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D2993-98 – Standard Test Method Technical Guide
This specification covers one grade of rubberized tar for use in construction of rubberized tar concrete pavement. The material consists of unvulcanized acrylonitrile butadiene rubber (NBR) preblended with high‑temperature residual coke oven tar, free from asphalt or petroleum contamination.
🛢️ Material Composition and Blending
The rubberized tar shall contain unvulcanized NBR with necessary additives. Blending must occur in equipment free from contamination by asphaltic or petroleum materials. The blend is stored for a minimum of 20 hours or until testing is complete.
Table 1 summarizes the physical requirements for the base tar.
| 🟦 Property | 📏 Requirement | 📐 ASTM Method |
|---|---|---|
| Float test (50°C) | 150–200 s | D 139 |
| Specific gravity (25/25°C) | ≥ 1.20 | D 70 |
| Total bitumen soluble in CS₂ | ≥ 75 wt% | D 2042 |
| Water content | ≤ 0.05 vol% | D 95 |
| Softening point (residue to 300°C) | 42–52°C | D 2398 |
📊 Rubberized Tar Cement Specifications
The rubberized tar cement must meet the properties in Table 2, tested according to Test Methods D 2994.
| 🟦 Property | 📏 Requirement | ⚡ Test Condition |
|---|---|---|
| Penetration (25°C) | 100–250 mm/10 (fuel immersed) 100–225 mm/10 (non‑immersed) Difference ≤ 50 |
D 2994 |
| Volume change | ≤ 2.5% | D 2994 |
| Weight change | ≤ 2.0% | D 2994 |
| Flow (38°C) | ≤ 40 mm | D 2994 |
| Softening point | ≥ 34°C | D 2994 |
| Viscosity (90°C) | 4,800–18,500 cP | D 2994 |
| Viscosity (105°C) | 2,050–7,600 cP | D 2994 |
| Viscosity (120°C) | 860–3,050 cP | D 2994 |
🧪 Sampling and Test Methods
Sampling must follow Practice D 140. All property tests for the rubberized tar cement are performed as specified in Test Method D 2994.
⚠️ Ensure that blending equipment is free from asphaltic or petroleum contamination to avoid compromising the material’s integrity.
💡 The rubberized tar should be stored for at least 20 hours before testing to allow proper conditioning.
The physical requirements for the base tar (Table 1) are determined using various ASTM methods, including D 139, D 70, D 2042, D 95, D 20, D 2398, and D 872.
❓ Frequently Asked Questions
🔍 What is the primary application of this rubberized tar?
This specification covers one grade of rubberized tar for use in constructing rubberized tar concrete pavement.
💡 What type of rubber is used in the blend?
The rubberized tar contains unvulcanized acrylonitrile butadiene rubber (NBR), which is preblended with high‑temperature residual coke oven tar.
⚡ What are the key viscosity ranges specified for the cement?
Viscosity at 90°C: 4,800–18,500 cP; at 105°C: 2,050–7,600 cP; at 120°C: 860–3,050 cP, as per Table 2.
📌 Why is a 20‑hour storage period required?
The rubberized tar blend must be held in storage for a minimum of 20 hours to ensure uniformity and allow testing to be completed before use.