies a "leg up" on implementation of the design procedures being developed for inclusion in the 2002 AASHTO Guide for Design of New and Rehabilitated Pavement Structures. Their use will provide: (1) improved designs, (2) more realistic estimates of pavement performance, and (3) more consistent use of the AASHTO design parameters. The procedures presented were developed through analysis of the Long-Term Pavement Performance (LTPP) data, documented in the report Analyses Relating to Pavement Material Characterization and Their Effects on Pavement Performance, FHWA-RD-97-085.Īpplication of the procedures and guidelines developed through this analysis will facilitate and improve application of the AASHTO Guide flexible pavement design procedures. Two companion pamphlets-Design Pamphlet for the Determination of Design Subgrade Moduli in Support of the 1993 AASHTO Guide for the Design of Pavement Structures (FHWA-RD-97-083) and Design Pamphlet for the Back-calculation of Pavement Layer Moduli in Support of the 1993 AASHTO Guide for the Design of Pavement Structures (FHWA-RD-97- 076)-provide additional, related guidance on interpretation of pavement deflection data and characterization of the subgrade soil. This design pamphlet addresses this problem by presenting procedures for selecting appropriate design values to characterize the pavement materials. Until now, the information available to help engineers choose appropriate values has been incomplete. PDF files can be viewed with the Acrobat® Reader® FOREWORDĪ key challenge faced by engineers using the 1993 AASHTO Guide for Design of Pavement Structures (AASHTO Guide) is the selection of appropriate design values for the subgrade soil and for the pavement materials.
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