420.02 Materials.
POLYME R MODIFIED OPEN GRADED FRICTION COURSE
420.01 Description.
The work covered by this Section shall consist of constructing a hot mixed, hot laid polymer modified open graded friction course wearing layer generally placed on an existing pavement. The typic al cross section and the average weight per square yard will be shown on the plans. Requirements for all hot mix asphalt pavements as specified in Section 410 are applicable to this Section, subject to any exceptions contained herein. Quality Control/Quali ty Assurance (QC/QA) requirements as specified in Section 106 are applicable to this Section, subject to any exceptions contained herein.
420.02 Materials.
The materials furnished for use shall comply with the requirements of Section 410 and the following:
a.Aggregates . The aggregate shall be limited to 100% crushed aggregates of the following: granite, quarried quartzite, slag, sandstone or manufactured lightweight aggregate, all of which shall be from approved sources and meet the appropriate requirements of Sections 801 and 802. However, if additional dust (- 200 {- 75 µm} material) is needed, mineral filler (meeting the requirements of Section 805) or agricultural limestone may be used. If agricultural limestone is used, it shall meet the requirements of ASTM C 602, Standard Specification for Agricultural Liming Materials, for Class E agricultural limestone, so that a minimum of 80.0 % of the material will pass the No. 8 {2.35 mm} sieve and 25.0 % will pass the No. 60 {0.250 mm} sieve. In addi tion, a minimum of 5.0 % will pass the No. 200 {75 µm} sieve. No more than 10.0 % agricultural limestone shall be used. The aggregate shall be combined into a total blend that will produce an acceptable job mix within the gradation limits shown in the following table. The blend shall be made from at least two stockpiles of different gradations. At least 10% of the blend sha ll be taken from each stockpile. AGGREGATE GRADATION FOR OPEN GRADED FRICTION COURSE Sieve (Square Mesh Type) Percent Passing By Weight {Mass} 3/4 inch {19.0 mm} 100 1/2 inch {12.5 mm} 85 - 100 3/8 inch {9.5 mm} 55 – 65 No. 4 {4.75 mm} 10 - 25 No. 8 {2.36 mm} 5 - 10 No. 200 {75 µm} 2 - 4 As stated in Article 410.02 no RAP or RAS is Allowed .
b.Liquid Asphalt Binder . The liquid binder shall be a polymer modified PG 76 -22 meeting the requirements of Section 804. The proportion of liquid asphalt binder to total sample by weight {mass} shall be 6.0 % to 9.0 %. The exact proportion shall be fixed by the job mix formula. Additives or modifiers shall be used to prevent stripping of liquid asphalt binder. These additives or modifiers shall be furnished and used at no additional cost to the State.
c.Polymer . The polymer additive shall meet the requirements of Section 811.
d.Liquid Asphalt Binder Draindown . A fiber stabilizer or Evotherm 3G meeting the requirements given in Section 410 shall be incorporated into the mix to produce a maximum liquid asphalt binder cement draindown of 0.30 % or less when tested at 325°F {163°C} and 350°F {176°C} in accordance with AASHTO T305. The fiber shall be blended into the mix in accordance with the requirements given in Section 410.
420.03 Design
e.Tack Coat Materials Tack coat materials shall either be a CQS -1hp asphalt emulsion used in conjuncti on with the spray paver equipment as required in Subarticle 420.04 (d) or “PG Asphalt for Trackless Tack” with conventional paving equipment. All tack coat materials shall meet the requirements given in Section 804 except as modified by the requirements gi ven herein. The CQS -1hp shall be smooth and homogeneous and shall meet the requirements shown in the following table: CQS-1hp MODIFIED ASPHALT EMULSION TEST OF EMULSION Parameter Test Method Value Viscosity @ 77 ° F, SF AASHTO T 59 20 Min. 150 Max. Sieve Test, % AASHTO T 59 - 0.1 Max.1 24-Hour Storage Stability, % AASHTO T 59 - 1.0 Max. 2 Residue By Distillation AASHTO T 59 60 Min. - Oil Distillate, by Volume of Emulsion, % AASHTO T 59 - - Particle Charge AASHTO T 59 Positive 3 TEST OF RESIDUE FROM EMULSION Solubility in TCE, % AASHTO T 44 4 97.5 Min. - Elastic Recovery @ 50 °F AASHTO T 301 60.0 Min. - Penetration @ 77 °F AASHTO T 49 60 Min. 110 Max. Ductility @ 77.0 °F AASHTO T 51 40 Min. -
1.Sieve test may be waived based on successful application in the field.
2.After standing undisturbed for 24 hours, the surface shall show no white, milky -colored substance, but shall be a smooth homogeneous color throughout the sample.
3.If the Particle Charge Test is inconcl usive, a pH test (AASHTO T 200) shall be used with a maximum of 6.7 allowable.
4.ASTM D 5546 may be used when polymers block the filter during the test. The original "PG Asphalt for Trackless Tack" (no RTFO or PAV testing) shall conform to the physica l requirements shown in the following table: SPECIFICATIONS FOR PG ASPHALT FOR TRACKLESS TACK Parameter Specification Test Method Rotational Viscosity Maximum 3 Pa •s @ 135 °C AASHTO T 316 Penetration Maximum 25 @ 77 °F {25 °C}, 100 g. 5s AASHTO T49 Softening Point (°C) Minimum 70 AASHTO T 53 Dynamic Shear, G*/sin δ Minimum 1.0 kPa @ 82 °C AASHTO T 315
420.03 Design
The Open Graded Friction Course shall be designed with a minimum air void content of 12% according to ALDOT -259, OPEN GRADED ASPHALT CONCRETE FRICTION COURSE DESIGN METHOD. The contractor shall have the responsibility for the design of Section 420 mixes. The laboratory compacted density as determined in the j ob mix formula design shall not exceed 150 pounds per cubic foot {2400 kg/m3}; this corresponds with a maximum specific gravity value of 2.837 or a bulk specific gravity of 2.411. The work will be accepted on a LOT by LOT basis in accordance with the applicable requirements. Pay factors for air voids and density shall not apply.
420.04 Construction Requirements.
a.General . The requirements of Articles 410.03 through 410.07 shall apply except as modified hereinafter in this Article.
b.Rate of Placement of Tack Coat . The rate of application of the tack coat on the asphalt surface shall be 0.13 to 0.18 gallons per square yard within a tolerance of - 0.02 and +0.02 gallons per square yard for the PG Asphalt for Trackless Tack. CQS -1hP asphalt emulsion shall be applied at a rate of 0.18 - 0.23 gallons per square
423.01 Description.
yard within a tolerance of - 0.02 and +0.02 gallons per square yard. A uniform distribution of tack coat across the mat shall be enforced and streaked tack shots shall not be accepted.
c.Conventional Paving Equipm ent with the use of “PG Asphalt for Trackless Tack ” The use of conventional paving equipment shall be allowed when the tack coat material used is “PG Asphalt for Trackless Tack” meeting the requirements given in Subarticle 420.02. "PG Asphalt for Trackless Tack" shall be applied at a temperature of 300 °F to 375 °F, on a clean dry surface.
d.Spray Paver Paving Equipment with the use of CQS -1HP Asphalt Emulsion The requirements given in Article 410.03 shall be applicable to the construction of the open gra ded friction course except for the following: • The paving machine shall incorporate a tack distribution system, receiving hopper, feed conveyor, and a variable width, heated, ironing or vibratory type screed. • The tack distribution system shall include meter ed mechanical pressure sprayer to accurately apply and monitor the rate of application of the emulsion for the tack. The rate shall be uniform across the entire paving width. It shall be applied at a temperature of 140 – 180 °F. Application shall be immedi ately in front of the screed unit. No wheel or other part of the paving machine shall come in contact with the tack before the paving mix is applied. • Extensions added to the screed shall be provided with the same heating capability as the main screed unit , except for use on variable width tapered areas as approved by the Engineer.
e.Compaction Equipment . Item 410.03(a)5 is amended to require that steel wheel tandem (7 ton {6 metric ton} minimum size) rollers shall be furnished in sufficient numbers based on the quantity of material being placed to provide effective compaction coverage within the workable time period of the mix as designated by the Engineer. Rubber -tire rollers shall not be used.
f.Weather and Temperature Limitations . The weather, air, and surface temperature limitations for (polymerized) HMA mixes are found in Subarticle 410.03(b).
g.Compacting . Subarticle 410.03(g) is amended to require that rolling shall be as approved by the Engineer; no density tests will be required.
420.05 Method of Measurement.
The accepted quantities of polymer modified open graded friction course will be measured as provided in Article 410.08. The CQS -1hp emulsion or “PG Asphalt for Trackless Tack” for the tack coat will be measured in gallons in accordance with the requirements given in Article 109.02.
420.06 Basis of Payment.
a.Unit Price Coverage . Polymer Modified Open Graded Friction Course, measured as noted above, will be paid for at the contract unit price bid in accordance with Article 410.09. The unit price of the Open Graded Friction Course Tack Coat shall be full compensation for all materials, equipment, and labor required to furnish and place the tack.
b.Payment will be made under Item No .: 420 - A Polymer Modified Open Graded Friction Course – per ton {metric ton} 420 - B Open Graded Friction Course Tack Coat – per gallon SECTION 423 STONE MATRIX ASPHALT (SMA) (FIBER STABILIZED ASPHALT CONCRETE)
423.01 Description.
The work covered by this Section shall consist of constructing a hot mix asphalt layer of fiber stabilized stone matrix asphalt pavement on a prepared surface in accordance with these specifications
Source: Alabama Standard Specifications for Highway Construction, 2022 Edition. Pages 230–231 of 934.