A Review of Aggregate and Asphalt Mixture Specific Gravity ...

More documents

Recommendations

Info

List of TablesTABLE 1 AASHTO T 85 and ASTM C127 Precision Estimates ............................... 3TABLE 2 AASHTO T 85/ASTM C127 Precision Estimates Reported by AMRL .... 4TABLE 3 Advantages and Disadvantages of Alternative Methods for DeterminingG sb of Coarse Aggregate ............................................................................. 5TABLE 4 AASHTO T 84 and ASTM C128 Precision Estimates ............................... 7TABLE 5 AASHTO T 84/ASTM C128 Precision Estimates Published by AMRL ... 7TABLE 6 Modifications of Standard Test Methods for Determining SSD Conditionof Fine Aggregate ....................................................................................... 8TABLE 7 Advantages and Disadvantages of Alternative Methods for DeterminingG sb of Fine Aggregate ............................................................................... 10TABLE 8 AASHTO T 209 Precision Estimates for G mm .......................................... 15TABLE 9 ASTM D2041 Precision Estimates for G mm .............................................. 15TABLE 10 Precision Estimates for ASTM D2041 Evaluated in NCHRP 9-26 .......... 16TABLE 11 AASHTO T 209/ASTM D2041 Precision Indices Published by AMRL . 16TABLE 12 Advantages and Disadvantages of Alternate Methods for G mm ................ 17TABLE 13 ASTM D2726 Precision Estimates for G mb .............................................. 20TABLE 14 NCHRP 9-26 Recommended Precision Estimates for AASHTO T 166 .. 20TABLE 15 Advantages and Disadvantages of Alternative Methods for G mb ............. 21TABLE 16 NCHRP 9-26 Recommended Precision Estimates for ASTM D6752 ...... 24TABLE 17 Average Corrections for Air Voids when Using T 331 Instead of T 166..27List of FiguresFIGURE 1 Effect of Reducing G mb or G sb Standard Deviation on VMA StandardDeviation. .......................................................................................................................... 26FIGURE 2 Comparison of Air Voids for Field Cores Using G mb from AASHTO T 166and Vacuum Sealing Methods (16). .................................................................................. 28vi
1 INTRODUCTIONCurrent practices for asphalt mix design and acceptance testing rely on volumetricproperties. Vital to the calculation of mix volumetric properties are specific gravitymeasurements of the mixture and the aggregate in the mixture. In essence, the specificgravity measurements are conversion factors that allow conversion of mass percentagesto volume proportions/percentages. The accuracy and reliability of the specific gravitymeasurements are therefore fundamental to the business of building quality hot-mixasphalt (HMA) pavements.This paper documents a critical review of specific gravity measurement methods.This review was conducted as part of a task group consisting of the authors under thedirection of the FHWA Asphalt Mix and Construction Expert Task Group. Theobjectives of this review are to summarize problems and issues with current methods,examine possible improvements and/or alternate methods, and identify areas that needfurther research and development.The approach to this review has been to separately examine three specific gravitydeterminations, namely, the bulk specific gravity of the aggregate (G sb ), the maximumspecific gravity of asphalt mixtures (G mm ), and the bulk specific gravity of compactedspecimens (G mb ). The review draws upon information from recently published researchstudies, information from state DOTs and equipment manufacturers, and precisioninformation cited in AASHTO and ASTM standards and published on the AASHTOMaterials Reference Laboratory (AMRL) website (1). This report is organized bydiscussion of each of these measurements followed by a summary that considers theoverall effect of the measurements on asphalt mixture volumetric properties and currentcriteria for mix design and acceptance. The view of the task group has been thatchange(s) to the current specific gravity methods may be motivated by one or more of thefollowing three reasons:1. The change(s) or new method(s) will provide specific gravity results closer to thetruth (i.e., greater accuracy),2. The change(s) or new method(s) will yield more repeatable results (i.e., betterprecision), and3. The change(s) or new method(s) will be faster, easier, and/or less expensive.1
Page 1 and 2: NCAT Report 12-06A REVIEW OF AGGREG
Page 3 and 4: Objective and Process of the Review
Page 5 and 6: warranted in these methods at this
Page 7: Table of Contents1. Introduction ..
Page 11 and 12: 3 BULK SPECIFIC GRAVITY OF AGGREGAT
Page 13 and 14: TABLE 3 Advantages and Disadvantage
Page 15 and 16: TABLE 4 AASHTO T 84 and ASTM C128 P
Page 17 and 18: TABLE 6 Modifications of Standard T
Page 19 and 20: In 2000, Kandhal et al. (7) conduct
Page 21 and 22: angular fine aggregate with higher
Page 23 and 24: ASTM does not specify an absorption
Page 25 and 26: 4.3. Alternatives to Current Standa
Page 27 and 28: 5 BULK SPECIFIC GRAVITY OF COMPACTE
Page 29 and 30: TABLE 15 Advantages and Disadvantag
Page 31 and 32: inaccurate sample volumes caused by
Page 33 and 34: For G sb , the specific gravity val
Page 35 and 36: line). Since it may be more desirab
Page 37 and 38: Both standard test procedures, incl
Page 39 and 40: 8 RECOMMENDATIONSBased on the revie
Page 41 and 42: REFERENCES1. The Proficiency Sample

A Review of Aggregate and Asphalt Mixture Specific Gravity ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?