A. Conventional Chip Seal Binder: Asphalt Emulsion, typically a Polymer-Modified Emulsified Asphalt (PME), meeting MassDOT's latest specifications (e.g., M3.06, M3.12). The specific grade (e.g., CRS-2P, CSS- 1hP) will be selected by the Engineer based on the design mix. B. 20% Rubber Chip Seal Binder: 20% Asphalt Rubber (AR) binder, composed of asphalt cement, an extender oil (if needed), and approximately 20% Crumb Rubber Modifier (CRM) by weight of the total binder. The AR must be a hot-applied, reacted blend. Blending and Reaction: The asphalt and CRM must be combined at the production site and allowed to react for a specified period (e.g., a minimum of 45 minutes) at elevated temperatures (e.g., 350°F to 425°F as per typical MassDOT/agency special provisions. The final binder must meet all specified performance-graded (PG) asphalt requirements (e.g., M320) and exhibit a minimum elastic recovery (e.g.,>60%). Aggregate (Chips): Durable, uniform-quality aggregate (crushed stone or crushed gravel) meeting MassDOT's material specifications (e.g., M4.05.0) for chip sealing. Aggregate gradation shall be specified (e.g., typically a No. 8 or No. 7 stone). Chips must be clean and dust-free.
