Bitumen Density Calculator

Calculate asphalt mix properties, VMA, VFA, VTM, and theoretical maximum density. Professional tool for civil engineers and road contractors.

Bulk Specific Gravity Formula: Gmb = Wdry / (Wssd - Wsub)

Where: Wdry = Dry weight, Wssd = SSD weight, Wsub = Submerged weight

g
Mass of dry sample in air
g
Mass of surface saturated dry sample in air
g
Mass of sample submerged in water
% by weight
Percentage of bitumen in the mix
Bulk specific gravity of aggregate
Specific gravity of bitumen (typically 1.01-1.06)

Voids Formulas: VTM = 100 × (1 - Gmb/Gmm), VMA = 100 - (Gmb × Ps / Gsb), VFA = 100 × (VMA - VTM) / VMA

Where: Ps = Aggregate percentage = 100 - Pb

Bulk specific gravity of compacted mix
Maximum specific gravity of loose mix
% by weight

Temperature-Density Relationship: ρT = ρ15 × [1 - α(T - 15)] where α ≈ 0.00065 per °C for bitumen

kg/m³
Density at reference temperature (15°C)
°C
-10°C 25°C 200°C
Slide to adjust target temperature
per °C
Typically 0.00065 for bitumen, 0.00023 for asphalt mix
Calculating...

Bitumen & Asphalt Properties

Bitumen, also known as asphalt binder, is a viscous liquid or semi-solid form of petroleum used primarily in road construction. Its density and physical properties vary with temperature and composition, affecting asphalt mix design and performance.

Key Asphalt Mix Design Properties:

  • Bulk Specific Gravity (Gmb): Ratio of the mass in air of a unit volume of compacted asphalt mix to the mass of an equal volume of water
  • Theoretical Maximum Specific Gravity (Gmm): Specific gravity of the asphalt mix when there are no air voids
  • Voids in Total Mix (VTM): Percentage of total volume occupied by air voids
  • Voids in Mineral Aggregate (VMA): Percentage of volume occupied by intergranular void space
  • Voids Filled with Asphalt (VFA): Percentage of VMA filled with asphalt binder

Typical Bitumen Density Values

Bitumen Grade Density at 15°C (kg/m³) Specific Gravity Penetration (dmm) Softening Point (°C)
Pen 40/50 1020-1040 1.02-1.04 40-50 48-56
Pen 60/70 1010-1030 1.01-1.03 60-70 46-54
Pen 80/100 1005-1025 1.005-1.025 80-100 42-52
VG-10 1010-1030 1.01-1.03 80-100 40-50
VG-30 1015-1035 1.015-1.035 50-70 47-55
VG-40 1020-1040 1.02-1.04 30-50 50-58
PMB (Polymer Modified) 1010-1030 1.01-1.03 40-100 55-75
Cutback Bitumen 950-1050 0.95-1.05 100-300 30-60

Asphalt Mix Design Standards

1

Marshall Mix Design: Traditional method using impact compaction. Target VTM: 3-5% for surface courses, 3-6% for base courses. VMA requirements vary with nominal maximum aggregate size.

2

Superpave Mix Design: Performance-based system using gyratory compaction. VTM target: 4% for design traffic levels. Includes performance tests for rutting, fatigue, and low-temperature cracking.

3

Voids Requirements: VMA minimum values depend on nominal maximum aggregate size (NMAS). For NMAS of 19mm, minimum VMA is 13%. VFA requirements vary with traffic level (65-78% for high traffic).

Temperature-Density Relationship

The density of bitumen decreases with increasing temperature due to thermal expansion. The relationship is approximately linear for typical pavement temperature ranges:

Formula: ρT = ρ15 × [1 - α(T - 15)]

Where: ρT = Density at temperature T (°C), ρ15 = Density at 15°C, α = Thermal expansion coefficient (≈0.00065 per °C for bitumen)

Factors Affecting Asphalt Density

  • Aggregate Properties: Shape, texture, gradation, and specific gravity
  • Bitumen Properties: Grade, viscosity, and temperature susceptibility
  • Mixing & Compaction: Temperature, method, and energy
  • Environmental Conditions: Temperature during placement and service
  • Mix Design: Binder content, aggregate gradation, and additives

Frequently Asked Questions

Bitumen is the binder (a viscous petroleum product) that holds asphalt together. Asphalt (or asphalt concrete) is the composite material consisting of mineral aggregate bound together with bitumen. In many countries, "asphalt" refers to the mixture, while "bitumen" refers to the binder.

Voids in Mineral Aggregate (VMA) is critical because it provides space for the bitumen coating on aggregate particles and for slight compaction under traffic. Insufficient VMA can lead to bleeding and rutting, while excessive VMA can result in durability problems and permeability.

Asphalt must be compacted at the proper temperature range (typically 135-165°C for hot mix asphalt). If the temperature is too low, the mix becomes stiff and difficult to compact, resulting in higher air voids. If too high, the mix may become unstable under compaction equipment, leading to aggregate rearrangement and density variations.

Most specifications require achieving 92-96% of theoretical maximum density (Gmm). This corresponds to 4-8% air voids. For high-traffic roads, the target is usually 93-97% density. The specific requirements depend on traffic level, climate, and pavement layer (surface vs. base).

Polymer Modified Bitumen (PMB) typically has similar density to conventional bitumen (1010-1030 kg/m³ at 15°C). However, the polymer additives can alter the temperature-density relationship slightly and significantly improve performance properties like elasticity, rutting resistance, and temperature susceptibility.