Calculator
Formula used
- G = (B − A) / ((D − A) − (C − B)) for binder using pycnometer masses.
- Gmb = A / (B − C) for bulk compacted mix (dry, SSD, submerged).
- Gmm = A / (A + B − C) for maximum theoretical specific gravity (Rice).
Density estimate: ρ ≈ SG × ρwater. Use a temperature-correct water density when needed.
How to use this calculator
- Choose a calculation type that matches your lab method.
- Enter all masses using one consistent mass unit.
- Keep the same temperature for water-related weighings.
- Set water density if you want a better density estimate.
- Press Calculate to view results above the form.
- Use CSV or PDF buttons to save your report.
Example data table
| Method | Inputs (example) | Specific gravity |
|---|---|---|
| Binder (pycnometer) | A=250.10 g, B=310.55 g, C=780.20 g, D=740.05 g | 1.0309 |
| Bulk compacted mix | A=1245.2 g, B=1260.8 g, C=720.4 g | 2.3106 |
| Maximum theoretical (Rice) | A=2500.0 g, B=4000.0 g, C=6120.0 g | 2.4038 |
Examples are illustrative and may differ from your procedure.
Article
1) Why specific gravity matters in asphalt
Specific gravity (SG) compares a material’s density to water and is central to asphalt mix volumetrics. When SG values are consistent, you can trust density targets, air-void calculations, and pay-factor decisions. This calculator helps you compute binder SG, bulk mix SG, and maximum theoretical SG with quick validation.
2) Binder specific gravity using a pycnometer
Asphalt binder SG is typically close to 1.00, often about 1.01–1.05 depending on crude source and modifiers. The pycnometer approach uses four masses to estimate water displaced by the binder. A small weighing error can shift SG noticeably, so clean glassware and stable temperature are important.
3) Bulk specific gravity of compacted specimens (Gmb)
Bulk specific gravity (Gmb) is used to represent the compacted asphalt mixture in the field and lab. It relies on dry mass in air, saturated surface-dry (SSD) mass, and submerged mass. Because water can fill connected voids, careful SSD conditioning and blotting helps prevent biased results.
4) Maximum theoretical specific gravity (Gmm) and air voids
Maximum theoretical specific gravity (Gmm), often determined by the Rice method, represents the mix with no air. Air voids are commonly computed as VTM = 100 × (Gmm − Gmb) / Gmm. Small changes in either value affect VTM, so compute both with the same units and consistent procedure.
5) Water density and temperature effects
SG is dimensionless, but the optional density estimate depends on water density. Water density is about 1000 kg/m³ near 4°C and decreases slightly as temperature rises. If your lab reports densities at 25°C or another standard, enter a temperature-correct water density for better estimates.
6) Typical ranges and quick sanity checks
Many aggregates have SG around 2.50–2.80, so compacted mixes often fall in a similar band for Gmb and Gmm. Binder SG is much lower and near 1.0. If the calculator flags a negative denominator, your inputs likely violate the expected mass relationships for the chosen method.
7) Reducing error in measurements
Use a calibrated balance, avoid drafts, and let samples reach thermal equilibrium. Remove trapped air by agitation or vacuum where your method requires it. For submerged weighings, ensure the specimen is fully immersed and not touching container sides. Record masses promptly to avoid evaporation and temperature drift.
8) Using results in mix design and quality control
Once you have Gmb and Gmm, you can track compaction, air voids, and production stability across lots. Many agencies use these properties to evaluate density bonuses or penalties and to check mixture consistency. Exporting CSV or PDF from this calculator supports traceable reporting and quick review in project documentation.
FAQs
1) Is specific gravity the same as density?
No. Density has units (like kg/m³). Specific gravity is a ratio to water, so it is unitless. This tool can also estimate density when you provide water density.
2) Do I need to match mass units across fields?
Yes. Keep all masses in the same unit (g, kg, or lb) within the selected method. The SG calculation uses ratios, so consistent units prevent errors.
3) Why does the calculator show a denominator error?
Denominator errors occur when the input masses do not satisfy the physical relationships of the method, such as B − C ≤ 0 for bulk SG. Recheck labels, tare, and recording.
4) Which method should I choose for air voids?
Use bulk SG (Gmb) for the compacted specimen and maximum theoretical SG (Gmm) for the mix with no air. Together they are used to compute air void percentage.
5) What water density should I enter?
If you need only SG, the default is fine. For a better density estimate, enter water density for your test temperature. Water density is slightly lower at warmer temperatures.
6) Can I use this for aggregates only?
This page focuses on binder, compacted mix, and maximum theoretical mix calculations. Aggregate SG tests use different setups and mass definitions, so use an aggregate-specific method for best results.
7) Why export CSV and PDF?
CSV is ideal for spreadsheets and trending across lots. PDF creates a clean report for field documentation, lab records, or client submittals using the exact inputs and computed values.