Aggregate Quality Requirements for Pavements (2018)

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44 4.1 Introduction This chapter presents information related to the procedures used by transportation agencies to approve or certify aggregate sources. Agencies often consider various criteria or guidelines to allow a certain type of aggregate source to be used in construction of a specific pavement layer. Appropriate classification and use of different aggregate materials—for example, by considering different aggregate quality classes when building bound and unbound pavement layer applications— will dictate the end performance under different loading and environmental conditions. The frequency of aggregate approval and the number of quality classes defined for construction of individual pavement layers are discussed in this chapter. 4.2 Methods Used to Approve Aggregate Sources Methods of approving an aggregate source vary depending on the agency practices. Transpor- tation agencies commonly provide lists of pre-approved/approved sources of aggregates for use in pavement construction on their website. Approving an aggregate source may require that certain aggregate materials pass some quality requirements from that aggregate source. For example, Kansas DOT requires both DOT laboratory inspection and contractor’s inspection of aggregates, and the contractor is held responsible in case any material fails the quality tests at the job site (Kansas DOT 2017). Oklahoma DOT requires both a geologic assessment report and several labo- ratory test results for each coarse aggregate material, and supplemental testing is often necessary to consider an aggregate source to be qualified for use in Oklahoma DOT construction projects (Oklahoma DOT 2009). The source approval procedure is often straightforward. For example, New Jersey DOT procedure for aggregates source approval starts with a request from the aggregate producer. The request includes full contact information, rock type, and the reporting of the New Jersey DOT standard test results for several aggregate samples collected over several weeks with tests performed by the producer’s laboratory or an independent laboratory. The agency office in charge, often the bureau of materials at agency offices, evaluates the sources, obtains several samples (minimum of three) from the source for testing over a period of several weeks, and then approves the source if the three samples comply with the specifications of the agency. New Jersey DOT also has acceptance requirements at the project level for aggregates used in concrete and HMA mixes and an approved mix design (New Jersey DOT 2015). For unsurfaced pavements, the FHWA’s 2015 gravel roads, construction, and maintenance guide proposes following state specifications to ensure that approved high quality aggregates are being received from the different sources. For example, a “Class I Surface Aggregate” with C H A P T E R 4 Procedures for Approving Aggregate Sources

Procedures for Approving Aggregate Sources 45 specific state quality requirements shall be tested to qualify for the surface course use for gravel roads (FHWA 2015). The methods used by transportation agencies to approve aggregates are summarized in Figure 4-1 above. The results show that 72% of the responding agencies use their own laborato- ries for approving aggregates, and 30% of the responding agencies do not have an approved list and test aggregates prior to use on every major construction job. Only Maryland, New Mexico, and North Dakota state DOTs reported that they use “Pre-approval—Option B,” which is collecting aggregate source property data from a third party certified aggregate testing lab on a periodic basis. Furthermore, only eight agencies (15%) mentioned other methods for approving aggregate sources, as listed in Table 4-1. 30% 30% 6% 72% 15% 16 16 3 38 8 0 10 20 30 40 50 0% 20% 40% 60% 80% 100% No Approved List of Aggregates: Aggregates are tested prior to use on every major pavement construction job. Preapproval – Option A: Aggregate source property data are collected from producer and checked for approval on a periodic basis. Preapproval – Option B: Aggregate source property data are collected from a third-party certified aggregate testing laboratory on a periodic basis. Approval by Agency Lab: Aggregate samples collected from producer and tested at your agency lab for approval on a periodic basis. Other Number of Responses Percentage of Survey Respondents 53 survey respondents Figure 4-1. Methods used by transportation agencies to approve aggregates. Description of Aggregate Approval Procedure Meet specifications; contractor may select a source other than specified. Qualified aggregate material source list is maintained for asphalt mixture aggregate, concrete aggregate, and base aggregate. Contractor must reapply every 2 years. Pre-approval samples are collected and tested at our lab to add source to the list of approved materials. Site visits and collection of samples are conducted annually at each source to ensure quality. Acceptance samples are collected on material supplied to state projects and tested at our labs. Source approval is performed by department; subsequent physical testing is performed by independent laboratories and reviewed by the department. Pre-approved but still tested on a project level basis at frequencies specified in material sampling guide. Sources are prequalified to businesses by meeting personnel testing and quality control requirements. Aggregates are approved through an initial battery of tests and a continued tonnage and risk-based approach. Active commercial sources are routinely tested year round; irregularly used sources are tested prior to paving. Agency British Columbia Idaho Kentucky Montana Nebraska Ohio Oregon Saskatchewan Ministry does not have any requirement for approval of aggregate source. Regular QA testing is done during the course of project. Table 4-1. Alternative aggregate approval procedures.

46 Aggregate Quality Requirements for Pavements Those agencies that indicated that they used Preapproval Option A or B or Approval by Agency Lab (see Figure 4-1) were asked to report how often they performed the approval process. The results are presented in Figure 4-2. It was found that 47% of the agencies do the approval once a year, while 18% of the agencies perform the approval based on the producer request. Only Maryland DOT indicated approval of aggregate sources once every 3 years. Eleven agen- cies (32%) mentioned other frequencies for approving aggregate sources, as listed in Table 4-2. 4.3 Aggregate Quality Classes Agencies have established aggregate quality classes associated with the use of aggregate material in a certain pavement layer application. For example, Indiana DOT has three general ratings for fine aggregates: A5 is for natural sands approved in all pavement applications; B5 is for applica- tions that allow usage of manufactured sands or fine aggregates; and G5 is for fine aggregates that 47% 12% 3% 18% 32% 16 4 1 6 11 0 10 20 30 0% 20% 40% 60% 80% 100% Once a year Once every two years Once every three years Based on producer requests Other frequencies Number of Responses Percentage of Survey Respondents 34 survey respondents Figure 4-2. Frequency of aggregate approval by agencies using Preapproval Option A or B or Approval by Agency Lab. Frequency for Approving Aggregates Once during the preconstruction/design phase of the specific project. Before material used on a project or historical results of alternative sources. Approved aggregate sources remain in effect unless mine commits an infraction. Certification of products is continuously based on QA program 23CFR627B. Once on design–build project. Department performs testing for initial source approval and boundary extensions. As indicated in material sampling guide, every 3,000-ton or 6,000-ton depending on mix design. Once a year but AASHTO T 161 “Freeze thaw testing of concrete aggregates” is performed less frequently. Twice per year. Contractors are required to submit producer or third party testing from state certified labs prior to start of any project. 1 year for quarry spalls, riprap, scour, and rock for rock walls and 5 years for mineral aggregate and concrete aggregate. Quality concern sources are on stockpile approval. Agency Alaska British Columbia Florida Manitoba Montana Nebraska Oklahoma Tennessee Utah Washington State Wisconsin Every 3 years for quarries and every 5 years for pits. Table 4-2. Alternative frequency and conditions for approving aggregate sources.

Procedures for Approving Aggregate Sources 47 are not approved for usage (Indiana DOT 2017a). Indiana DOT has more detailed quality class designations for coarse aggregates, including Class AP (highest quality aggregates that meet the specifications for any use), Class AS, and Classes A, B, C, D, and F. Indiana DOT also requires an absorption value measurement not to exceed 5% for those aggregates to be classified in Classes AP, AS, A, B, or C (Indiana DOT 2017a). Refer to Appendix D, in which there are links provided to detailed aggregate specifications as well as material approval lists for different agencies. Minnesota DOT divides the virgin aggregates used for base and surface applications into seven quality classes. These are Classes 1, 2, 3, 4, 5, 5Q, and 6. The different quality requirements are listed in Table 4-3 (Table 3138-1, Minnesota DOT 2016). For recycled materials used in base and surface applications, Minnesota DOT also defines six quality classes, that is, Classes 1, 3, 4, 5, 5Q, and 6. The requirements for these classes are listed in Table 4-4 [as defined by Minnesota DOT 2016 (Table 3138-2)]. Michigan DOT has published comprehensive requirements for different aggregate classes qualified as coarse aggregates, open-graded aggregates, and dense-graded aggregates. Table 4-5 *Material crushed from quarries is considered crushed material. Note: NA indicates not applicable, which means that no limit or quality measurement has been specified for that property. Quality Requirements for Virgin Materials Requirements 1 and 2 (%) 3 and 4 (%) 5 and 5Q (%) 6 (%) Max Shale, if No. 200 7 % by mass Max Shale, if No. 200 7 % by mass Minimum crushing requirements* Maximum Los Angeles Rattler loss from carbonate quarry rock Maximum insoluble residue for the portion of quarried carbonate aggregates passing the No. 200 sieve NA NA NA 40 10 10.0 7.0 NA 40 10 10.0 7.0 10 40 10 7.0 7.0 15 35 10 Class Table 4-3. Aggregate classes and quality requirements for surface and base virgin aggregates. Table 4-4. Aggregate classes and quality requirements for surface and base recycled aggregate materials, as specified by Minnesota DOT.

(a) (b) (c) (d) (e) (f) (g) (h) (i) (j) (k) (l) (m) Material Series/ Class Crushed Material, % min (MTM 117) Los % max, Los Angeles Abrasion (MTM 102) Soft Particles, % max (MTM 110) Sum of Soft Particles and Chert, % max (MTM 110) Sum of Coke and Coal Particles, % max (MTM 110) Flat and Elongated Particles, ratio- % max (ASTM D4791) Freeze-Thaw Dilation, % per 100 cycle max (MTM 115) (d) Freeze-Thaw Dilation, % per 100 cycles max (MTM 115) (d) Chert, % max (MTM 110) Slag (a)Gravel, Stone, and Crushed Concrete Coarse Aggregates Open-Graded Aggregates Dense- Graded Aggregates (1) Table 4-5. Aggregate classes and limits on physical properties for gravel, crushed stone, crushed concrete aggregate, and slag in Michigan.

Procedures for Approving Aggregate Sources 49 presents a summary of the different aggregate classes and the physical property and quality requirements for different aggregate materials. Limits and physical properties are included for gravel, crushed stone, crushed concrete aggregate, slag materials, and other types of aggregates. Physical properties include LAA loss, freeze-thaw dilation, percentage crushed materials, and flat and elongated ratio of particles (Michigan DOT 2009). In total, 18 agencies indicated that they have established at least one quality class for one of the following aggregate types: coarse and fine virgin aggregates, RAP, RCA, SFS, and BFS. Table 4-6 lists the different number of quality classes established for each aggregate type by the 18 transportation agencies. Agencies that are not listed in Table 4-6 did not report any defined quality classes for the types of aggregates mentioned above. For further details related to the number of quality classes listed in Table 4-6, refer to Appendix D, in which the links to agency specifications are provided. 4.4 Aggregate Quality Classes for Pavement Layer Applications The survey results showed that 18 U.S. DOTs and five Canadian provinces classify aggregate quality based on utilization of aggregate in a certain pavement layer. Subsequently, those 23 agencies identified individual pavement layers and the associated aggregate quality class numbers required by their agencies. The results related to each pavement layer are presented in the following subsections. 4.4.1 Asphalt Surface Coarse Minnesota DOT divides aggregates into five different quality classes for concrete applications. Four classes (Class A through Class D) are for virgin aggregates, based on the degree of crushing Type of Aggregate r Agency Alaska Alberta Florida Illinois Indiana Kentucky Mississippi Montana Nevada New York New Brunswick Ontario Oregon Pennsylvania Tennessee Wisconsin Wyoming Yukon RAP - - One Two One - - One One One - Two - One - One - - RCA - - One Four - - - One - One - - - One - One - - SFS - - - One - One - - - One - - - One Four One - - BFS - - - Four - One - - - One - - - One - One - - Note: Hyphens indicate zero (0) quality class for certain types of aggregate. - - One Three One Three Three One One One Two Five One Five - One Five Three Fine Virgin Five Five One Four One Five Three One One One Two Five One Three Fou One Five Three Coarse Virgin Table 4-6. Number of quality classes used by transportation agencies for different aggregate types.

50 Aggregate Quality Requirements for Pavements and the geological origin, and the fifth class (Class R) is for recycled concrete aggregates. Qual- ity requirements for aggregates used in concrete include limits on gradations and quantities of deleterious materials. Quality tests with which the aggregates must comply include LAA loss (<40%), freeze-thaw loss after 16 cycles (<12%), and magnesium sulfate soundness loss for the coarse fractions after five cycles (<15%) (Minnesota DOT 2005, 2016). For HMA layers, Iowa DOT specifies five different aggregate classes (Types 1–5), mainly based on frictional characteristics. Aggregates within Type 1 have the best frictional properties and have the highest hardness values, ranging from 7 to 9 on Mohs scale of hardness. Type 1 includes sev- eral synthetic aggregates, Type 2 natural aggregates include crushed quartzite, Type 3 is crushed gravel with >40% igneous and metamorphic rocks, and Types 4 and 5 are crushed dolomite and limestone, respectively. Iowa DOT accepts the use of any aggregate material of the five types in their HMA mixes unless otherwise specified in the contract to use a certain class of aggregates (Iowa DOT 2016). Furthermore, Iowa DOT also divides aggregates for HMA into two broader types: Type A and Type B. Type A is for higher volume road applications and surface coarse mixtures (Iowa DOT 2017). Note that some agencies do not allow (or limit) the utilization of a certain aggregate for construction of a specific pavement layer. For example, Minnesota DOT specifications do not allow the use of crushed concrete aggregates or RCA in wearing surface courses (Minnesota DOT 2016). Participating transportation agencies reported the required quality classes for different types of aggregates used for the construction of asphalt surface course. The results are summarized in Table 4-7. The number of quality classes established by different agencies have been listed in Table 4-6. 4.4.2 Asphalt Base Course Iowa DOT has two general classes for aggregates in HMA: Type A (higher quality) and Type B (lower quality). The use of Type B aggregates is listed for asphalt base course applications as well as Agency Type of Aggregate Fine Virgin Coarse Virgin RAP RCA SFS BFS Alaska - A, B, Superpave - - - - Alberta - Designation 1 Classes 10,12.5, 16 mm - - - - Illinois B B B B B B Indiana - B - - B B Ontario RAP from Category D and Category E mixes - - - Tennessee 1, 2, 3, 4 1, 2, 3, 4 Texas - Surface Aggregate Classification A or B as indicated by plans - - - - -- - - Yukon Sand mix Paving Aggregate 12.5 mm - - - - Note: Hyphens indicate no quality class has been established for certain types of aggregates. Refer to Appendix D, in which links to agency specifications are provided. Traffic Categories A, B, C, D, E Traffic Categories A, B, C, D, E Table 4-7. Quality classes for aggregates used in asphalt surface course.

Procedures for Approving Aggregate Sources 51 for low-volume and secondary roads (Iowa DOT 2017). Minnesota DOT permits the use of sev- eral different aggregate classes for plant-mixed asphalt mixtures, including (1) Class A crushed igneous rocks; (2) Class B crushed rock other than Class A; (3) Class C natural or partially crushed gravel; (4) Class D crushed natural gravel; (5) Class E mixture of two or more aggregates from Classes A, B, and D; (6) steel slag in a proportion of 25% or less of the total aggregates mix; (7) RAP, for which the quality must be checked for the final angularity of the mixture, Los Angeles Rattler test (Minnesota DOT Procedure 1210) and soundness (Minnesota DOT Procedure 1219), spall materials and lumps (Minnesota DOT Procedure 1219), as well as insoluble residue test (Minnesota DOT Procedure 1221); and (8) RCA or crushed concrete with a proportion not exceeding 50% of the total mix (Minnesota DOT 2016). Participating transportation agencies reported the required quality classes for fine and coarse virgin aggregates, RAP, RCA, SFS, and BFS used for construction of asphalt base course. The results are summarized in Table 4-8. Note that the description for each aggre- gate quality class can be found in the relevant agency specifications with links provided in Appendix D. 4.4.3 Asphalt Surface Treatment Different agencies have specifications for the quality of the aggregate materials used for asphalt surface treatments. For example, Michigan DOT specifies requirements for fine aggregates used in HMA and surface treatments. For slurry seals, Michigan DOT requires using a fine aggregate material complying to their 2FA gradation band. The fines can consist of crushed material, gravel, slag, or a blend and must have LAA loss not exceeding 45%. For microsurfacing, Michigan DOT allows using 2FA or 3FA fine gradations and the fine aggregate material must have an angularity index exceeding 4, a sand equivalent exceeding 60%, and LAA loss not exceeding 45% (Michigan DOT 2009). Virginia DOT uses emulsion asphalt and aggregates conforming to the No. 8 or No. 8P gradations for surface treatment (Virginia DOT 2012). For microsurfacing treatments, Minnesota DOT specifies the use of Class A aggregates or taconite tailings. A blend of Class A and Class B aggregates is also allowed if the quantity of material passing the 3/8-in. (9.5 mm) sieve and retained on sieve mesh No.16 (1.18 mm) is 90% or greater by weight from the Class A aggregates, taconite tailings, or a mixture of both (Minnesota DOT 2016). The quality requirements for durability for aggregates used for microsurfacing are listed in Table 4-9, which is adapted from Minnesota DOT (2016). Agency Type of Aggregate Fine Virgin Coarse Virgin RAP RCA SFS BFS Alaska - A, B, Superpave - - - - Alberta - Designation 1 Class 25 mm - - - - Illinois C C C C - C Indiana - D - - D D Ontario Traffic Categories A, B, C, D, E Traffic Categories A, B, C, D, E - - - - - - - -Yukon Fines between 3%– 10% Granular "A" Note: Hyphens indicate no quality class has been established for certain types of aggregates. Refer to Appendix D, in which the links to agency specifications are provided. Table 4-8. Quality classes for aggregates used in construction of asphalt base course.

52 Aggregate Quality Requirements for Pavements Participating transportation agencies reported the required quality classes for fine and coarse virgin aggregates, RAP, RCA, SFS, and BFS used for construction of asphalt surface treatment. The results are summarized in Table 4-10. 4.4.4 Portland Cement Concrete For coarse aggregates used in PCC, AASHTO M 80, Standard Specification for Coarse Aggre- gate for Hydraulic Cement Concrete, divides aggregates into five classes from A to E, based on abrasion resistance, sodium sulfate soundness, quantities of clay lumps and deleterious materials, and the percentage of fines passing No. 200 (0.075 mm) sieve. The specification proposes using the Types A through C for concrete bridge decks and Types B through D for concrete pavements, based on the degree of exposure to weathering (severe, moderate, or negligible), with higher quality aggregates used for higher severity of weathering. These five classes of aggregates and the quality requirements for each class are given in Table 4-11 (AASHTO 2013). For RCA aggregates used in hydraulic cement concrete applications, including PCC pavements, AASHTO MP 16 divides the RCA aggregates into three classes based on the maximum allow- able quantities of deleterious materials found in the aggregates. These three classes are listed in Table 4-12 (Reza and Wilde 2017, adapted from AASHTO 2015), and the quantities of Microsurfacing Aggregate Durability Requirements (originally Table 3139-11 in specification) Tests on Aggregate Test Requirement, % Sand equivalent AASHTO T 176 60 30 25 Abrasion and resistance* AASHTO T 96 Soundness (using MgSO4)+ AASHTO T 104 * Use Grade C for Type 3 material. Use Grade D for Type 1 and Type 2 material. + Perform the soundness test on the Class B aggregate of the blend, if applicable. ≥ ≤ ≤ Table 4-9. Minnesota DOT aggregate quality requirements for aggregates used in microsurfacing applications. Agency Type of Aggregate Fine Virgin Coarse Virgin RAP RCA Alaska A to G gradations - - Alberta - Seal Coat - Designation 3 Classes 12.5A, 12.5B, 12.5C, and 16 mm - - Illinois B B - B Indiana - B - - Ontario Gradation Classes 2, 4 Gradation Classes 1, 2, 3, 4, 5, 6 - - Texas - Surface Aggregate Classification A or B as indicated by plans - - - - - - SFS - - B B - - BFS - - B B - - Yukon Fines not more than 5% Coarse aggregate 20 mm Note: Hyphens indicate no quality class has been established for certain types of aggregates. Refer to Appendix D, in which links to agency specifications are provided. Table 4-10. Quality classes for aggregates used in construction of asphalt surface treatment.

Procedures for Approving Aggregate Sources 53 deleterious substances for each quality class were previously listed in Table 3-8 (AASHTO 2015). Similarly, Butler et al. (2013) proposed to divide RCA aggregates into four quality classes, in which an aggregate material must meet at least three of the four quality property requirements to be associated with a class, as listed in Table 4-13 (adapted from Butler et al. 2013). Iowa DOT divides coarse aggregates used in concrete pavements into three classes based on durability levels as Class 2, Class 3, and Class 3i, in which Class 3i is the most durable one. Dura- bility of aggregates is determined based on performance monitoring and results of laboratory testing (Iowa DOT 2016). Minnesota DOT divides aggregates used in PCC into five classes. Class A includes crushed aggregates from quarries with rock types such as gneiss (metamorphic rock), quartzite, and granite. Class B typically covers all non-Class A crushed rocks. Class C includes natural and partially crushed gravels, while Class D is a mixture of two or more classes of aggregates. Finally, Class R is for RCA aggregates and requires a concrete engineer to decide on the possibility and proportioning of these aggregates that can be used in PCC applications (Minnesota DOT 2016). Participating transportation agencies reported the required quality classes for fine and coarse virgin aggregates, RAP, RCA, SFS, and BFS used for construction of PCC slabs. The results are Class Designation Maximum Allowable (%) Coal and Lignite Abrasionb Sodium Sulfate Soundness (5 Cycles)c A 2.0 3.0 3.0 1.0d 0.5 50 12 B 3.0 3.0 5.0 1.0d 0.5 50 12 C 5.0 5.0 7.0 1.0d 0.5 50 12 D 5.0 8.0 10.0 1.0d 0.5 50 12 E 10.0 — — 1.0d 1.0 50 — Note: SSD = saturated surface dry. Dashes represent that no limit has been established. a These limitations apply only to aggregate in which chert appears as an impurity. They are not applicable to gravels that are predominantly chert. Limitations on soundness of such aggregate must be based on service records in the environment in which they are used. b Crushed air-cooled, BFS is excluded from the abrasion requirements. The unit mass (by rodding or jigging) of crushed air-cooled, BFS shall be not less than 1,120 kg/m3 (70 lb/ft3). The grading of slag used in the unit mass test shall conform to the grading to be used in the concrete. Abrasion loss of gravel, crushed gravel, or crushed stone shall be determined on the test size or sizes most nearly corresponding to the grading or gradings to be used in the concrete. When more than one grading is to be used, the limit on abrasion loss shall apply to each. c The allowable limits for soundness shall be 18% if magnesium sulfate is used. If the salt to be used is not designated, the aggregate will be acceptable if it meets the indicated limit for either sodium sulfate or magnesium sulfate. d In the case of crushed aggregates, if the material finer than the 75-µm (No. 200) sieve consists of the dust fraction, essentially free from clay or shale, this percentage may be increased to 1.5. Clay Lumps and Friable Particles Chert (≤ 2.40 Specific Gravity SSD)a Sum of Clay Lumps, Friable Particles, and Chert (≤ 2.40 Specific Gravity SSD)a Material Finer than 75-µm (No. 200) Sieve Table 4-11. Aggregate classes and aggregate quality requirements for coarse aggregates used in concrete pavements. Table 4-12. Aggregate classes for RCA in concrete applications.

54 Aggregate Quality Requirements for Pavements summarized in Table 4-14. Note that the description for each aggregate quality class can be found in the relevant links to agency specifications presented in Appendix D. 4.4.5 Aggregate Base Course The following properties of recycled aggregates have been identified by NCHRP Report 598 as relevant to their use in unbound pavement layers (Saeed 2008): (1) shear strength, (2) California bearing ratio (CBR), (3) cohesion and angle of internal friction, (4) resilient or compressive modulus, (5) density, (6) permeability, (7) frost resistance, (8) durability index, and (9) resistance to moisture damage (Saeed 2008). California DOT (Caltrans) specifies the use of two aggregate classes for base course materials according to Class 2 and Class 3 designations. The classes are based on aggregate gradation, Numbera Aggregate Property Class A1 Class A2 Class B Class C 1 Relative density (oven dry) Refer to Part 2 of Table 4-13 below or to the Canadian Standards Association CAN/CSA A23.1-09 (2009) 2.3 and above 2.0 to 2.3 Below 2.0 2 % adhered mortarb 50 and below Above 50 Above 50 3 Absorption (%) 3 or less 3 to 6 6 or greater 4 Abrasion loss (micro- deval method) (%) 19 to 22 22 to 25 Above 25 a To be designated as Class A2, B, or C, at least three of the four aggregate properties tested must fall within the range defined by a specific class. b Determined by using thermal treatment method (Fathifazl 2008) or other suitable method that ensures complete removal of adhered mortar. Coarse Aggregate Property Natural Aggregates RCA-1 RCA-2 RCA-3 Adhered mortar content (%)a na 46 56 50 Relative density (SSD) 2.71 2.48 2.43 2.41 Relative density (oven dry) 2.67 2.36 2.28 2.22 Oven-dry rodded bulk density (kg/m3)b 1,744 1 ,536 1,458 1,395 Absorption % (by mass) 1.52 4.66 6.15 7.81 Absorption rate (h)c 2 4 7 8 Abrasion resistance (%)d 11.9 15.1 22.1 25.0 Aggregate crushing value 18.2 23.1 26.0 28.5 Note: na = not applicable; natural aggregates contain no adhered mortar. a Based on the thermal expansion method proposed by De Juan and Gutiérrez (2009). b To convert from kg/m3 to lb./yd3 multiply values by 1.69. c Time required for the aggregate to reach its SSD condition. d Abrasion loss was determined using the micro-deval method (percent mass loss). Table 4-13. Proposed aggregate property limits for RCA classes considering performance. Agency Type of AggregateFine Virgin Coarse Virgin RAP RCA SFS BFS Illinois A A - A - A Indiana - AP - - AP AP Tennessee - Types 1, 2, 3, 4 Types 1, 2,3, 4 - - - Note: Hyphens indicate no quality class has been established. Refer to Appendix D, in which links to agency specifications are provided. Table 4-14. Quality classes for aggregates used in Portland cement concrete pavements.

Procedures for Approving Aggregate Sources 55 compliance to certain operational criteria, property ranges, and contract compliance for the sand equivalent, durability index, and R-value tests. Caltrans requires that the durability tests be conducted on the untreated aggregates for eligibility of use in treated base applications. For example, the grain size distribution and the quality requirements for a Class 2 aggregate used for base materials are listed in Table 4-15 (Caltrans 2015). Similarly, Colorado DOT identifies seven classes for aggregates used in base layers, with Aggregate Base Course (ABC) Class 6 being the predominant class of aggregates used through- out the state. According to Colorado DOT, the PI for aggregates used in ABC layer does not exceed 6. Additionally, the LL values for aggregates used in ABC do not exceed 36 for aggregate Class 1, 2, and 3 or Class 30 for aggregate Classes 4 through 7 (Locander 2009). Locander (2009) also proposed that the requirements for RAP used as a base course material had to be similar to those of Classes 4 through 7, with a PI of less than 6 and an LL lower than 30. NCHRP Synthesis 598 studied the feasibility of using RAP as a construction material in unbound layers. Laboratory tests conducted on blends of RAP and other virgin aggregates indicated that based on toughness, stiffness, and monotonic triaxial testing-based strength characteristics, RAP was identified as a suitable construction material in unbound aggregate layers for high-volume roads in nonfreezing conditions. Repeated load triaxial tests indicated the suitability of RAP in unbound layers for moderate traffic levels in nonfreezing temperatures (Saeed 2008). Different agencies have different regulations regarding the usage of RAP and its proportioning in unbound aggregate layers (Hoppe et al. 2015). Hawaii DOT allows use for up to 10% RAP by weight in base course layers but requires information on the composition of the stockpiled RAP before usage and limits the maximum quantity of deleterious materials in RAP to 3%. Composi- tion might be known for previous DOT projects, and when the composition is unknown, samples are collected to check the gradation and the quantities of deleterious materials. Minnesota DOT allows a maximum of 3.5% of binder content in aggregate base layers (determined by extraction). Percentage Passing 1-1/2" Maximum 3/4" Maximum Contract Compliance Contract Compliance Operating Range Sieve Size 2" 1-1/2" 1" 3/4" No. 4 No. 30 No. 200 Operating Range 100 90–100 - 50–85 25–45 10–25 2–9 100 87–100 - 45–90 20–50 6–29 0–12 - - 100 90–100 35–60 10–30 2–9 - - 100 87–100 30–65 5–35 0–12 Test for Aggregate Quality Requirement Operating Range Contract Compliance Resistance (R-value, minimum) - Sand equivalent (minimum) 25 Durability index (minimum) - 78 22 35 Note: Hyphens indicate no quality class has been established. Table 4-15. Aggregate gradation and quality requirements for a Class 2 aggregate material used as a base course material by California DOT (Caltrans).

56 Aggregate Quality Requirements for Pavements Texas DOT and Washington State DOT allow a maximum of 20% RAP by weight in unbound aggregate bases. Texas DOT allows up to 50% RAP by weight in cement-treated base layers. Wisconsin DOT has no limits on the quantity of RAP used in 1¼-in. and 3-in. top size dense- graded aggregate base layers. Participating transportation agencies reported the required quality classes for fine and coarse virgin aggregates, RAP, RCA, SFS, and BFS used for construction of aggregate base course. The results are summarized in Table 4-16. Note that the description for each aggregate quality class can be found in the relevant links to agency specifications presented in Appendix D. 4.4.6 Aggregate Subbase Course Michigan DOT is one of the few agencies that provide specifications for aggregate materi- als used in subbase layers. Michigan DOT requires aggregates used for subbase layers to pass their permeability design considerations and does not allow materials with cementitious properties or foundry sands to be used as a subbase or fill material (Michigan DOT 2009). As summarized by Hoppe et al. (2015), Hawaii DOT allows usage for up to 25% RAP by weight in unbound subbase layers but requires information on the composition of the stockpiled RAP before use and limits the maximum quantity of deleterious materials in RAP to 5%. Idaho Transportation Department allows mixing RAP with other granular materials for up to 50:50 proportion and limits the maximum RAP aggregates size to 3 in. (76 mm). Iowa DOT allows up to 50% of RAP by weight in unbound aggregate subbases. Minnesota DOT allows a maximum of 3% of binder content in aggregate subbase (determined by extraction) (Hoppe et al. 2015). Participating transportation agencies reported the required quality classes for fine and coarse virgin aggregates, RAP, RCA, SFS, and BFS used for construction of aggregate subbase course. The results are presented in Table 4-17. Note that the description for each aggregate quality class can be found in the relevant links to agency specifications presented in Appendix D. 4.4.7 Permeable Drainage Layer Kazmierowski et al. (1994) evaluated the field performances of several types of open-graded base course permeable layers, including layers stabilized with 200 and 300 lb/yd3 cement, asphalt stabilized with 1.8% binder content, and unstabilized aggregates. The quality was checked for all the aggregates used with 100% crushed faces. All the layers showed relatively low falling Type of Aggregate Fine Virgin Coarse Virgin - C-1 and D-1 gradations - Designation 2 Class 20, Class 25, and 40 mm - D - D - Granular A, M, or O RAP - - - - - RCA - - D - - SFS - - - D - BFS - - D D - - - - - Agency Alaska Alberta Illinois Indiana Ontario Yukon Fines not more than 6% Granular A Note: Hyphens indicate no quality class has been established. Refer to Appendix D, in which links to agency specifications are provided. Table 4-16. Quality classes for aggregates used in construction of aggregate base course.

Procedures for Approving Aggregate Sources 57 weight deflectometer deflections on top of the drainage layers. These were typically 19 mils for the unstabilized aggregates and 13 mils for the cement-stabilized open-graded drainage layers (Kazmierowski et al. 1994). Michigan DOT allows four classes of granular materials, I through IV, with gradations as listed in Table 4-18 (adapted from Grove 2004), to be used for porous fill materials. Participating transportation agencies reported on the required quality classes for fine and coarse virgin aggregates, RAP, RCA, SFS, and BFS used for construction of permeable drainage pavement layer. The results are summarized in Table 4-19. Although Michigan DOT did not report any quality classes, their aggregate specification lists four different gradation-based classes. Type of Aggregate Fine Virgin RAP RCA SFS BFS - - - - - Agency Alaska Alberta Illinois Indiana Ontario Yukon Fines not more than 8% Coarse Virgin A to E gradations Designation 6 Class 80 or 125 mm D D Granular BI, BII, or BIII Granular B, C, or E - - - - - - - - D - - - - - - D - - - - D D - - Note: Hyphens indicate no quality class has been established. Refer to Appendix D, in which links to agency specifications are provided. Table 4-17. Quality classes for aggregates used in construction of aggregate subbase course. Material Class Total Percent Passing Sieve Size (%) 1 in. (25 mm) I 2 in. (50 mm) 100 0.5 in. (12.5 mm) 45–85 No. 4 (4.75 mm) 20–85 No. 30 (0.595 mm) 5–30 II 2.5 in. (63 mm) 100 60–100 No. 100 (0.149 mm) 0–30 III** IV*** 3 in. (75 mm) 100 100 Loss by Washing* (%) 0–5 0–7 0–10 0–25 * Loss by washing had to be determined on the portion of the sample passing the 1.5-in. sieve. ** Maximum size could be increased to 6 in. if used as peat swamp backfill. *** Could be used only for fill or backfill below the bottom of subbase at locations on the plans or if authorized. Table 4-18. Aggregate gradations for aggregate classes used as a porous fill in Michigan. Type of Aggregate Agency Illinois Indiana Fine Virgin B - Coarse Virgin D D RAP - - RCA D - SFS - D BFS D D Note: Hyphens indicate no quality class has been established. Refer to Appendix D, in which links to agency specifications are provided. Table 4-19. Quality classes for aggregates used in construction of permeable drainage pavement layer.

58 Aggregate Quality Requirements for Pavements 4.4.8 Filter Material for PCC Pavements Permeable subbases are generally constructed as the foundation of concrete pavements by using crushed aggregates with reduced amount of fines. They are often constructed where previ- ous experience has indicated pavement faulting and pumping are observed distresses of concern. Most agencies place a layer of dense graded aggregates between the permeable subbase and subgrade to act as a filter layer (see Figure 4-3) (ACPA 1995). The filter materials used in these layers need to satisfy certain aggregate quality and gradation requirements. Participating transportation agencies reported on the required quality classes for fine and coarse virgin aggregates, RAP, RCA, SFS, and BFS used for construction of filter layer. Illinois DOT reported that they use “quality Class B” for virgin fine aggregates and “quality Class D” for coarse virgin, RCA, and BFS aggregates used in filter layer. Additionally, Alberta province indi- cated that they use “Designation 8 Class 25 mm” for coarse virgin aggregates for the construction of filter layer. Further details about these quality classes can be found in Appendix D, in which the links to agency specifications are provided. Figure 4-3. Filter layer used in permeable subbases as the foundation of concrete pavements.