National Academies Press: OpenBook

Practices for Unbound Aggregate Pavement Layers (2013)

Chapter: Appendix C - Survey Responses

« Previous: Appendix B - Respondent Information
Page 144
Suggested Citation:"Appendix C - Survey Responses ." National Academies of Sciences, Engineering, and Medicine. 2013. Practices for Unbound Aggregate Pavement Layers. Washington, DC: The National Academies Press. doi: 10.17226/22469.
×
Page 144
Page 145
Suggested Citation:"Appendix C - Survey Responses ." National Academies of Sciences, Engineering, and Medicine. 2013. Practices for Unbound Aggregate Pavement Layers. Washington, DC: The National Academies Press. doi: 10.17226/22469.
×
Page 145
Page 146
Suggested Citation:"Appendix C - Survey Responses ." National Academies of Sciences, Engineering, and Medicine. 2013. Practices for Unbound Aggregate Pavement Layers. Washington, DC: The National Academies Press. doi: 10.17226/22469.
×
Page 146
Page 147
Suggested Citation:"Appendix C - Survey Responses ." National Academies of Sciences, Engineering, and Medicine. 2013. Practices for Unbound Aggregate Pavement Layers. Washington, DC: The National Academies Press. doi: 10.17226/22469.
×
Page 147
Page 148
Suggested Citation:"Appendix C - Survey Responses ." National Academies of Sciences, Engineering, and Medicine. 2013. Practices for Unbound Aggregate Pavement Layers. Washington, DC: The National Academies Press. doi: 10.17226/22469.
×
Page 148
Page 149
Suggested Citation:"Appendix C - Survey Responses ." National Academies of Sciences, Engineering, and Medicine. 2013. Practices for Unbound Aggregate Pavement Layers. Washington, DC: The National Academies Press. doi: 10.17226/22469.
×
Page 149
Page 150
Suggested Citation:"Appendix C - Survey Responses ." National Academies of Sciences, Engineering, and Medicine. 2013. Practices for Unbound Aggregate Pavement Layers. Washington, DC: The National Academies Press. doi: 10.17226/22469.
×
Page 150
Page 151
Suggested Citation:"Appendix C - Survey Responses ." National Academies of Sciences, Engineering, and Medicine. 2013. Practices for Unbound Aggregate Pavement Layers. Washington, DC: The National Academies Press. doi: 10.17226/22469.
×
Page 151
Page 152
Suggested Citation:"Appendix C - Survey Responses ." National Academies of Sciences, Engineering, and Medicine. 2013. Practices for Unbound Aggregate Pavement Layers. Washington, DC: The National Academies Press. doi: 10.17226/22469.
×
Page 152
Page 153
Suggested Citation:"Appendix C - Survey Responses ." National Academies of Sciences, Engineering, and Medicine. 2013. Practices for Unbound Aggregate Pavement Layers. Washington, DC: The National Academies Press. doi: 10.17226/22469.
×
Page 153
Page 154
Suggested Citation:"Appendix C - Survey Responses ." National Academies of Sciences, Engineering, and Medicine. 2013. Practices for Unbound Aggregate Pavement Layers. Washington, DC: The National Academies Press. doi: 10.17226/22469.
×
Page 154
Page 155
Suggested Citation:"Appendix C - Survey Responses ." National Academies of Sciences, Engineering, and Medicine. 2013. Practices for Unbound Aggregate Pavement Layers. Washington, DC: The National Academies Press. doi: 10.17226/22469.
×
Page 155
Page 156
Suggested Citation:"Appendix C - Survey Responses ." National Academies of Sciences, Engineering, and Medicine. 2013. Practices for Unbound Aggregate Pavement Layers. Washington, DC: The National Academies Press. doi: 10.17226/22469.
×
Page 156
Page 157
Suggested Citation:"Appendix C - Survey Responses ." National Academies of Sciences, Engineering, and Medicine. 2013. Practices for Unbound Aggregate Pavement Layers. Washington, DC: The National Academies Press. doi: 10.17226/22469.
×
Page 157
Page 158
Suggested Citation:"Appendix C - Survey Responses ." National Academies of Sciences, Engineering, and Medicine. 2013. Practices for Unbound Aggregate Pavement Layers. Washington, DC: The National Academies Press. doi: 10.17226/22469.
×
Page 158
Page 159
Suggested Citation:"Appendix C - Survey Responses ." National Academies of Sciences, Engineering, and Medicine. 2013. Practices for Unbound Aggregate Pavement Layers. Washington, DC: The National Academies Press. doi: 10.17226/22469.
×
Page 159
Page 160
Suggested Citation:"Appendix C - Survey Responses ." National Academies of Sciences, Engineering, and Medicine. 2013. Practices for Unbound Aggregate Pavement Layers. Washington, DC: The National Academies Press. doi: 10.17226/22469.
×
Page 160
Page 161
Suggested Citation:"Appendix C - Survey Responses ." National Academies of Sciences, Engineering, and Medicine. 2013. Practices for Unbound Aggregate Pavement Layers. Washington, DC: The National Academies Press. doi: 10.17226/22469.
×
Page 161
Page 162
Suggested Citation:"Appendix C - Survey Responses ." National Academies of Sciences, Engineering, and Medicine. 2013. Practices for Unbound Aggregate Pavement Layers. Washington, DC: The National Academies Press. doi: 10.17226/22469.
×
Page 162
Page 163
Suggested Citation:"Appendix C - Survey Responses ." National Academies of Sciences, Engineering, and Medicine. 2013. Practices for Unbound Aggregate Pavement Layers. Washington, DC: The National Academies Press. doi: 10.17226/22469.
×
Page 163
Page 164
Suggested Citation:"Appendix C - Survey Responses ." National Academies of Sciences, Engineering, and Medicine. 2013. Practices for Unbound Aggregate Pavement Layers. Washington, DC: The National Academies Press. doi: 10.17226/22469.
×
Page 164
Page 165
Suggested Citation:"Appendix C - Survey Responses ." National Academies of Sciences, Engineering, and Medicine. 2013. Practices for Unbound Aggregate Pavement Layers. Washington, DC: The National Academies Press. doi: 10.17226/22469.
×
Page 165
Page 166
Suggested Citation:"Appendix C - Survey Responses ." National Academies of Sciences, Engineering, and Medicine. 2013. Practices for Unbound Aggregate Pavement Layers. Washington, DC: The National Academies Press. doi: 10.17226/22469.
×
Page 166
Page 167
Suggested Citation:"Appendix C - Survey Responses ." National Academies of Sciences, Engineering, and Medicine. 2013. Practices for Unbound Aggregate Pavement Layers. Washington, DC: The National Academies Press. doi: 10.17226/22469.
×
Page 167
Page 168
Suggested Citation:"Appendix C - Survey Responses ." National Academies of Sciences, Engineering, and Medicine. 2013. Practices for Unbound Aggregate Pavement Layers. Washington, DC: The National Academies Press. doi: 10.17226/22469.
×
Page 168
Page 169
Suggested Citation:"Appendix C - Survey Responses ." National Academies of Sciences, Engineering, and Medicine. 2013. Practices for Unbound Aggregate Pavement Layers. Washington, DC: The National Academies Press. doi: 10.17226/22469.
×
Page 169
Page 170
Suggested Citation:"Appendix C - Survey Responses ." National Academies of Sciences, Engineering, and Medicine. 2013. Practices for Unbound Aggregate Pavement Layers. Washington, DC: The National Academies Press. doi: 10.17226/22469.
×
Page 170
Page 171
Suggested Citation:"Appendix C - Survey Responses ." National Academies of Sciences, Engineering, and Medicine. 2013. Practices for Unbound Aggregate Pavement Layers. Washington, DC: The National Academies Press. doi: 10.17226/22469.
×
Page 171

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

144 aPPENDIX C Survey Responses COMPILaTION OF SURVEY RESPONSES NCHRP PROJECT 20-5 TOPIC 43-03 PRaCTICES FOR UNBOUND aGGREGaTE PaVEMENT LaYERS Background and Purpose The Transportation Research Board (TRB) is preparing a Synthesis on “Practices for Unbound Aggregate Pavement Layers.” This is being done for NCHRP, under the sponsorship of the American Association of State Highway and Transportation Offi- cials (AASHTO), in cooperation with the Federal Highway Administration (FHWA). Granular aggregate base and subbase layers are very important in pavement construction and performance. Properly designed and constructed bases have the potential to improve pavement performance and longevity while also addressing today’s issues like the costs of other pavement materials, the need to save energy, and to reduce green-house gas emissions associated with the construction and reconstruction of pavements. A synthesis is being undertaken concerning the full range of granular aggregate base and subbase issues for both flexible and rigid pavement systems. States have diverse specifications and construction practices for unbound aggregate pavement layers; sharing this information among the states will most likely lead to better design and construction practices. Information is being gath- ered through literature review, survey of the members of the AASHTO Highway Subcommittee on Materials (including Canadian Provinces), and selected interviews. Gaps in knowledge and current practices will be noted, along with research needs to address these gaps. This synthesis will ultimately provide information for harmonization of specifications (par- ticularly on a regional basis) to ultimately benefit both States and material producers without adverse impacts on pavement performance. This questionnaire is being sent to state departments of transportation. Your cooperation in completing the questionnaire will ensure the success of this effort. If you are not the appropriate person at your agency to complete this questionnaire, please forward it to the correct person. General: Use of Unbound Aggregate Base and Subbase Layers 1) Is it common practice for your agency to incorporate unbound aggregate layers into the design and construc- tion of pavement structures? (Note that this survey focuses on unbound aggregate layers in asphalt, concrete and composite pavements only, and does not include unbound aggregate layer applications in unsurfaced pavements and gravel roads). If your answer to this question is “No,” you do not need to complete this survey. Please include comments in the textbox regarding why your agency does not prefer to construct unbound aggregate layers as pave- ment base and subbase courses [46] Yes - 100% [0] No - 0% 46 Respondents 2) What types of unbound aggregate layers are commonly constructed by your agency? (Please check all that apply.) [44] Base course - 95.7% [30] Subbase course - 65.2% [11] Open graded drainage layer - 23.9% [21] Pavement working platforms for subgrade stability applications - 45.7% 46 Respondents

145 3) What types of pavement structures designed and constructed by your agency commonly incorporate unbound aggregate layers? (Please check all that apply.) [46] Flexible pavements (comprising hot mix or warm mix asphalt surface layer) - 100% [32] Rigid pavements (comprising portland/hydraulic cement concrete slabs) - 69.9% [14] Rehabilitated pavements (asphalt overlay over concrete, etc.) - 30.4% [10] Others such as composite pavements, inverted pavements, etc. (please specify) - 21.7% 46 Respondents “Others” responses • All of our pavements have had a subbase beneath them since at least the 1950s. • Composite pavements • Foamed Asphalt base (FASB) • Have done one inverted pavement, but are considering more. • Inverted pavement • We have one inverted pavement project underway right now • Composite (listed 3 times) • Composite bases with a layer of crushed stone over a soil cement layer 4) What primary functionalities are unbound aggregate layers intended to serve in pavement systems designed and constructed by your agency? (Please check all that apply.) [43] Dense graded base courses as primary structural layers - 93.5% [11] Open graded layers under rigid pavements for uniform support and providing drainage - 23.9% [24] Pavement construction platforms to protect weak subgrade layers from excessive rutting under heavy construction equipment loading - 52.2% [4] Others (please specify): - 8.7% 46 Respondents “Others” responses • Control expansion • Gravel Subbase is most commonly used • On a geotextile or geogrid for pavement construction platform • These are the main three, but the first is the primary use, with occasional uses for the other two. Category 1: Material Selection and Construction Practices 5) How frequently does your agency check the acceptance of materials obtained from commonly used and/or approved aggregate sources? [18] Prior to the use on every major construction project - 39.1% [2] More than twice every year - 4.3% [1] Twice every year - 2.2% [5] Once every year - 10.9% [3] Less than once every year - 6.5% [17] Other (please explain): - 37% 46 Respondents “Others” responses • 1/2,000 tons on every project • Acceptance is done on delivered materials on every major project • Aggregate base is approved by stockpile to be used in each project. • Gradation and density every 2500 tons • QA every 10 days interval during production and delivery to the project site • QC/QA on each project • Subbase material is placed in stockpiles and every pile is sampled and tested.

146 • The aggregate base is checked for acceptance for any project that has least 500 cu. yd or more. • Soundness and durability are done annually, gradations and densities are performed every 1,000 CY • Aggregates are accepted from a Certified Aggregate Producer. INDOT audits these plants on an annual basis. • QA on a project basis—aggregate sources are glacio-fluvial deposits and often a source is used infrequently. • Aggregate soundness is annual. Other properties are at the start of the project and typically every 2000 tons thereafter. • Once a year for contractor furnished sources—Make state leased sources available to the contractor, dig test pits, perform quality tests, and make information available to contractors before the pit or quarry is opened. • Unbound aggregate is tested under ODOT certification program before shipment to the jobsite for gradation. Source materials are quality testing from once to 4 times a year. • Quarries are qualified annually or biennially depending on the characteristics of the materials, and then accep- tance samples are taken from the roadway during construction. • All aggregate sources and each material from a source are sampled and requalified every two years. • Once the source is tested and approved for durability, we run gradation and deleterious materials acceptance samples approx. every 1,000 cu. yards of material. 6) What tests are used by your agency for evaluating quality aspects of virgin aggregate materials for pavement base and subbase applications? (Please check all that apply) [26] Na2SO4/MgSO4 Soundness Test - 56.5% [39] Los Angeles Abrasion and/or Micro Deval Test - 84.8% [43] Sieve Analysis - 93.5% [30] Percent Deleterious Materials - 65.2% [22] Other (please indicate): - 47.8% 46 Respondents “Others” responses • Absorption and Specific Gravity • Absorption and Specific Gravity, by either T84/85 or by TP77 • Atterberg Plasticity Index • Freeze Thaw • Idaho IT-15 Idaho Degradation • LAR & -#200 Insoluble Residue • Limerock Bearing Ratio (LBR) • Liquid Limit, Fracture Face, CBR, Dry-rodded Weight • PI • Petro Number • Plastic Index • Plasticity Index, Fractured Coarse Aggregate Particles • R-Value • Sand equivalent, durability, R value • Thin & Elongated, Crushed Fragments, & Unit Weight • Volume Swell (MT-305) • WSDOT Degradation Test, Sand Equivalent • Washington Degradation • Atterberg limits • Plasticity, unconfined freeze-thaw, permeability • ODOT TM 208 degradation test. It checks the soundness of aggregate in wet conditions by agitating crushed aggregate with bubblers under water, and then performing a sand equivalency type evaluation. • Texas Triaxial strength, Plasticity Index with liquid limit separate, wet-ball mill (hardness), aggregate type (morphology) 7) Does your agency permit the use of uncrushed aggregates in pavement base and subbase applications? [20] Yes - 43.5% [20] No - 43.5% [6] Other (please explain): - 13% 46 Respondents

147 “Others” responses • A minimum of 30% fractured coarse aggregate is required. • Natural rough surfaced gravel • Subbase only • Allowed in subbase but not in base • Only with a stabilized sand clay gravel material • Spec Requirement: Aggregates shall consist of Granular material of which 30% of the particles retained on the No. 4 sieve shall contain one or more fractured faces. 8) What is the maximum aggregate particle size (Dmax) in inches allowed by your agency in the following con- structed unbound aggregate layers? 46 respondents [44] Dense graded base: ¾ of the lift thickness (1 agency) 1 in. (11 agencies) 1.5 in. (21 agencies) 1.75 in. (1 agency) 2 in. (4 agencies) 2 in. for graded aggregate base; 3.5 in. for coquina shell base; 1.5 in. for sand-clay base (1 agency) 2.5 in. max is allowed, but 1 in. max is almost always used (1 agency) 3 in. (2 agencies) 3.5 in. (1 agency) 4 in. (1 agency) [36] Dense graded subbase ¾ of the lift thickness (1 agency) 0.75 in. (1 agency) 1 inch (1 agency) 1.5 in. (11 agencies) 1.75 in. (1 agency) 2-in. (8 agencies) 2.5 in. (1 agency) 3 in. (5 agencies) 3 in. in the top of the layer, 4 in. if a lower layer (1 agency) 4 in. (2 agencies) 5 in. (1 agency) 5.9 (150 mm) (1 agency) 6 in. (2 agencies) [16] Open graded base as drainage layers 0.375 in. (1 agency) 0.75 in. (3 agencies) 1 in. (4 agencies) 1.5 in. (2 agencies) 2 in. (2 agencies) 2.25 in. (1 agency) 3 in. (1 agency) 8 in. (1 agency) N/A (1 agency) [12] Open graded subbase as drainage layers 0.375 in. (1 agency) 0.75 in. (1 agency) 1 in. (3 agencies) 1.5 in. (2 agencies) 2.25 in. (1 agency)

148 3 in. (1 agency) 4 in. (1 agency) 8 in. (1 agency) N/A (1 agency) [4] Other (please list) Break run 6 in. (1 agency) Dense graded top course - 0.5 in. (1 agency) N/A (2 agencies) 9) What is the maximum amount of fines (material finer than 0.075 mm or passing sieve No. 200) allowed by your agency for aggregates to be used for unbound aggregate base and subbase course applications? 46 respondents [44] Dense graded base (% fines) 5 (2 agencies) 6 (1 agency) 7 (1 agency) 7.5 (1 agency) 8 (6 agencies) 9 (1 agency) 10 (8 agencies) 11 (2 agencies) 12 (11 agencies) 13 (1 agency) 15 (2 agencies) 18 (2 agencies) 20 (1 agency) None—typ. 10–20% (1 agency) Silicate aggregates—11%, carbonate aggregates—15% (1 agency) specification state “well graded to dust” (1 agency) 12% for granite-derived or recycled concrete graded aggregate; 20% for marine limestone-derived graded aggregate; 30% for coquina shell base; 33% for sand-clay base (1 agency) Up to 20% in theory. However, fines are controlled by Sand Equivalency testing and a statement “of the fraction passing the 1/4 in. sieve, 50% to 60% shall pass the No. 10 sieve.” We are in the initial stages of adding a No. 200 sieve wash requirement. (1 agency). [35] Dense graded subbase (% fines) 6 (2 agencies) 7 (1 agency) 8 (4 agencies) 9 (1 agency) 10 (7 agencies) 12 (3 agencies) 13 (1 agency) 15 (6 agencies) 18 (2 agencies) 20 (1 agency) 25 (1 agency) 34 (1 agency) 10% (Class 4 & 5), 15% (Class 6) (1 agency) Fines are limited by a maximum 10% passing the #100 sieve (1 agency) None—typically 10–20% (1 agency) Not Specified (1 agency) Silicate aggregates—11%, carbonate aggregates—15% (1 agency) [17] Open graded base/subbase as drainage layers (% fines) 1.5 (1 agency) 2 (4 agencies)

149 3 (2 agencies) 5 (4 agencies) 7 (1 agency) 10 (1 agency) 5% max passing #4 (1 agency) 3% passing the #100 sieve (1 agency) N/A (1 agency) Not specified but typical (1 agency) 10) Does your agency specify different allowable percent fines (material finer than 0.075 mm or passing sieve No. 200) for aggregates having nonplastic and plastic fines? [1] Yes (please give the specified values below) - 2.2% [1] Base, Nonplastic (%): 8% fines [0] Base, Plastic (%) [0] Subbase, Nonplastic (%): [0] Subbase, Plastic (%): [45] No - 97.8% 46 Respondents 11) What is the maximum value of plasticity index (PI) allowed by your agency for the fines fraction of aggregate materials to be used in the following unbound pavement layers? 46 respondents [44] Dense graded base: 0 (5 agencies) 3 (2 agencies) 4 (1 agency) 5 (1 agency) 6 (18 agencies) 6 for graded aggregate base and coquina base; 9 for sand-clay base (1 agency) 7 (1 agency) 8 (1 agency) 10 (1 agency) 12 (1 agency) 15 (1 agency) AASHTO M147 (1 agency) LL (1 agency) N/A (4 agencies) No specification (3 agencies) SE 40 minimum (1 agency) We have no PI requirement. However, the sand equivalency of “not less than 30” has helped eliminate plastic fines (1 agency) [33] Dense graded subbase: 0 (5 agencies) 4 (1 agency) 5 (3 agencies) 6 (11 agencies) 8 (1 agency) 9 (1 agency) 12 (1 agency) 15 (1 agency) LL (1 agency) N/A (3 agencies) No specification (3 agencies) SE 35 minimum (1 agency) We have no PI requirement. However, the sand equivalency of “not less than 25” has helped eliminate plastic fines. (1 agency)

150 [12] Open graded base as drainage layers: 0 (2 agencies) 2 (1 agency) 6 (3 agencies) LL (1 agency) N/A (3 agencies) No specification (2 agencies) [7] Open graded subbase as drainage layers: 0 (2 agencies) 6 (1 agency) LL (1 agency) N/A (2 agencies) No specification (1 agency) 12) Does your agency have a list of approved aggregate types and sources for base and subbase course applications? [21] Yes (please reference document/web site) - 45.7% [25] No - 54.3% [0] Other (please explain): 46 respondents Document/website • Georgia: QPL2- http://www.dot.ga.gov/doingbusiness/Materials/qpl/Documents/qpl02.pdf • Florida: ftp://ftp.dot.state.fl.us/fdot/smo/website/sources/aggregatesource.pdf • Oregon: ftp://ftp.odot.state.or.us/techserv/construction/TrainingManuals/MFTP/2011/09_section_4a.pdf • Mississippi: http://sp.gomdot.com/Materials/Pages/Producer-Supplier.aspx • Alabama: http://www.dot.state.al.us/mtweb/Testing/MSDSAR/doc/QMSD/Li01.pdf • Louisiana: http://www.dotd.la.gov/highways/construction/lab/qpl/qpl%2002%20aggregates.pdf • Washington State: http://www.wsdot.wa.gov/Business/MaterialsLab/ASA.htm • North Carolina: https://apps.dot.state.nc.us/vendor/approvedproducts/ • Indiana: www.in.gov/indot • South Carolina: www.scdot.org/doing/ConstructionDocs/pdfs/Materials/2%20QPL%20102411.pdf • Ohio: http://www.dot.state.oh.us/Divisions/ConstructionMgt/Materials/Aggregate1/S1069%20Aggregate%20 Producer%20Suppliers.pdf • Pennsylvania: http://www.dot.state.pa.us/Internet/ConstrBulletins.nsf/frmBulletin14info?OpenFrameset (Material Code 203, Material Class C2A) • Arkansas: http://arkansashighways.com/materials_division/Division%20300%20Bases/303020%20Aggregate% 20Suppliers.pdf • New Jersey (for Base only): http://www.state.nj.us/transportation/eng/materials/qualified/QPLDB.shtm 13) If you answered “Yes” to Question 12, does your agency frequently allow new materials into the list of approved aggregate types and sources for base and subbase course applications? [14] Yes - 73.7% [4] No - 21.1% [1] Other (please explain: As needed) - 5.3% 19 Respondents (out of 21 selecting YES to Question #12) 14) Does your agency have specific guidelines regarding the transportation and storage (stockpiling) of aggregate materials for base and subbase construction? [17] Yes (please reference document/web site) - 37.8% [25] No - 55.6% [4] Other (please explain): - 8.9% 46 respondents

151 Document/website • Montana: Transport Bulk materials in vehicles that do not cause material loss or segregation • Indiana: Indiana Test Method 211 • Missouri: MoDOT Spec. 1001.10 • Wyoming: Require moisture to be added in a pugmill • Georgia: SOP-1 http://www.dot.ga.gov/doingbusiness/TheSource/sop/sop01.pdf • Texas: Standard Specifications Item 247.4 Construction • Nevada: Standard Specifications for Construction • Kansas: Subsection 1100 of Standard Specifications • Alabama: http://www.dot.state.al.us/mtweb/Testing/testing_manual/doc/pro/ALDOT175.pdf • Louisiana: http://www.dotd.la.gov/highways/specifications/ • Pennsylvania: ftp://ftp.dot.state.pa.us/public/bureaus/design/pub408/pdf%20for%20printing%202011%203/106. pdf (See Sections 106.05 & 106.06) • Arizona: http://azdot.gov/Highways/ConstGrp/Contractors/Useful_Information.asp (Division I—section 106.09 and 106.10) • New Hampshire: http://www.nh.gov/dot/org/projectdevelopment/highwaydesign/specifications/documents/2010_ Division_300.pdf • New York: Section 304 in https://www.dot.ny.gov/main/business-center/engineering/specifications/updated-standard- specifications-us and GCP-17 in https://www.dot.ny.gov/divisions/engineering/technical-services/geotechnical- engineering-bureau/manuals “Other” responses • Mississippi: Samples for job acceptance are obtained from the job site • Florida: Source Quality Control Plan is required to designate methods • Oregon: We require plant mixing and adding water at the source. • Louisiana: Look in Section Ten, 1003.03, on page 767, also part three. 15) What is the maximum construction lift thickness for unbound aggregate layers permitted by your agency? [17] 6 in. - 37% [12] 8 in. - 23.9% [4] 10 in. - 8.7% [6] 12 in. - 13% [6] Other (please indicate): - 15.2% [1] No such restrictions - 2.2% 46 respondents “Other” responses • 3 in., 6 in. when a vibratory steel drum roller is used • 4 in. • 9 in. • Depends on the field compaction equipment being used by the contractor • Placement thickness will be shown on plans • Up to 24 in. total, in lifts of 3-6 in. • Conventional dense-graded base is 4 in. by design, but will allow thicker lifts on case-by-case basis. Also have 18” rock base option, which is basically shot rock or reclaimed PCC balded and rolled into place with no sieve control other than for fines—MoDOT Spec 303. 16) Does your agency allow the construction of multiple unbound aggregate layers placed on top of each other (e.g., dense graded base over an open graded drainage layer)? [24] Yes - 52.2% [12] No - 26.1% [10] Other (please explain): - 21.7% 46 respondents

152 “Other” responses • Base courses constructed in 2 lift (typically 6 in. & same material) • Only with a geotextile separation fabric. • We would have multiple lifts of dense graded base. • Yes, but infrequent and discouraged. • Occasionally—generally there is only one 6 to 8 in. crushed stone base • Special provision • Not really but if the compaction equipment is weak then we would require the buildup of one layer using multiple compacted layers • Open graded drainage layer over a dense graded base or a dense graded base over a dense graded subbase • In general, this does not apply. Special applications where large rock is used to bridge soft soils, dense graded base is allowed, but a placement of a geotextile is recommended prior to dense graded base placement. • We used to allow unbound aggregate Open-Graded Subbase to be placed over unbound aggregate dense-graded sub- base, but now have discontinued the unbound open-graded subbase in lieu of treated permeable base courses as the drainable layer above the dense-graded unbound aggregate layer beneath rigid pavements. 17) If you answered “Yes” to the above question, do you separate the two unbound aggregate layers by any kind of constructed aggregate separation (i.e., filter) layer? [4] Yes - 16.7% [16] No - 66.7% [4] Other (please explain): - 16.7% 24 Respondents (out of 24 selecting YES to Question #16) “Other” responses • Choker material is placed over crushed bedrock. • Open graded aggregates are typically separated from soil layers with a filter fabric. • Sometimes as required by the project special • Sometimes-filter, geogrid, etc. 18) Does your agency allow the construction of unbound aggregate layers over or under pavement layers stabilized/ treated with lime, fly ash, cement, or bitumen? [30] Yes - 65.2% [10] No - 21.7% [6] Other (please explain): - 13% 46 respondents “Other” responses • Allowed but seldomly used • It is neither required nor discouraged. No one does it. • This might be something called out in design, but no policy • This situation has not been encountered to date. • Yes, under • Not as a rule—could occur in a type of sandwich layer construction if vertical grade was changing. 19) If you answered “Yes” to the above question, please give typical thicknesses of such constructed layers: [29] Thickness (in.) of stabilized layer 3-4 in. (1 agency) 4 in. (3 agencies) 4 to 12 in. (1 agency) 6 in. (8 agencies) 6 to 8 in. (2 agencies) 6 to 12 in. (2 agencies) 6+ in. (1 agency)

153 7 in. for cement stabilized, 8 in. for lime stabilized (1 agency) 8 in. (1 agency) 12 in. (4 agencies) 12 to 16 in. (1 agency) 12 to 24 in. (1 agency) 18 in. (1 agency) Not specified (site specific design thickness) (1 agency) Variable (1 agency) [26] Thickness (in.) of unbound aggregate layer 3 to 8 in. (1 agency) 4 in. (2 agencies) 4 to 6 in. (1 agency) 4 to 12 in. (1 agency) > 4 in. (1 agency) 6 in. (9 agencies) 6 to 8 in. (3 agencies) 6 to 10 in. (1 agency) 8 to 10 in. (1 agency) 10 to 12 in. (1 agency) 12 in. (2 agencies) Based on pavement structural design (1 agency) Variable (2 agencies) Category 2: Unbound Aggregate Base Characterization and Design 20) Who is responsible for testing/characterizing aggregate materials and providing input properties for the design of pavements with unbound granular layers? [39] Geotechnical/Materials laboratory - 84.8% [1] University laboratory (under research subcontract) - 2.2% [8] Field Engineer - 17.4% [12] Other (please indicate) - 26.1% 46 respondents “Other” responses • Assigned Structural Coefficient • Consultants for project specific designs • Engineering Division • Layer coefficients provided in Design Standards • Modulus is standard at 20,000 psi and layer coefficient of 0.10 for AASHTO 1993 • Regional Materials section/lab • We currently use a single layer coefficient under AASHTO 93 independent of the aggregate source. • Standard sections utilized • Pavement sections are designed with “assumed” aggregate properties. Testing is performed to ensure minimum specifications are met. • The materials laboratory and field engineer test aggregate materials for acceptance. The Pavement Design Engineer decides the input properties of aggregate materials for pavement design. • Pavement Engineer specifies minimum quality levels, and the Contractor is required to provide material that meets or exceeds these requirements. • Pavement Engineer in each district or designer with assistance from the district materials laboratory. 21) What laboratory tests are conducted by your agency for strength, deformation and modulus characterization of unbound aggregates used in base and subbase course applications? (Please check all that apply.) [20] Strength index tests (e.g., CBR, Hveem stabilometer, etc.) - 43.5% [6] Triaxial shear strength tests - 13%

154 [12] Repeated load triaxial tests for resilient modulus (standard tests such as AASHTO T 307, NCHRP 1-28, etc.) - 26.1% [2] Repeated load triaxial tests for permanent deformation behavior - 4.3% [21] Other (please indicate) - 45.7% 46 respondents “Other” responses • Basis for design is backcalculation of moduli from FWD data. • Depends on the existing soil being tested. • DynaFlect, FWD • Grain Size Analysis correlated with Mri • None of the above (8 agencies) • None. Will be looking at as we look more at DARWin-ME • RLTT, for research purposes • Standard structural number of 0.14 • Back-calculated FWD data • Gradation and proctor for subbase. Gradations for base. • Use uniform relative strength coefficient based on full-scale tests done by Clemson University in the late 1960s. 22) What field tests are conducted by your agency for strength, deformation and modulus characteristics of in- service unbound aggregate layers? (Please check all that apply.) [0] Plate Load tests - 0% [12] Dynamic Cone Penetrometer (DCP) tests - 26.1% [30] Falling Weight Deflectometer (FWD) tests - 65.2% [4] Light Weight Deflectometer (LWD) tests - 8.7% (MD, LA, OK, IN) [1] Soil Stiffness Gauge tests (e.g., GeoGauge, etc.) - 2.2% (MD) [17] Other (please indicate) - 37% 46 respondents “Other” responses • Compaction/Density (4 agencies) • None for acceptance, only gradation and density • None of the above (7 agencies) • Roller Pattern/control strip • We have FWD capabilities but used in a limited capacity • We have done all of these tests, but only at the research level. • FWD of in-service pavements but not on unsurfaced roads and not specifically to look at aggregate characteristics. 23) How often are these laboratory/field tests conducted to characterize aggregate materials for use in granular base and subbase layers? [5] Once on limited aggregate types/materials commonly used by the agency - 10.9% [27] On a project-need basis - 58.7% [0] Once on all agency-approved aggregate sources - 0% [3] At regular intervals on agency-approved aggregate sources to establish a database - 6.5% [11] Other (please indicate) - 23.9% 46 respondents “Other” responses • As needed • FWD conducted only on local roads, per local agency request • None (6 agencies) • None on new materials. Nearly every project for in-service materials. • Only when the information is needed. • Assumed values

155 24) Is the structural contribution of open graded aggregate drainage layers taken into account in pavement thick- ness design by your agency? [11] Yes - 23.9% [11] No - 23.9% [19] Open Graded Aggregate Drainage Layers are Not Used - 41.3% [5] Other (please explain) - 10.9% 46 respondents “Other” responses • N/A (4 agencies) • Used only on widening to match existing design 25) What method is used by your agency to design pavements with unbound aggregate base and subbase layers? [4] 1972 AASHTO Design Guide - 8.7% [1] 1986 AASHTO Design Guide - 2.2% [28] 1993 AASHTO Design Guide - 60.9% [14] Mechanistic-Empirical Pavement Design Guide (MEPDG) - 30.4% [5] Agency-Specific Mechanistic Procedure: - 10.9% AKFPD: AK Flexible Pavement Design Cal-ME Modified Shell Method (M-E) Winflex MnPAVE, mechanistic procedure developed in Minnesota for flexible pavements - program can be found on MnDOTs Pavement Design website [5] Agency-Specific Empirical Procedure: - 10.9% Idaho R-Value MTO standard section tables R value https://www.dot.ny.gov/divisions/engineering/design/dqab/cpdm Flexpave, MN Investigation 183 that is based on R-values and pavement deflection, RigidPave, rigid design based on a modified 1981 AASHTO Interim Guide Procedures, both programs can be found on MnDOTs Pavement Design website [10] Other (please indicate) - 21.7% Beginning to use MEPDG Defer to PMU Moving toward MEPDG Not sure PerRoad Contact Jeff Lambert Getting ready to move to MEPDG Standard sections Our official policy calls for the use of the 1993 AASHTO Design Guide, but we also check with the MEPDG for information and back-up purposes FPS21 (flexible pavement design system) a mechanistic-empirical system based on SCI or deflections 46 respondents (although 67 selections were made, indicating some agencies use more than one method) 26) What aggregate properties and/or characteristics are used as inputs for the design of pavements with granular base/subbase layers by your agency? (Please check all that apply.) [18] Percent passing sieve sizes (gradation) and/or maximum aggregate particle size - 39.1% [9] Particle shape and angularity (crushed or uncrushed) - 19.6% [12] Compaction characteristics; i.e., optimum moisture content and maximum dry density- 26.1% [2] Shear strength properties (e.g., friction angle, CBR, etc.) - 4.3% [21] Resilient modulus - 45.7% [22] Other (please indicate): - 47.8% 46 respondents

156 “Other” responses • Current policy assigns a structural number to the subbase layers for flexible pavement designs. • Defer to PMU • Gravel Equivalence (G.E.) or back-calculated FWD modulus • Hveem R-Value (3 agencies) • Modulus from backcalculation of FWD data • With respect to compliance with specifications. • Contact Jeff Lambert • Not sure • Structural layer coefficient (10 agencies) • Modulus is standard at 20,000 psi and layer coefficient of 0.10 for AASHTO 1993. Gradation, angularity, compaction characteristics, and resilient modulus are used for MEPDG. • All subbases meeting our specifications are considered equal. It is not an efficient use of time to design pavements AFTER the contractor has chosen his subbase source. 27) What approach is adopted by your agency for assigning resilient modulus values to unbound aggregate base and subbase layers? [10] Modulus is not used in pavement design - 21.7% [26] Single modulus is assigned to the entire layer - 56.5% [0] Stress-dependency of aggregate layer modulus is considered during pavement design - 0% [1] Based on research by the International Center for Aggregate Research (ICAR), anisotropy (directional dependency) of aggregate layer modulus is considered - 2.2% [9] Other (please indicate) - 19.6% 46 respondents “Other” responses • Contact Jeff Lambert • Defer to PMU • MEPDG default values • Back-calculated FWD modulus from MnROAD & various county projects around the state • Established value • Nil • Not sure • Characterization of unbound aggregate materials is being done for MEPDG local calibration. Modulus is not con- sidered in current design methodology. 28) How does your agency determine the resilient modulus of unbound aggregate materials for use in granular base and subbase layers? [10] Resilient modulus testing in the laboratory - 21.7% [23] Empirical correlations with index properties like CBR, gradation parameters, etc. - 50% [14] In-place modulus measurement of constructed layers by deflection-based methods such as FWD, LWD, etc. - 30.4% [15] Other (please indicate) - 32.6% 46 respondents “Other” responses • Defer to PMU • Do not use resilient modulus (6 agencies) • FWD on Local jobs & grain size analysis on state jobs • Modulus is standard at 20,000 psi and layer coefficient of 0.10 for AASHTO 1993 • Resilient modulus for base materials used for research purposes • Resilient modulus is only used for the subgrade layer in the pavement design. • Standard inputs correlated from AASHTO recs and typical aggregate properties • Assumed values in design

157 29) Does your agency have specific guidelines for including new and/or locally available “marginal” aggregates in the thickness design of unbound base and subbase layers? [6] Yes - 13% [38] No - 82.6% [2] Other (please explain): - 4.3% 46 respondents “Other” responses • Treated base should be used where a “binder” should be incorporated. • No—the modulus of the material is either determined or estimated from lab testing (Strength in comparison to typi- cal materials). Category 3: Compaction, Quality Control and Field Performance 30) How are aggregate compaction characteristics established in the lab by your agency? [42] Drop-hammer based methods like the standard and modified Proctor tests - 91.3% [0] Static compaction methods - 0% [2] Vibratory compaction methods - 4.3% [0] Gyratory compaction methods - 0% [0] Kneading compaction methods - 0% [7] Other (please indicate) - 15.2% 46 respondents “Other” responses • CT method • DCP, modified Penetration Index, can be found on the MnDOTs Grading & Base website • Proctor • We don’t establish compaction characteristics • Method based compaction • Not in laboratory in field • Generally done in the field, but occasional proctor test to verify or resolve field dispute or conflict 31) List typical equipment used for placement and construction of unbound aggregate base/subbase layers in your state (please check all that apply). [26] Dump truck - 56.5% [5] Material Transfer Device - 10.9% (CA, NV, IL, MS, OH) [39] Trucks and graders - 84.8% [24] Aggregate spreaders - 52.2% [4] Other (please indicate below) - 8.7% 46 respondents “Other” responses • For big projects we may ask for the drop box • Any of the above, depending on the job size • Compactors, rare use of aggregate spreader • Truck and grader for small quantity 32) Please describe briefly the preferred method of placement and construction of unbound aggregate base and subbase layers in your state. • Use of drop box rather use of dozer • Jersey spreader

158 • Deliver the aggregate to the grade, uniformly spread the uncompacted material, then compact with proper equipment until minimum compaction levels are achieved • Up to Contractor • Preferred would be an auto-grader, but commonly it is dump trucks and graders. • Aggregate Spreaders, Subsection 305.3c Standard Specifications • Plant-mixed aggregate base, moisture conditioned at the plant, and spread by graders and compacted in 6-in. lifts. • Uniform spreading of layers • Placement in 8 in.–12 in. lifts followed by compaction. • Trucks and Graders • We do not specify placement method, although spreaders are common. However, we do sample and accept the base from the roadway after placement, with emphasis on sampling areas that appear to be segregated. Contractors and suppliers must be aware and account for breakdown during compaction. • Use of dump trucks and spreaders • Specified depth w/near optimum moisture and mechanical densification (rolling w/pneumatic and/or steel roller in vibratory mode. • Preferred by whom? DOTD or the contractors? We do not require specific equipment. Contractor given flexibility but must meet density requirements. • Don’t have a specified or preferred method. • None, only concerned about avoiding segregation. • Tucks and graders • Material is placed by belly dumps in a windrow, blade processed while moisture conditioned, spread, and compacted to grade. • ftp://ftp.dot.state.fl.us/LTS/CO/Specifications/SpecBook/2010Book/200.pdf • Use of spreader box • Contractor preference • Truck delivery, bladed to grade, watered and compacted, finish grading, watered surface and rolled finish. • Spread by excavator or dozer and compact with vibratory steel drum rollers in horizontal layers • Central mixed and placed with aggregate spreader. • Do not dictate construction methods. Contractor choice of methods. Must perform. No locations where method of placement has affected pavement life/performance. • Graders • Trucks and graders are most commonly used. Transfer devices or aggregate spreader to remix material help with aggregate segregation. • Aggregate spreader and vibratory compaction • Placement, grading or spreading and compaction • Placed by a dump truck, spread by a grader and moisture conditioned (as needed) by a water truck. Each layer is then compacted using vibratory rollers. • Trucks, graders, rollers • Dump, spread, roll, final grade • Windrow aggregate with a belly dump trailer and spread with a grader. Compact in maximum 8 in. lifts to 98% of modified Proctor. • Specifications require adjustable, self-propelled mechanical spreaders capable of placing and screeding material without segregation with automatic grading machine trimmer. • Base layers are placed by windrowing, using a grader to work the material to the desired crossfall while compact- ing with wobbly compaction equipment. Compaction requirements are based on a specified set of compaction equipment. • Trucks and graders • Not one preferred method. Different ways have been used and our specifications are not written in a manner to specify any one method. End result. • Windrowed material is spread out with graders in lifts less than 6 in., and compacted • Contractor controlled. Acceptance on lot-by-lot basis. Must meet compaction, grade requirements • Pug-milled base material placed by mechanical spreader • Belly dumps and graders, the method of placement is determine by the contractor • Aggregate Spreaders • T & G

159 33) How is moisture content of constructed/compacted unbound aggregate base and subbase controlled in the field? [2] According to quarry reported moisture content - 4.3% [14] Sampled during construction/compaction for laboratory testing - 30.4% [35] Measured through field testing using (Please indicate) - 76.1% • 0 • AASHTO T255 • CT 226 Moisture content • Compaction is controlled based on a control strip method. • GDT21 http://www.dot.ga.gov/doingbusiness/TheSource/gdt/gdt021.pdf • Indiana Test Method 506 • Nuclear compaction and within 2% of optimum • Nuclear density method (16 agencies) • Nuclear gauge/speedy moisture • Sample taken from in-place material • Speedy moisture tester • Compacted density, moisture content • Moisture pan & density gauge • Nuclear device checks, but QA samples taken and dried in oven • Nuclear or burn off method • Using surface nuclear gauge • Specified Density Method—not less than 65% of optimum moisture of standard proctor, Quality Compaction Method—not less than 5% of dry weight, modified Penetration Index Method - not less than 5% of dry weight, Can be found in the Standard Specifications for Construction (spec 2211) found on the MnDOT Grading & Base website [6] Other (please indicate) - 13% 46 respondents “Other” responses • Controlled totally by contractor. • Material is required to be damp. • Visual • Control of moisture content is the responsibility of the contractor; base accepted on gradation and compaction level. • Measurement is often following compaction. Compaction control is often left to the contractor as a QC function. • Based on visual inspection and ability to achieve a practical target density and resulting constructed density per lot placed. Procedures are outlined within the Materials Procedure governing placement and compaction of aggregate bases. 34) What is an acceptable variation from optimum moisture content for constructed/compacted unbound aggregate base and subbase allowed by your agency? • ±2 % over optimum • <2% • Not specified • Aggregate shall be maintained substantially at optimum moisture. • N/A • ±3% of optimum • Plus or minus 2% of optimum • += 2% • ±2% is desired, but required provided dry density is attained. • Not specified • Do not specify. • As required to produce a density of 100% T180 • Minus 2% to plus 1% • Plus or minus 2% of optimum MC

160 • Plus 2% to minus 4% • We don’t specify the optimum moisture content, simply that 95% of max. dry density is achieved. • 95% density • No moisture requirement • Compaction controlled. No variation in moisture content specified. • Need to obtain target density in the field • ±2% points • No requirement. • Not less than 1% below optimum but as much as 2% above. • Enough to obtain the specified compaction, but not too much to cause pumping and rutting • 3% • Varies but generally ±2% • ±2% • 0 to 5% above optimum • There is no allowable variation for moisture. Acceptance is based on acceptable density. • 2% of optimum • Don’t have one. • Not specified • Plus or minus 2% • No requirement on moisture content • Optimum moisture is not specified for base and subbase. • Required to be damp. • N/A • Approx 2% • There is no target moisture content and therefore no tolerance established. • No specified value • +1%, -2% • 2% • 3 and -1 % of optimum moisture content • No set variation; however experience shows that we end up with -2% to +1% of optimum w 35) What is the primary approach used by your agency for evaluating degree of compaction and construction qual- ity control of unbound aggregate base and subbase layers? [14] Gradation - 30.4% [3] Proof-rolling - 6.5% [41] Measurement of constructed layer density - 89.1% [3] Field measurement of constructed layer modulus - 6.5% [0] Continuous compaction control by means of Intelligent Compaction (IC) equipment - 0% [4] Other (please indicate) - 8.7% 46 respondents “Other” responses • DCP, modified Penetration Index • Non-movement under compaction equipment. • Nuclear density gauge • Control strip. Comparing density achieved to that achieved by the specified compaction equipment/effort. 36) If your answer to the previous question was “Measurement of constructed layer density,” what method is commonly used by your agency for measuring constructed layer densities in the field? [39] Nuclear density methods (ASTM D 2922 / AASHTO T310 or T238) - 88.6% [7] Sand cone method (ASTM D 1556 / AASHTO T191) - 15.9% [1] Balloon method (ASTM D 2167) - 2.3% [0] Oil or water method - 0% [0] Drive cylinder method (ASTM D 2937) - 0%

161 [0] Rapid method (ASTM D 5080) - 0% [0] Electrical density measurement method (ASTM D 7698) - 0% [5] Other (please indicate) - 11.4% 44 respondents “Other” responses • AASHTO TP 68 • CT 216 • GDT59 http://www.dot.ga.gov/doingbusiness/TheSource/gdt/gdt059.pdf • Illinois Modified AASHTO 310 • N/A 37) Is it common practice for your agency to construct “test strips” to establish roller patterns and check for com- paction density growth of unbound aggregate base and subbase layers? [13] Yes - 28.3% [31] No - 67.4% [2] Other (please explain) - 4.3% 46 respondents “Other” responses • No, but currently considering. • Yes, but usually part of project, start of placement. 38) If your answer to the above question was “Yes,” do you primarily use nuclear density measurement method for this purpose? [12] Yes - 92.3% [0] No - 0% [1] Other (please explain) - 7.7% 13 respondents “Other” responses • We are transitioning from the nuclear gauge to the LWD for stiffness and both are used on the test strip. 39) What is the primary mode of nuclear gauge operation used by your agency for density checks on constructed unbound aggregate base and subbase layers? [33] Direct Transmission - 76.7% [7] Backscatter - 16.3% [5] Not applicable (nuclear density measurement not used) - 11.6% 43 respondents 40) If your agency uses the “drop-hammer based” methods to establish compaction characteristics of aggregates in the laboratory, please select all applicable options from the list below regarding the minimum compaction requirements in the field: 90% 95% 100% Other Responses % # % # % # % # # Flexible Base Standard Proctor 4.3% 1 47.8% 11 21.7% 5 26.1% 6 23 Flexible Base Modified Proctor 9.1% 2 27.3% 6 18.2% 4 45.5% 10 22 Flexible Subbase Standard Proctor 4.8% 1 52.4% 11 23.8% 5 19.0% 4 21 Flexible Subbase Modified Proctor 12.5% 2 50.0% 8 12.5% 2 25.0% 4 16 Rigid Base/Subbase Standard Proctor 4.3% 1 43.5% 10 26.1% 6 26.1% 6 23 Rigid Base/Subbase Modified Proctor 11.1% 2 44.4% 8 5.6% 1 38.9% 7 18

162 41) If you selected “Other” as one of the responses to the above question, please specify the answer below (submit your answer in the format: Flexible Base-Standard Proctor-xx %). • Flexible Base Modified Proctor-98% • 98% of modified proctor • Compact to within 97 percent of optimum for flexible and rigid 42) If your agency does NOT use “drop-hammer based” methods to establish compaction characteristics of aggre- gates in the laboratory, please specify the relative compaction requirements for the following unbound aggre- gate base/subbase applications: 90% 95% 100% Other Responses % # % # % # % # # Flexible Base 11.1% 1 22.2% 2 0% 0 66.7% 6 9 Flexible Subbase 0% 0 25% 2 0% 0 75% 6 8 Rigid Base/Subbase 0% 0 29.6% 8 11.1% 3 59.3% 16 27 43) If you selected “Other” as one of the responses in the above question, please specify the details below: 97% for the unbounded aggregate on top 12” Type A Subbase requires 95%, Type A Base requires 100%; regardless of pavement type 98% of control strip density 44) Is there common interest among engineers in your agency to implement non-nuclear density measurement methods for construction quality control of unbound aggregate base/subbase layers? [24] Yes (please select all possible reasons) - 52.2% [17] Safety concerns [19] Nuclear certification too expensive [20] Nuclear certification too inconvenient [3] Non-nuclear methods provide better results [19] No - 41.3% [8] Other (please explain): - 17.4% 46 respondents “Other” responses • Don’t know • Speed of testing. • We have investigated non-nuclear methods, but have not seen equivalent performance so far • If served as better and simpler, we would use • Reduction in staffing levels to support program • Trying to find reliable, practical measurement of strength, not just density • MnDOT does not use nuclear density measurement for quality acceptance, contractors can use nuclear density mea- sure methods for process or quality control • Some. Our agency has not started to use mechanistic design as the staple for our pavements yet. But we are starting to use it for many cases and the need to develop inputs for these methods will lead to more of a need to utilize methods to control field measurements that mirror these inputs. 45) Has your agency ever participated in demonstration projects involving continuous compaction control of unbound aggregate base/subbase layers using Intelligent Compaction (IC) techniques? [17] Yes - 37% [27] No - 58.7% [2] Other (please explain): - 4.3% 46 respondents

163 “Other” responses • Doing that summer of 2012 (UT) • Research yes, but not within a road that remained property of the state (DE) 46) Has your agency actively implemented IC techniques to construct in-service pavements with unbound aggregate base/subbase layers? [1] Yes - 2.2% (TX) [42] No - 91.3% [3] Other (please explain): - 6.5% 46 respondents “Other” responses • Georgia: Have plans to let another demonstration project in April 2012 • Louisiana: It is been looked at and tried on a few projects • Indiana: We have just let our first contract for QC/QA Soil Embankment that requires the Contractor to implement IC Technology. 47) If your answer to the above question was “Yes,” does your agency have a specification for continuous compac- tion control using IC techniques and construction of unbound aggregate base/subbase layers? [1] Yes - 100% (TX) [0] No 48) Does your agency implement modulus-based compaction control for the construction of unbound aggregate base/subbase layers? [2] Yes - 4.3% (IN, GA – demo only) [44] No - 95.7% 46 respondents 49) If you answered “Yes” to the previous question, what method is used for measuring the field modulus of con- structed unbound aggregate layers? [0] Falling Weight Deflectometer (FWD) [1] Light Weight Deflectometers (LWD) - Indiana [0] Soil Stiffness Gauge (e.g., GeoGauge) [0] Seismic testing such as the Portable Seismic Pavement Analyzer based on spectral analyses of surface waves [1] Other (please indicate) – Georgia: Intelligent Compaction-Demo only 2 respondents 50) If you answered “Yes” to question No. 48, what percentage of construction projects in your agency involve modulus based compaction control? [ ] <10% [ ] 10–30% [1] 30–60% - Indiana [ ] >60% 1 respondent 51) Does your agency use any non-traditional compaction technique (e.g., South African “slushing” technique) during the construction of unbound aggregate base/subbase? [2] Yes (please name the technique and give brief details) - 4.3% [NM, RI] [44] No - 95.7% 46 respondents “Details for Yes” responses • Rhode Island: Use test strip to obtain a maximum density value by testing the same spot until the density no longer increases. Compare other values to that value.

164 • New Mexico: As indicated above, we are doing one inverted project in which we will be utilizing the slushing effort as a part of the effort. 52) Does your agency perform FWD tests to assess the structural condition of unbound aggregate base and subbase layers in existing in-service pavements? [27] Yes - 58.7% [11] No - 23.9% [8] Other (please explain): - 17.4% 46 respondents “Other” responses • Defer to PMU • FWD is used for determination of in-place embankment resilient modulus • For research purposes only • For specific purposes but not routinely • Non-standard testing, but we have performed in the past • Only when needed by research • Used on a limited capacity • Project-specific and research projects 53) If your answer to the previous question was “Yes,” what back calculation program/software/approach does your agency use to determine granular base/subbase modulus from the FWD test results? (Please indicate below.) • Deflexus AARA program designed for our State • ELMOD • DELMAT A forward calculation based program (DELMAT) developed by Makbul Hossain of our staff • Evercalc • Darwin, Evercalc, BACKFA, and/or AASHTO 1993 equations • Calback • SCDOT-specific, similar to 1993 AASHTO • Contact LTRC Doc Zhang (225)767-9162 • ModTag • Modulus • Illi-Pave • Modulus 6.0 • MODULUS6.0 • FWD AREA Program • Modulus • Elmod • ELMOD • Internally developed at Ohio DOT • Modtag • I don’t know • We utilize the “modulus” backcalculation software • DARWin Software multiplied by C = 0.25 correction factor • ELMOD, Looking at Modtag, others • Unknown • Dynatest’s ELMOD 6 54) What tests are commonly used by your agency to evaluate the field-performance of existing pavements with unbound aggregate base and subbase layers? (Please list all.) • FWD • We run IRI for HPMS and have an annual visual rating program that uses cracking, rutting, raveling, etc. • Pavement Condition Surveys • FWD

165 • Primarily a visual assessment, but FWD and coring are also done. • FWD, DCP • Visual assessment, coring, indirect tensile testing of cores, TSR of cores, bulk and component properties of cores, DCP, geoprobes (for samples), and FWD. Considering using a recently purchased APA for testing in-service HMAC cores. • IRI, FWD • None • FWD—project specific and research projects • FWD analysis • Defer to PMU • FWD • Dyna-flect, FWD LWFWD, DCP • FWD • DCP, FWD • FWD, Depth Check and Line Sampling • FWD • Annual condition surveys • Layer thickness based on cores • FWD • FWD • DCP, FWD, GPR • Rideability • FWD • DCP, FWD • No testing on the unbound layer of the pavement section. Measure thickness of constructed road and assign structural number to the various layers based upon accepted layer coefficients. • FWD • FWD with cores taken to evaluate layer thicknesses • Not really tests. We have a pavement evaluation system • None • FWD along with sampling the existing materials and testing for R-Value, gradation and soil classification • FWD on asphalt or concrete pavements • I don’t know • We use FWD to test all of MDT’s pavements on a 5-year rotation (i.e., it takes 5 years to complete all roads). We also annually access the condition of our pavements using automated pavement distress collection vans. The vans characterize pavement condition using ride (international roughness index), alligator cracking, longitudinal and transverse cracking, and rut depth. • FWD, Ride Quality (IRI), Automated Pavement Distress Surveys • Field performance is based on characteristics such as ride, strength, and surface distresses. • Nil • SPT, Compaction and FWD • Benkelman Beam and Falling Weight Deflectometer on a trial basis at this time • Surficial distress observations, rutting, smoothness, pavement condition evaluation • None • FWD • FWD • FWD • No specific test, however rut depth and IRI are collected as part of PMS Category 4: Recycling Aggregates and Recycled Granular Materials Note: Recycled Granular Materials in this questionnaire refer to Recycled Concrete Aggregates (RCA) and Reclaimed Asphalt Pavement (RAP) materials only. 55) Does your agency commonly recycle unbound aggregate materials from base and subbase layers of existing pavements for application in new and rehabilitated pavement construction? [24] Yes - 52.2% [15] No - 32.6%

166 [7] Other (please explain) - 15.2% 46 respondents “Other” responses • Occasionally with Full Depth Reclamation • RAP is used a lot. RCA not as much due to environmental runoff issues and breakdown • As needed • Base only • If applicable—however, we do not reconstruct very often • Left in place and regarded for rehabilitation projects • Used occasionally 56) If your answer to the previous question was “Yes,” what tests are used by your agency for evaluating the quality of these recycled aggregates? (Please check all that apply.) [9] Na2SO4/MgSO4 Soundness Test - 19.6% [14] Los Angeles Abrasion and/or Micro Deval Test - 30.4% [24] Sieve Analysis - 63.0% [15] Percent Deleterious Materials - 32.6% [8] Other (please indicate): - 45.7% 24 respondents “Other” responses • Limerock Bearing Ratio after removal • PI, R value • Plastic Index • Rare opportunity and case-by-case • Asphalt content • Restrictions on RCA that can be found in spec 2211 & 3138 Standard Specifications • We recycle from our own pavement so assume quality equal to original. Sieve analysis is used for control. • If used as granular fill then no acceptance criteria - if used as base then would meet new requirements. 57) What other tests are used by your agency to characterize recycled aggregates from existing base and subbase courses for acceptance and design? (Please list all.) Only 5 responses—PI, pH, R-value, % recycled pavement, % bitumen content, our primary method of recycling base course is by pulverizing it and mixing it with the existing hot mix asphalt surface, Our only requirement is that the resulting blended mix consists of no more than 50% RAP by volume. 58) Is the use of recycled aggregates from existing base and subbase courses incorporated into your agency specifications? [21] Yes - 45.7% [22] No - 47.8% [3] Other (please explain): - 6.5% 46 respondents “Other” responses • They are not prohibited, but they would need to meet same requirements as virgin aggregate. • Not specified but common knowledge is that this is an acceptable substitution as no cost betterment. • The final mixture of recycled aggregates from existing base and subbase courses must meet specifications. 59) Does your agency allow contractors to use locally available “marginal or out of specification” aggregates for unbound aggregate base and subbase layer applications? [2] Yes - 4.3% [38] No - 82.6%

167 [6] Other (please explain): - 13% 46 respondents “Other” responses • Do not readily do, but has been done due to economic considerations. • In some locations, agency specifies marginal aggregate sources for sub-base. • Only if allowed. They would not be allowed as a substitute. • Recycled aggregates must meet the requirements of the virgin aggregate for gradation. • Lower quality “Stone Embankment” material is sometimes substituted during design for a sub-base. • The gradation does not change when recycled materials are used. The virgin materials must still meet specifications, before the recycled material is added. 60) What other recycled granular materials are approved for use by your agency in unbound aggregate layer construction? (Please check all that apply.) [31] Reclaimed Asphalt Pavement (RAP) - 67.4% [37] Recycled Concrete Aggregates (RCA) - 80.4% [10] Other (please indicate): - 21.7% [2] None of the above (please skip to Category 5 of the survey) - 4.3% 46 respondents “Other” response • Air cooled blast furnace slag • Glass • Glass, blast furnace slag • On occasion RAP is used in shoulder areas as a substitute for aggregate base • Blast furnace slag • Glass • Glass cullet • Glass, whiteware, slags • Glass cutlet, aggregate blended with oil field waste, others that meet specification requirements 61) What tests are used by your agency for evaluating the material quality of recycled granular materials (RCA, RAP, and/or others from question No. 60) for base and subbase applications? (Please check all that apply.) [8] Na2SO4/MgSO4 Soundness Test - 32% [12] Los Angeles Abrasion and/or Micro Deval Test - 48% [22] Sieve Analysis - 88% [11] Percent Deleterious Materials - 44% [3] Other (please indicate): - 12% 25 respondents “Other” response • Sand equivalent (2 agencies) • Dry rodded weight, fractured face and permeability 62) What other tests are used by your agency to characterize recycled granular materials (RCA, RAP, and/or others from question No. 60) for acceptance and design? (Please list all) • Atterberg limits (5 agencies) • R-value (3 agencies) • Degradation-sand equivalent (3 agencies) • RAP ac content (3 agencies) • Micro-Deval • Micro-Deval on RAP

168 • DCP • FWD • Dynaflect • 50% RAP blend with virgin, max • Visual observation of stockpiles • LBR for RCA • CBR for RCA • RCP-pH • Durability • Sulfates • Fractured faces • pH • RAP limited to shoulders • Freeze/thaw soundness for RCA • Must meet same criteria as virgin aggregate 63) Does your agency have environmental concerns regarding the use of recycled granular materials (RCA, RAP, and/or others from question No. 60) in unbound aggregate base and subbase layers? [6] Yes - 24% [17] No - 68% [2] Other (please explain): - 8% 25 respondents 64) If your answer to the above question was “Yes,” what environmental issues is your agency particularly concerned about (e.g., leaching, etc.)? • RCP leachate (3 agencies) • RAP leachate • pH levels • Leaching (2 agencies) • Only use RCP • Toxicity • Hydroxide levels 65) Does your agency require strength, deformation and modulus testing and characterization of recycled aggre- gates (from existing base and subbase courses) as well as recycled granular materials (RCA, RAP, and/or others from question No. 60)? [7] Yes - 28% [16] No - 64% [2] Other (please explain): - 8% 25 respondents 66) If you answered “Yes” to the previous question, are these characterization tests the same as those used for virgin aggregates? [7] Yes - 100% [0] No (please indicate how the test methods are different) 7 respondents Category 5: Climatic Effects and Drainage 67) Are climatic effects on pavement subgrade performance a major concern for your agency? [28] Yes - 60.9% [16] No - 34.8%

169 [2] Other (please explain): - 4.3% 46 respondents “Other” response • Freeze-thaw on silty subgrade caused problems (pavement heave) on some projects • Only changes in subgrade moisture 68) If your answer to the above question was “Yes,” please check all factors that contribute to this concern: 28 respondents [16] Groundwater table (GWT) is often shallow (can be less than 5 ft deep) under the pavements - 57.1% [22] Native soils primarily fine-grained (e.g., silts, clays, etc.) and may get wet of optimum due to upward movement of moisture from the GWT - 78.6% [13] In-service pavement subgrades are often under “wet of optimum” moisture conditions—46.4% [24] Seasonal fluctuations cause significant changes in subgrade soil properties - 85.7% [17] Subgrades stay frozen for extended periods (one month or longer) - 60.7% [19] More than 10 freeze-thaw cycles per year are experienced at the subgrade level - 67.9% [17] Spring thaw weakening and timing of spring load restrictions - 60.7% [16] Subgrade soils are primarily frost-susceptible (i.e., silty soils) - 57.1% 69) Are aggregate materials selected for use in granular base/subbase applications by your agency tested for climatic effects (e.g., soil water characteristic curve, freeze-thaw durability, suction characteristics of fines, etc.)? [7] Yes (please indicate the test types) - 15.2% • Expansion test • Freeze Thaw • Idaho IT-116, Ethylene Glycol • LAR & -#200 insoluble residue for carbonate materials • Soundness Testing (include AASHTO T 103, Sodium Sulfate, or Brine Freeze-Thaw) • Freeze-thaw • Unconfined freeze-thaw durability [36] No - 78.3% [3] Other (please explain): - 6.5% 46 respondents “Other” response • Not on a regular basis. The specifications were written to minimize these problems. • Grain size analysis to determine % silt. • Currently testing subbase materials for information gathering including % water absorption, freeze/thaw, British frost heave. 70) Does the pavement design procedure used by your agency consider the effects of climatic changes on unbound aggregate layer performance? [9] Yes - 19.6% [27] No - 58.7% [10] Other (please explain): - 21.7% 46 respondents “Other” response • Adjust Structural Coefficient based on a drainage factor • Defer to PMU • I don’t think it does.

170 • MEPDG designs only • Not sure • To the respect that subgrade stiffness affects base stiffness (modulus ratio of 3-5). • Yes, in that our granular materials are chosen to minimize these effects. • Contact Jeff Lambert • Reduction in embankment Mr due to base clearance < 3 ft • Use soaked CBR 71) If your answer to the above question was “Yes,” what unbound aggregate layer properties are adjusted in your pavement design procedure to account for detrimental climatic effects on pavement performance? [4] Layer structural coefficients - 44.4% [7] Resilient modulus - 77.8% [1] Shear strength - 11.1% [2] Other (please indicate): - 22.2% 9 respondents “Other” response • Drainage coefficient • Minimum thickness 72) Are there different gradations specified by your agency for unbound aggregate applications targeting drainable vs. low permeability aggregate layers? [19] Yes - 41.3% [24] No - 52.2% [3] Other (please explain): - 6.5% 46 respondents “Other” response • Don’t know • We’ve tried without much success. • Yes, but typically our “drainable” layers are a soil, not aggregate. For an unbound aggregate layer, the gradation would be gap graded, not dense graded. We don’t specify “low permeability” layers—these would be based upon need for pavement structure. 73) If drainage is one of the primary functions of your flexible pavement unbound aggregate base/subbase layer, what approach is adopted by your agency to facilitate the drainability of dense-graded base courses? [17] Limiting the maximum allowable percent fines (material passing sieve No. 200) - 37% [2] Increasing the maximum aggregate size - 4.3% [6] Adjusting the constructed layer gradation toward a more open-graded layer - 13% [8] Other (please explain): - 17.4% [23] Drainage is NOT one of the primary functions of flexible pavement unbound aggregate base/subbase layers - 50% 46 respondents “Other” response • Fines are limited by sand equivalence and split sieve gradations. • N/A- do not use drainage layers • None • We install edge drain systems for all new pavement • Minimize micaceous mineral content • Not for flexible pavements • Drainage layers are not part of the pavement structure. Drainage of the unbound layer would be accomplished through edge drains using open graded aggregate wrapped in filter fabric of some type.

171 • A drainage layer is not often designed as a layer in TX flexible pavements, but when it is gradations are more uniform (less fines and coarse). 74) Does your agency distinguish between crushed and uncrushed aggregate types while constructing open-graded drainage layers? [14] Yes - 30.4% [10] No - 21.7% [16] Open-graded drainage layers are not used - 34.8% [6] Other (please explain) - 13% 46 respondents “Other” response • 85% two face crush • Base is required to be crushed, subbase is assumed to be uncrushed • N/A • Not exactly; we require uncrushed gravel to have a minimum crush count • Unbound open-graded drainage layers were used in past, but discontinued in lieu of treated permeable base courses. The unbound open-graded and treated permeable base required minimum crushed particles. 75) How is the effectiveness of an open-graded aggregate drainage layer measured by your agency? [2] In-situ permeability measurements - 4.3% [8] Laboratory tests to measure the permeability of aggregate samples - 17.4% [9] Empirical correlations to estimate the permeability from aggregate physical properties like gradation, dry density, specific surface, and void ratio (or porosity) - 19.6% [23] Open-graded drainage layers are not used - 50% [9] Other (please explain) - 19.6% 46 respondents “Other” response • DRIP Program • Historical performance is basis • N/A • No testing. Rarely use them. • None • Not measured. • Gradation • Nil • Two passes with a double drum roller and a 5 gal. pail of water passes through the material before it starts to puddle. 76) For pavement structures with aggregate drainage layers, is it common practice in your agency to include a filter layer underneath to protect the drainage layer from clogging? [5] Yes (open graded aggregates commonly used to construct the filter layer) - 10.9% [12] Yes (geosynthetics commonly used as the mode of filtration) - 26.1% [9] No (no extra layer constructed for filtration purposes) - 19.6% [22] Open-graded drainage layers are not used - 47.8% 46 respondents 77) How common is it for your agency to construct subsurface drainage systems like “edge-drains” under unbound aggregate base and subbase layers? [12] Yes, very common - 26.1% [21] Yes, for specific projects when required by the design - 45.7% [14] No, not common at all - 30.4% 46 respondents

Next: Appendix D - Review of Current Resilient Modulus Models »
Practices for Unbound Aggregate Pavement Layers Get This Book
×
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

TRB’s National Cooperative Highway Research Program (NCHRP) Synthesis 445: Practices for Unbound Aggregate Pavement Layers consolidates information on the state-of-the-art and state-of-the-practice of designing and constructing unbound aggregate pavement layers. The report summarizes effective practices related to material selection, design, and construction of unbound aggregate layers to potentially improve pavement performance and longevity.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  6. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  7. ×

    View our suggested citation for this chapter.

    « Back Next »
  8. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!