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Aggregate Primary function:

TRH 3 : Surface Seals for Rural and Urban Roads Components. Aggregate Primary function:. Resistance to abrasion of base. Transfer of wheel load to pavement structure. Skid resistance. Structure for accommodating binder (water proofing). Protection of binder from UV.

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Aggregate Primary function:

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  1. TRH 3 : Surface Seals for Rural and Urban Roads Components Aggregate Primary function: • Resistance to abrasion of base • Transfer of wheel load to pavement structure • Skid resistance • Structure for accommodating binder (water proofing) • Protection of binder from UV Additional characteristics: • Light absorbing qualities to reduce glare • Differing texture or colour to define areas

  2. TRH 3 : Surface Seals for Rural and Urban Roads Components Aggregate : Factors affecting performance: • Shape • Nominal size • Grading • Hardness, durability, abrasion • Porosity / absorption • Cleanliness, dust content • Spread rate

  3. TRH 3 : Surface Seals for Rural and Urban Roads Components Aggregate : Factors affecting performance: • Shape – affects interlock and thus stability • Shape and size – affects void content / macro texture, binder application • Grading – affects interlock, contact area, noise • Strength – affects breakdown during construction and service • Wear – affects abrasion or polishing / micro texture (skid resistance) • Porosity – affects absorption of lighter fraction of binder (durability) • Cleanliness – affects adhesion

  4. TRH 3 : Surface Seals for Rural and Urban Roads Components Warning Seal design method is based on strict standards w.r.t size, shape and grading. Changes to these standards could lead to current design approach being inappropriate with possible reduced performance.

  5. TRH 3 : Surface Seals for Rural and Urban Roads Components Binder function: • Waterproof pavement structure • Retain aggregate Performance influenced by: • Adhesion properties • Cohesion properties

  6. TRH 3 : Surface Seals for Rural and Urban Roads Components Binder factors affecting seal performance: • Binder type and properties • Grade of binder • Spray rate • Viscosity at application • Stiffness, R & B ??

  7. TRH 3 : Surface Seals for Rural and Urban Roads Components Binder type: Penetration grade Cut-backSABS Emulsion Homogeneous modified (PMB) Non-homogeneous modified (Bit-rubber) Modified emulsions (various grades and binder content Cutting back of binder – NOT generally recommended

  8. TRH 3 : Surface Seals for Rural and Urban Roads Components Factors influencing selection of binder: • Purpose of application i.e. tack coat, penetration spray etc. • Min. temp. at application and early life • Min. temp. during service life • Max. temp. during service life • Road geometry e.g. gradients, tight curves etc. • Traffic • Pavement deflection • Aggregate characteristics

  9. TRH 3 : Surface Seals for Rural and Urban Roads Components Properties of polymer modified binder for hot sealing applications

  10. TRH 3 : Surface Seals for Rural and Urban Roads Components Properties of polymer modified emulsions for surface seals

  11. TRH 3 : Surface Seals for Rural and Urban Roads Components Properties of bitumen-rubber for use in surface seals and asphalt

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