BC + RAP Mix Design

1. Sample details

Source of aggregate, by fraction

One field per saved Individual Gradation fraction, below (including RAP's own source/stockpile) — add, rename or remove fractions there and this list follows.

2. Mix parameters

Combined aggregate gradation (virgin + RAP blend) is checked separately in the Gradation for Bituminous Concrete module (MoRTH Table 500-17) — this page assumes a job mix meeting that gradation and focuses on the bitumen-content / volumetrics determination.

3. RAP (Reclaimed Asphalt Pavement)

Practical RAP incorporation range per IRC:120-2015 for hot-mix plants is roughly 10–35% (batch mix) / 10–50% (drum mix, higher end needs a dedicated RAP heating arrangement). Above ~20% RAP, binder-property evaluation of the recovered RAP binder is essential. This project's stated hot-mix-plant limit for BC is 20% max — edit the field above if your project practice differs.

4. Individual Gradation — Summary

One card per saved aggregate fraction (hot bin) — including RAP's own extracted gradation — 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 below; pick it from "Load saved fraction" there.

4b. Combined Gradation (Proportion of Hot Bin Aggregates)

Set each fraction's Rate of Blending (%) — including RAP's own share of the total mix (e.g. 80% virgin fractions : 20% RAP) — must total 100% — to get the combined job-mix gradation, checked against the MoRTH gradation limits for the grading selected above (section 2).

Physical verification: sieve-analyse aggregate (including RAP) actually drawn from the hot bins in the blended proportions above, and check it against the same MoRTH spec limits. 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.

5. Cleanliness Index

Dust/clay wash test on the combined hot-bin aggregate — Cleanliness Index, % = ((W1−W2)/W1)×100.

Remarks: As per MoRTH Cleanliness Max. 5% Passing 0.075mm sieve for BC.

6. 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. RAP is always tested by the pycnometer method (it can't be tested in a wire basket).

One worksheet per Individual Gradation fraction (section 4, above) — including RAP's own extracted aggregate. Add/rename/remove a fraction there and its table here follows automatically.

7. Specific Gravity of Bitumen (Gb)

8. 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 4b, above, which includes RAP) 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).

Asphalt Viscosity Blending — Select Grade of New Asphalt

Given the theoretical total bitumen demand P (above) and this project's RAP content/RAP binder content (section 3, above), the new (virgin) asphalt's share of total binder is R = 100×(added virgin bitumen)/P. On a semi-log plot of viscosity vs. % new asphalt in the blend, the aged (RAP) and new asphalt viscosities join by a straight line (Asphalt Institute MS-2); this solves that line for the new-asphalt viscosity needed to hit your target blended viscosity at that R, so you can pick a virgin bitumen grade whose viscosity is close to it.

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.

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

Gse = Ps ÷ (100⁄Gmm − Pb⁄Gb), computed for every binder content entered above (10) and averaged into the Gse used for Gmm reference alongside the Trial mixes, below.

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

Gsb = ΣP ÷ Σ(P⁄G) — P is each fraction's Rate of Blending (4b, above, including RAP's own share), G is that fraction's Average Specific Gravity (6, above). Both feed in automatically. This composite Gsb is what drives the Trial mixes / OBC volumetrics below, replacing the old separate Virgin Gsb + RAP Gsb fields (section 2/3, now legacy).

—

13. Apparent Specific Gravity of Combined Aggregate (Gsa)

Gsa = ΣP ÷ Σ(P⁄G) — P is each fraction's Rate of Blending (4b, above), G is that fraction's Average Apparent Specific Gravity (6, above).

—

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

15. Graphical Analysis of Marshall Test

16. Additional requirements (single-point tests)

17. Optimum (Total) Bitumen Content (OBC)

Selection of Optimum Bitumen Content

OBC is the total bitumen content (virgin + RAP-contributed) at which the Air Voids curve (section 15) crosses the target design air voids (section 2), 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.

Narrow Range Acceptable Limit

21. 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.

22. 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.