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60 CHAPTER 3 SURVEY OF CURRENT STATE AGENCY SPECIFICATIONS 3.1 INTRODUCTION the sand equivalent value. They do not believe these fines to be detrimental. A survey of U.S. state agencies was conducted to assess the adoption of the Superpave consensus and source aggre- gate properties, gradation bands, and volumetric properties. In 3.2.2 Fine Aggregate Angularity addition, the survey included questions regarding problematic aggregates, importation of aggregates, and future research Superpave specifies the uncompacted voids in fine aggre- needs. A copy of the survey is included in the appendix. In gate test (AASHTO T304 or ASTM C1252, Method A) to total, 48 agencies--47 U.S. states and 1 Canadian province-- ensure that the blend of fine aggregates in an HMA mixture responded to the survey. has sufficient angularity, texture, or both to provide resis- tance to rutting. Prior to the adoption of the Superpave method, many states had limited the amount of natural sand in mixes. 3.2 SUPERPAVE CONSENSUS AGGREGATE In 1997, 23% of states responding to the NCHRP Project 4-19 PROPERTIES survey on aggregate properties specified limits on natural sand (170); however, not all natural sands are rounded. Therefore, 3.2.1 Sand Equivalent Test it was felt that a test such as AASHTO T304 could better The sand equivalent test (AASHTO T176) is used to iden- qualify fine aggregate. tify the quantity of clay-like fines in a sample of fine aggre- Of the states responding to the current survey, 85% stated gate. Clay-like fines may coat the aggregate such that the that they specify AASHTO T304 or ASTM C1252 Method A asphalt coating the aggregate particles will adhere to the clay to determine FAA. Arizona uses its own modified version of instead of to the aggregate particles. In the presence of mois- the test. Oregon ran AASHTO T304 for a period of 2 years ture, the asphalt can then separate from the clay-coated aggre- and determined that only two sources produced fine aggre- gate, leading to moisture damage. AASHTO T76 is specified gate with FAA values below 45, so the test was discontinued. by 92% of the states that responded to the survey. Two of those Five other state agencies (10%) do not specify any test to states, California and Texas, specify agency test methods that measure FAA. All of these states limit the amount of natural are essentially the same as AASHTO T176. Nevada specifies sand that may be used in HMA from 0% to 15%. Texas spec- AASHTO T90, "Plastic Limit and Plasticity Index." Mis- ifies the Hamburg test to measure the rutting propensity of sissippi specifies AASHTO T88, "Particle Size Analysis of the HMA mixture in lieu of a test to measure FAA. Califor- Soils." Alaska does not specify a test to address plastic fines. nia has its own test procedure, CTM 205, which measures the For the states specifying AASHTO T176, 56% specify the number of crushed particles retained on the 4.75-mm and same minimum criteria as in AASHTO M323. Four agen- 2.36-mm sieves. California requires 70% crushed particles in cies specify less restrictive criteria, the lowest being Geor- the fine aggregate. gia DOT's specification minimum of 28 for limestone aggre- Only 51% of the agencies specifying AASHTO T304 spec- gates. Minnesota eliminated the sand equivalent requirement ify the requirements outlined in AASHTO M323. The remain- for less than 3 million ESALs. The majority of the remaining ing agencies' criteria are summarized in Table 13. Six of the 10 agencies specify a minimum of 45 for all traffic levels or 17 states report relaxed criteria; the remaining states have for up to 30 million ESALs, above which a minimum of 50 is more stringent criteria. Oklahoma is considering reducing specified in accordance with AASHTO M323. Hawaii requires the minimum to 43 for blends that do not include natural sand a minimum of 50 and Arizona a minimum of 55 for all traffic or gravel. Ontario allows fine aggregate with a minimum levels. Louisiana only requires the sand equivalent test to be uncompacted void content of 43% if the mixture meets all of run on natural sands. The frequency distribution of sand equiv- the volumetric requirements. alent specifications by traffic level is shown in Figure 25. One reported concern is that states were being forced to Some aggregate producers have noted that crushed fines from import fine aggregate to meet FAA requirements. Of the states some aggregate types can produce clay-size fines, which lower responding, 28% reported that they imported some aggregate.
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90 80 70 60 Frequency, % 50 40 30 20 10 0 28 35 37 40 45 50 55 Sand Equivalent Value 30 million Figure 25. Frequency distribution of sand equivalent specifications by traffic level. TABLE 13 Summary of AASHTO T304 Specifications differing from AASHTO M323 U.S. State Agency/ Minimum FAA Specifications Canadian Province Arizona 42 =3 M. ESALs Colorado 45 for all traffic levels Iowa Use original 7 traffic levels: 40 < 3 M. ESALs, 43 for 3 to 10 M. ESALs, 45 >= 10 M. ESALs Kansas Surface Mixes (< 100 mm from surface): 42 3 million ESALs, 40 Shoulder Base Mixes (> 100 mm from surface): 42 30 M. ESALs, 40 Shoulder Kentucky Surface Mixes: 40 = 3 M. ESALs Base Mixes: 40 = 30 M. ESALs Louisiana 40 3 M. ESALs Michigan Same except 43 for 1 to 3 M. ESALs when gradation enters restricted zone Minnesota Surface Mixes: 40 > 1 M. ESALs, 42 for 1 to 3 M. ESALs, 44 for 10-30 M. ESALs, 45 >= 30 M. ESALS Non Wear Mixes: 40 for all traffic levels Mississippi 4.75 mm NMAS mixes: 45 for all traffic levels 9.5 mm NMAS mixes: 40 10 M. ESALs All other mixes must be coarse graded unless FAA > 44 Missouri Eliminated reduced requirements for > 100 mm from surface in AASHTO M323 Nebraska 40 for low traffic, 43 for medium traffic, 45 for Interstate pavements New Mexico Eliminated reduced requirements for > 100 mm from surface I M323 Ohio 44 for single source or blend, all traffic levels Ontario Allow 43 if mixture volumetric properties are satisfied. Utah 45 for all traffic levels Virginia 45 for all traffic levels, 40 for 9.5 mm NMAS Subdivision mix Washington 45 for all traffic levels Wisconsin 40 3 M. ESALs