4−46 Specifications for Road and Bridge Construction, with the following additions and amendments.
411.02 Materials.
411.02.1 Modified Asphalt Binder. This shall consist of a blend of neat asphalt cement and
crumb rubber, which are chemically bonded to produce a modified asphalt binder that complies with all the requirements of AASHTO MP1a for PG 76-34, with a separation less than 5% (AASHTO PP 5-93, Section 8.3). The modified asphalt binder shall not contain any particles of rubber or elastomeric material when tested in accordance with AASHTO T 44. It shall incorporate an aromatic VOC inhibitor to mitigate odors at a dosage rate that conforms to the manufacturer’s recommendation. The modified asphalt binder shall contain no polyphosphoric acid. In addition, the dynamic shear of the pressure aging vessel residue shall not exceed 5000 kPa at 7 oC. The elastic recovery at 4oC (AASHTO T301) shall be not less than 70%. The supplier of the modified asphalt binder shall certify the composition and PG grade of the modified asphalt binder. Asphalt Cement. The high temperature grade (AASHTO MP1a) of the neat asphalt cement shall not exceed PG 58-XX. Anti-Stripping Agent. An anti-stripping agent that heat stable and approved by the Engineer may be added to the neat asphalt cement prior to blending with the crumb rubber. The dosage (not exceeding 1.0% by weight of asphalt cement) shall be within the manufacturer’s specified range and shall be determined during the course of the mix design. (Note: Notwithstanding the addition of an anti-stripping agent, the asphalt binder grade shall be PG 76-34.) Crumb Rubber. The asphalt binder shall have a crumb rubber content of not less than 7% by weight of asphalt cement. The maximum size of the crumb rubber shall be 80 mesh. Chemical Bonding Agent. The chemical bonding agent shall be heat stable and compatible with asphalt and rubber.
411.02.2 Aggregate. The coarse aggregate shall be virgin crushed quarry rock from a RIDOT
approved source. Processed gravel shall not be permitted. There shall be no more than 10% flat or elongated particles (ASTM D4791). The aggregate wear, from resistance to abrasion, shall be a maximum of 30% as determined by the Los Angeles Abrasion Test (AASHTO T 96). The fine aggregate shall be crushed stone screenings, natural sand, or a blend thereof. No more than 10 percent of the total aggregate blend may be natural sand.
411.02.3 Mix Design. The mix design shall be in accordance with Subsection 401.02.5 of the RI
Standard Specifications, with the following exceptions:
a.The job-mix formula shall be within the following master range: Sieve Size Percent Passing 1/2" 100 3/8" 91 - 95 #4 40 - 45 #8 22 - 26 #30 9 - 12 #50 6 - 8 #200 4.0 4−47
b.The modified asphalt binder shall be the same grade and shall consist of the same components in the same proportions as the asphalt binder that will be used in production. The mixing and compaction temperatures shall be the same as those that will be used in production. The optimum modified asphalt binder content shall be not less than 6.0%.
c.The Marshall specimens shall be compacted with 50 blows on each side. The Moisture Sensitivity shall be determined in accordance wi th AASHTO T-283. At the optimum modified asphalt binder content, the mix shall satisfy the following requirements: Property Requirement Stability (lb) 1000 min. Flow (1/100 in.) 8 - 16 Voids (%) 4 -6 V M A ( % ) 1 8 m i n . Moisture Sensitivity (%) 80 min.
411.03 Construction Methods .
411.03.1 Surface Preparation. All surface preparations shall be completed prior to applying the
PPEST. All manhole covers, water boxes, catch basins and other such structures shall be adjusted prior to paving. These shall be covered and the location of each referenced for cleaning after paving. All localized depressions, ruts, trench cu ts, utility settlements and joint settlements shall be brought to grade with a Type I-2 hot mix or high performance cold patch shim course. A tack coat shall be applied to these surfaces before the shim course is placed. High spots, localized bumps and joints shall be brought to grade by milling or other treatments approved by the Engineer. The entire perimeter of the pavement on which the PPEST is to be placed shall be milled. The milled wedge shall be 3 feet wide, triangular in shape and 1-1/4 inches at the extreme edge and feathered at the inside edge. At the limits of the work and at all cross streets, driveways, and any other locations where the PPEST will adjoin an existing pavement, the milling shall facilitate a smooth transition of the profile between the PPEST and the existing pavement. The transition shall be prior to the termini of any traffic detector loops. The surface shall be swept and thoroughly cleaned of vegetation, debris, loose aggregate, soil and dust, particularly soil that is bound to the surface. All matter shall be legally disposed off site. Prior to application of the surface treatment, the Contractor shall obtain from the Engineer approval and acceptance of the surface preparation.
411.03.2 Production Tolerances. The aggregate gradation and asphalt binder content of the
production mix shall comply with the job-mix form ula and optimum asphalt binder content, within the following tolerances: Sieve Size Tolerance 1/2" - 3/8" ±5% #4 ±7% #8 ±4% #30 ±4% #50 ±3% #200 ±1.5% Asphalt Binder ±0.3%
411.03.3 Mixing and Compaction Temperatures. The mixing and compaction temperatures
shall be as recommended by the supplier of the modified asphalt binder.
Source: Rhode Island Standard Specifications (Bluebook), 2024 Edition. Pages 224–225 of 826.