4−49SECTION 412 RUBBERIZED ASPHALT CHIP SEALING
412.01 DESCRIPTION. This specification covers all materi als, equipment, constr uction, application
and post-placement procedures for the rubberized asphalt chip sealing of existing paved surfaces at the locations designated on the plans and as directed by the Engineer. The work shall consist of an application of rubberized asphalt binder followed by an application of pre-coated cover aggregate in accordance with this specification and as directed by the Engineer.
412.02 Materials.
412.02.1 Asphalt Cement. Neat asphalt cement for the rubberized asphalt shall meet all the
requirements of AASHTO MP1a for PG 58-28. The high temperature grade shall not exceed PG 58.
412.02.2 Anti-Stripping Agent. If necessary for water resistance, an anti-stripping agent that is
heat stable and approved by the Engineer shall be added to the neat asphalt cement prior to blending with the granulated rubber. The dosage (up to 1.0% by weight of neat asphalt cement) shall be determined during the course of the surface treatment design.
412.02.3 Granulated Rubber. The granulated rubber shall be vulcanized rubber from the ambient
temperature processing of scrap pneumatic tires. The granulated rubber shall meet the following gradation. No substitutions will be accepted. Sieve % Passing #10 100 #16 90-100 #30 25-75 #80 0-20 The use of rubber of multiple types from multiple sources is acceptable provided that the overall blend of rubber meets the gradation requirements. The length of the individual rubber shall not exceed 1/8". Certification shall be provided by the rubber supplier.
412.02.4 Cover Aggregate. The cover aggregate shall be virgin crushed quarry rock from a
RIDOT approved source. Processed gravel will not be permitted. For the material retained on the #4 sieve, no more than 10% of the particles shall have a flatness or elongation ratio greater than 3:1 (ASTM D4791). The aggregate wear, from resistance to abrasion, shall be a maximum of 30% as determined by the Los Angeles Abrasion test (AASHTO T96). The aggregate shall be pre-heated to a temperature between 280º F and 320º F and be uniformly and completely pre-coated with a PG 64-28 or PG 58-28 prior to application. The asphalt content for the pre-coating shall be determined by laboratory and field testing and be approved by the Engineer. The gradation shall meet the following limits: Sieve Size % Passing 1/2" 100 3/8" 85-100 1/4" 0-25 # 4 0 - 5 # 8 0 - 3 #200 0-2 4−50 412.02.5 Engineering. The contractor shall determine the asphalt content and mixing time of the pre-coated aggregate to obtain a uniform and complete pre-coating. Samples of the same shall be forwarded to the Engineer for approval. Design of the rubberized asphalt chip seal surface treatment shall be the responsibility of the contractor. The application rate of the rubberized asphalt shall be at least 0.60 gallons per square yard. The application rate of the pre-coated cover aggregate shall be between 30 and 40 pounds per square yard. No later than two weeks before work commences, the contractor shall submit for the approval of the Engineer the surface treatment design, with supporting test data, specifying the additives for the rubberized asphalt, application rate of the rubberized asphalt, and the source, composition, and application rate of the cover aggregate. Samples of each material shall be included with the submittal. Once the materials and design are approved, no substitution will be permitted unless approved by the Engineer.
412.02.6 Rubberized Asphalt. Granulated rubber shall be added to the PG58-28 asphalt cement
at a rate of 20 ± 3% by total weight (i.e., asphalt cement plus granulated rubber). The supplier of the rubberized asphalt shall certify the percent of granulated rubber in the blend. The temperature of the asphalt cement shall be between 350ºF and 425ºF at the time the granulated rubber is added. The asphalt cement and granulated rubber shall be combined and mixed together in a blender unit and reacted for a minimum of one hour. The temperature of the rubberized asphalt shall be above 325º F during the reaction period.
412.02.7 Delays. When a job delay occurs after full reaction, the rubberized asphalt may be
allowed to cool. The rubberized asphalt shall be reheated slowly just prior to application, but not to a temperature exceeding 375ºF. An additional quantity of granulated rubber or additive not exceeding 3% by volume of the rubberized asphalt may be added after reheating.
412.02.8 Field Viscosity Tests. Viscosity tests shall be run by the contractor on each load of
rubberized asphalt using a H aake-type field viscometer. One viscosity test shall be run prior to, and another after, the addition of diluent (if used). The viscosity of the final product shall be in the range of 1000 to 3000 centipoise.
412.03 Construction Methods.
412.03.1 Equipment
a.Mechanical Blender. A mechanical blender for proper proportioning and thorough mixing of the asphalt-cement and granulated rubber is required. This unit shall be equipped with: an asphalt totaling meter (gallons); a flow rate meter (gallons per minute); a positive displacement auger to feed the rubber properly to mixing chamber at the specified rate; and a static motionless mixer. The blender will have a separate asphalt cement feed pump and finished product pump to maximize production, and shall be capable of providing 100% proportional mix at any given time during the blending cycle; supporting documentation from the manufacturer shall be submitted to the Engineer.
b.Distributor Truck. On projects exceeding 35 tons of rubberized asphalt, at least two pressure-type bituminous distributor trucks in good condition will be required. The distributor shall be equipped with an internal heating device capable of heating the material evenly up to 425ºF, an 4−51internal agitation unit capable of maintaining a proper mix of asphalt cement and granulated rubber, have adequate pump capacity to maintain a high rate of circulation in the tank and to spray the rubberized asphalt at a viscosity of 1000 to 3500 centipoise, and have adequate pressure devices and suitable manifolds to provide constant positive cut-off to prevent dripping from the nozzles. The distributor shall be equipped with an electronically controlled computerized compensation unit for controlling application rates at various width and speed changes. The application unit shall have electronic controls and a digital read-out install ed and operated from the inside of the cab of the distributor. The distributor bar shall be fully circulating. Any distributor that produces a streaked or irregular distribution of the material shall be promptly repaired or removed from the project. The distributor equipment shall include a tachometer, pressure gauges, volume measuring devices, and a thermometer for reading temperature of tank contents. Controls for the width and rate of spray from the spray bar shall be located in the cab of the truck, and shall enable uniform applications to be made at the specified rate per square yard within a tolerance of 0.05 gallons per square yard. A “bootman” shall accompany the distributor and ride in a position so that all spray bar nozzles are in full view and readily accessible for unplugging.
c.Hauling Equipment. Trucks for hauling cover aggregate shall be rear discharge conveyor-fed or “live bottom” trucks and shall be equi pped with a device to lock onto the hitch at the rear of the aggregate spreader to prevent spillage. Sufficient hauling vehicles will be available to ensure continuous operation of the distributor and aggregate spreader.
d.Aggregate Spreader. The aggregate spreader shall be hydrostatically driven and self- propelled. It must be equipped with a hydraulically controlled variable adjustable head that is capable of spreading cover aggregate in widths from 4.5 to 18 feet. The spreader shall be mounted on pneumatic tires, and shall apply the cover aggregate on the road surface in a manner that ensures that the tires do not contact the road surface until after the cover aggregate has been applied. The unit shall be equipped with an electronic radar type sensor used to measure ground speed and that will automatically adjust the co ver aggregate application rate depending on width of application and the speed of the spreader. It shall have the ability to apply cover aggregate at a uniform coverage on any grade from 0 - 6%. The spreader shall be equipped with an integral hopper with a minimum capacity of 5 tons of cover aggregate which shall be filled by trucks in a manner which ensures that the truck tires never come in contact with rubberized asphalt treated road surfaces until the cover aggregate has been properly applied. To maintain constant cover aggregate application, a self-locking truck hitch will permit towing of aggregate trucks without stopping the spreader. It will be capable of maintaining positive engagement over irregular terrain.
e.Pneumatic Tire Rollers. A minimum of two self-propelled, multiple wheel pneumatic tire rollers shall be used. Each shall weigh a minimum of 10 tons, have a total compacting width of at least 56 inches, and a minimum tire pressure of 100 psi.
412.03.2 Weather Limitations. The rubberized asphalt shall not be applied when weather
conditions are unfavorable to obtaining a uniform spread. Construction s hall proceed only when the surface temperature is at least 50ºF and rising. No water or moisture shall be present on the road surface.
412.03.3 Surface Preparation. The area to be sealed shall be swept and thoroughly cleaned of
4−52 vegetation, debris, loose aggregate and soil, particularly soil that is bound to the surface. All cracks shall be thoroughly cleaned. All localized depressions, trench cuts, utility settlements, and joint settlements shall be brought to grade with hot mix Type I-2 shim course. A tack coat shall be applied to the surfaces before the shim course is placed. High spots, localized bumps and joints shall be brought to grade by milling or other treatm ents as approved by the Engineer. At the limits of the work, there shall be a smooth milled transit ion of the profile between the existing pavement and the rubberized asphalt chip seal. All thermoplastic pavement markings shall be removed and disposed off site. Manholes, valve boxes and other service entrances will be protected from the applied material. Bridge joints, appurtenances, drainage openings, etc., shall be covered and sealed so as not to clog or permit the entry of loose aggregate. Prior to application of the rubberized asphalt chip seal, the Contractor shall obtain from the Engineer approval and acceptance of the surface preparation.
412.03.4 Construction Procedures.
a.Treatment of Distressed Areas. Prior to rubberized asphalt chip sealing of the entire roadway within the specified limits, a rubberized as phalt chip seal shall be applied to any distressed areas within these limits, as directed by the Engineer. The Construction Procedure shall be as specified under Rubberized Asphalt Application, A ggregate Application, and Rolling. This quantity of work shall be measured and paid under Sections 412.04 and 412.05 of this specification.
b.Rubberized Asphalt Application. The rubberized asphalt shall be applied uniformly at double coverage at a temperature of 325ºF to 425ºF at the approved design application rate within a tolerance of ± 0.05 gallons per square yard. The application rate shall be not less than 0.60 gallons per square yard. Longitudinal joints shall be reasonably true to line and parallel to centerline. Where any construction joint occurs, the edges shall be broomed back and blended so there are no gaps and the elevations are the same, and free from ridges and depressions. Longitudinal joints shall be overlapped from 4 to 6 inches. During application, adequate provision shall be made to prevent marring and discoloration of adjacent pavements, curbing, st ructures, vehicles, foliage or personal property.
c.Cover Aggregate Application. The application of cover aggregate shall follow as close as possible behind the application of the rubberized asphalt which shall be applied no further in advance of the aggregate spreader than can be immediately covered. Construction equipment or other vehicles shall not drive on the uncovered rubberized asphalt. The cover aggregate shall be spread uniformly and completely across the hot r ubberized asphalt by a self-propelled spreader at the approved design application rate within a tolerance of + 5 pounds per square yard. In no case shall the application rate shall be less than 30 pounds per square yard. Any deficient areas shall be covered with additional cover material to provide complete coverage.
d.Rolling. Rolling with pneumatic tire rollers shall commence immediately following spread of pre-coated aggregate. There shall be at l east three passes of a roller to embed the cover aggregate particles firmly into the rubberized asphalt. No steel wheel rollers will be allowed.
e.Initial Sweeping. After the aggregate has been rolled and embedded into the rubberized asphalt and the pavement has cooled, all loose material shall be swept and removed offsite. This shall be done at a time and in a manner so as to not displace any embedded aggregate or damage the rubberized asphalt surface. The accumulations of the sweepings shall be collected and disposed properly off site. 4−53f. Site Clean Up. The contractor shall uncover and unseal all drainage openings and clean any covers or grates that the cover aggregate and rubberized asphalt may have adhered to, and shall remove any excess material in areas such as driveways, gutters, and intersections as specified by the Engineer. The contractor shall, on a daily basis, remove any debris associated with the performance of the work.
g.Traffic. Traffic will not be permitted on the surface until the rubberized asphalt binder has cured sufficiently to minimize any dislodging of cover aggregate. The pilot car shall be used to guide and control speed of traffic. The contractor shall be responsible for any damage done to vehicles as a result of the operation. Any damage to the rubberized asphalt chip seal shall be repaired by the contractor, to the satisfaction of the Engineer and at no additional cost to the State.
h.Post Placement Sweepings. There shall be post placement sweepings at the following times:
1.Seven to ten days after the rubberized asphalt chip sealing operation; 2. Three to five weeks after the rubberized asphalt chip sealing operation; 3. At the end of the first winter after the rubberized asphalt chip sealing operation. For each sweeping, all loose cover aggregate shall be removed from the pavement surface, including the shoulders. The accumulations of sweepings shall be collected and properly disposed off-site.
412.04 METHOD OF MEASUREMENT. “Rubberized Asphalt Chip Sealing” will be measured by
the number of square yards of rubberized asphalt chip seal completed in place in accordance with the contract or as directed by the Engineer.
412.05 BASIS OF PAYMENT. The accepted quantities of “Rubberized Asphalt Chip Sealing” will
be paid for at the contract unit price per square yard of the type and application rate specified. The price so-stated shall constitute full and complete compensation for traffic control and pilot car; mobile phones; surface preparation; furnishing, transporting, handling, placing and rolling the material specified; initial sweeping and removal of excess aggregate; site clean up; furnishing of all labor, tools, equipment and incidentals for the satisfactory completion of this item; and all other work not specifically identified in the Contract Provisions as separate items of work. The shim course, including tack coat, and each post placement sweeping will be paid for under separate items in the contract. Ten percent of the total amount due the contractor will be withheld until the final sweeping and at least 60 days after all the rubberized asphalt chip seal locations have been open to traffic and it has been determined that the rubberized asphalt chip seal is performing satisfactorily. SECTION 413 [SECTION NOT USED]
Source: Rhode Island Standard Specifications (Bluebook), 2024 Edition. Pages 227–231 of 826.