2011_AAPA_Study_Tour.. - Aapaq.org

4. Surface Treatments Questions and Responses AAPA 2011 Study Tour Group ReportSource – van Zyl 2011Q 13. What has been the experience with performance of SBS seals with the onset of winter?The use of SBS binder leading into winter is considered a high risk activity especially consideringthe reluctance to use cutters due to the risk of bleeding in the following summer. In thesecircumstances modified emulsions are used particularly for new works.Some concern was expressed over stone loss occurring on SBS seals in winter months hence theneed for an embargo. Banded softening point limits have been introduced in the TG1specifications for PMB’s to avoid over modification.Q 14. Have performance or functional specifications been used in the purchase of surface seals?These are yet to be introduced.Q 15. Are there best practice procedures for:a. surface pre-treatments including rut filling,b. surface rejuvenation and crack sealing;c. cutting back of binders,d. the use of bitumen emulsions;e. use of self propelled chip spreaders versus spreader boxes,f. calibration of sprayers,g. on site blending of bitumen rubber,h. pre-coating of aggregates, andi. priming of base courses.Sabita (South African Bitumen Association), SANRAL and the Asphalt Academy have publishedmanuals, guidelines and codes of practice that cover these topics. Several are in the process ofbeing updated. Publications of particular relevance include• TRH 3, Technical Recommendations for Highways, Design and Construction ofSurfacings Seals.• Manual 31: Guidelines for calibrating a binder distributor and ensuring satisfactoryperformance• TG1: The use of modified binders in road construction• Manual 26: Interim guidelines for primes and stone precoating fluidsV4-2 Page 31