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