Bitumen and Bituminous Products

Bitumen is a product of Crude oil Distillation. It is a semi-solid hydrocarbon product produced by removing the lighter fractions (such as liquid petroleum gas, petrol and diesel) from heavy crude oil during the refining process. As such, it is correctly known as refined bitumen.

Bitumen Applications

Known for its adhesive and cohesive assets, bitumen is mostly utilised in the construction industry. Bitumen is applied on road paving because it is viscous when hot, but solid once it cools down. Therefore Bitumen operates as the binder/glue for pieces of the aggregate.

The vast majority of refined bitumen is used in construction: primarily as a constituent of products used in paving and roofing applications. According to the requirements of the end use bitumen is produced to specification. This is achieved either by refining process or blending.

It is estimated that the current world use of bitumen is approximately 102 million tonnes per year. Approximately 85% of all the bitumen produced is used as the binder in asphalt for roads.

Bitumen is applied in construction and maintenance of:


  • Highways
  • Airport runways
  • Footways / Pedestrian Ways
  • Car parks, Race tracks
  • Tennis courts, Roofing
  • Damp proofing
  • Dams Reservoir and pool linings
  • Sound proofing
  • Pipe coatings
  • Cable Coatings
  • Paints, Building Water Proofing
  • Tile underlying water proofing
  • Newspaper Ink Production
  • and many other applications

In order realize the complexity of bitumen as a product an in-depth knowledge and detailed understanding for one of the way the roads are built is crucial. Specialists in bitumen know bitumen as an advanced and complex construction material, not as a mere by-product of the oil refining process. The ultimate paving material (also referred to hot mix asphalt concrete – HMAC or HMA) consists of about 93 – 97% mineral aggregate (stone), sand and filler. The remaining percentage is bitumen.

BITUMEN EMULSION

Bitumen emulsions are usually dispersions of minute droplets of bitumen in water and are examples of oil-in-water emulsions.
The bitumen content can be varied to suit different requirements and is typically between 30% and 70%. The primary objective of emulsifying bitumen is to obtain a product that can be used without the heating normally required when using cutbacks and paving grade bitumen. In the manufacture of bitumen emulsions, hot bitumen is sheared rapidly in water containing an emulsifying chemical (emulsifier). This produces very small particles of bitumen (the dispersed phase) dispersed in water (the continuous phase). The bitumen particles are stabilised in suspension and do not readily coalesce due to the presence of the emulsifier, which is concentrated on the surface of the bitumen particles. During application, the water in a bitumen emulsion is either lost by evaporation, or it may separate from the bitumen because of the chemical nature of the surface to which the emulsion is applied. This process is referred to as breaking. Because bitumen has a density only slightly higher than water, sedimentation of the bitumen droplets in an emulsion during storage is very slow. Emulsions can usually be regenerated after long storage times by gentle stirring to re-disperse the bitumen droplets.

Types of Bitumen Emulsions

Bitumen emulsions are available in many different forms, either cationic or anionic, with varying breaking or setting rates and binder types and contents.
The two most common basic emulsion types are designated by the letter 'C' for cationic emulsions, as in CRS (cationic rapid setting), and by the letter 'A' in anionic emulsions, as in ASS (anionic slow setting).

Cationic Bitumen Emulsion

When the emulsion is being produced the cations are adsorbed by bitumen droplets, negatively ions remain in the water. The undeniably most complete field of use is represented by the rapid setting emulsions.

Anionic Bitumen Emulsion

Most often, fatty acid and resin acid alkaline salts are used. They are obtained by saponification of the liquid resin, called Tall-Oil. This substance is a residual, distilled substance, a by-product of the paper pulp industry from resinous wood treated using the “sulfate” process. The Co2Na group is the hydrophilic polar part. When in a solution in the continuous aqueous phase, the soap molecules become ionized; the Na (or K) ions are the cations adsorbed by the water and the rest of the molecules are the anions adsorbed by the bitumen globules.
The characteristics of an emulsion are designated by the terms rapid (R), medium (M) and slow (S).
The main grades for bitumen emulsions are classified as follows:

Cationic Emulsified Bitumen Specification (AASHTO M208, ASTM D2397)

Type Rapid-Setting Medium-Setting Slow-Setting
Grade CRS-1 CRS-2 CMS-2 CSS-1 CSS-1h
Min Max Min Max Min Max Min Max Min Max
Test on emulsions:
Viscosity, SayboltFurol at 25°C SFS 200 100 20 100
Viscosity, SayboltFurol at 50°C 20 100 100 400 50 450
Storage stability test, 24-h, %B 1 1 1 1 1
Demulsibility, 35 mL, 0.8% dioctyl sodium sulfosuccinate,% 40 ... 40 ...
Coating ability and water resistance:
Coating, dry aggregate
Coating, after spraying
Coating, wet aggregate
good
fair
fair
Coating, after spraying fair
Particle charge test positive positive positive positive positive
Sieve test,%B 0.1 0.1 0.1 0.1 0.1
Cement mixing test,%
Distillation:
Oil distillate, by volume of emulsion,% 3 3 12
Residue,% 60 65 65 57 57
Tests on residue from distillation test:
Penetration, 25°C, 100g, 5s 100 250 100 250 100 250 100 250 40 90
Ductility, 25°C, 5 cm/min, cm 40 40 40 40 40
Solubility in trichloroethylene, % 97.5 97.5 97.5 97.5 97.5

Cutback Bitumen is made by reducing the viscosity of and ordinary bitumen by adding mostly petroleum type solvent. Cutback Bitumen are used because their viscosity is lower than that of neat asphalt and can thus be used in low temperature applications. After a cutback is applied the solvent evaporates away and only the Bitumen is left. A cutback bitumen is said to cure as the petroleum solvent evaporates. Cutback bitumen are typically used as prime coats and tack coats. Generally are divided into three groups depending on their volatility of the solvent added:

Slow Curing often called "road oils," are usually a residual material produced from the fractional distillation of certain crude petroleums. Traditionally any kind of aromatic, naphthenic and paraffinic oils are used. Slow Curing liquid bitumen materials can be prepared by blending bitumen with an oily petroleum fraction.

Medium Curing are a blend of Bitumen with lighter hydrocarbons such as kerosene.

Rapid Curing products are prepared with a light, rapidly evaporating diluent such as a naphtha or gasoline.

As a solvent required to produce a cutback asphalt, it is possible to use not only the above described petroleum type solvent but also a coal type solvent or may be a mixture of various solvents and an additive in order to further improve the performance of final products (e.g. anti stripping effect).

Each of these three types of liquid asphaltic materials is produced in six standard grades. The prefix of each grade denotes the type: SC for Slow Curing, MC for Medium Curing, and RC for Rapid Curing. The suffix, or grade number, denotes the consistency range of the material. In each type, grade 0 is the most liquid, grade 5 the most viscous, with the intermediate grades ranging in consistency in an orderly progression. At room temperature, the consistency of grade 0 materials resembles that of heavy cream while grade 5 materials have the consistency of heavy molasses in cold weather. These products "cure" by the evaporation of the petroleum diluent. Formerly the advantage of application of cutback asphalt mixtures is a difference in the reduced paving temperature. However in these days cutback asphalt are used mostly as prime coat and/or tack coat.

When cutback asphalts are used as a prime coat, the cutback asphalt is sprayed to the surface of untreated sub grade or base layers in order to fill the surface voids and protect the sub-base from water penetration; stabilize the fines and preserve the sub-base material and/or promote bonding to the subsequent pavement layers. When used as a tack coat, the cutback asphalt is applied between hot mix asphalt pavement lifts to promote adequate bonding. This cutback promoted adequate bonding between construction lifts and especially between the existing road surface and an overlay is critical in order for the completed pavement structure to behave as a single unit and provide adequate strength. If adjacent layers do not bond to one another they essentially behave as multiple independent thin layers, none of which are designed to accommodate the anticipated traffic imposed bending stresses. Inadequate bonding between layers can result in delamination (de-bonding) followed by longitudinal Wheel path cracking, fatigue cracking, potholes, and other distresses such as rutting that greatly reduce pavement life.

Slow Curing Cutback Bitumen Specification (ASTM D2026)

Slow Curing (SC) SC-70 SC-250 SC-800 SC-3000 Test Methods
Property Min Max Min Max Min Max Min Max
Kinematic viscosity at 60°C, mm2/s 70 140 250 500 800 1600 3000 6000 ASTM D-2170
Flash point (Cleveland open cup), °C 66 - 79 - 93 - 107 - ASTM D-92
Distillation test: ASTM D-402
Total distillate to 360°C, volume % 10 30 4 20 2 12 - 5
Solubility in trichloroethylene, % 99 - 99 - 99 - 99 - ASTM D-2042
Kinematic viscosity on distillation residue at 60°C, mm2/s 400 7000 800 10000 2000 16000 4000 35000 ASTM D-2170
Asphalt residue: ASTM D-243
- Residue of 100 penetration, % 50 - 60 - 70 - 80 - ASTM D-5
- Ductility of 100 penetration residue at 25°C, cm 100 - 100 - 100 - 100 - ASTM D-113
Water, % - 0.5 - 0.5 - 0.5 - 0.5 ASTM D-95

Medium Curing Cutback Bitumen Specification (ASTM D2027 or AASHTO M82-75 2008)

Medium Curing (MC) MC-30 MC-70 MC-250 MC-800 MC-3000 Test Methods
Property Min Max Min Max Min Max Min Max Min Max
Kinematic viscosity at 60°C, mm2/s 30 60 70 140 250 500 800 1600 3000 6000 ASTM D-2170
Flash point (Cleveland open cup), °C 38 - 38 - 66 - 66 - 66 - ASTM D-92
Distillation test: Distillate, volume percent of total distillate to 360°C: ASTM D-402
to 225°C - 35 - 25 - 20 - - - -
to 260°C 30 70 10 70 5 55 - 40 - 15
to 316°C 75 95 65 93 60 90 45 85 15 75
Residue from distillation to 360°C, percent volume by difference 50 - 55 - 67 - 75 - 80 -
Tests on residue from distillation:
Viscosity at 60°C, Pa 30 120 30 120 30 120 30 120 30 120
Ductility at 25°C, cm 100 - 100 - 100 - 100 - 100 - ASTM D-113
Solubility in trichloroethylene, % 99 - 99 - 99 - 99 - 99 - ASTM D-4
Water, % - 0.2 - 0.2 - 0.2 - 0.2 - 0.2 ASTM D-95

Rapid Curing Cutback Bitumen Specification

Rapid Curing (RC) RC-70 RC-250 RC-800 RC-3000 Test Methods
Property Min Max Min Max Min Max Min Max
Kinematic viscosity at 60°C, mm2/s 70 14 25 500 800 1600 3000 6000 ASTM D-2170
Flash point (Cleveland open cup), °C - - 27 - 27 - 27 - ASTM D-92
Distillation test: Distillate, volume percent of total distillate to 360°C: ASTM D-402
to 190°C 10 - - - - - - -
to 225°C 50 - 35 - 15 - - -
to 260°C 70 - 60 - 45 - 25 -
to 316°C 85 - 80 - 75 - 70 -
Residue from distillation to 360°C, percent volume by difference 55 - 65 - 75 - 80 -
Tests on residue from distillation:
Viscosity at 60°C, Pa 60 240 60 240 60 240 60 240
Ductility at 25°C, cm 100 - 100 - 100 - 100 - ASTM D-113
Solubility in trichloroethylene, % 99 - 99 - 99 - 99 - ASTM D-4
Water, % - 0.2 - 0.2 - 0.2 - 0.2 ASTM D-95

Gilsonite is a natural, resinous hydrocarbon found in the Uintah Basin in northeastern Utah; thus, it is also called Uintahite. This natural asphalt is similar to a hard petroleum asphalt and is often called a natural asphalt, asphaltite, uintaite, or asphaltum. Gilsonite is soluble in aromatic and aliphatic solvents, as well as petroleum asphalt. Due to its unique compatibility, Gilsonite is frequently used to harden softer petroleum products. Gilsonite in mass is a shiny, black substance similar in appearance to the mineral obsidian. It is brittle and can be easily crushed into a dark brown powder. When added to asphalt cement or hot mix asphalt in production, Gilsonite helps produce paving mixes of dramatically increased stability.

Gilsonite General Specification

Parameters Unit Results Test Method
Ash Content %Wt 2.0 - 10.0 ASTM D-3174
Moisture Content %Wt 1.0 - 3.0 ASTM D-3173
Volatile Matter %Wt 63 ASTM D-3175
Fixed Carbon %Wt 29 ASTM D-3172
Solubility in CS2 %Wt 81.0 ASTM D-4
Specific Gravity at 25°C 1.01 - 1.06 ASTM D-3289
Normal HepthanInsolubles %Wt 79 ASTM D-3279
Color in Mass Black -
Color in Streak or Powder Brown -
Softening Point °C 180 - 205 ASTM D-36
Penetration at 25°C 0.1MM 0.0 ASTM D-5
Element Analysis
Carbon %Wt 74 ASTM D-5291
Hydrogen %Wt 9.1 ASTM D-5291
Nitrogen %Wt 1.67 ASTM D-5291
Oxygen %Wt 3.1 ASTM D-5291
Sulphur %Wt 0.5 Leco(S) Analyzer

OXIDIZED BITUMEN

Blown bitumen grades or Oxidized Bitumen are produced by passing air through the penetration grades. This process gives the bitumen more rubbery properties than its original formula and they are simply harder bitumen. Hard bitumen under controlled temperature conditions is widely used as an anti-slip layer compound in the piling industry, for manufacture of roofing felts, the roofing and waterproofing industries, for sound dampening felts and under carriage sealant in the automotive industry, electric cable joint protection, joint filling compound, sealant compound and many others. Also used in sealing saw cuts and joints where expected movements are minimum. It is also used in the manufacturing of bituminous marine mastic for the oil & gas pipeline joints.

Application:
  • Oxidized Bitumen has a wide variety of industrial applications
  • As a bonding bitumen for roofing sheet membranes.
  • As a hot applied waterproofing layer.
  • Carpet tile manufacture.
  • As a raw material for liquid bitumen coatings
  • For production of bituminous pains, mastic
  • For rust proof pipe coatings
  • Used as an anti-slip layer compound in the piling industry
  • Used for production of roofing and sound dampening felts, Used as under carriage sealant in the automobile industry, electric cable joint protection, joint filling compound, sealant compound and many more in our day to day life.

Oxidised Bitumen Specification

PARAMETERS GRADES TEST METHOD
BITUMEN R 85/25 BITUMEN R 85/40 BITUMEN R 95/25 BITUMEN R 95/40 BITUMEN R 115/15
Relative Density at 25 deg C, g/ml 1.00-1.06 1.00-1.05 1.00-1.05 1.00-1.05 1.00-1.06 ASTM D70
Softening Point (Ring and Ball), dec C 80-90 80-90 90-100 90-100 110-120 ASTM D36
Penetration at 25 °C, 0.1 mm 20-30 35-45 20-30 35-45 42663 ASTM D5
Flash Point ( Cleveland open Cup), °C, Min 200 200 200 200 200 ASTM D92
Loss on heating % by mass 0.2 0.5 0.2 0.5 0.2 ASTM D6
Ductility at 25 °C cm, min 2 2 2 2 2 ASTM D113
Solubility in toluene % wt min 99 99 99 99 99 EN12592:2000

Penetration Grade Bitumen is Bitumen classified using the penetration property. Penetration grading’s basic assumption is that the less viscous the asphalt, the deeper the needle will penetrate. Bitumen which is produced during the process of oxidation of vacuum bottom (the Bitumen production feedstock that derives from distillation tower residue in vacuum oil refineries) at bitumen production unit in a manner that its penetration point (kind of test to indicate the hardness of bitumen) in specified group is classified in different grade of Bitumen. Penetration Grade Bitumen is commonly used in road surfacing, and some industrial applications. Additional processing yields other grades of bitumen products and their application

Penetration Grade Bitumen Specification (AASHTO M 20 and ASTM D 946)

Units 40/50 60/70 80/100 100/120 Test Methods
Specific Gravity @25°C - 1.01-1.06 1.01-1.06 1.01-1.05 1.01-1.04 ASTM D-70
Penetration @25°C, 100gm, 5sec 0.1MM 40-50 60-70 80-100 100-120 ASTM D-5
Softening Point, Ring & Ball °C 52-60 49-56 45-52 42-49 ASTM D-36
Ductility @25°C, after TFOT, Min CM 100 100 100 100 ASTM D-113
Loss on Heating, Max %Wt 0.2 0.2 0.5 0.5 ASTM D-6
Drop in Penetration after Heating, Max % 20 20 20 20 ASTM D-6 & D-5
Flash Point Cleveland open cup, Min °C 250 250 232 250 ASTM D-92
Solubility in CS2, Min %Wt 99.5 99.5 99.5 99.5 ASTM D-4
Organic Matter Insoluble in CS2, Max %Wt 0.5 0.5 0.5 0.5 ASTM D-4
Sport Test - Negative Negative Negative Negative *A.A.S.H.O.T.102

Performance Grade (PG) bitumen is bitumen which is graded based on its performance at different temperatures. The Long-Term Pavement Performance(LTPP) has given certain algorithm to calculate the temperature of the pavement based on the temperature of the air above. From this, the highest and the lowest temperatures of the pavement is calculated and the bitumen that performs well in that temperature range is selected. Penetration grading and viscosity grading are somewhat limited in their ability to fully characterize asphalt binder for use in Hot Mix Asphalt(HMA) pavement. Therefore, as part of the Superpave research effort new binder tests and specifications were developed to more accurately and fully characterize asphalt binders for use in HMA pavements. These tests and specifications are specifically designed to address HMA pavement performance parameters such as rutting, fatigue cracking and thermal cracking.

PG 46-34 PG 46-28 PG 52-28 PG 58-28 PG 58-22 PG 64-22 AASHTO Method
Flash Point, COC,°C 240 T-48
Flash Point, P-M, °C NS >204 ASTM D-93
Rotational Viscosity @ 135°C, Pa•s 3 T - 316
Dynamic Shear @ Grade Temperature,°C 46 46 52 58 58 64 T - 315
G*/sin @ 10 rad/sec, kPa >1.00
RTFOT Residue
Mass Loss, % <1.00 T - 240
Dynamic Shear @ Grade Temperature,°C 46 46 52 58 58 64 T- 315
G*/sin @ 10 rad/sec, kPa 2.2
PAV Residue (Aging Temperature, °C) 90 100 R - 28
Dynamic Shear @ Grade Temperature,°C 10 13 16 19 22 25 T - 315
G*/sin @ 10 rad/sec, kPa 5000
Creep Stiffness -24 -18 -18 -18 -12 -12
S, Mpa <300 T - 313
m-value >0.30 T - 313

Polymer modified emulsions have more durability and flexibility in comparison to standard emulsions and are usually recommended for better performance and durability, permitting to reduce life cycle costs when compared to regular emulsions. These modifications on normal emulsions by the use of modified bitumen have exhibited and demonstrate reductions in rutting, thermal cracking and increase significantly the resistance generally in traffic-subjected stress pavements.

Designation Elastomeric Thermoplastic Based Plastomeric Thermoplastic Based Natural Rubber Modified Binders Crumb Rubber Modified Binders Merthod of tests
PMB 120 PMB 70 PMB 40 PMB 120 PMB 70 PMB 40 NRMB 120 NRMB 70 NRMB 40 CRMB 50 CRMB 55 CRMB 60
Penetration at 25°C, 0.1mm,100g.5 Sec 90 to 150 50 to 90 30 to 50 90 to 150 50 to 90 30 to 50 90-150 50-90 30-50 <70 <60 <60 IS: 1203-1978
Saftening Point (R&B)°C Minimum 50 55 60 50 55 60 50 55 60 50 55 60 IS:1205-1978
Ductility at 27°C cm. +75 +60 +50 +50 +40 +30 +75 +60 +50 - - - IS:1208-1978
Fraass Breaking Point°C Max -24 -18 -12 -20 -16 -12 -20 -16 -12 - - - IS:9381-1979
Flash Point by COC°C Minimum 220 220 220 220 220 220 220 220 220 220 220 220 IS:1209-1978
Elastic Recovery of Half Thread in Ductilometer at 15°C, %, Min 75 75 75 50 50 50 50 40 30 50 50 50 Appendix-1 IRC:SP:53 2002
Separation Differnce in softening Point R&B°C, Maximum 3 3 3 3 3 3 4 4 4 4 4 4 Appendix-2 IRC:SP:53 2002
Viscosity at 150°C poise 1-3 2-6 3-9 1-3 2-6 3-9 - - - - - - IS:1206-1978
Thin Film Oven Test (TFOT) on Residue (IS:9382-1992)
Loss in Weight, %, Maximum 1.0 1.0 1.0 1.0 1.0 1.0 - - - - - - IS:9382-1979
Increase in Softening Point °C, Maximum 7 6 5 7 6 5 7 6 5 7 6 5 IS:12QS.1978
Reduction in Penetration of Residue at 25°C, Maximum 35 35 35 35 35 35 - - - - - - IS:1203-1978
Penetration at 25°C 0.1 mm, 100g, 5 Sec. Minimum % of original - - - - - - 60 60 60 60 60 60 IS:1203-1978
Elastic Recovery of Half thread in Ductilometer at 25°C, % Minimum 50 50 50 35 35 35 35 30 25 35 35 35 Appendix-1 IRC:SP:53 2002

There are two methods of grading:
Standard Viscosity Grade Bitumen (AC-Grades), in which the Viscosity of the standard bitumen (asphalt) is measured at 60 ºC (140 ºF).
RTFOT Viscosity Grade Bitumen (AR-Grades), in which the Viscosity of bitumen (asphalt) is measured at 60 °C (140 °F) after the roll on thin film oven test.

Viscosity grade bitumens have a thermoplastic property which causes the material to soften at high temperatures and to harden at lower temperatures. This unique temperature/ viscosity relationship is important when determining the performance parameters such as the adhesion, rheology, durability and application temperatures of bitumen. In the Viscosity Graded Bitumen specifications further special emphasizes is placed on the Bitumen ductility.

Viscosity Grade Bitumen Specification
Property Units VG-10 VG-20 VG-30 VG-40 Test Methods
Penetration at 25°C, 100g, 5sec, Min 0.1MM 80 60 45 35 IS 1203
Absolute viscosity at 60°C P 800-1200 1600-2400 2400-3600 3200-4800 IS 1206 (Part 2)
Kinematic viscosity at 135°C, Min cSt 250 300 350 400 IS 1206 (Part 3)
Flash point (Cleveland open cup), Min °C 220 220 220 220 IS 1448 [P : 69]
Solubility in trichloroethylene, Min %Wt 99 99 99 99 IS 1216
Softening point (R&B), Min °C 40 45 47 50 IS 1205
Tests on residue from thin film oven test:
- Viscosity ratio at 60°C, Max 4 4 4 4 IS 1206 (Part 2)
- Ductility at 25°C, Min CM 75 50 40 25 IS 1208