Gradation Test of Bituminous Mix(IS 2386 Part 1 · MoRTH Section 500)
Sieve analysis of aggregate recovered from bituminous mixes after binder extraction — verifying the as-produced grading against the approved Job Mix Formula and the MoRTH Section 500 envelopes for BC, DBM and other mixes.
What is the Gradation Test of a Bituminous Mix?
The performance of Bituminous Concrete (BC), Dense Bituminous Macadam (DBM) and other hot-mix asphalt layers depends critically on the aggregate grading actually produced at the plant matching the approved Job Mix Formula (JMF). MoRTH Specifications for Road and Bridge Works (Fifth Revision), Section 500, defines the grading envelopes and the permissible tolerances on each sieve for every mix type — and requires routine verification on production samples.
Global Lab first extracts the bituminous binder from the mix sample (centrifuge extraction per ASTM D2172), then performs a full sieve analysis of the recovered aggregate per IS 2386 (Part 1):1963. The resulting grading curve is overlaid on the JMF and the MoRTH envelope, with each sieve checked against its tolerance — identifying segregation, blending errors or cold-feed drift before they translate into premature pavement failure.
How the Gradation Test of Bituminous Mix is Conducted
- 1
Sampling of the Mix
A representative hot-mix sample is taken from the plant, paver or transport vehicle per MoRTH sampling frequency requirements and weighed. - 2
Binder Extraction
The bituminous binder is removed by centrifuge extraction with solvent per ASTM D2172, leaving clean aggregate; binder content is recorded from the same operation. - 3
Drying & Recovery of Aggregate
The recovered aggregate (including filler correction for material retained in the extract) is dried to constant mass at the specified temperature. - 4
Sieve Analysis
The aggregate is sieved through the full IS sieve set applicable to the mix (45mm down to 75 micron as per grading), per IS 2386 (Part 1):1963, and the mass retained on each sieve recorded. - 5
Grading Curve & Envelope Check
Percent passing each sieve is computed and plotted against the approved JMF and the MoRTH Section 500 envelope, with per-sieve tolerance compliance flagged. - 6
Reporting
The grading table, curve overlay and pass/fail verdict per sieve are issued via Autovity QLMS.
Applicable Test Standards
| Standard | Title | Scope | Type |
|---|---|---|---|
| IS 2386 (Part 1):1963 | Methods of Test for Aggregates for Concrete — Particle Size and Shape (Reaffirmed) | Sieve Analysis | Indian Standard |
| ASTM D2172/D2172M | Standard Test Methods for Quantitative Extraction of Asphalt Binder from Asphalt Mixtures | Binder Extraction | ASTM Standard |
| MoRTH (5th Rev.) Sec. 500 | Specifications for Road and Bridge Works — Bituminous Courses | Grading Envelopes & Tolerances | MoRTH Spec |
| IRC:111-2009 | Specifications for Dense Graded Bituminous Mixes | DBM / BC Requirements | IRC Code |