Testing and Standards
Bitumen is a visco-elastic material, whose properties are affected by both the temperature and the time during which a force is applied to it (loading time). Different grades of bitumen reflect differing (visco-elastic) resistance to deformation.
To measure this resistance, many generic characterisation tests have been devised including measures of brittleness, temperature susceptibility (penetration index), softening point, penetration value and viscosity. Additionally, more fundamental tests have been developed such as kinematic viscosity, dynamic shear rheometry, bending beam rheometry and direct tension testing. These are all used to characterise the relative performance of the bitumen at different temperatures.
The two traditional tests used to characterise bitumens, and to designate the different grades, are the penetration value (usually at 25ºC) and the softening point (Ring & Ball).
Other tests used in UK bitumen specifications to cover the main quality parameters are:
- Resistance to Hardening (Ageing) - tendency for bitumen to harden under the action of heat and air
- Flash Point - information required for safety in handling
- Solubility - indicates the purity (lack of contamination) of the product
Many other properties are of course measured in bitumen development work and to assess performance characteristics in the various applications.
The types of bitumen in the UK are covered by the following British Standards:
- BS EN 12591: 2009 Bitumen and bituminous binders - Specifications for paving grade bitumens
• This European standard was published in September 2009 and is in use in the UK for supply of paving bitumens. It includes a National Annex, which gives guidance on the use of the standard in the UK. It covers:
- Paving grade bitumens (Grades: 20/30, 30/45, 35/50, 40/60, 50/70, 70/100, 100/150, 160/220, 250/330 pen)
- BS EN 13924 : 2006 Bitumen and bituminous binders – Specifications for hard paving grade bitumens
• This European standard was published in 2006 and is used for supply of hard paving bitumens. A UK National Annex, which gives guidance on the use of the standard in the UK, was published in December 2007. It covers:
- Hard paving grade bitumens (Grades: 10/20, 15/25 pen)
- BS EN 14023 : 2010 Bitumen and bituminous binders – Specification framework for polymer modified bitumens
• BS EN 14023 was originally published in 2005 as part of a programme of harmonisation of European Standards for bituminous binders. The standard has been reviewed to further harmonise the original standard and update Annex ZA, which allows CE marking to be attached. It includes a UK National Annex, which gives guidance on the use of the standard in the UK. It covers:
- Polymer modified bitumens (The standard is a framework of classes for the characteristics that may need to be specified.)
- BS EN 13304 : 2009 Bitumen and bituminous binders – Oxidised bitumens
• This European standard was published in 2003 and is used for the supply of oxidised bitumens. It covers:
- Oxidised bitumens (The standard is a framework of properties for typical grades)
- BS EN 13305 : 2009 Bitumen and bituminous binders – Framework specification for hard industrial bitumens
• This European standard was published in 2003 and is used for the supply of hard industrial bitumens. It covers:
- Hard industrial bitumens (The standard is a framework of properties for typical grades)
Bitumen test methods
The test methods associated with these bitumen standards are as follows:
Bitumen emulsion standards
- BS EN 13808 : 2005 Bitumen and bituminous binders – Framework for specifying cationic bituminous emulsions
• This European standard has been in use for supply of bitumen emulsions since 1 January 2008. It covers:
- Cationic bitumen emulsions (There are no designated grades. The standard is a framework of classes for the characteristics that may need to be specified.)
- BS 434 : 1984 : Bitumen road emulsions
• BS 434 - Part 1: Specification for bitumen road emulsion
• This standard is now obsolescent. It is still in use for :
- Anionic road emulsions (Grades: A1-60, A1-55, A1-40, A2-57, A2-50, A3, A4)
• BS 434 - Part 2: Code of Practice for use of bitumen road emulsions
- This document is provides guidance on the usage of bitumen emulsions on roads and other surfaces.
- BS 3690 : 1989: Bitumens for building and civil engineering
• BS 3690 - Part 1: Specification for bitumens for roads and other paved areas
- This standard is now replaced. Paving grade bitumens are covered by BS EN 12591, hard paving grade bitumens are covered by BS EN 13924 and cut-back bitumens are covered by BS EN 15322.
• BS 3690 - Part 2: Specification for bitumens for industrial purposes
- This standard is now replaced. Oxidised bitumens are specified in BS EN 13304 and hard industrial grades are specified in BS EN 13305:2003.
• BS 3690 - Part 3: Specification for bitumen mixtures
- This standard covers blends of bitumen with other components, such as Trinidad Lake Asphalt (TLA).
- Specification Developments
• The CEN organisation (European Committee for Standardisation) continues to develop harmonised standards for construction materials, including various types of bituminous binder, to ensure 'no barriers to trade' throughout the European common market. Most are now in place but development work is continuing on performance-related specifications.
• The RBA Brochure describing the Specification Framework for Polymer Modified Bitumen
(RBA Guidance on British Standard BS EN 14023: 2010) can be obtained here [Link]
• The RBA Brochure describing the Specifications for Paving Grade Bitumens
(RBA Guidance on British Standard BS EN 12591:2009) can be obtained here [Link]