7-77 Section 716 – Bituminous Concrete Mixtures
716.01 GENERAL REQUIREMENTS . Bituminous concrete mixtures shall be produced in accordance with an Agency approved mix design, using aggregates and asphalt binder from Agency approved sources, at an approved bituminous concrete production facility . Asphalt binder for bituminous concrete mixtures shall meet the requirements of Subsection 702.0 1. WMA technologies and anti -strip additives, if used, shall meet the requirements of Subsection 702.03 and Subsection 702.04 , respectively. Aggregates for b ituminous concrete mixtures and recycled asphalt materials (RAM) shall meet the requirements of Subsection 704.10 and Subsection 704.2 2, respectively. 716.02 BITUMINOUS CONCRETE MIXTURES .
a.General Bituminous Concrete Mixture Design Requirements . Mix de signs for all mixtures covered in this subsection shall be submitted in accordance with the Agency’s Bituminous Concrete Policy Manual . No paving of a mix design shall be started until the Contractor has submitted, and the Agency has approved the mix design, including cold feed gradations, mixing times, the percentage of each ingredient, including asphalt binder , the job mix formula (JMF ) from such a combination, and the optimum mixing and compaction temperatures. The design shall also include the control limits for quality control. A copy of all design test data used in developing the mix design, including graphs, may be required with t he submittal of the mix design or at any time when directed by the Agency. The stockpile gradation data shall be derived by wet sieve analysis. Coarse aggregates for Superpave shall be furnished with at least three stockpiles for mixes with a nominal maxi mum aggregate size (NMAS) greater than or equal to 1 inch (25.0 mm), two stockpiles for mixes with a NMAS greater than or equal to 1/2 inch (12.5mm) and greater than 3/8 inch (9.5 mm), and one stockpile for mixes with a NMAS less than or equal to 3/8 inch (9.5 mm). No change in the JMF may be made without Agency approval. The Agency may approve changes in the design’s JMF or discontinue use of the design if placement, finishing, or compaction characteristics are determined to be unsatisfactory. At the time that the mix design is submitted, the Contractor shall provide batched asphalt mixture to the Agency, for determining asphalt ignition oven calibration, in accordance with the Agency’s Bituminous Concrete Policy Manual .
7-78 A minimum of 21 cale ndar days shall be allowed for the testing and evaluation of the submitted
mix design. Once a mix design is approved, the JMF will be valid until a change is made in aggregate source, RAM source, or asphalt binder grade. If a change is made in aggregate so urce or asphalt binder grade, a new mix design shall be submitted and a minimum 21 calendar day evaluation period shall be allowed prior to resuming production. If a change in the asphalt binder supplier is proposed, it shall be from an approved supplier a nd be in accordance with the Agency’s Bituminous Concrete Policy Manual . If aggregates prone to stripping are used in the mixture, an anti -strip additive meeting the requirements of Subsection 702.04 may be required as specified in Subsection 704.10 .
b.Superpave Mixtures .
1.Design Ranges and Values . The gradation of the c oarse aggregate, fine aggregate, and recycled asphalt materials (if used) shall be such that, when combined, the composite aggregate will meet the gradation requirements of Table 716.02A for the applicable bituminous concrete mixture type. The process of b lending the coarse aggregate, fine aggregate, and recycled asphalt materials (if used) shall be accomplished using separate bins. Blending in the stockpile will not be permitted. For each mix type, the JMF target value for each sieve shall be within the ra nges specified in Table 716.02A , and the JMF target value for other mixture properties shall meet the requirements specified in Table 716.02B . The value of N design will be determined by the Agency based on Design Lane/Design Life ESALs and shall be as spe cified on the Plans. The values of N initial and N max shall be as specified in Table 716.02C for a given value of N design. If the value of N design is not specified on the Plans, it shall be determined based on the number of Design Lane/Design Life ESALs as specified in Table 716.02C . If both the Design Lane/Design Life ESALs and the number of gyrations at N design are not specified in the Plans, then Ndesign shall be 65, except for Type IS mixtures, where N design shall be 50. The asphalt binder grade and traffic designation shall be as listed on the Plans . If the asphalt binder grade and traffic designation are not specified on the Plans , then paver placed pavement shall use grade 58E -28, and material used for surface preparation , temporary pavement, and non -paver placed pavement shall use grade 58S -28.
7-79 Table 716.02a – Gradation Design Ranges
Sieve Designation Percentage by Mass (Weight) Passing Square Mesh Sieves (Minimum – Maximum) Type IS Type IIS Type IIIS Type IVS Type IVSB 2 inch (50.0 mm) -- -- -- -- -- 1-1/2 inch (37.5 mm) 100 -- -- -- -- 1 inch (25.0 mm) 93 – 100 100 -- -- -- 3/4 inch (19.0 mm) X – 87 93 – 100 100 -- -- 1/2 inch (12.5 mm) -- X – 87 93 – 100 100 100 3/8 inch (9.50 mm) -- -- X – 87 93 – 100 93 – 100 No. 4 (4.75 mm) -- -- -- X – 87 X – 87 No. 8 (2.36 mm) 21 – 43 25 – 47 30 – 56 34 – 65 34 – 65 No. 16 (1.18 mm) -- -- -- -- -- No. 30 (0.600 mm) -- -- -- -- -- No. 50 (0.300 mm) -- -- -- -- -- No. 100 (0.150 mm) -- -- -- -- -- No. 200 (0.075 mm) 1.5 – 6.5 2.5 – 7.5 2.5 – 9.5 2.5 – 9.5 2.5 – 9.5 TABLE 716.02B – OTHER MIXTURE PROPERTY DESIGN RANGES AND VALUES Property Type IS Type IIS Type IIIS Type IVS Type IVSB Nominal maximum aggregate sieve size 1 inch (25.0 mm) 3/4 inch (19.0 mm) 1/2 inch (12.5 mm) 3/8 inch (9.50 mm) 3/8 inch (9.50 mm) Air voids 4.0% 4.0% 4.0% 4.0% 3.0% Voids in mineral aggregate 13.0% min. 14.0% min. 15.0% min. 16.0% min. 16.0% min. Dust proportion range (dry sieve) 0.50 – 1.20 0.50 – 1.20 0.50 – 1.00 0.50 – 1.00 0.50 – 1.00
7-80 Table 716.02c – Number of Gyrations By Traffic Level
Design Lane/ Design Life ESAL Value ESALs < 300,000 300,000 ≤ ESALs < 3,000,000 ESALs ≥ 3,000,000 Ninitial 6 7 8 Ndesign 1 50 65 80 Nmax 75 115 160 1 All Type IS mixtures shall have an N design value of 50 gyrations. All Type IVSB mixtures shall have an N design value of 65 gyrations.
2.Use of Recycled Asphalt Materials . The Contractor may choose to use RAM, consisting of RAP or RAS used either individu ally or in combination, as aggregate in Superpave bituminous concrete pavement mixtures. The amount of RAM used, expressed as a percentage of the total weight of aggregate in the mixture (including the RAM), shall not exceed the limits specified in Table 7 16.02D . TABLE 716.02D – MAXIMUM ALLOWABLE AMOUNT OF RAM BY MIX TYPE Property Type IS Type IIS Type IIIS Type IVS Type IVSB Maximum RAS content 1 3% 3% 3% 3% 0% Maximum combined RAP and RAS content 50% 25% 20% 20% 0% 1 RAS shall not be used in the wearing course. When RAM is used, the following conditions shall apply:
a.For Type IS, only 75% of the total RAM binder content shall be credited toward the design asphalt binder content.
b.When any amount of RAP is used, an analysis of the RAP material , including the extracted aggregate gradation, coarse aggregate specific gravity, fine aggregate specific gravity, and asphalt content shall be provided in the mix design.
c.When any amount of RAS is used, an analysis of the RAS material containing the extracted aggregate gradation, coarse aggregate specific gravity, fine aggregate specific gravity, asphalt content, and extracted binder performance grade shall be provided in the mix design.
7-81 Additionally, all provisions of AASHTO R 114 shall apply when developing the mix
design. Asphalt b inder shall specifically meet the quality requirements of AASHTO R 114, Section 7.1 through AASHTO R 114, Section 7.3 , with the extracted binder having a ΔT c value greater than -5.0°C when measured in accordance with AASHTO PP 113 and meeting the grades and traffic designations of asphalt binder specified on the Plans. The use of recycling agents or rejuvenators is not permitted .
d.Any change in the amount or c ombination of recycled materials shall require a new mix design unless otherwise approved by the Agency.
e.Should the characteristics of any proposed recycled material be such that an acceptable mixture cannot be produced or maintained, the recycled material will not be allowed for use on the Contract.
3.Superpave Mixture Design Process . AASHTO R 35 will be the method used to develop a mix that will meet the specified design criteria in accordance with AASHTO M 323 , unless otherwise noted. The Superpave mixture shall be designed using the following methodology:
a.Select materials (aggregate, aspha lt binder, additives).
b.Select design aggregate structure.
c.Select design asphalt binder content.
d.Evaluate moisture sensitivity and rutting susceptibility using the Hamburg wheel tracker test (HWTT) in accordance with AASHTO T 324 to ensure the crit eria outlined in Table 716.02E are met . Specimen fabrication, conditioning, and procedures for the HWTT shall be in accordance with the Agency’s Bituminous Concrete Policy Manual . The HWTT will not be applicable to material used non - paver placed pavement, surface preparation, temporary pavement, curbs, gutters, or sidewalks. TABLE 716.02E – HAMBURG WHEEL TRACKER TEST REQUIREMENTS Traffic (ESALs) Maximum Rut Depth Minimum Number of Passes Minimum Stripping Inflection Point (SIP) All 12.5 mm (1/2 in.) 20,000 passes 15,000 passes
7-82 e. Determine the cracking tolerance index (CT -Index) using the indirect tensile
cracking test in accordance with ASTM D8225 . Specimen fabrication, conditioning, and procedures for determination of the CT -Index shall be in accordance with the Agency’s Bituminous Concrete Policy Manual . The indirect tensile cracking test will not be applicable to material used non-paver placed pavement , surface preparation, temporary pavement , curb s, gutter s, or sidewalk s.
f.For mixes containing stripping prone aggregate, determine if anti -stripping additive is needed, and if so the correct dosage, using ASTM D3625 .
4.Super pave Job Mix Formula . The job mix formula for each mixture shall contain all of the following information :
a.A single percentage of aggregate passing each sieve identified in Table 716.02A .
b.When applicable, a single percentage of RAP and a single perc entage of RAS in the mixture.
c.A single percentage of asphalt binder to be added to the aggregate.
d.When applicable, a single percentage for every additive in the mixture. Each additive shall be identified by name and purpose (e.g. anti -strip, WMA tech nology).
e.A single percentage for air voids.
f.A single percentage for voids in mineral aggregate.
g.The values of N initial, Ndesign, and N max.
h.The mixing temperature.
i.The design compaction temperature. The Contractor’s mix design may specify either hot mix asphalt (HMA), or warm -mix asphalt (WMA). WMA shall be produced with a warm -mix asphalt technology meeting the requirements of Subsection 702.03 and at a lower mixing temperature.
5.Control Limits . Each mix design shall establish an upper and lower control limit (as applicable) for every JMF parameter to determine when action should be taken or production should be suspended.
7-83 (c) Bonded Wearing Course Mixtures .
1.General Requirements . Bonded w earing course (BWC) mixtures shall not contain any RAM, and WMA technology additives shall not be incorporated unless the additive also acts as an anti -strip agent and is dosed to abate stripping in accordance with Subsection 702.04 . The gradation of the coarse and fine aggregate shall be such that, when combined, the composite aggregate will meet the gradation requirements of Table 716.02F for the applicable bonded wearing course mixture type. The process of blending the coarse and fine aggregate shall be accomplished using separate bins. Blending in the stockpile will not be permitted. For each mix type, the JMF target value for each sieve shall be within the ranges specified in Table 716.02F , and the JMF target value for asphalt binder content shall be within the ranges specified in Table 716.02G . The asphalt binder grade and traffic designation shall be as listed on the Plans . If the asphalt binder grade and traffic designation are not speci fied on the Plans , then it shall be grade 58E-28. TABLE 716.02F – GRADATION DESIGN RANGES Sieve Designation Percentage by Mass (Weight) Passing Square Mesh Sieves (Minimum – Maximum) Type A Type B Type C 3/4 inch (19.0 mm) -- -- 100 1/2 inch (12.5 mm) -- 100 87 – 100 3/8 inch (9.50 mm) 100 87 – 100 48 – 83 No. 4 (4.75 mm) 41 – 54 25 – 37 25 – 40 No. 8 (2.36 mm) 22 – 31 22 – 31 22– 32 No. 16 (1.18 mm) 17 – 25 17– 22 16 – 25 No. 30 (0.600 mm) 13 – 17 13 – 17 12 – 19 No. 50 (0.300 mm) 9 – 12 9 – 12 9 – 15 No. 100 (0.150 mm) 6 – 9 6 – 9 6 – 9 No. 200 (0.075 mm) 4.0 – 6.0 4.0 – 6.0 4.0 – 6.0
7-84 Table 716.02g – Asphalt Binder Content Design Ranges
Property Type A Type B Type C Asphalt binder content design range 4.9% – 5.8% 4.8% – 5.6% 4.6% – 5.6%
2.Bonded Wearing Course Mixture Design Process . Bonded wearing course mixture shall be designed using the following methodology:
a.Select materials (aggregate, asphalt binder, additives).
b.Select design aggregate structure.
c.Select design asphalt binder content.
d.Conduct drain -down in accordance with AASHTO T 305. The loose mixture shall not exceed 0.10% drain -down when tested at a temperature equal to the mixing temperature plus 60°F, but not exceeding 360°F.
3.Bonded Wearing Course Job Mix Formula . The job mix formula for each mixture shall contain all of the following information :
a.A single percentage of aggregate passing each sieve specified in Table 716.02 F. Sieves that do not have a specified design range for a given mix type do not need to be included.
b.A single percentage of asphalt binder to be added to the aggregate.
c.When applicable, a single percentage for every additive in the mixture. Each additive shall be identified by name and purpose (e.g. anti -strip).
d.The design mixing temperature.
e.The design compaction temperature.
4.Control Limits . Each mix design shall establish upper and lower control limits (as applicable) for every JMF paramet er, to determine when action should be taken or production should be suspended.
7-85 716.03 BITUMINOUS MIXING PLANT AND LABORATORY . Bituminous concrete mixtures shall
come from approved producers, and shall be made in accordance with an approved plant QC plan. The requirements for plant QC plans are detailed in the Agency’s Bituminous Concrete Policy Manual . The bituminous mixing plant and laboratory shall meet the requirements detailed in the Agency’s Bituminous Concrete Policy Manual . 716.04 PREPARING AND MIXING BITUMINOUS CONCRETE MIXTURES . Bituminous concrete mixtures shall be prepared and mixed in accordance with AASHTO M 156 and the following:
a.Preparation of Asphalt Binder . The asphalt binder shall be uniformly heated to the temperature specified in the approved mix design. A continuous supply of the asphalt binde r at a uniform temperature shall be provided to the mixer at all times.
b.Preparation of Aggregates . The aggregates for the mixture shall be dried and heated at the mixing plant before being placed in the mixer. Flames used for drying and heating shall b e properly adjusted to avoid damage to the aggregate and to avoid depositing soot or unburned fuel on the aggregate. Mineral filler may be added to meet gradation requirements. The method of introducing the mineral filler into the mix shall be approved by the Agency. For batch plants, immediately after heating, the aggregates shall be screened and conveyed into separate bins ready for batching and mixing with asphalt binder.
c.Mixing . The dried aggregates shall be combined in the mixer at the appropriat e proportions required to meet the JMF and thoroughly mixed prior to adding the asphalt binder. All plants shall have a means of preventing oversized and foreign material from being incorporated into the mixer. For mix designs containing RAM, the dry and w et mixing times shall be adjusted to ensure that moisture from the RAM is completely dissipated prior to adding the liquid asphalt binder. The quantity of asphalt binder introduced into the mixer shall be the percentage specified in the accepted JMF. The mass or percentage of asphalt binder in the mix shall be specified on the weigh slip or demand ticket. After the required amounts of constituent material have been introduced into the mixer, the materials shall be mixed until a complete and uniform coati ng of the particles and a thorough distribution of the asphalt binder throughout the aggregate is obtained. If complete and uniform coating of the particles is not achieved, the wet mixing time shall be adjusted as approved by the Agency. The mixture, when discharged from the mixing unit, shall be at the temperature specified on the approved mix design unless otherwise approved by the Agency.
7-86 Sectio N 719 – Epox Y Resin Materials
719.0 1 EPOX Y BONDIN G SYSTEMS . Epoxy bonding systems shall be a grade and class adhesive conforming to the requirements of AASHTO M 235 . Systems shall be evaluated in accordance with the AASHTO Product Evaluation & Audit Solutions committee work plan for Evaluation of Epoxy Resin Based Adhesiv e Bonding Systems , be one of the products listed on the Agency’s Approved Products List , and meet the following requirements:
a.Epoxy Bonding System, Type IV . Type IV systems shall conform to the requirements of AASHTO M 235 for Type IV adhesives. Type I V systems shall be for use in load -bearing applications for bonding hardened concrete to hardened concrete and other materials and as a binder for epoxy mortars and concretes.
b.Epoxy Bonding System, Type V . Type V systems shall conform to the requirements of AASHTO M 235 for Type V adhesives and shall bond freshly mixed concrete to steel. Type V systems shall be for use in load -bearing applications for bonding freshly mixed concrete to hardened concrete and freshly mixed concrete to steel.
c.Epoxy Bonding System, Type VI . Type VI systems shall conform to the requirements of AASHTO M 235 for type VI adhesives. Type VI systems shall be for bonding and sealing segmental precast elements, as in segment -by-segm ent erection and for span -by-span erection when temporary post tensioning is applied. Elongation at break will not be required.
Source: Vermont Standard Specifications for Construction, 2024 Edition. Pages 1229–1237 of 1,380.