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D5973-97 – Standard Test Method Technical Guide
📐 Scope and Materials
ASTM D5973 – 97 (Reapproved 2017) specifies the material requirements for preformed elastomeric strip seals used in expansion joint sealing, along with their corresponding steel locking edge rails. The scope specifically addresses non-reinforced strip seals that mechanically lock into structural steel locking lugs. The sealing element can be a single layer strip or have multiple internal webs tailored to the project’s demands.
The steel locking edge rail is a critical load-bearing component that must be anchored into the structure per the purchaser’s specific details. Standard inch-pound units are used throughout the specification. The standard was developed in accordance with international principles on standardization (WTO TBT).
⚙️ Material Requirements and Testing Regimen
The standard delineates strict guidelines for two primary materials: the structural steel locking edge rail and the elastomeric sealing compound.
Structural Steel Locking Edge Rails (Section 4.2)
The locking edge rail must be manufactured from structural steel conforming to one of three primary ASTM specifications. The choice of steel depends on the structural load requirements and the desired corrosion protection strategy for the bridge or structure.
| 🟦 Steel Type | 📏 Applicable ASTM Specification | 🎯 Typical Application / Characteristic |
|---|---|---|
| Carbon Steel | A36 / A36M | General structural fabrication where painting is required. |
| High-Strength Low-Alloy | A572 / A572M | Higher strength-to-weight ratio for longer spans or reduced material cost. |
| Weathering Steel | A588 / A588M | Atmospheric corrosion resistance for uncoated applications (per FHWA T 5140.22). |
⚠️ Technical Advisory: When utilizing weathering steel (A588) for locking edge rails, the standard explicitly references FHWA Technical Advisory T 5140.22. Designers must ensure environmental conditions are suitable for uncoated weathering steel to prevent staining or accelerated corrosion.
Elastomeric Strip Seal Compound (Section 4.1)
The preformed seals are manufactured from a durable elastomeric compound. While D5973 focuses on material requirements, it establishes the mandatory testing framework through a critical suite of ASTM test methods to verify compound quality and durability.
| 🟦 Test Method | 📏 Property Measured | ⚡ Significance |
|---|---|---|
| D2240 | Durometer Hardness | Ensures the seal has the correct stiffness for insertion and movement. |
| D412 | Tensile Strength / Elongation | Measures the seal’s ability to stretch without tearing under joint opening. |
| D395 | Compression Set | Determines the seal’s ability to maintain a watertight seal under constant compression. |
| D1149 | Ozone Cracking Resistance | Critical for long-term durability in outdoor environmental exposure. |
| D471 | Effect of Liquids (Oil/Swell) | Evaluates resistance to oils, fuels, and de-icing chemicals on the rubber. |
| D573 | Heat Aging | Accelerated aging test to predict long-term performance in service. |
| D4070 | Adhesive Lubricant | Required specification for the lubricant used during installation of the seal into the rail. |
💡 Pro Tip: Although D5973 focuses on the materials for fabrication, Section 1.1 strongly recommends the development of a practical watertightness test (either in the field or in a testing lab) to validate the system’s performance against water ingress after installation.
🛠️ Fabrication and Installation Guidelines
Fabrication of the seal is specified as preformed elastomeric strips that can feature single or multiple internal webs for enhanced performance (Section 1.1). The locking edge rail is fabricated from structural steel and typically involves welding; therefore, fabrication must comply with American Welding Society (AWS) standards as implied by the terminology section. The standard explicitly states that the steel edge rail design and anchorage are the responsibility of the purchaser, ensuring site-specific structural calculations are handled appropriately. Critical considerations specifically called out for highway bridge applications include limits on maximum joint opening and minimum steel thicknesses.
❓ Frequently Asked Questions
🔍 What is the primary purpose of ASTM D5973?
Its primary purpose is to establish the material requirements for the two main components of a preformed strip seal expansion joint system: the elastomeric sealing element and the steel locking edge rail.
⚡ Does D5973 specify the structural design of the expansion joint assembly?
No. While it covers the material specifications for the locking edge rail (steel type), the structural design, anchorage details, and required steel thicknesses are left to the purchaser’s specific engineering requirements and calculations.
💡 Which ASTM steel grades are approved for the locking edge rail?
The standard explicitly lists A36/A36M (Carbon Steel), A572/A572M (High-Strength Low-Alloy), and A588/A588M (Weathering Steel) as the approved material specifications.
📌 What test methods are essential for qualifying the rubber compound?
Key test methods referenced include D2240 (Hardness), D412 (Tensile Strength & Elongation), D395 (Compression Set), D1149 (Ozone Resistance), D471 (Oil & Liquid Resistance), and D573 (Heat Aging). These ensure the seal performs under movement, load, and environmental exposure.