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D43 – Standard Test Method Technical Guide
📋 Scope and Application of ASTM D43 / AASHTO M121
This specification, designated under ASTM D43/D43M (Reapproved 2024) and as AASHTO No. M121, covers the requirements for coal tar primer intended for use with coal tar pitch in roofing, dampproofing, and waterproofing systems. The primer is suitable for application to concrete, masonry, and existing coal tar surfaces, both below and above ground level.
🛠️ Unit Systems Requirement: Per Section 1.2, the values stated in SI units or inch-pound units are to be regarded separately as standard. Each system must be used independently of the other to ensure full conformity with this specification.
Developed in accordance with internationally recognized principles on standardization, this specification has been approved for use by agencies of the U.S. Department of Defense. It is the responsibility of the user to establish appropriate safety, health, and environmental practices prior to use.
📊 Physical Properties and Specification Limits
Coal tar primer must be a distillate of coal-gas tar or coke-oven tar, conforming to strict physical requirements. The key properties verified during testing are summarized in the table below.
| 🟦 Property | 📐 Specification Requirement | ⚡ Test Method |
|---|---|---|
| Water Content | Not more than 1 % | Practice D370 |
| Consistency at 5°C [41°F] | Entirely fluid and crystal free | Section 3.1, Note A |
| Specific Gravity (38/15.5°C) [100/60°F] | Not less than 1.06 | Test Method D368 |
| Insoluble Matter | Not more than 0.5 % | Test Method D367 |
| Distillation, Up to 210°C [410°F] | Not more than 1 % | Test Method D246 |
| Distillation, Up to 235°C [455°F] | Not more than 10 % | Test Method D246 |
| Distillation, Up to 355°C [670°F] | Not less than 65 % | Test Method D246 |
| Coke Residue | Not more than 2 % | Test Method D168 |
⚠️ Compliance and Safety Notice: The user of this standard is responsible for establishing appropriate safety, health, and environmental practices. The “crystal free” requirement is verified by maintaining a 100 mL sample at 5°C [41°F] for 3 hours in a 125 mL Erlenmeyer flask with occasional stirring—no crystals may form.
🧪 Sampling and Test Methodology
Sampling of the coal tar primer must be performed in accordance with Practice D140/D140M. The properties listed in Section 3 are verified using established methods: water content by Practice D370, specific gravity by Test Method D368, and insoluble matter by Test Method D367. The distillation profile and coke residue are determined using Test Methods D246 and D168, respectively. Volume and specific gravity corrections are applied per Tables D347.
❓ Frequently Asked Questions
🔍 What are the primary applications of D43 coal tar primer?
The primer is specifically formulated for use with coal tar pitch systems in roofing, dampproofing, and waterproofing. It is designed for application to concrete, masonry, and existing coal tar surfaces both below and above ground level.
💡 What does the distillation profile indicate about the primer’s quality?
The strict distillation limits (no more than 10% up to 235°C [455°F] and no less than 65% up to 355°C [670°F]) ensure the primer has the correct balance of volatile solvents for application fluidity and non-volatile base components for long-term durability and adhesion.
⚡ What is the specific gravity requirement for this primer?
The specific gravity, determined by Test Method D368 at 38/15.5°C [100/60°F], must be not less than 1.06. This is a critical marker for the density and compositional consistency of the