Aggregate Quality Requirements for Pavements (2018)

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8 2.1 Introduction Both short- and long-term performance of any constructed pavement system largely depends on the quality of materials used in different layers. To ensure adequate performance of pavements under traffic loading and environmental conditions, transportation agencies have developed specifications to check source properties considering aggregate quality. This chapter provides a brief introduction to different types of aggregate materials available as natural resources and mined from sand and gravel pits and crushed stone quarry operations throughout the United States. Furthermore, important aggregate properties with respect to application in a certain pavement layer, types, sources, tests, and quality aspects used by transportation agencies are described. Finally, quality-related source properties, provisional testing methods, and restric- tions put in place for using recycled, artificial/byproduct aggregates as well as blended and sta- bilized aggregates are presented. 2.2 Aggregate Types and Sources Based on the nature of their extraction from natural resources, the Aggregate Handbook (2nd ed.) divides aggregates used in pavement applications into two broad categories: stone deposits and sand and gravel deposits (National Stone, Sand and Gravel Association 2013). Industrial byproduct materials, such as slags, have also been specified and used in bound, asphalt concrete and concrete, and unbound, granular base/subbase, pavement layer applica- tions in some states (Morian et al. 2012, Stroup-Gardiner and Wattenberg-Komas 2013a). 2.2.1 Stone Deposits Stone deposits can be broadly classified based on origin into the following three categories: (a) sedimentary rocks, (b) igneous rocks, and (c) metamorphic rocks (Langer 1988). A brief discussion of the mechanism of formation for these three rock types is presented below, along with examples of each rock type. Sedimentary Rocks. These rock types are formed by chemical precipitates and the settlement of sediments or organic matter at or near the earth’s surface and usually within bodies of water. Examples of sedimentary rocks include limestone, dolomite or dolostone, shale, and sand- stone. Limestone and dolomite constitute approximately 70% of crushed stone production in the United States (Willett 2011). Igneous Rocks. These rock types are formed by the cooling and solidification of magma or lava. Igneous rocks formed below the earth’s surface are called intrusive or plutonic rocks, whereas igneous rocks formed on the earth’s surface are called extrusive or volcanic rocks. C H A P T E R 2 Aggregate Sources, Recycling, and Blending

Aggregate Sources, Recycling, and Blending 9 Intrusive igneous rocks have a chance to grow large enough minerals to give it a coarse- grained texture, whereas extrusive igneous rocks cool more rapidly and can be more fine grained. Igneous rocks often have high amounts of silica. Examples of igneous rocks used in pavement applications include granite (intrusive), basalt (extrusive), and rhyolite (extrusive). Granites account for approximately 16% of crushed stone production in the United States (9% of total aggregate production). Granite is usually classified as excellent crushed stone, but some granitic type aggregates are weak and brittle due to their poorly bonded mineral grains. Fine-grained igneous rocks are often “trap rocks,” which are dark-colored, fine-grained, volcanic rocks, and which make up about 9% of the crushed stone production (5% of the total aggregate production) (Tutumluer 2013). Examples of trap rock are basalt and diabase. Trap rocks are classified as excellent crushed stone materials due to their resistance to chemical reactions and ability to withstand high mechanical stresses (Willett 2011). Metamorphic Rocks. These rock types are formed by the transformation of existing rocks (may be sedimentary or igneous) under heat and pressure. Examples of metamorphic rocks include quartzite, marble, slate, and gneiss. Metamorphic rocks as aggregates can have widely variable characteristics. Many quartzite and gneiss aggregates can have properties similar to granite, whereas shale can be slabby and schist can be soft and flaky because of its high mica content (National Stone, Sand and Gravel Association 2013). 2.2.2 Sand and Gravel Deposits Apart from crushing, aggregates are also extracted from sand and gravel pits where the par- ent material has been transported from another location either by fluvial, glacial, or alluvial processes to form loose deposits of natural sand and gravel. They are usually found in existing or historic river valleys or older, consolidated bedrock, glacial deposition, and mountain allu- vial fans. Sand and gravel make up approximately 42% of the total aggregate production in the United States (Langer 2011). Apart from the above two types of natural sources, other sources of aggregates include recycled materials and industrial byproducts. A detailed discussion on different recycled materi- als and industrial byproducts used in the construction of pavement layers will be presented later in this chapter. 2.2.3 Aggregate Source Selection Figure 2-1 shows the relative locations of aggregate resources in the contiguous United States (Langer 2011). As indicated, there is a limited supply of natural aggregates in the Coastal Plain and Mississippi embayment, Colorado Plateau and Wyoming Basin, glaciated Midwest, High Plains, and the nonglaciated Northern Plains. As a result, construction projects in these regions often require transportation of “good quality” natural aggregates from far away sources to be used in pavement applications. The locations and sources of different types of aggregates in each state play an important role in achieving cost-effective and efficient pavement construction. Aggregates Industry Atlas provides one good source, which includes state maps identifying the locations of crushed stone and sand/gravel sources relative to the available highway network (Aggregates Manager 2016, http://www.aggman.com/). The survey questionnaire included questions related to aggregate source and properties. About 55% of the respondent agencies (27 U.S. DOTs as well as Ontario and Yukon provinces) indicated they have lists of approved aggregate types or sources in their prospective agencies for different pavement construction applications, while 38% (17 state DOTs and three Canadian

10 Aggregate Quality Requirements for Pavements provinces) reported that they do not have any approved lists of aggregates. Additionally, 17% (seven U.S. DOTs in addition to British Columbia and Saskatchewan provinces) indicated some other alternatives regarding approved list of aggregate sources. These included (1) an approval process for aggregates used in HMA and PCC pavements and testing aggregates per project used in unbound layers; (2) specifications for aggregates to be used for base, subbase, asphalt concrete, and so forth, considering that an agency owns a number of gravel pits that have been used on various projects; (3) once a certain aggregate source is approved on a project, using some aggregates in some cases for other projects for up to a year; or (4) pre-approving the aggregate producers but still requiring quality testing. Among the transportation agencies that have an approved list of aggregate types and sources, 93% (26 state DOTs and Ontario province) indicated that they update their list periodically to include new/other materials into the list of their approved aggregate sources. These transporta- tion agencies also reported the frequencies when they update their approved list (see Table 2-1). Only 7% (Washington State DOT and Yukon province) reported that they do not allow new materials into their approved list of aggregates. The use of different sources of crushed stone sources was also investigated. The results are summarized in Figure 2-2, which indicates that the majority of the respondent agencies use crushed stone aggregates. Half of the participating agencies reported that they use igne- ous (extrusive) rocks (e.g., basalt or scoria). Note that only Saskatchewan province indicated that they do not have crushed stone sources. Additionally, New Jersey DOT reported that they exclude shale, schist, slate, and most sandstones although these sources could be approved if classified as quartzite and meet physical test requirements. As discussed in the previous section, the geology and rock origin of natural virgin aggregates is an important controlling factor of the quality of aggregates. Survey results show that 60% of the Figure 2-1. Generalized locations of aggregate resources in the contiguous United States (Langer 2011).

Aggregate Sources, Recycling, and Blending 11 respondents (26 U.S. DOTs and five Canadian provinces) do not receive information regarding the geologic origins of natural (virgin) aggregates from producers, and 40% (19 U.S. DOTs and two Canadian provinces) do. Among those agencies that do not receive information regarding the geologic origins of natural (virgin) aggregates, 71% (19 U.S. DOTs and three Canadian provinces) indicated that this information is not required/requested by their corresponding agency, while only 29% (seven U.S. DOTs and two Canadian provinces) reported that geologic origin is identified in-house by a geologist or petrographer working for the agency. Information related to different sources of sand and gravel used by participating agencies is summarized in Figure 2-3. Approximately 71% of the respondent agencies use glacial and fluvial Transportation Agency Frequency or Condition for Updating Approved Aggregate List Ohio and Oklahoma Daily Wisconsin Every 2 to 4 weeks Alabama and New York Monthly Kansas Updated on a monthly basis based on prequalification procedures Illinois and Maryland Every 3 months North Carolina, South Carolina, Arkansas, and Rhode Island Annually or on request Idaho Contractors or suppliers may add sources when they need them. Approval is good for a 2-year period. Arizona Proposed by contractor and approved by agency (Section 1001 material sources of Arizona standard specifications for road and bridge construction) New Jersey, Georgia, Nebraska, Pennsylvania, Mississippi, Iowa, and Indiana Continually, depending on requests and successful approvals or re-approvals Texas Through aggregate quality monitoring program. List is updated in June and December. Kentucky, Tennessee, and Virginia Updated as new sources are approved or changes need to be made to existing sources. Michigan Very infrequently Table 2-1. Frequencies when transportation agencies update their approved aggregate lists. 2% 85% 51% 81% 72% 2% 1 45 27 43 38 1 0 10 20 30 40 50 0% 20% 40% 60% 80% 100% Do not have crushed stone sources Sedimentary rocks (e.g., limestone, dolomite, sandstone) Igneous (extrusive) rocks (e.g., basalt, scoria) Igneous (intrusive) rocks (e.g., granite, gabbro) Metamorphic rocks (e.g., quartzite, gneiss) Other Number of Responses Percentage of Survey Respondents 53 survey respondents Figure 2-2. Crushed stone sources reported in agency surveys.

12 Aggregate Quality Requirements for Pavements (river) deposits. On the other hand, use of marine, lacustrine (lake), and eolian (windblown) deposits was found to be less common. Arizona and New Mexico DOTs did not report about gravel sources, probably because gravel particles can sometimes be found in large sizes and crushed to be called rock in these states. This is often the case for coarse aggregate materials when they are referred to as “sand and rock” in the western United States. In addition to virgin aggregate sources, large quantities of construction and demolition wastes are produced each year in the United States. The U.S. Environmental Protection Agency (EPA) estimated that 534 million tons of construction and demolition waste quantities were generated in the United States in 2014 alone. As shown in Figure 2-4, out of these 534 million tons, 70% was concrete and 14% was asphalt concrete (EPA 2016). 4% 71% 27% 39% 83% 31% 4% 2 37 14 20 43 16 2 0 10 20 30 40 50 0% 20% 40% 60% 80% 100% Do not have gravel sources Glacial deposits Marine deposits Lacustrine (lake) deposits Fluvial (river) deposits Eolian (windblown) deposits Other Number of Responses Percentage of Survey Respondents 52 survey respondents Figure 2-3. Sand and gravel sources reported in agency surveys. Figure 2-4. Composition of construction and demolition waste generation in 2014 in the United States by material before recycling (EPA 2016).

Aggregate Sources, Recycling, and Blending 13 2.3 Aggregate Applications in Pavement Construction As discussed in Section 1.1, many highway agencies have already established certain aggre- gate quality requirements associated with specific applications of aggregates in pavement construction. Accordingly, transportation agencies were asked to indicate which pavement layers are constructed with specific aggregate quality requirements. Figure 2-5 shows in per- centages the different types of pavement layers constructed with aggregates satisfying certain quality requirements. A great majority of the responses includes construction of asphalt concrete including surface and binder (or base) courses (100%), PCC (87%), and unbound/ stabilized aggregate base course (94%). Nearly half of the responding agencies indicated they commonly build open-graded drainage layers, and about one fourth of all respondents often constructed pavement working platforms for subgrade stability applications. The “others” category in the survey summary graphs presented in this synthesis comprise miscel- laneous responses reported by the surveyed agencies in lieu of the alternatives included in the questionnaire. A detailed compilation of all agency responses to the questionnaire is provided in Appendix C. The survey also collected information on whether any pavement layer was constructed with aggregate materials without checking aggregate quality requirements. According to the recorded responses, 91% (40 U.S. DOTs and eight Canadian provinces) indicated that they check aggre- gate quality requirements for construction of all pavement layers. However, 9% (five U.S. DOTs) do not check the aggregate quality for construction of a certain pavement layer in some spe- cial cases. This includes (1) checking only gradation requirements for construction of recycled pavement foundation applications—for example, crushed concrete, bituminous millings; (2) low quantities of asphalt and aggregates in minor construction projects that may be accepted by visual discretion of an engineer; and (3) pavement construction jobs for municipalities in order to keep the cost down. 100% 87% 94% 94% 68% 76% 59% 57% 36% 26% 6% 53 46 50 50 36 40 31 30 19 14 3 0 10 20 30 40 50 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Asphalt Concrete (AC) including surface and base course Portland Cement Concrete (PCC) Surface Treatment (ST) Unbound aggregate base course Stabilized (admixture treated) base course Unbound aggregate subbase course Stabilized subbase course Open graded drainage layer Separator/filter layer Pavement working platforms for subgrade stability applications Others such as streambed aggregates, drainable stable base Number of Responses Percentage of Survey Respondents 53 survey respondents Figure 2-5. Pavement layers constructed with specific aggregate quality requirements.

14 Aggregate Quality Requirements for Pavements As part of the questionnaire, the frequency in utilizing different aggregate sources in pave- ment construction was investigated. Figure 2-6 summarizes transportation agency responses, in which 94% indicated the use of RAP and almost 70% indicated the utilization of blended virgin aggregate sources. Additionally, 15% of the agencies reported the use of marginal aggregates while 21% of the respondents indicated that they use nontraditional large-sized aggregates. Also, about half of all responding agencies indicated that they use RCA in pave- ment applications. Artificial/byproduct and manufactured aggregates, such as SFS, BFS, and lightweight aggregate (LWA), were reported to be used by 45% of the responding agencies. The required quality tests for each of these aggregate sources will be further discussed in this synthesis report. 2.4 Tests to Check Source Properties for Aggregate Quality Agency specifications for aggregate usage in pavement applications include requirements related to particle size distribution, degree of crushing (percentage crushed or uncrushed and/or number of fractured faces), liquid limit (LL) and plasticity index (PI), durability, and soundness (National Stone, Sand and Gravel Association 2013). Commonly used specifications include those developed by AASHTO, ASTM, the U.S. Army Corps of Engineers, and individual state and provincial transportation agencies. Different tests can be required for different applica- tions and different aggregate types/sources. This section lists the most commonly used AASHTO and ASTM standards for virgin and recycled aggregates used in pavement applications. 2.4.1 Quality-Related Source Properties of Virgin Aggregates Several standard test methods are used to determine the physical properties of virgin aggre- gates used in pavement applications. For measuring the specific gravity, degree of absorption, unit weight, and voids content of coarse and fine aggregates, the following test methods are used: 94% 55% 45% 15% 21% 70% 55% 4% 50 29 24 8 11 37 29 2 0 10 20 30 40 50 0% 20% 40% 60% 80% 100% Recycled aggregates – Recycled Asphalt Pavement (RAP) Recycled aggregates – Recycled Concrete Aggregate (RCA) Marginal aggregates (out of specification) Nontraditional aggregate (e.g., large size aggregates, primary crusher run) Blended virgin aggregates Blended aggregates (virgin and recycled/artificial) Other sources Number of Responses Percentage of Survey Respondents 53 survey respondents Artificial/Byproduct aggregates such as Steel Furnace Slag (SFS), Blast Furnace Slag (BFS), and Light Weight Aggregates (LWA) Figure 2-6. Aggregate types and sources used in pavement layer construction.

Aggregate Sources, Recycling, and Blending 15 • For coarse aggregates, AASHTO T 85 or ASTM C127, Standard Method of Test for Specific Gravity and Absorption of Coarse Aggregate, is used. For example, Oklahoma DOT requires this test to be conducted on coarse aggregates at the quarries in order to qualify these materials to be used in construction projects (Oklahoma DOT 2016). Measuring bulk specific gravity and water absorption of LWA materials is needed, especially for concrete applications to acquire proper mix proportions (Byard and Schindler 2010, Deshpande and Hiller 2012, Kim et al. 2012). Bulk specific gravity is also measured for coarse aggregates used in HMA in order to achieve proper volumetrics. • For fine aggregates, AASHTO T 84 or ASTM C128, Standard Method of Test for Specific Gravity and Absorption of Fine Aggregate, is used. This test needs to be conducted on LWA used in pavement applications (particularly concrete applications) to ensure proper mix pro- portioning and the additional quantity of water required for the mix (Byard and Schindler 2010, Henkensiefken et al. 2010). • AASHTO T 19M/T 19 or ASTM C 29/C29M, Standard Test Method for Bulk Density (Unit Weight) and Voids in Aggregate. Several AASHTO and ASTM standards are designated to measure the morphological shape properties of coarse aggregates used in pavement applications. Morphological shape properties include angularity and flat and elongated ratio. The most common standards are • ASTM D4791, Standard Test Method for Flat Particles, Elongated Particles, or Flat and Elongated Particles in Coarse Aggregate. For example, Oklahoma DOT uses this test for open-graded Portland cement stabilized bases and has a limit of less than 10% (Oklahoma DOT 2009). • Standards for coarse aggregate angularity include AASHTO TP 61, Standard Method of Test for Determining the Percentage of Fracture in Coarse Aggregate, and ASTM D5821, Standard Test Method for Determining the Percentage of Fractured Particles in Coarse Aggregate. • Fine aggregate angularity (FAA) can be required for some pavement applications, such as Superpave asphalt concrete mix design (Prowell et al. 2005). Standard test methods include AASHTO T 304, Standard Method of Test for Uncompacted Void Content of Fine Aggregate, or ASTM C1252 Method A, Standard Test Methods for Uncompacted Void Content of Fine Aggregate (as Influenced by Particle Shape, Surface Texture, and Grading). The following test methods are used to characterize the durability and soundness of aggregate materials used in pavement applications: • AASHTO T 210 or ASTM D3744/D 3744M, Standard Method of Test for Aggregate Durabil- ity Index. For example, Oklahoma DOT requires this test for coarse aggregates at the quarries for qualifying their materials to be used in Oklahoma DOT construction projects (Oklahoma DOT 2016). • AASHTO T 104, Standard Method of Test for Soundness of Aggregate by Use of Sodium Sulfate or Magnesium Sulfate. • AASHTO T 103, Standard Method of Test for Soundness of Aggregates by Freezing and Thawing. The following test methods are used to characterize the resistance to abrasion and the toughness of aggregate materials for various pavement applications: • AASHTO T 327 or ASTM D6928, Standard Method of Test for Resistance of Coarse Aggre- gate to Degradation by Abrasion in the Micro-Deval Apparatus. For example, Kansas DOT requires this test as one of the quality tests for their coarse aggregates (Kansas DOT 2017). • AASHTO T 96 or ASTM C131, Standard Method of Test for Resistance to Degradation of Small-Size Coarse Aggregate by Abrasion and Impact in the Los Angeles Machine. For example, Kansas and Oklahoma DOTs require this test as one of the quality tests for coarse aggregates (Kansas DOT 2017, Oklahoma DOT 2016).

16 Aggregate Quality Requirements for Pavements Test methods are used for determining the quality of fines or finer particles (e.g., plasticity and degradation) and the quantities of deleterious materials in aggregates such as highly reactive clays, organic matter, and friable particles. These methods include the following: • The standard test methods for measuring the LL, plastic limit (PL), and PI are AASHTO T 89, Standard Method of Test for Determining the Liquid Limit of Soils, AASHTO T 90, Standard Method of Test for Determining the Plastic Limit and Plasticity Index of Soils, and ASTM D4318, Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils. Some agen- cies also use limits on the PI of fine aggregate materials used in certain applications (Prowell et al. 2005). For example, a PI limit of 6 is specified by Illinois DOT for unbound aggregate base course materials. • AASHTO T 21 or ASTMC40/C40M, Standard Test Method for Organic Impurities in Fine Aggregates for Concrete, is used by Kansas DOT as the standard test procedure when required by a project or an application (Kansas DOT 2017). • AASHTO T 176, Standard Method of Test for Plastic Fines in Graded Aggregates and Soils by Use of the Sand Equivalent Test, or ASTM D2419, Standard Test Method for Sand Equivalent Value of Soils and Fine Aggregate, also is used for this purpose. Sand equivalent test to deter- mine the ratio of plastic fines and/or clayey materials is required for Superpave as a standard test method for fine aggregates used in HMA mixes (Prowell et al. 2005). • Methylene blue test can be used to determine the amounts of harmful materials in fines, such as montmorillonite and organic matter (International Slurry Surfacing Associa- tion 1989). Standard test methods include AASHTO T 330, Standard Method of Test for the Qualitative Detection of Harmful Clays of the Smectite Group in Aggregates Using Methylene Blue. ASTM test designation for Methylene blue is ASTM C837, Standard Test Method for Methylene Blue Index of Clay; or ASTM C1777, Standard Test Method for Rapid Determination of the Methylene Blue Value for Fine Aggregate or Mineral Filler Using a Colorimeter, which is required for Superpave mixes (Prowell et al. 2005). • ASTM C142/C142M, Standard Test Method for Clay Lumps and Friable Particles in Aggregates, is used by Oklahoma DOT to test aggregates used in bituminous surface treat- ments (Oklahoma DOT 2009). Indiana DOT also uses AASHTO T 112 for their aggregate specification and requirements (Indiana DOT 2017a). • ASTM D7428, Standard Test Method for Resistance of Fine Aggregate to Degradation by Abrasion in the Micro-Deval Apparatus. Transportation agencies also identified the quality-related natural (virgin) aggregate properties that they collect from aggregate producers. The results are shown in Figure 2-7. Specific gravity, absorption, resistance to degradation, particle shapes, and percent deleterious materials were among the most common quality properties collected by the respondent agencies. Also, expansion from hydration reaction, harmful clay content, for example, through the use of Methylene blue test, and mineralogical composition turned out to be not so common properties collected by producers. Three transportation agencies reported specific tests or protocols that were required for determining the aggregate quality properties. These include • Iowa Pore Index, Iowa Quality Number, X-ray Fluorescence (XRF), X-ray Powder Diffraction (XRD), and Thermal Gravimetric Analysis (TGA); • Missouri DOT Test Method TM-14 Water/Alcohol Freeze Test; and • Alaska Nordic Abrasion test (ASTM 312). The test is performed to measure hardness of coarse aggregate to be used in surface course HMA. The Alaska Nordic abrasion test is similar to the micro-deval test but uses a larger drum, with three metal strips in the drum. Transportation agencies were asked to report if they used natural (virgin) aggregate sources from other states/provinces. Out of 53 agencies, 83% (41 U.S. DOTs and three Canadian provinces) indi- cated that they used natural (virgin) aggregates from other sources, while 17% (four U.S. DOTs

Aggregate Sources, Recycling, and Blending 17 and five Canadian provinces) reported that they do not. Those agencies that use aggregates from other states or provinces were asked to indicate the reasons for this practice. Figure 2-8 presents the results. Nearly half of the agency respondents indicated that they use natural (virgin) aggregates from other states or provinces due to budgetary or environmental concerns, while one fourth of the agency respondents reported the reason as “the need for a better quality aggregate source.” Half of the agency respondents stated other reasons for using aggregates from other sources. Some of these reasons are as follows: • Adding competition to the market, lowering prices, and improving quality. • Due to request from source near the state border. • Location of the job site being close to the border of other state. • Contractor’s decision to use sources in nearby states after meeting the quality requirements set by the project state. • Not having any aggregate quarries in the state. • Producers propose and use out-of-state sources. 2.4.2 Quality Related Source Properties of RAP RAP particles are created from the impact removal and/or reprocessing of existing asphalt layers. RAP particles contain a combination of asphalt and aggregates with varying degrees of 66% 81% 51% 75% 55% 15% 66% 23% 79% 47% 92% 49% 13% 19% 31 38 24 35 26 7 31 11 37 22 43 23 6 9 0 10 20 30 40 0% 20% 40% 60% 80% 100% Resistance to weathering by Na2SO4/MgSO4 Soundness Resistance to degradation, e.g., Los Angeles Abrasion test Resistance to polishing and degradation, e.g., Micro- Deval test Percent deleterious materials Plasticity properties such as Atterberg limits (LL, PI) of portion passing No. 40 (0.42 mm) Mineralogical composition Cleanliness, e.g., Sand Equivalent test Harmful clay content, e.g., Methylene Blue test Particle shape properties such as angularity, surface texture, flatness and elongation Durability, e.g., freeze-thaw resistance test Specific gravity and absorption Alkali Silica Reactivity or Alkali Carbonate Reactivity (ASR and/or ACR) Expansion from hydration reaction Other Number of Responses Percentage of Survey Respondents 47 survey respondents Figure 2-7. Quality-related natural (virgin) aggregate properties collected from aggregate producers by transportation agencies.

18 Aggregate Quality Requirements for Pavements coating and morphology. Particle size and shape properties, amount of asphalt coating the RAP particles, and the binder content of the RAP are among the important engineering properties that control the quality of this material. Since a principal constituent of RAP is its mineral aggregates, the overall chemical composition of RAP is similar to that of the mineral aggregates. RAP can be used as a granular base or subbase material in pavement structures (Bennert et al. 2000), in asphalt mixes (Copeland 2011), and in concrete mixes (Huang et al. 2005). When RAP is used as an aggregate in an unbound application, the volume of asphalt in the RAP reduces the specific gravity and the presence of asphalt seals most of the surface area of the particles. These characteristics result in a lower unit weight and a reduced amount of water needed to achieve the desired compaction level. The National Asphalt Pavement Association (NAPA) lists as standard test methods AASHTO T 308, Standard Method of Test for Determining the Asphalt Binder Content of Hot Mix Asphalt (HMA) by the Ignition Method, and ASTM D6307, Standard Test Method for Asphalt Content of Asphalt Mixture by Ignition Method, for recovering aggregates and calculat- ing the binder content in RAP. These tests are considered quick and easy to perform but require information about a correction factor for aggregates. Moreover, the asphalt binder content of the RAP to replace virgin binder in asphalt mixes containing RAP can be determined by using AASHTO T 164 or ASTM D2172/D2172M, Standard Test Methods for Quantitative Extraction of Asphalt Binder from Asphalt Mixtures. The use of propyl bromide and other nonhalogenated solvents is also mentioned by NAPA (National Asphalt Pavement Association 2015). The theoretical maximum specific gravity of RAP can be determined by using the standard test method of AASHTO T 209 (R2016), Standard Method of Test for Theoretical Maximum Specific Gravity (Gmm) and Density of Hot-Mix Asphalt (HMA). For RAP recovery, the standard specifications used are AASHTO R 59 or ASTM D1856, Standard Specification for Recovery of Asphalt Binder from Solution by Abson Method. If the viscosity of the extracted binder needs to be measured, the standard specifications to be followed are AASHTO T 202 or ASTM D2171/ D2171M, Standard Method of Test for Viscosity of Asphalts by Vacuum Capillary Viscometer. The transportation agencies were asked to indicate if they used RAP materials in the construction of pavement layers and also to report which quality-related source properties RAP materials were screened for. The findings are summarized in Figure 2-9. It was also found that most of the agencies examine the residual asphalt binder content of RAP sources. Moreover, specific gravity, residual asphalt binder property, and source properties of the aggregates were reported as the common 34% 25% 48% 52% 15 11 21 23 0 10 20 30 40 0% 20% 40% 60% 80% 100% Due to lack of adequate aggregate sources Due to the need for a better quality aggregate source Due to economical/environmental concerns Other Number of Responses Percentage of Survey Respondents 44 survey respondents Figure 2-8. Reasons why one agency may use natural (virgin) aggregate from other states or provinces.

Aggregate Sources, Recycling, and Blending 19 quality-related properties that are investigated by respondent agencies. Some agencies mentioned other quality-related properties associated with utilization of RAP that are listed as follows: • Effective specific gravity backcalculated from theoretical maximum specific gravity (Rice method) and asphalt content. • Decant, PI of fine portion. 2.4.3 Quality-Related Source Properties of RCA RCA is produced by crushing old concrete from sidewalks, pavements, and curbing and build- ing slabs into smaller pieces. According to the American Concrete Pavement Association (ACPA 2009), RCA is often very angular with higher water absorption capacity, lower specific gravity, lower strength, and lower abrasion resistance than conventional construction aggregates. Due to these properties, specific provisions might be needed for using RCA in pavement applications, especially in concrete mixes. AASHTO MP 16 and American Concrete Institute (ACI) 555R-01 can be used to check RCA performance in concrete pavements (AASHTO 2015, ACI 2001, Reza and Wilde 2017). ASTM C33/C33M, Standard Specification for Concrete Aggregates, is used by ACI Commit- tee 555 to check the quality of RCA used in concrete layers. For coarse aggregates, this standard provides procedures and ranges for tests of soundness, deleterious substances, and alkali-silica and alkali-carbonate reactions (ACI 2001). For RCA absorption, AASHTO MP 16 refers to the use of AASHTO T 85, Standard Method of Test for Specific Gravity and Absorption of Coarse Aggregate, which is similar to ASTM C27, Standard Test Method for Density, Relative Density (Specific Gravity), and Absorption of Coarse Aggregate (AASHTO 2015). If required by an agency or a project, ASTM C1567 provides guidance to check the effective- ness of alkali silica reactivity (ASR) mitigation. Additionally, for ensuring appropriate resistance of coarse and fine RCA particles to freezing and thawing, ASTM C33 and ACI 555R-01 lists ASTM C88, Standard Test Method for Soundness of Aggregates by Use of Sodium Sulfate or 4% 38% 88% 46% 58% 13% 13% 4% 27% 2 18 42 22 28 6 6 2 13 0 10 20 30 40 50 0% 20% 40% 60% 80% 100% Do not utilize RAP Source properties of the aggregate Residual asphalt binder content Residual asphalt binder property Specific gravity (bulk) Polishing properties, e.g., Micro-Deval loss Percent deleterious/contamination Freeze-thaw resistance Other Number of Responses Percentage of Survey Respondents 48 survey respondents Figure 2-9. Quality-related source properties for RAP materials examined by transportation agencies for pavement construction purposes.

20 Aggregate Quality Requirements for Pavements Magnesium Sulfate (ACI 2001). However, FHWA Technical Advisory Circular T 5040.37 men- tions using ASTM C666, Standard Test Method for Resistance of Concrete to Rapid Freezing and Thawing, for locations where freeze-thaw resistance needs to be checked (FHWA 2007). Similarly, the AASHTO MP 16 (2015) document lists several tests based on the expected distresses in the constructed concrete. For example, when D-cracking is a potential distress, AASHTO MP 16 proposes using AASHTO T 161, Standard Method of Test for Resistance of Concrete to Rapid Freezing and Thawing, as the test procedure (AASHTO 2015, Reza and Wilde 2017). For RCA aggregates where alkali-silica reactions and alkali-carbonate reactions are possible, AASHTO MP 16 states the uses of AASHTO T 303, Accelerated Detection of Potentially Delete- rious Expansion of Mortar Bars due to Alkali-Silica Reaction, and ASTM C586, Standard Test Method for Potential Alkali Reactivity of Carbonate Rocks as Concrete Aggregates (Rock-Cylinder Method), as standard test methods, respectively (Reza and Wilde 2017). ACI 555R-01 lists plaster, asphalt, wood, soil, gypsum, plastic, and rubber as some of the contaminants of RCA that can cause reductions in concrete compressive strength. Transportation agencies also reported whether they used RCA in pavement layer construction and also to indicate which quality-related source properties they screen for RCA sources. Figure 2-10 summarizes the results. About 40% of the respondents (15 U.S. DOTs and four Canadian provinces) reported that they did not use RCA in pavement construction. Moreover, Los Angeles Abrasion (LAA) loss, percent deleterious/contamination, and specific gravity (bulk)/absorption were found to be the most common quality properties of RCA that are generally screened by agencies. Only 9% of the agencies stated that they identified ASR for RCA sources. Some agencies also indicated that they checked the following quality properties related to RCA: • Aggregate durability index, AASHTO T 210 • Decant, organic impurities • Florida’s limerock bearing ratio test, similar to continuously reinforced concrete • Plasticity of fine particles • Washington State DOT degradation test 40% 17% 32% 17% 9% 21% 6% 9% 32% 19 8 15 8 4 10 3 4 15 0 10 20 30 40 50 0% 20% 40% 60% 80% 100% Do not utilize RCA Source properties of the aggregate Los Angeles Abrasion loss Specific gravity (bulk)/Absorption) Polishing properties, e.g., Micro-Deval loss Percent deleterious/contamination Freeze-thaw resistance Alkali Silica Reactivity (ASR) Other Number of Responses Percentage of Survey Respondents 47 survey respondents Figure 2-10. RCA properties examined by transportation agencies.

Aggregate Sources, Recycling, and Blending 21 2.4.4 Quality-Related Source Properties of Artificial/Byproduct Aggregates Common byproduct materials used in pavement applications are SFS, BFS, and QB. Ferrous slags (e.g., SFS and BFS) are obtained from the production of steel. SFS is a nonmetallic product consisting essentially of calcium silicates and ferrites combined with fused oxides of iron, aluminum, manganese, calcium, and magnesium that are developed simultaneously with steel in a basic oxygen furnace (BOF), electric arc furnace (EAF), or open-hearth furnace (OH). During the period of cooling and hardening from its molten state, BFS can be cooled in several ways to form any of several types of BFS products, including granulated slag (slag cement), air-cooled slag, pelletized or expanded slag, and air-cooled blast furnace quote. NCHRP Synthesis 435: Recycled Materials and Byproducts in Highway Applications: Volume 5: Slag Byproducts (Stroup-Gardiner and Wattenberg-Komas 2013a) lists some standards used to charac- terize SFS and BFS with their typical ranges for the engineering properties. Some of these standards that are also commonly performed on virgin aggregates listed previously include ASTM C127 and ASTM C128 for density, specific gravity and absorption, ASTM D6928 for micro-deval, ASTM C88 for sodium sulfate soundness, and ASTM C131 for LAA (Stroup-Gardiner and Wattenberg-Komas 2013a). Additional tests for BFS and SFS listed in NCHRP Synthesis 435: Volume 5 include • ASTM C566, Standard Test Method for Total Evaporable Moisture Content of Aggregate by Drying • ASTM D3319, Standard Practice for the Accelerated Polishing of Aggregates Using the British Wheel • AS 1141.22, Australian Test Method for Wet/Dry Strength Variation Aggregate quarry processes such as blasting, crushing, and screening of coarser grade aggre- gates produce byproduct mineral fine materials, commonly known as QB or quarry dust. QB are typically less than 6 mm (0.25 in.) in size and consist of mostly coarse, medium, and fine sand-sized particles, as well as small fractions of clay and silt-sized particles. Gradation of quarry fines can vary depending on the rock type quarried. Kalcheff and Machemehl (1980) investigated average particle size distributions for different types of rocks (flint, trachyte, limestone, diabase, granite, BFS, and quartzite). They reported similar trends for particle distributions from differ- ent rock types, with particles passing the No. 200 (0.075 mm) sieve ranging from 6% to 12%. According to Dumitru et al. (2001), mineralogical tests such as X-ray diffraction analysis should be conducted to determine the compositions of secondary minerals and to quantify amounts of harmful content that can be detrimental in some applications of QB. Many standard test meth- ods conducted on QB are similar to those conducted on fine virgin aggregates discussed above. NCHRP Synthesis 435: Recycled Materials and Byproducts in Highway Applications: Volume 4: Mineral and Quarry Byproducts summarizes the common standard tests conducted on mineral and QB materials (Stroup-Gardiner and Wattenberg-Komas 2013b). See also MIST project report (Manning 2004). Lightweight aggregates are used for replacement of normal-weight fine and coarse aggregates in pavement applications. LWAs can come from different sources and are manufactured from different materials, including expanded shale, expanded clay, expanded slate, expanded perlite, expanded slags, and waste fly ash with plastic, among others (Byard and Schindler 2010, Mallick et al. 2004). They are especially used in concrete applications to reduce internal stresses from autogenous shrinkage cracking (Byard and Schindler 2010). LWAs are also used for seal coat and chip seal applications. Kim et al. (2013) compared the performance of chip seal pave- ments containing different types of LWA or granite aggregates and concluded that pavements constructed with LWA had a higher initial mean profile depth but a higher drop rate in mean profile depth with traffic loading. Rahman et al. (2012) reported that the retention rate of LWA in chip seals was dependent on the source properties and the type of emulsion. According to

22 Aggregate Quality Requirements for Pavements the Expanded Shale, Clay and Slate Institute (ESCSI), LWA use in chip seals, compared with conventional aggregates, results in safer, cheaper, and longer lasting seal coats. This then results in better skid resistance, with higher skid numbers for LWAs used in chip seal and HMA appli- cations when compared with the case with limestone aggregates (ESCSI 2017). Browning et al. (2011) reported that using prewetted vacuum-saturated LWA in concrete exhibited less shrinkage after 1 year as compared with concretes with normal weight aggregates without a significant reduction in compressive strength. Higher curing time was also reported to result in less shrinkage (Browning et al. 2011). Mallick et al. (2004) reported enhancement for stiffness, rutting resistance, and susceptibility to moisture damage for HMA mixtures with up to 15% synthetic LWA (made with plastic and waste fly ash) by weight. Mixes with higher quantities of LWA (20%), on the other hand, were reported to have high absorption (Mallick et al. 2004). A similar trend for reduction in plastic shrinkage cracking was reported by Henkensiefken et al. (2010) for fine, manufactured expanded shale, and prewetted LWA volume replacement up to 33%. Deshpande and Hiller (2012) concluded that helium pycnometry could estimate the absorption of manufactured LWA more accurately than the standard ASTM C127 test with 24 hours of immersion, due to the higher ability of the helium gas to fill the smaller voids when compared with water (Deshpande and Hiller 2012). AASHTO M 195 and ASTM C330 standards cover specifications and procedures for LWA used in structural concrete. Some of the standards that can be performed for testing LWA, which are also applicable to virgin aggregates, include ASTM D6928 for micro-deval, ASTM C88 for sodium sulfate soundness, and ASTM C131 for LAA. Due to the LWA high porosity and the long duration it takes to fill all the voids when immersed in water, ASTM C127 and ASTM C128 standards for density, specific gravity, and absorption are not commonly used for LWA. Information was collected from transportation agencies to determine whether artificial/ byproduct aggregates such as SFS and BFS were used in pavement layer construction and also which quality-related source properties were examined for these materials. The results are pre- sented in Figures 2-11 and 2-12. It was found that more than half the survey respondents do not use SFS or BFS in pavement construction. Agencies that used SFS or BFS reported that specific 55% 17% 5% 41% 10% 19% 17% 23 7 2 17 4 8 7 0 10 20 30 40 0% 20% 40% 60% 80% 100% Do not utilize Chemical composition Mineralogical properties Specific gravity (bulk) Polishing and degradation properties, e.g., Micro-Deval loss Freeze-thaw resistance Expansion properties Number of Responses Percentage of Survey Respondents 42 survey respondents Figure 2-11. SFS properties examined by transportation agencies.

Aggregate Sources, Recycling, and Blending 23 gravity, freeze-thaw resistance, and expansion properties were the common quality properties that were tested or screened. Note that expansion properties here refer to general expansion regardless of use in PCC or HMA. High contents of free calcium and magnesium oxides in SFS expand when hydrated (Brand and Roesler 2015). Only nine agencies reported that they check mineralogical properties and chemical compositions of SFS and BFS sources. Alabama DOT and Texas DOT require both the SFS and BFS materials to undergo all tests that a virgin coarse aggregate would to be considered for source approval. Furthermore, nine agencies reported other/additional quality properties associated with SFS and BFS that are listed below: • SFS: LAA, soundness, wear, specific gravity, and absorption • BFS: Flat and elongated (F&E) ratio, LAA, wear, soundness, specific gravity, and absorption. 2.4.5 Restrictions for Utilizing Recycled and/or Artificial/Byproduct Aggregates Transportation agencies were asked to report any restrictions that they have put in place regarding the use of recycled and/or artificial/byproduct aggregates in pavement construction. The findings are summarized in Table 2-2. There are some technical and environmental issues associated with using recycled and/or artificial/byproduct aggregates in pavement construction. RCA contains calcium hydroxide from the original cement hydration reaction. It is water soluble and when water flows through an RCA stabilized base/subbase, some calcium hydroxide will dissolve into water. Eventually, it interacts with atmospheric carbon dioxide to form calcium carbonate, precipitating out of solution and leaving deposits where the water flows. This can cause problems if the precipitate clogs up components of a pavement drainage system such as filter fabrics, drainage pipes, and outlets (ACPA 2009). The volumetric instability of SFS granular base (due to lime and dolomite hydration reactions) may result in expansive reactions (Chesner et al. 1998). BFS is brittle and easy to breakdown when subjected to impact loading. No correlation between LAA test for BFS and its degradation 52% 16% 5% 39% 11% 25% 14% 23 7 2 17 5 11 6 0 10 20 30 40 0% 20% 40% 60% 80% 100% Do not utilize Chemical composition Mineralogical properties Specific gravity (bulk) Polishing and degradation properties, e.g., Micro-Deval loss Freeze-thaw resistance Expansion properties Number of Responses Percentage of Survey Respondents 44 survey respondents Figure 2-12. BFS properties examined by transportation agencies.

24 Aggregate Quality Requirements for Pavements performance in field has been reported. Therefore, some agencies do not consider the degra- dation requirements based on LAA testing for utilization of BFS [Recycled Materials Resource Center (RMRC) 2008]. Leachate from BFS poses a potential risk to the environment and remains an aesthetic concern. Therefore, the odor and discoloration of water need to be checked and the properties of leachate from BFS such as pH and redox conditions need to be determined (Chesner et al. 1998). 2.5 Blending to Meet Aggregate Quality Requirements NCHRP Synthesis 445: Practices for Unbound Aggregate Pavement Layers states that pavement projects using granular layers will have to be sustainable and cost effective by (1) making more effective use of locally available materials through beneficiation and use of marginal aggre- gate materials, where appropriate; (2) increasing effective use of RCA and reclaimed asphalt pavement (RAP); and (3) targeting long life and improvement in pavement performance (Tutumluer 2013). Bennert et al. (2000) evaluated RCA and RAP for resilient modulus and permanent deforma- tion trends and compared performance with a dense-graded aggregate base course (DGABC) material commonly used in roadway base applications in New Jersey. Both RCA and RAP were Transportation Agency Restriction Considering Quality Concerns for Using RAP, RCA, SFS, or BFS Arkansas RCA: Only used in unbound base courses. British Columbia RCA: Only for base and subbase. RAP: Only for asphalt pavement. Florida RAP: Minimum 4% AC and mix must meet Florida DOT specifications. Minimum 2.5% AC for coarse portion above No. 4 sieve if fractionated. RCA: Not permitted in new concrete pavement. In addition, RCA is not permitted in new asphalt pavement unless the concrete came from a Florida DOT project. Illinois RAP and SFS: Not allowed in concrete pavement. Kentucky RAP: Only allowed as part of the aggregate blend for asphalt layers. SFS: Only allowed in asphalt surface layers. Maryland RCA: Toxicity characteristic leaching procedure may be required. Specific gravity and LAA are performed routinely. BFS: Only in concrete to remediate. ASR is an issue in concrete. Michigan SFS: Not permitted in asphalt or concrete pavement. BFS: Not permitted in concrete pavements. Nebraska RCA: Not used in PCC or AC. New Hampshire RAP: Dust-to-asphalt ratio as identified in AASHTO M 323; stockpiles must be tested for gradation and asphalt content every 1,000 tons during manufacture. New Jersey RCA: Allowed only in subbase. North Carolina RCA: Limited to use in base applications. Have not allowed to be used in concrete mixes. Ohio SFS: Only allowed in intermediate mixes. BFS: Allowed in asphalt surface and intermediate mixes. Oklahoma RCA: Only as an unbound aggregate base course layer. Ontario SFS: Not allowed in HMA. Pennsylvania RCA: Only used for subbase and fill. SFS and BFS: Only for subbase and fill. Utah RCA: Not allowed for concrete use. Virginia RCA: Not used as subbase or aggregate base when any subsurface drainage system is present except when crushed hydraulic cement concrete is cement stabilized. Wisconsin SFS and BFS: May be used as base but must be blended with virgin aggregate. Yukon Does not use RCA, BFS, or SFS. Table 2-2. Restrictions on the use of RAP, RCA, SFS, or BFS.

Aggregate Sources, Recycling, and Blending 25 mixed at various percentages with the DGABC to evaluate whether an optimum mix blend could be formulated. They reported that RAP, RCA, and DGABC-blended materials obtained higher resilient modulus values than the currently used virgin aggregates, while RCA mixed samples resulted in the lowest amount of permanent deformation. Similarly, Arulrajah et al. (2012) reported that in terms of usage in pavement subbases, RCA and waste rock have geotech- nical engineering properties equivalent or superior to those of typical quarry granular subbase materials. Other research has reported similar findings for the use of RAP, RCA, or blends with virgin aggregates for unbound applications (Arulrajah et al. 2013) and cement-treated applica- tions (Mohammadinia et al. 2014). Kazmee and Tutumluer (2015) evaluated the field performance of blended RCA and RAP test sections, mixed at a ratio of 3:2, respectively, and tested for construction platform and low- volume road applications using accelerated pavement testing. Laboratory evaluations showed lower abrasion loss for this blend, compared with other virgin materials inspected. The RCA–RAP blend exhibited a relatively higher field modulus compared with other constructed test sections and accumulated the least amount of permanent deformation after a specified number of wheel passes (Kazmee and Tutumluer 2015). A recent study by Qamhia et al. (2017a) evaluated construction platforms and subbase applications of blended materials, QB, and primary crusher run aggregates (PCR), having a top size of 6 in. to improve stability. To study the packing of the QB with the PCR and deter- mine the optimum quantities of QB to be mixed, a laboratory study was conducted using a steel box with dimensions conforming to ASTM recommendations. The large aggregates were added in one or two equal lifts, and the QB materials were evenly spread on the surface and then compacted. Preliminary test results from the accelerated pavement testing (a short-term field test) showed satisfactory performance of the 25% QB blend by weight of the PCR con- structed in two lifts and 17% QB blend constructed in one lift. Test sections survived 20,000 load repetitions of a 455/55R22.5 super-single tire without accumulating more than 76-mm or 3-in. rutting, using a wheel load of 10 kips and a tire pressure of 110 psi (Qamhia et al. 2017a, 2017b, 2017c). Blending of different aggregate sources for Portland cement applications is also a common practice to achieve the required properties/quality when marginal or recycled aggregates are used. Reza and Wilde (2017) suggested blending RCA aggregates with high quality conven- tional aggregates to mitigate the higher likelihood of alkali-silica reactions and issues with freeze-thaw due to the use of RCA. They proposed using “mechanical interlock blending” or “belt blending” to ensure the uniformity of mixing for the different aggregate sources. Brand et al. (2012) evaluated the use of fractionated RAP (FRAP) in concrete mixes, blended with virgin coarse aggregates in ratios of 0%, 20%, 35%, and 50% by weight of the coarse aggregates. The FRAP was found to reduce the concrete (compressive, split tension, and flexural) strength, elastic and dynamic modulus, and the unit weight but increase the workability of the mixes. Such blending application aims to use the ever-increasing quantities of RAP being produced due to rehabilitation activities while maintaining the quality of the produced concrete. Results indicated acceptable paving concrete could be produced for up to 50% FRAP replacement (Brand et al. 2012). Agencies can have different requirements for blending. For example, the state of Minnesota’s standard specification book mentions that if the magnesium sulfate soundness requirement of <15% loss for coarse aggregates used in Portland cement concrete applications is not met after five cycles for one aggregate source, then blending of materials from two sources is not permitted for achieving this requirement (Minnesota DOT 2005). For HMA, Michigan DOT determines that the aggregate blend used in the mix meet specifications for the content of soft particles and sand equivalent minimum requirements (Michigan DOT 2014). Kansas DOT, on the other

26 Aggregate Quality Requirements for Pavements hand, does not allow blending any two aggregate sources for mineral fillers used in HMA mixes and limits the usage to one mineral filler source per HMA design (Kansas DOT 2015). Out of the 53 agencies who responded, 77% (35 U.S. DOTs and six Canadian provinces) blend aggregate from different sources while 23% (10 U.S. DOTs as well as Alberta and Prince Edward Island provinces) do not. Reasons for blending aggregates are shown in Figure 2-13. As indicated, most of the agencies blend aggregates to meet either asphalt or concrete mixture design requirements. Additionally, 63% of the agencies indicated that they blend aggregates to improve quality. Nearly half of the agencies blend aggregates to use marginal aggregate sources. Some agencies also reported the following other reasons for blending aggregates: • Conserving pure silica sand sources for concrete pavement and Surface Aggregate Classifica- tion “A” for asphalt pavements. • Supporting batch plants that are not near pit sources. Information related to different types of materials that are generally used for blending in order to meet aggregate quality requirements for constructing pavement layers is presented in Figure 2-14. Most of the transportation agencies blend virgin aggregates with either other virgin materials or with recycled aggregates, for example, RAP, RCA, or artificial aggregates. In addition, 28% of the agencies blend virgin aggregates with QB. 2.6 Special Provision for Using Nontraditional or Marginal Aggregate Sources Nontraditional large size aggregates might be pit-run, quarry-run, or crusher-run materials that may be used for different purposes. A research study recently conducted at the Illinois Center for Transportation evaluated the performance of large-size virgin and recycled aggregate materials used as subgrade replacement or granular subbase over weak subgrade soils. The findings clearly showed that penetration of these large rocks, referred to as aggregate subgrade by Illinois DOT, into very soft subgrade improved the weak subgrade soils and 63% 39% 93% 68% 46% 32% 22% 26 16 38 28 19 13 9 0 10 20 30 40 0% 20% 40% 60% 80% 100% To improve the quality To meet target gradation specification for unbound subbase/base course To meet target gradation specification for asphalt mixture design To meet target gradation specification for concrete mixture design To utilize marginal or out of specification aggregate sources To utilize quarry byproduct Other Number of Responses Percentage of Survey Respondents 41 survey respondents Figure 2-13. Reasons stated for blending aggregates by transportation agencies.

Aggregate Sources, Recycling, and Blending 27 95% 38% 80% 28% 3% 38 15 32 11 1 0 10 20 30 40 0% 20% 40% 60% 80% 100% Virgin + Virgin Virgin + Marginal Virgin + Recycled (RAP or RCA or artificial aggregates) Virgin + Quarry Byproduct Other Number of Responses Percentage of Survey Respondents 40 survey respondents Figure 2-14. Materials used for blending to meet aggregate quality requirements. effectively established a stable working platform for pavement construction (Kazmee and Tutumluer 2015). Transportation agencies were asked to indicate if they had any special provision for using nontraditional or marginal aggregate sources such as recycled glass, recycled aggregates, QB, and large size aggregates for pavement construction. The results are summarized in Figure 2-15, which shows that only 26 agencies out of 53 survey participants have specifications or provisions for utilizing alternative materials. Note that out of eight agencies that marked “other,” three agencies, that is, Arizona and New Brunswick and Yukon provinces, reported that they do not have any standard for using nontraditional or out-of-specification aggregate sources. The other five agencies and their considerations are listed in Table 2-3. 23% 15% 35% 31% 12% 31% 31% 6 4 9 8 3 8 8 0 10 20 0% 20% 40% 60% 80% 100% Number of Responses Percentage of Survey Respondents 26 survey respondents Marginal (out of specification) virgin aggregate Marginal (out of specification) recycled aggregate Quarry byproduct (less than 6 mm in size) Filter aggregates, e.g., for pavement interlayers Recycled glass, as a base material Other Nontraditional aggregate, e.g., large size virgin or recycled aggregate, e.g., above 1.5-in. top size or primary crusher run size material Figure 2-15. Agencies with specifications or special provisions for constructing pavement layers with nontraditional and/or out-of-specification aggregate sources.

28 Aggregate Quality Requirements for Pavements Transportation Agency Restriction Considering Quality Concerns Alaska Up to 10% by weight crushed glass (cullet) smaller than 3/8 in. may be blended uniformly with natural soil-aggregate material before project delivery and placement. Blended material should meet the gradation specification requirements of the layer in question (base, subbase, and so forth). British Columbia Must meet specifications. New Jersey Glass application has stopped after federal bonus payment was removed. Use 15% RAP in surface course and 25% in base course. Pennsylvania For asphalt and concrete aggregates, quality requirements need to be met before being incorporated. How and with what that is done are proposed in a quality control plan and approved/rejected. Washington State See Washington State DOT standard specification 9-03.21(1)C and 9-03.21(1)E. Table 2-3. Agencies with certain procedures for using nontraditional and/or out-of-specification aggregate sources.