AASHTO T 346-22 PDF

Full title and description

St AASHTO T 346-22 — Standard Method of Test for Glass Beads Used in Pavement Markings. This method specifies procedures for sampling, preparing, and testing glass beads used to produce reflectorized pavement markings, including gradation, roundness, refractive index, and a set of referee and alternative tests for flow, coating adhesion, flotation, and moisture resistance.

Abstract

AASHTO T 346-22 defines laboratory and sampling methods for evaluating the physical and optical characteristics of glass beads intended for traffic and pavement markings. The standard is organized into sections covering sampling during production and shipments, sieve analysis (gradation), roundness measurement, refractive index determination, and several referee or alternative tests (flow characteristics, moisture-resistant coating, flotation, and adherence/oven tests). It is intended to support specification compliance and quality control for beads used with reflectorized pavement markings.

General information

• Status: Active.
• Publication date: 2022.
• Publisher: American Association of State Highway and Transportation Officials (AASHTO).
• ICS / categories: 93.080 - Road engineering.
• Edition / version: Designation T 346-22 (2022).
• Number of pages: 8 pages.

Scope

The scope of T 346-22 covers methods for obtaining representative samples of glass beads (during production and from bulk shipments) and laboratory procedures to determine bead gradation, percent roundness, refractive index, and other performance attributes. The standard includes referee procedures and permits alternative tests when allowed by the purchasing agency. It is used to verify material conformance to specifications for reflectorized pavement markings.

Key topics and requirements

• Sampling protocols for production lots and bulk shipments (vertical sampling from containers).
• Gradation (sieve analysis) to classify bead sizes and types.
• Roundness measurement to assess sphericity (affects retroreflection and flow).
• Refractive index testing to classify optical performance of beads.
• Flow characteristics test (referee method) to evaluate discharge and application behavior.
• Moisture-resistant coating and flotation referee tests to evaluate coatings and bead buoyancy/cleanliness.
• Adherence/coating oven test (referee) and permitted alternative adherence tests.
• Use of referee procedures and allowance for alternative methods when specified by the purchasing agency.

Typical use and users

AASHTO T 346-22 is used by state transportation departments, materials laboratories, pavement-marking manufacturers and suppliers, quality-control/assurance personnel, and procurement/specification writers to evaluate and accept glass beads for road and airport pavement markings. It is commonly applied alongside specification AASHTO M 247 (Standard Specification for Glass Beads Used in Pavement Markings) when qualifying materials for purchase lists and project acceptance.

Related standards

The test method is routinely used with AASHTO M 247 (Specification for Glass Beads Used in Pavement Markings). Other related and referenced test methods and specifications include ASTM methods for sieve analysis and optical measurement (examples cited in industry guidance include ASTM D1214 and ASTM E1967) and national material specifications for traffic beads; purchasing agencies may reference additional or alternative test procedures as allowed by T 346.

Keywords

glass beads, pavement markings, retroreflective beads, gradation, roundness, refractive index, sampling, flow characteristics, moisture-resistant coating, flotation, adherence testing, AASHTO M247.

FAQ

Q: What is this standard?

A: AASHTO T 346-22 is a standardized test method that specifies how to sample and test glass beads used to create reflectorized pavement markings (e.g., beads dropped on or premixed into traffic paint or thermoplastic).

Q: What does it cover?

A: It covers sampling procedures, gradation (sieve) analysis, roundness (sphericity), refractive index, flow characteristics, moisture-resistant coating evaluation, flotation, and adherence/coating oven referee tests, plus permitted alternative tests as specified by the purchasing agency.

Q: Who typically uses it?

A: State DOTs, materials and testing laboratories, bead manufacturers and suppliers, pavement-marking contractors, and procurement/specification staff use T 346-22 for quality control, acceptance testing, and supplier qualification.

Q: Is it current or superseded?

A: As published with the 2022 designation (T 346-22), the standard is listed as active/current in product and standards listings; users should confirm the latest status via AASHTO or official standards distributors before procurement.

Q: Is it part of a series?

A: T 346 is a test-method standard intended to be used with material specifications such as AASHTO M 247 (Standard Specification for Glass Beads Used in Pavement Markings). Agencies commonly reference both the test method (T 346) and the specification (M 247) when qualifying and accepting beads.

Q: What are the key keywords?

A: Glass beads, pavement markings, retroreflection, gradation, roundness, refractive index, sampling, quality control, AASHTO M247.