Cover Image

Not for Sale

View/Hide Left Panel
Click for next page ( 63

The National Academies of Sciences, Engineering, and Medicine
500 Fifth St. N.W. | Washington, D.C. 20001

Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement

Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 62
62 Some of these states only imported aggregate close to their (2-D) of the particle. The original ASTM D5821 test method borders where it was actually cheaper to bring in material from included a provision for a "questionable" pile. The technician out of state. Most state agencies stated that they had done so could place an aggregate particle in the questionable pile if prior to the use of Superpave. Three states reported importing he or she were unsure that the fractured face was at least 25% aggregate to meet frictional requirements. Only one state, New of the projection or if the fractured face had been weathered Hampshire, cited importing aggregate to meet FAA values. since the fracture occurred. The mass of particles in the ques- Two other states, Mississippi and Oklahoma, reported that tionable pile could not be more than 15% of the mass of the meeting FAA values could be difficult. Three states reported total sample. This provision is still included in AASHTO that minimum VMA requirements were difficult to meet-- TP61. AASHTO M323 specifies a percentage of both one this may be related to the angularity of the locally available and two fractured faces, by mass, to help provide resistance fine aggregate. to rutting. FAA requirements and the restricted zone were designed The coarse aggregate angularity test is used by 83% of the to limit the amount of rounded natural sand allowed in responding agencies who specify ASTM D5821, AASHTO HMA based on "performance" criteria. However, 46% of the TP61, or an agency version of the test reported to be similar responding states continue to limit natural sand by specifica- to ASTM D5821 or AASHTO TP61. Twelve of those agen- tion; 79% of these also have FAA requirements. As shown in cies (25%) specify their own test methods, which are similar Figure 26, the limits on natural sand ranged from 0% to 50% to ASTM D5821 or AASHTO TP61. An additional three with most falling between 10% and 15%. Some states had states (6%) have a test method but did not indicate whether more than one criterion, depending on expected traffic, mix this method was similar to ASTM D5821, and copies of the type, or frictional properties. Prior to the adoption of the method have not been obtained. Five states (11%) specify a Superpave method, FHWA recommended limiting natural crushed percentage by definition. sand to less than 15%. Only 14 agencies (39% of those using ASTM D5821 or a similar procedure) reported that their specified criteria matched 3.2.3 Coarse Aggregate Angularity AASHTO M323. Four states (11%)--Missouri, North Car- olina, Nebraska, and Wyoming--do not use AASHTO's The coarse aggregate angularity test is used to measure the reduced fractured face requirements for pavement layers number of fractured faces on a coarse aggregate particle deeper than 100 mm (4 in.) in the pavement structure. Altered according to ASTM D5821 or AASHTO TP61-02. A frac- criteria for the remaining states are shown in Table 14. The tured face is defined as a fractured area having sharp edges altered criteria for one state were not obtainable. Missis- whose area is equal to at least 25% of the greatest projection sippi's specification addresses previously expressed concerns 35 30 25 Frequency, Percent 20 15 10 5 0 0 10 15 20 25 30 50 Maximum Allowable Percentage of Natural Sand Figure 26. Frequency distribution of natural sand specifications.