DBM Mix Design

1. Sample details

Source of aggregate, by fraction

One field per saved Individual Gradation fraction, below — add, rename or remove fractions there and this list follows.

2. Individual Gradation — Summary

One card per saved aggregate fraction (hot bin), with every sample's % passing side by side and an Average column — matching the lab sheet. Enter or edit a fraction's sieve analysis in the calculator on the right (section 3 sets the sieve list, per MoRTH Table 500-10); pick it from "Load saved fraction" there.

2b. Blending — Combined Aggregate Gradation

Set each fraction's Rate of Blending (%) — must total 100% — to get the combined job-mix gradation, checked against MoRTH Table 500-10 for the grading selected below (section 3).

Physical verification: sieve-analyse aggregate actually drawn from the hot bins in the Job Mix Formula proportions, and check it against the JMF band established above (2b). Add another gradation table for a second location/sample set if needed — each is independently editable and removable. Enter the sieve analysis in the calculator on the right (screen 2); the result and graph appear here.

3. Mix parameters

Combined aggregate gradation is built from Individual Gradation and Blending, above (section 2/2b) — changing the grading here updates the sieve list and MoRTH Table 500-10 limits used there.

4. Specific Gravity & Water Absorption — By Wire Basket / Pycnometer (IS 2386, Part-3)

Wire basket method for aggregate retained on 4.75 mm IS sieve; pycnometer method for aggregate passing 4.75 mm (fine aggregate, 8–4 mm, 4–0 mm, filler/dust). The method is picked automatically from the fraction name — override it per fraction if needed.

One worksheet per Individual Gradation fraction (above, section 2) — add/rename/remove a fraction there and its table here follows automatically.

5. Specific Gravity of Bitumen (Gb)

6. Theoretical Bitumen Content — Asphalt Institute MS-2

P = 0.035a + 0.045b + Kc + F — a, b and c are derived automatically from the combined gradation (section 2b, Blending) at the 2.36 mm and 0.075 mm sieves; K is selected from c; F is the surface constant (project input, 0–2%, suggested default 0.7).

One table per trial binder content — type the binder content (%) you tested at into each table's heading. Add another table for each additional binder content; at least one stays on screen.

9. Effective Specific Gravity of Mixed Aggregate (Gse) — Asphalt Institute MS-2

Gse = Ps ÷ (100⁄Gmm − Pb⁄Gb), computed for every binder content entered above (8) and averaged into the Gse used for Gmm in the Marshall trial table, below.

10. Bulk Effective Specific Gravity of Combined Aggregate (Gsb)

Gsb = ΣP ÷ Σ(P⁄G) — P is each fraction's Rate of Blending (2b, above), G is that fraction's Average Specific Gravity (4, above). Both feed in automatically.

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11. Apparent Specific Gravity of Combined Aggregate (Gsa)

Gsa = ΣP ÷ Σ(P⁄G) — P is each fraction's Rate of Blending (2b, above), G is that fraction's Average Apparent Specific Gravity (4, above).

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12. Marshall Test Result at Optimum Bitumen Content

Corrected stability = Dial Gauge Reading × Correction Ratio × Proving Ring Factor.

13. Trial mix graphs

Test Property Curves for Hot Mix Design Data by Marshall Method

14. Additional requirements (single-point tests)

15. Optimum Bitumen Content (OBC)

Selection of Optimum Bitumen Content

OBC is the bitumen content at which the Air Voids curve (section 13) crosses the target design air voids (section 3), found by linear interpolation between the two bracketing trial points. Other properties at OBC are interpolated the same way — treat this as a first estimate; confirm against the fitted best-practice curves in your lab records.

Selection of Optimum Bitumen Content from Bar Chart

Narrow Range Acceptable Limit

19. Tensile Strength Ratio (TSR)

Tensile Strength Ratio (TSR) — Marshall Immersion Test

AASHTO T283 / MoRT&H Table 500-11 — 3 specimens tested dry, 3 conditioned by vacuum-saturation and 24 h water-bath immersion at 60°C.

1. TSR limit as per MORT&H 5th Rev. = 80% Minimum.
2. If Degree of Saturation (S') is between 55% and 80%, continue with the test specimens.
3. If Degree of Saturation (S') is less than 55%, repeat the procedure with new test specimens.
4. If Degree of Saturation (S') is more than 80%, discard the test specimens.
5. Mould should be compacted to 7±1.0% air voids, or a void level expected in the field.

20. Report

This app saves everything (test data) for the active project in your browser, tied to this folder. Logos and project details are entered once on the main Projects page and shared by every module.