| IS Sieve Size (mm) | Wt. Retained (g) | Cumulative Wt. Retained (g) | Cumulative % Retained | % Passing | MORTH Limit (Passing %) |
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Comprehensive Guide to MORTH WBM Grading 2 Sieve Analysis
In highway engineering and massive infrastructure projects like canal service roads, the foundation is everything. Water Bound Macadam (WBM) is a traditional, highly effective base course construction method where clean, crushed coarse aggregates are mechanically interlocked by rolling, and then bound together with screening material and water.
To ensure this layer can distribute heavy traffic loads without failing, the size and distribution of the coarse aggregates must be strictly controlled. This automated Sieve Analysis Generator evaluates coarse aggregate specifically for Grading 2 (63 mm to 40 mm), ensuring absolute compliance with the Ministry of Road Transport and Highways (MORTH) Table 400-8 specifications.
1. What is WBM Grading 2?
MORTH classifies coarse aggregates for WBM into three distinct gradings based on their nominal size. Grading 2 consists primarily of stones ranging from 63 mm down to 40 mm.
- Application: Grading 2 is the most widely used size for the base course and sub-base layers of flexible pavements. It provides a robust, highly stable matrix that resists shearing under heavy vehicular loads.
- Layer Thickness: When using Grading 2 aggregates, the compacted thickness of a single WBM layer is typically restricted to 75 mm to ensure proper interlocking and compaction density.
2. Decoding MORTH Table 400-8 Passing Limits
If all the stones in the base course were exactly the same size, they would not interlock properly, leaving massive voids. The MORTH limits are designed to force a specific size distribution. Here is the engineering logic behind the sieve limits used in our calculator:
90 mm & 63 mm Sieves
100% passing 90 mm ensures there are no massive, oversized boulders that would protrude through the 75 mm compacted layer. 90-100% passing 63 mm ensures the bulk of the material is smaller than the maximum nominal size.
53 mm Sieve (25-75% Passing)
This is the most critical control point. By forcing the 53 mm passing rate to be between 25% and 75%, MORTH guarantees a healthy mix of both larger (63-53mm) and smaller (53-40mm) stones, creating the perfect interlocking puzzle.
45 mm & 22.4 mm Sieves
0-15% passing 45 mm and 0-5% passing 22.4 mm strictly limits undersized material and stone dust. If there is too much fine material in the coarse aggregate, the WBM layer will lose its structural friction and become unstable when wet.
3. Quality Control (QC) Testing Procedure
To physically verify the aggregate at the site laboratory, QC engineers conduct a mechanical sieve analysis:
- A representative sample of the crushed aggregate is taken from the stockpile. For Grading 2, a substantial sample weight (often 10 kg to 20 kg) is required to ensure accuracy.
- The material is oven-dried and passed through a stack of standard IS sieves (90mm, 63mm, 53mm, 45mm, and 22.4mm) using a mechanical shaker or manual agitation.
- The weight retained on each individual sieve is carefully recorded in grams.
- The cumulative weight retained, cumulative percentage retained, and final percentage passing are calculated and checked against the MORTH Table 400-8 parameters.
4. How to Use This Automation Tool
This calculator is designed to assist material engineers in rapidly formatting compliance reports, verifying physical data, and generating theoretical gradation curves for mix design simulations.
- Input Sample Weight: Enter your total testing weight in grams (e.g., 10000 for 10 kg).
- Generate Data: Click the button to instantly reverse-calculate a mathematically flawless set of retained weights that perfectly align with MORTH specifications.
- Print Report: Use the print function to export a clean, distraction-free table ready for QA/QC signature and filing.
Disclaimer: This application provides simulated, mathematically compliant gradation data based on established MORTH limits. It is strictly intended as a formatting and educational aid. Always rely on actual physical laboratory testing for official RFI approvals and site execution.