DEVELOPMENT OF BITUMEN SPECIFICATIONS: THE EUROPEAN EXPERIENCE

Transcription

1 DEVELOPMENT OF BITUMEN SPECIFICATIONS: THE EUROPEAN EXPERIENCE Mike Southern Technical Director Eurobitume, Boulevard du Souverain 165, B 1160 Brussels, Belgium Abstract The European Union (EU) now comprises 27 member states, with a further four European Free Trade Association countries. In order to ensure an open market for exchange of goods and services across national boundaries it is essential to develop common specifications. This paper describes the mechanism by which specifications are developed within Europe, the current structure of the standards for bituminous materials and the mechanism by which functional, performance related specifications are to be developed. Current European specifications for bituminous materials are based upon empirical test methods, although the process towards developing performance based specifications has been underway for some time. Eurobitume is participating in, and contributing to, the development of Performance Based Specifications. Key to the success of this process is maintaining credibility and support of all stakeholders, whilst complying with national and EU-wide requirements. Performance Based Specifications will take time to be implemented into European member states. However, the building blocks are in place and a process exists to ensure a smooth introduction. Eurobitume is present in the process and is doing its part to ensure that the process moves forward. 1 INTRODUCTION The European Union (EU) now comprises 27 * countries and the European Economic Area (EEA) includes a further four EFTA (European Free Trade Association) countries. A founding principal of the union is free trade between member states. A key to this is the ability to prevent barriers to trade that might prevent the movement of goods across national boundaries. The large number of countries and the wide spread of climatic conditions presents a number of challenges in ensuring free trade, in particular due to historic differences in specifications. Common specifications are desirable, even necessary, in order to permit manufacturers to produce goods that can be sold throughout the market. This is achieved by the implementation into each member states national legislation of a series of directives covering broad areas of activity, such as Construction Products. The Construction Products Directive (CPD) is most relevant for bituminous binders and sets out criteria for products used within the EU by specifying a series of Essential Requirements. At the practical level the requirements of the CPD mean that * Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, The Netherlands, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, United Kingdom Iceland, Liechtenstein (not a CEN member), Norway, Switzerland Proceedings of the 9 th Conference on Asphalt Pavements for Southern Africa (CAPSA 07) 2 5 September 2007 ISBN Number: Gaborone, Botswana Produced by: Document Transformation Technologies cc 10

2 National Standards for construction products, including bituminous binders, must be harmonised so that common specifications can be used throughout the EU. 2 CEN 1 COMITÉ EUROPÉEN DE NORMALISATION CEN, the European Committee for Standardisation, was founded in 1961 by the national standard s bodies in the European Economic Community and EFTA countries. CEN's National Members are the National Standards Organisations of 30 European countries. There is only one member per country. They have voting rights in the General Assembly and Administrative Board of CEN and provide delegations to the Technical Board which defines the work programme. CEN is a system of formal processes to produce standards. The responsibilities are shared principally between: - 30 National Members and the representative expertise they assemble from each country. These members vote for and implement European Standards (ENs); - Seven Associate Members and two Counsellors; - The CEN Management Centre, Brussels. CEN works closely with the European Committee for Electrotechnical Standardisation (CENELEC), the European Telecommunications Standards Institute (ETSI), and the International Organisation for Standardisation (ISO). It also has close liaisons with European trade and professional organisations, for example Eurobitume. 2.1 National Members The National Standards Bodies of the 27 European Union countries plus the National Standards Bodies of European Free Trade Area countries compose CEN's National Membership. The National Members: make up the delegations to the technical committees by finding expertise in each country; vote for, and implement, European Standards as national standards; provide the secretariats of the committees; finance more than 50 % of the work; In turn they are largely financed by industry, the sale of standards, and government grants. It is the responsibility of the CEN National Members to implement European Standards as national standards, to distribute and sell them and to withdraw any conflicting national standards. 2.2 Associate Members Associate Members are broad-based European organisations, representing particular sectors of industry as well as consumers, environmentalists, workers, and small and medium-sized enterprises. Other organisations fitting these criteria may become Associate Members. Eurobitume (and EAPA, the European Asphalt Paving Association) are associate members of the Technical Committees overseeing the standardisation process for bitumen and asphalts. 11

3 The rights and responsibilities of associate members are to: Undertake to promote CEN and European standardisation; Participate in the General Assembly (without voting rights); Sit on the Administrative Board when policy matters are being discussed; Sit on the Technical Board and any other technical body; Receive all relevant documentation and information, including draft standards. CEN does not implement the standards itself, instead the standards are agreed and harmonised within CEN and then implemented within member states national legislation by the national standardisation body. 2.3 Support for European Union and EFTA policies CEN supports the policies of the EU and EFTA, not just by requiring free trade between member states, but also in other key areas of support including: Worker and consumer safety; Interoperability of networks; Environmental protection; Exploitation of research and development programmes; Public procurement. 2.4 Mandates On behalf of governments, the European Commission or EFTA Secretariat may request the European Standards organisations to develop standards in support of their policies by issuing formal 'mandates'. For bituminous binders the main relevant directive is the Construction Products Directive (CPD) The 'new approach 3 Some European Standards are drawn up to support this policy, adopted in 1985, which decided that: legislative harmonisation is limited to the 'essential requirements', these being obligatory and formulated in general terms; writing of the detailed technical specifications necessary for the implementation of directives is entrusted to the European, voluntary standards organisations like CEN; the standards are not mandatory, but products manufactured according to such 'harmonised' standards gives a 'presumption of conformity' to the essential legal requirements in the directives; compliance results in the right of the product to bear the CE marking of conformity and market release throughout Europe. The CPD contains a list of Essential Requirements, all of which are relevant to building products, but not all of which are necessarily relevant to every construction product. Products supplied to the requirements of the CPD must be suitable for construction works which (as a whole and in their separate parts) are fit for their intended use (account being taken of economy) and must satisfy the following essential requirements (ER) where the works are subject to regulations containing such requirements. 12

4 1. Mechanical resistance and stability; 2. Safety in case of fire; 3. Hygiene, health and the environment; 4. Safety in use; 5. Protection against noise; 6. Energy economy and heat retention. Such requirements must, subject to normal maintenance, be satisfied for an economically reasonable working life. 3 HISTORY OF BITUMEN STANDARDISATION As is the case with many legislative issues the process for harmonisation of standards is highly bureaucratic. Standards are normally produced by technical committees, comprised of representatives nominated by their national standards body (or associate member body). Work items, proposed by working groups (WG s) are approved during plenary meetings and the work is carried out in either task groups (TG s, that report to working groups), or in the working group directly. Shortly after CEN was set up a technical committee responsible for standardising petroleum products was formed; TC19. Some years later a working group was formed to standardise bituminous binders, this was split into 5 groups to standardise different types of binder, ranging from penetration (paving) grade bitumens, through Industrial (oxidised) bitumens, cutback and fluxed binders, bitumen emulsions and polymer modified binders. Today only two working groups are still active; WG1 Paving bitumens and WG2 bitumen emulsions, cutback & fluxed bitumens. The structure of the working groups is shown in Figure 1. The focus of this paper is on bituminous binders, in particular bitumen for paving applications, but it will be noted that derivatives from coal pyrolysis (Tar and tar containing products) also appear in figure 1. The standardisation activity for such products is mainly limited to terminology and classification standards. Standards with characteristics and test methods were published. Before finalising those standards CEN/TC 317 decided to add guidance for use similar to the safety data sheets used by the industry. Many of the coal tar residual products are classified as carcinogenic in the EU, therefore their use is limited by directives aimed at ensuring the safety of exposed individuals to such materials, this ensures that the criteria for ER 3 are addressed. CEN/TC351 - Construction products - Assessment of release of dangerous substances, has been formed as a horizontal technical committee, i.e. applicable to all construction products. The function of this TC is specifically to address ER 3 (Hygiene, health and the environment), by developing harmonised test methods for the assessment of release of dangerous substances from construction products. At the time of writing TC351 is only addressing release to soil, groundwater and surface water (WG1), and Emissions to indoor air (WG2). Representatives from TC 336 attend these meetings to ensure that the standards developed are suitable for bituminous binders. 13

5 Hydrocarbon binders Bituminous binders Tar and Tar containing binders (TC317) Petroleum bitumens and derivatives (TC336) Paving bitumen EN Hard paving bitumen pren Soft bitumen Bitumen in natural asphalt Industrial Bitumen Oxidised bitumen EN Special bitumen Hard Industrial bitumen EN Modified bitumen Polymer modified bitumen EN Petroleum cut-back Bitumen pren Petroleum fluxed bitumen Bitumen emulsion Cationic bitumen emulsion EN Key EN pr TC European Norm Provisional Standard Bitumen Bituminous preparation/derivative Substance other than bitumen CEN Technical Committee Polymer modified bitumen emulsion Anionic bitumen emulsion Figure 1 - Structure of Bituminous binders working groups 3.1 First generation: harmonised specifications For bituminous binders the appropriate essential requirements are 1, 2, 3 and 4 (as listed in Section 2.5). The mandate for the Construction Products Directive requires specifications to address the Essential Requirements within the specifications to ensure compliance with the directive. A first step in harmonising standards for bituminous materials in EU was to ensure that test methods and grades of bitumen & bituminous materials could be specified across all member states. The second step was to produce fully harmonised standards, albeit still based upon existing test methods. This is the stage at which European standards for bitumen and bituminous preparations are currently in the EU. At the time of writing the standards for Paving bitumen (EN12591), Hard paving grade bitumens (EN13924) and polymer modified binders (EN14023) are under revision prior to introduction as harmonised standards. 14

6 3.2 Second generation: performance based, specifications The mandate for the CPD (Mandate M/124 4 ) requires that harmonised standards should be expressed as far as possible in terms which are performance based. Most conventional standards are based on empirical (historic) test methods, therefore do not currently comply with the performance based requirements of the mandate. However, CEN/TC336 is currently in the process of moving towards a performance-based approach to bitumen standardisation. A Task Group has been established (TG5) to oversee the development of the next generation of specifications. A stepwise approach is being followed to maintain the commitment of all member states. The first step in the process was orchestrated by Eurobitume in 1995 with a European workshop in rheology 5. This was followed in 1999 by an International workshop on performance related properties for bituminous binders 6. The workshop aimed to identify key properties of binders associated with pavement failure. The workshop was a great success and the proceedings were published by Eurobitume 7 as a summary of properties believed to be associated with performance, and to highlight areas where further research was necessary. The workshop concluded that the following binder properties were related to mixture, or pavement properties (Table 1): Table 1: Binder Properties linked to Asphalt Performance Performance Requirements for Pavement/ Mix Resistance to permanent deformation Resistance to surface cracking due to binder ageing Structural strength Resistance to low temperature cracking Resistance to fatigue cracking Manufacturing and laying Binder Properties Rheological property at elevated service temperature Ageing behaviour: short term and long term Rheological property: complex modulus Combination of rheological and failure properties Failure property Viscosity vs temperature Storage stability Following the rheology workshop, Eurobitume, in conjunction with other associate members, arranged a series of seminars known as BitSpec (Bitumen Specifications) with the aim of determining the needs of the producers and users of bitumen. This took place during Liaison with all stakeholders was essential to ensure that the needs of all parties were taken into account. The seminars were well attended by over 1000 representatives from all parts of the industry and the outputs from that project were made available to WG1 and given in the Eurobitume BiTSpec Proceedings 8. In 2002 Eurobitume published a position paper on Performance Related Specifications 9. The main criteria for any future specifications were outlined as; 15

7 The specification system is expected to be suitable throughout Europe, for all types of climatic conditions, traffic and pavement applications. It should be applicable to all categories of binders: conventional, special and modified bitumens. It should also ensure sufficient flexibility to comply with the different kinds of asphalt pavement contracts in use in Europe: from recipe specifications, to performance based specifications for the asphalt mix and to end use specifications for the asphalt pavement. 3.3 BiTVal The Bitumen Test Validation (BiTVal) project was set up by FEHRL (the Federation of European Highway Research Laboratories) in response to a request from TC 336,, together with other stakeholders in the industry to assess the relevance of the results of bitumen tests on the required properties of asphalt mixtures. It is envisaged that there will be the following three phases to the project: Phase 1; A review of existing data on bitumen tests used by TC336 WG1; Phase 2; A study of the gaps in the knowledge identified in Phase 1; Phase 3; A study of any bitumen test methods missing from the original list. Phase 1 has now been completed. The key outputs of Phase 1 of the BiTVal project were a database, covering publications of the identified bitumen properties and their relationship to asphalt properties and/or road performance, and a FEHRL report 10 to TC336 WG1 summarising the performance-related aspects for each test method, together with recommendations for their use in the next generation of standards. The report assesses bitumen tests in terms of the following critical performance characteristics, in asphalt mixture tests and/or pavement performance assessments and concludes that the following test methods are promising candidates: Permanent Deformation; - Zero Shear Viscosity by oscillation Dynamic Shear Rheometer is the preferred method - More (correlation) work needed on Equi-Viscous Temperature approach Stiffness; - Penetration, or - Dynamic Shear Rheometer stiffness (esp. for PmBs) Low Temperature Cracking; - Bending Beam Rheometer limiting temp, and/or a Direct Tension Tester parameter - Longer term: a fracture property (eg. Fracture Toughness) Fatigue Cracking; - Further research is required on relationship of binder fatigue to mixture fatigue - Best criteria currently remain: - Penetration/R&B/rheology before & after aging Adhesion; - Much research, BUT conclusions not straightforward - Tests need to involve an aggregate - Work on standard aggregates is suggested 16

8 3.4 CEN technical report CEN/TC336 WG1 produced a CEN Technical Report (TR) 11 summarising the status of work towards performance related specifications. The document contains a synthesis of TC 336 WG 1 (Paving bitumens) work on the development of second generation (performance-related) specifications for paving grade bitumens. It will be regularly updated by TC 336 when new information or test methods become available. The TR summarises and illustrates the ongoing work in the standardisation area with reference to the process of developing from traditional empirical based specifications to new performancerelated specifications for paving bitumens, as required by the Mandate M/124. It was decided that it would be better to maintain such a report as an informative document, which can be regularly amended and updated by TC 336 WG 1 as appropriate. The technical report contains a list of candidate test methods for high, medium and low temperature properties as well as ageing regimes. The list of tests can be seen in Figure Eurobitume data collection project Eurobitume has started a data collection project in which the members will provide a snapshot of European paving binders, tested using the CEN data collection framework. The project is currently underway, but the database containing the results will be made available to CEN/TC336 WG1 TG5 when complete, thereafter non-eurobitume members will be able to add data to the database. When the database has been populated it will be reviewed to identify promising candidate test methods for performance measurement. The review process will entail the following: - Test methods will be reviewed one by one; - Recognition of difficulties in applying the test methods including availability of equipment, needed time, precision; - Summary of changes of test method protocols during process of data collection; - Do the test methods differentiate performance between binders (irrespective of their nature)? - Check correlations between test methods; - Comparison with conclusions from BiTVAL report; - Suitability of test methods for different purposes; - Recommendations for use of test methods for specifications. The database is currently partially populated, when complete it the database will be passed to CEN/TC 336 so that further data can be added. 17

9 Product type Normal Paving Grade Hard Grade PMB Special bitumen PART 1: PRODUCT DESCRIPTION ACCORDING TO CONVENTIONAL CHARACTERISTICS EN Paving Grades - pren Hard Grades - EN Polymer Modified Bitumens Characteristic Test method Unit Measured value Binder condition Fresh STA (a) LTA (b) Nominal penetration range EN ,1 mm Penetration at 25 C EN ,1 mm Softening point R&B EN 1427 C Penetration index EN (2) - Dynamic viscosity at 60 C EN Pa.s Kinematic viscosity at135 C EN mm 2 /s Fraass breaking point EN C Elastic recovery at 10 C & 25 C (1) EN % Storage stability (1) EN Resistance to hardening EN Change in mass EN % Retained penetration at 25 C EN 1426 % Increase in softening point R&B EN 1427 C Flash point EN ISO 2592 C Solubility EN % Density pren (1) to be reported for PMB's only (2) Normative Annex B of EN 12591:1999 Calculation of the penetration index (I p Pfeiffer) (a) STA: Short Term Aged binder (b) LTA: Long Term Aged binder PART 2: PERFORMANCE-RELATED PROPERTIES This is not a specification but a framework for data collection. These tests are at various stages of development, however collection of data is encouraged on all of these tests in order to facilitate further selection for use in future specifications. Indicate the long term ageing procedure: PAV at... C [EN 14769] RCAT [pr EN 15323] PAV at... C [EN 14769] Characteristics Test method Unit At high service temperature Complex modulus (DSR) : G* and Delta EN kpa / C - for temperature sweep C (at certain frequencies) - for frequency sweep Hz (at certain temperatures) Measured value Binder condition Fresh STA (a) LTA (b) Low Shear Viscosity (DSR) Equiviscous temperature EVT1 at LSV = 2,0 kpa.s and 0,1 rad/s Equiviscous temperature EVT2 at LSV = 2,0 kpa.s and 0,001 rad/s pren pren C C Zero Shear Viscosity (DSR) Zero shear viscosity (creep mode) at 60 C pren kpa.s At intermediate service temperature Complex Modulus (DSR): G* and Delta EN kpa / C - for temperature sweep C (at certain frequencies) - for frequency sweep 0,1-10 Hz (at certain temperatures) At low service temperature Stiffness at -16 C EN MPa Bending Beam Rheometer (BBR); temperature at 300 MPa EN C Cohesion Force ductility at 5 / 10 C + whole curve Tensile test at 5 / 10 C + whole curve EN EN EN EN J/cm 2 J/cm 2 Vialit pendulum: maximum + whole temperature curve EN J/cm 2 (a) STA: Short Term Aged binder (b) LTA: Long Term Aged binder Figure 2 - Data Collection framework for the CEN Data Collection project 18

10 4 NEXT STEPS A key aspect in moving forward is to maintain credibility in the process, whilst complying with national and EU-wide requirements. Many of the newly standardised test methods do not have repeatability or reproducibility data and a number have not been widely used. Therefore, experience is required to ensure that future specifications are useable for the purposes of contractual agreements. Furthermore, a key element of the CEN process is that it should not exclude products with proven performance, thus measurement data on commercially available binders is necessary in order to set appropriate limits for specifications. For rational specification development the following requirements should be met: - Each element of a specification should measure a functional property; - Each test should have a sound scientific basis; - Tests should be practical and simple; - The specification should be validated in the field. Performance Based Specifications will take time to be implemented into European member states. However, the building blocks are in place and a process exists to assist the smooth introduction. Eurobitume is present in the process and is doing its part to ensure that the process moves forward. 5 REFERENCES [1] [2] [3] [4] Mandate to CEN/CENELEC concerning the execution of standardisation work for harmonised standards on road construction products. M 124 [5] First European Workshop in the Rheology of bituminous binders, organised by Eurobitume. ISBN [6] Eurobitume workshop 99; Performance Related Properties for Bituminous Binders, Workshop Briefing. ISBN [7] Eurobitume Workshop 99 on Performance Related Properties for Bituminous Binders; Workshop Proceedings. ISBN [8] European BiTSpec Seminar; Bituminous Binder Testing and Specifications. ISBN [9] Eurobitume position on future specification system for Bituminous paving binders [10] BitVal - Analysis of Available Data for Validation of Bitumen Tests. (download from [11] CEN/TR 15352:2006 Bitumen and bituminous binders Development of performance-related specifications: status report 2005 KEYWORDS Bitumen, Specifications, CEN, Eurobitume, BiTVal, performance-based 19