A platform for research: civil engineering, architecture and urbanism
A platform for research: civil engineering, architecture and urbanism
Significance of Restricted Zone in Superpave Aggregate Gradation Specification
SHRPs asphalt research was primarily aimed at the properties of asphalt binders and paving mixes and their effect on asphalt pavement performance. The SHRP study of aggregate particles (including gradation) was intentionally excluded from the asphalt program, yet SHRP had to recommend a set of aggregate properties and an aggregate gradation specification for use in mix design without any experimentation. In order to recommend aggregate properties and gradations, SHRP formed an Aggregate Expert Task Group (ETG) consisting of 14 acknowledged experts. In lieu of formal experimentation, the Aggregate ETG used a modified Delphi approach to develop a set of recommended aggregate properties and criteria that are now included in the Superpave volumetric mix design method. The modified Delphi process used five rounds of questionnaires to narrow a wide list of aggregate properties and criteria to those recommended in Superpave. The final recommended aggregate gradation criteria included control points through which gradations must fall between and a restricted zone that lies along the maximum density line (MDL) between the intermediate sieve sizes either 4.75 or 2.36 mm depending upon the nominal maximum aggregate size (NMAS) of the gradation and the 0.3-mm sieve size.
Significance of Restricted Zone in Superpave Aggregate Gradation Specification
SHRPs asphalt research was primarily aimed at the properties of asphalt binders and paving mixes and their effect on asphalt pavement performance. The SHRP study of aggregate particles (including gradation) was intentionally excluded from the asphalt program, yet SHRP had to recommend a set of aggregate properties and an aggregate gradation specification for use in mix design without any experimentation. In order to recommend aggregate properties and gradations, SHRP formed an Aggregate Expert Task Group (ETG) consisting of 14 acknowledged experts. In lieu of formal experimentation, the Aggregate ETG used a modified Delphi approach to develop a set of recommended aggregate properties and criteria that are now included in the Superpave volumetric mix design method. The modified Delphi process used five rounds of questionnaires to narrow a wide list of aggregate properties and criteria to those recommended in Superpave. The final recommended aggregate gradation criteria included control points through which gradations must fall between and a restricted zone that lies along the maximum density line (MDL) between the intermediate sieve sizes either 4.75 or 2.36 mm depending upon the nominal maximum aggregate size (NMAS) of the gradation and the 0.3-mm sieve size.
Significance of Restricted Zone in Superpave Aggregate Gradation Specification
L. A. Cooley (author) / J. Zhang (author) / P. S. Kandhal (author) / A. J. Hand (author) / A. E. Martin (author)
2002
28 pages
Report
No indication
English
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