BS 434-2:2006 pdf download – Bitumen road emulsions – Part 2: Code of practice for the use of cationic bitumen emulsions on roads and other paved areas
4.1 General The UK specification for bitumen emulsion (BS 434-1) was last published in 1984 and has remained substantially unchanged since then apart from two minor amendments. It has recently been replaced by BS EN 13808 which is a significantly different document. This clause attempts to explain the differences within the context of the changes that have occurred since 1984.
4.2 BS 434-1 classification In BS 434-1:1984 emulsions are classified on the basis of:
a) polarity – anionic or cationic (A or K);
b) emulsion stability (on a scale of 1-rapid, 2-medium, 3-slow breaking);
c) binder content.
Thus a K1:70 emulsion is a rapid breaking cationic emulsion with a nominal binder content of 70%. An A2:50 emulsion is a medium breaking anionic emulsion with a nominal binder content of 50%. The stability of emulsions can be changed by altering the type or quantity of emulsifier used in their manufacture. In recent years the development of tests to measure the break of the emulsion has resulted in numerical values, of breaking value or breaking index, being attributed to emulsion. This more accurately reflects their stability than the traditional allocation of 1, 2 or 3 in BS 434-1:1984 (see above) as an indication of stability, and has allowed the stability of emulsion to be defined numerically (breaking index) in BS EN 13808. 4.3 BS EN 13808 classification BS EN 13808 classifies emulsions in a more detailed way than BS 434-1 utilizing up to seven characters, on the following basis:
• polarity, e.g. C;
• nominal binder content, e.g. 67;
• indicate type of binder:
• B paving grade bitumen (BS EN 12591);
• P addition of polymer;
• F addition of more than 2% flux;
• class of breaking value (from 0 to 7) (see 4.5).
Thus for example a C70 B2 emulsion is a cationic bitumen emulsion with a 70% nominal binder content, produced from paving grade bitumen (conforming to BS EN 12591) with a class 2 breaking value. Similarly a C60 BPF6 emulsion is a cationic bitumen emulsion with a nominal binder content of 60% containing polymer and flux and having a class 6 breaking value.
4.4 Polymer modified bitumen products
4.4.1 Background At the time of publication of BS 434-1:1984 almost all bitumen emulsions were produced using paving (penetration) grades of bitumen. A significant change since the initial publication of that British Standard has been the introduction and development of polymer modified bitumen products, the growing use of which has presented problems of specification. Initially these products were sold as proprietary products to specifications produced by manufacturers, a situation which leads to confusion with no standard specifications for them. This problem was recognized by the introduction of an assessment and certification scheme for such products under the HAPAS (Highway Authorities Product Approval Scheme) administered by the British Board of Agrément (BBA) which produced a list of tests, including ageing and rheology, against which emulsions can be assessed. If the performance of the emulsion satisfies the requirements of the scheme it is eligible to receive a BBA Roads and Bridges Certificate. The testing under this scheme goes beyond the requirements of BS 434-1 in that for surface dressing, for example, it not only requires testing of the emulsion and of the recovered binder from the emulsion (as in BS EN 13808) but also evidence of two years’ satisfactory performance on the road at a minimum of three appropriate sites. Many of the binder testing requirements of the HAPAS binder specifications for polymer modified bituminous emulsions are also stipulated in the Specification for Highway Works (SHW) [1], Clauses 919 and 922 for surface dressing, Clause 920 for bond coats and Clause 918 for slurry surfacing and the Notes for Guidance and Appendices relating to them.BS 434-2 pdf download.