2011_AAPA_Study_Tour.. - Aapaq.org

4. Surface Treatments Questions and Responses AAPA 2011 Study Tour Group Reportand the local maintenance capability. For example Cape seals may be specified where there is alow level of maintenance expected.Guidance on the use of particular treatment is provided in TRH3 Design and Construction ofSurfacing Seals.Q 7. Is the type of binder to be used included in the selection process or is that determined bythe seal design process?The type of binder is a function of the traffic, road geometry and pavement condition and so formspart of the selection process. On national roads this process is undertaken by a consultantappointed by SANRAL who recommends a treatment and provides a basis for the selection. TG1provides guidelines on the selection of the binder type which should be used. SANRAL only usemodified binders on all their seals.Q 8. Are polymer modified emulsions used in sprayed sealing? If yes what are the keymotivators and what are the operational and cost implications?Modified emulsions are used extensively due to ability to be applied in a wider range of climaticconditions and as a SAM treatment. There is a cost penalty which ranges from 10 to 50% extra incomparison to a hot unmodified binder.Q 9.Does the public sector participate in sprayed sealing (percentage private to public)?This varies between the Provinces, but some still undertake their own sealing on low volumeroads. The majority of work is undertaken via contract.Q 10. Are binders bought in bulk by the client? If yes how is binder allocated to contracts?Generally no however there are instances when a client will purchase directly from a refinery onan ad-hoc basis.Q 11. Are newer sprayers with different international technologies being used?Sprayers are mostly sourced from the United States (Bearcat, Etnyre, Rosco) and France (Acmar).Features of some of these sprayers include oil jacketed spray bars, extendable spray bars andcomputer controlled spray nozzles.Q 12. Has the comparative performance of the various polymer modified binders and rubberbitumen used in seals been reviewed?Studies have been undertaken in the past but nothing recently. Data from PMS systems as shownin the figure below give an indication. This together with field observations suggest that thatcrumb rubber binders are providing superior performance and longevityV4-2 Page 30