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D3320 – Standard Test Method Technical Guide
📦 Scope and Material Composition
This specification, designated D3320/D3320M −18 (Reapproved 2024), covers mineral-colloid-stabilized, emulsified coal-tar pitch suitable for use as a weather-protective and aliphatic-solvent resistant coating over bituminous pavements of airports, parking areas, and driveways. The emulsion must be manufactured using tars having viscosities of RT-11 or higher, conforming to the requirements of Specification D490.
Mineral fillers, referred to as mineral colloids, shall consist of finely ground clay, silica, or other inert inorganic materials. The standard provides a specific Warning that bentonitic or highly expansive clays may cause drying and shrinkage problems that affect the durability of the pavement sealer. When specified, the emulsion may be fortified with antifreeze.
📐 Physical Properties and Application Parameters
The emulsion must be of suitable consistency for application by brush, squeegee, roller, or suitable spray equipment. It must be used as received, and shall not be diluted with water or thinned by heating. The material shall bond firmly to properly prepared damp or primed surfaces.
The product must have a smooth, uniform consistency without settlement or segregation in storage that cannot be readily dispersed by ordinary stirring. The material must conform to the physical properties outlined in the table below.
⚠️ Critical Application Conditions: Pavement and ambient temperature must be no less than 7 °C [45 °F] at the time of application and for at least 12 hours thereafter. No precipitation (rain, snow, etc.) should occur until the emulsion has fully dried. Failure to adhere to these conditions severely compromises bond strength and overall durability.
| 📏 Property | ⚡ Specification Requirement | 📐 Performance / Limit |
|---|---|---|
| Tar Base Viscosity | ≥ RT-11 | Conforms to D490 |
| Application Rate | Single Coat Application | 0.3 to 0.4 L/m² [¾ to 1 gal/100 ft²] |
| Drainage Resistance | No appreciable drainage | Up to 0.8 % incline [0.1 in./ft] |
| Application Method | Brush, squeegee, roller, or spray | No dilution or heating allowed |
| Service Temperature | Minimum ambient & pavement temp | 7 °C [45 °F] |
⚖️ Test Methods and Compliance
Conformance to D3320/D3320M requires adherence to referenced standards. Test Methods D2939 are referenced for evaluating emulsified bitumens used as protective coatings. Practice D140/D140M governs the sampling of asphalt materials. Kerosine used in testing must conform to Specification D3699 or Federal Specification VV-K-211.
Values stated in either SI units or inch-pound units are to be regarded separately as standard. Combining values from the two systems may result in nonconformance with the standard.
🚨 User Safety Responsibilities: This standard does not purport to address all safety concerns, if any, associated with its use. The user of this standard bears the responsibility for establishing appropriate safety, health, and environmental practices and determining the applicability of regulatory limitations prior to use.
❓ Frequently Asked Questions
🔍 What is the minimum application temperature for an emulsified coal-tar pitch sealer per D3320?
The pavement and ambient temperature must be no less than 7 °C [45 °F] at the time of application and for at least 12 hours following the application to ensure proper curing and film adhesion.
💡 Can the emulsified coal-tar pitch be diluted with water or thinned by heating?
No. The standard strictly specifies that the material shall be used as received. It shall not be diluted with water or thinned by heating, as altering the formulation can negatively impact performance and will void conformity with the specification.
📌 What type of mineral filler is required in a mineral-colloid-stabilized emulsion?
The mineral filler must consist of finely ground clay, silica, or other inert inorganic materials. The specification specifically warns against using bentonitic or highly expansive clays, which can lead to drying and shrinkage problems.
⚡ What are the required coverage rates and drainage limits for the applied coating?
The material must be suitable for application in single coats of approximately 0.3 to 0.4 L/m² [¾ to 1 gal/100 ft²] without appreciable drainage on inclines up to 0.8% [0.1 in./ft].