Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D5643 – Standard Test Method Technical Guide
📐 Scope, Materials, and Composition
ASTM D5643/D5643M – 06 (Reapproved 2024) defines the specification for coal tar roof cement that is specifically formulated without asbestos fibers. This standard covers cement intended exclusively for trowel application in coal tar roofing and flashing systems. The material must be manufactured from a processed coal tar base, compounded with volatile solvents and mineral stabilizers. The finished compound must be mixed to a smooth, uniform consistency that facilitates effective hand troweling.
⚠️ Critical Material Restriction: This standard explicitly mandates that the cement is asbestos free. All mineral stabilizers utilized in the formulation must comply with this strict compositional requirement, aligning with modern health and safety regulations.
⚙️ Performance Requirements and Test Methods
The specification imposes rigorous performance criteria to ensure reliability in the field. The cement must exhibit excellent uniformity; a thoroughly stirred sample stored in a closed container for 72 hours at room temperature shall show no solvent separation or permanent settling. For workability, the cement must spread readily and permit the troweling of smooth coatings between 1.6 and 3.2 mm [1/16 to 1/8 in.] thick on vertical surfaces. Heat resistance is validated by testing behavior at 60°C [140°F], where the material must show no evidence of blistering, and sag or slide must not exceed 6 mm [1/4 in.]. Adhesion to damp or wet surfaces is quantified per Test Method D3409/D3409M, requiring a minimum average adhesion of 75%.
| 🟦 Property | 📏 Requirement / Limit | 📐 Test Method |
|---|---|---|
| Uniformity | No separation after 72h at room temp. | Section 5.1 / D140 |
| Workability (Vertical Surface) | 1.6 – 3.2 mm [1/16 – 1/8 in.] | Section 5.2 |
| Behavior at 60°C [140°F] | Sag ≤ 6 mm [1/4 in.]; No blistering | D6511/D6511M, §12 |
| Adhesion to Wet Surfaces | Min. average 75% | D3409/D3409M |
| ⚡ Flash Point | 38°C [100°F] minimum | D3143/D3143M |
💡 Sampling Best Practice: Sampling must be conducted in strict accordance with Practice D140/D140M. Material must be drawn from the original container immediately after stirring to a uniform consistency. Samples must be restirred thoroughly before withdrawing portions for individual tests to ensure representative results.
📊 Key Measured Properties and Limits
Beyond the performance tests, the standard defines specific chemical composition and analytical procedures. The base material must be processed coal tar. Water content is determined via Test Method D95. Nonvolatile matter is analyzed following Section 7 of Test Methods D6511/D6511M. Insoluble matter is measured using Procedure No. 2 of Test Method D4.
| 🎯 Analyte / Component | ⚡ Requirement / Standard Method |
|---|---|
| Base Material | Processed Coal Tar |
| Mineral Stabilizers | Asbestos Free |
| Water Content | Per Test Method D95 |
| Nonvolatile Matter | Per D6511/D6511M, Section 7 |
| Insoluble Matter | Per Test Method D4, Procedure No. 2 |
🚨 Safety Compliance: With a minimum flash point of 38°C [100°F], this material is considered flammable. Users must strictly adhere to all local, state, and federal regulations regarding the handling, storage, and disposal of solvent-bearing bituminous compounds. Ensure adequate ventilation and eliminate all ignition sources during application.
❓ Frequently Asked Questions
🔍 How does D5643/D5643M differ from traditional coal tar cement specifications?
The primary distinction is the absolute prohibition of asbestos fibers. This specification mandates that the mineral stabilizers must be entirely asbestos free, requiring alternative reinforcing fillers to achieve the necessary consistency and performance.
💡 What does the adhesion to wet surfaces test measure?
This critical test, conducted per D3409/D3409M, evaluates the cement’s ability to bond effectively with damp, wet, or underwater surfaces. The material must retain a minimum average of 75% adhesion, which is essential for reliable performance in typical roofing and flashing repair scenarios where substrates are not perfectly dry.
⚡ Why is the flash point specified at 38°C (100°F)?
The flash point requirement is a fundamental safety parameter. It defines the lowest temperature at which the material’s volatile solvents can produce an ignitable mixture in air. This 38°C [100°F] minimum threshold drives safe storage, handling, and application protocols to mitigate fire and explosion risks.
📌 What is the recommended application thickness for vertical surfaces?
The standard requires the cement to be workable enough to be troweled into smooth coatings ranging from 1.6 mm [1/16 in.] to 3.2 mm [1/8 in.] thick on vertical surfaces. This thickness range ensures adequate coverage and performance without excessive sagging or sliding.