A platform for research: civil engineering, architecture and urbanism
A platform for research: civil engineering, architecture and urbanism
Critical Review of VMA Requirements in Superpave
Reports of increased difficulties in meeting the minimum voids in mineral aggregate (VMA) requirements have surfaced with the recent use of Superpave volumetric mix design. The low VMA of Superpave mixes can generally be contributed to the increased compactive effort by Superpave gyratory compactor. This has led to the increased use of coarser asphalt mixes (gradations near the lower control points). However, the minimum VMA requirements in Superpave volumetric mix design for these coarse mixes are the same as those developed for the dense mixes designed by the Marshall method. Literature review has indicated that the rationale behind the minimum VMA requirement was to incorporate at least a minimum permissible asphalt content into the mix in order to ensure its durability. Studies have shown that asphalt mix durability is directly related to asphalt film thickness. Therefore, the minimum VMA should be based on the minimum desirable asphalt film thickness rather than a minimum asphalt content because the latter will be different for mixes with different gradations. Mixes with coarse gradation (and, therefore, low surface area) have difficulty meeting the minimum VMA requirement based on minimum asphalt content in spite of thick asphalt films. A rational approach based on a minimum asphalt film thickness has been proposed and validated. The film thickness approach represents a more direct, equitable, and appropriate method of ensuring asphalt mix durability and encompasses various mix gradations.
Critical Review of VMA Requirements in Superpave
Reports of increased difficulties in meeting the minimum voids in mineral aggregate (VMA) requirements have surfaced with the recent use of Superpave volumetric mix design. The low VMA of Superpave mixes can generally be contributed to the increased compactive effort by Superpave gyratory compactor. This has led to the increased use of coarser asphalt mixes (gradations near the lower control points). However, the minimum VMA requirements in Superpave volumetric mix design for these coarse mixes are the same as those developed for the dense mixes designed by the Marshall method. Literature review has indicated that the rationale behind the minimum VMA requirement was to incorporate at least a minimum permissible asphalt content into the mix in order to ensure its durability. Studies have shown that asphalt mix durability is directly related to asphalt film thickness. Therefore, the minimum VMA should be based on the minimum desirable asphalt film thickness rather than a minimum asphalt content because the latter will be different for mixes with different gradations. Mixes with coarse gradation (and, therefore, low surface area) have difficulty meeting the minimum VMA requirement based on minimum asphalt content in spite of thick asphalt films. A rational approach based on a minimum asphalt film thickness has been proposed and validated. The film thickness approach represents a more direct, equitable, and appropriate method of ensuring asphalt mix durability and encompasses various mix gradations.
Critical Review of VMA Requirements in Superpave
P. S. Kandhal (author) / K. Y. Foo (author) / R. B. Mallick (author)
1998
24 pages
Report
No indication
English
Construction Equipment, Materials, & Supplies , Highway Engineering , Hot mix paving mixtures , Aggregates , Asphalts , Literature review , Durability , Material properties , Requirements , Thickness , Volume , Asphalt pavements , Voids , Superpave , Voids in the Mineral Aggregate , VMA(Voids in the Mineral Aggregate)
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