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D4990-97 – Standard Test Method Technical Guide
📐 Scope and Classification
This specification covers glass felt impregnated with coal-tar intended for use with coal-tar pitch in built-up roofing and waterproofing systems. The material is classified as one type under Section 4.1. Key terminology includes “net dry mass,” defined as the mass of the coal-tar-impregnated glass felt exclusive of wrapping and packing material, after drying to constant weight and removing all detached comminuted surfacing material (Section 3.2.1). Values are stated in SI units as standard.
⚙️ Materials and Manufacture
The felt shall be a thin, porous sheet of uniformly distributed glass fibers, bonded with a water-resistant resinous binder. During manufacture, the felt is impregnated with coal-tar which may contain a mineral stabilizer, ensuring even distribution and coating of fibers. The product is surfaced with a fine comminuted material to prevent sticking in the roll, without interfering with ply adhesion (Section 5).
📊 Physical Property Requirements
Per Section 6, the material must conform to the physical properties, dimensions, and masses prescribed in Tables 1 and 2. The table below summarizes key requirements from the standard text.
| 🟦 Property | 📏 Condition | 🎯 Requirement |
|---|---|---|
| Unrolling Behavior | 10°C to 60°C (50°F to 140°F) | No cracking or sticking |
| Pliability Conditioning | 25 ± 1°C (77 ± 2°F) for at least 1 hour | Test in air at same temperature |
| Coal-Tar Extraction | Per D146/D146M Section 16 | Desaturated felt remains flat, unbuckled, with fibers firmly set |
Additional specifications such as net dry mass and dimensional tolerances are detailed in Tables 1 and 2 of the standard.
For pliability testing, ensure the specimen is conditioned in air at 25 ± 1°C (77 ± 2°F) for at least one hour prior to evaluation.
Safety concerns related to test methods are addressed in Section 8 of this standard. Users should establish appropriate health and safety practices before use.
❓ Frequently Asked Questions
🔍 What is the scope of ASTM D4990?
The scope covers coal-tar glass felt used with coal-tar pitch in built-up roofing and waterproofing systems.
💡 What are the material composition requirements?
The felt must be made of glass fibers bonded with water-resistant resin and impregnated with coal-tar, with optional mineral stabilizer.
⚡ What is the net dry mass definition?
Net dry mass is the mass of the impregnated felt after drying to constant weight and removing detached surfacing material.
📌 What temperature range is specified for unrolling?
The product must not crack or stick when unrolled between 10°C and 60°C (50°F to 140°F).