2011_AAPA_Study_Tour.. - Aapaq.org

5. Binders AAPA 2011 Study Tour Group ReportSpray bar operating requirements for different bindersPRODUCTNOZZLE OUTPUT(l/min)SYSTEM PRESSURE(kPa)Emulsion/Prime 7 – 9 100 - 150Bitumen/PMB’s 13 – 15 150 – 200Bitumen-Rubber 35 - 40 350 - 400Source: Kobus Louw3. Use of Polymer modified bitumen emulsionsEmulsions and polymer modified bitumen emulsions are used in various road construction andmaintenance applications in RSA including:• Dilute covers sprays on newly constructed spray seals to prevent early stone loss• ‘Oil in water’ and invert emulsion primes for granular bases• Tack coats and bond coats for ultra thin asphalt (without cutter)• Rejuvenator and enrichment sprays for aged seals• Construction of spray seals in winter especially Cape Seals• Rut filling and texture treatments• In-situ cold recycling of existing pavements• Cold mixes using carbonaceous shale• Cold pour crack sealantsBitumen emulsion is ideal for labour enhanced construction and maintenance given that there is abig drive to create employment component of the works. This has lead to the popularization ofcertain road maintenance treatments such as the hand application of a thin surface texturetreatment slurry prior to resealing and the applying of slurry by hand to fill the voids whenconstructing a Cape seal.TG1 provides specifications which cover the use of PMBE’s in spray seals, bond coats,microsurfacings and crack sealants.The PMBE’s used in RSA are 3 phase cationic emulsions systems which use SBR latex. PMBE’s aremainly used in winter to allow the construction of a seal on new or rehabilitated road to continuethrough out winter when road surface temperatures are as low as 10°C without disruption to theproject. Limited resealing is done with emulsions.V4-2 Page 52