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D5624-13 – Standard Test Method Technical Guide
📐 Overview and Significance
The ASTM D5624-13 standard provides a detailed procedure for determining the transverse-aggregate spread rate in approximately 0.33-m increments. This practice is essential for calibrating aggregate spreaders and verifying the uniformity of distribution across the pavement width before and during surface treatment construction. The standard mandates the use of SI units and emphasizes the user’s responsibility for safety and regulatory compliance.
| 🟦 Parameter | 📏 Requirement | 🎯 Application |
|---|---|---|
| Balance readability | 1 g | Transverse spread rate determination |
| Balance readability | 0.1 g | When moisture content is determined |
⚠️ Important: All balances must comply with Method E898 for top-loading, direct-reading laboratory scales.
⚙️ Apparatus and Test Procedure
Key apparatus includes a balance with appropriate accuracy, containers for sample collection, mats of known surface area, and a forced air oven set at 110 ± 5°C. The procedure involves placing mats side by side width-wise on the pavement with grooves perpendicular to the centerline. The aggregate spreader is driven over the mats with gates open, and the aggregate collected on each mat is weighed. The transverse distribution is then calculated.
| 🟦 Component | 📐 Specification | ⚡ Notes |
|---|---|---|
| Mats | Known surface area | Rubber floor mats or roofing felt used successfully |
| Oven | 110 ± 5°C | Forced air type for uniform temperature |
💡 Tip: Ensure mats have sufficient texture to prevent aggregate from rolling off during the test.
📊 Key Measured Properties and Calculations
The primary property measured is the mass of aggregate per unit area from each mat, which is used to compute the transverse spread rate. This data helps evaluate uniformity and allows for spreader adjustments. Collected samples can also be analyzed for moisture content (C566) and gradation (C136) for enhanced quality control during construction.
❓ Frequently Asked Questions
🔍 Question: Why is transverse-aggregate spread rate important in surface treatment?
Answer: It ensures uniform distribution of aggregate across the pavement, which is critical for the performance and longevity of the surface treatment.
💡 Question: What are the recommended mat materials?
Answer: Rubber floor mats and roofing felt have been used successfully due to their ability to stay in place and hold aggregate.
⚡ Question: How is moisture content of the aggregate determined?
Answer: According to Test Method C566, using a forced air oven at 110 ± 5°C.
📌 Question: Can this practice be used during construction for quality control?
Answer: Yes, it is valuable for monitoring the spread rate and making real-time adjustments if needed.