SAPEM Chapter 2 - Sanral

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Increased PD resistance, reduced flexibility South African Pavement Engineering Manual Chapter 2: Pavement Composition and Behaviour Bitumen None Low Intermediate High Cement Strongly cemented material Lightly cemented material Stiff, brittle behaviour behaviour Presumed not economically viable High Intermediate BSMs Low Unbound material: High quality crushed stone and aggregate Moderate quality natural gravel Low quality natural gravel (BSM-foam and BSM-emulsion) Stress Temperature dependent dependent, visco- behaviour elastic behaviour Asphalt concrete None Increased moisture resistance, flexibility Figure 10. Expected Behaviour of Material Types as a Function of Bitumen and Active Filler Content Section 5: Material Characteristics Page 13
South African Pavement Engineering Manual Chapter 2: Pavement Composition and Behaviour 6. PAVEMENT TYPES Road pavement types can be classified according to the type of materials used to construct the upper layers, and in particular the surfacing. The types of materials, whether flexible such as asphalt, or rigid such as concrete, determine the performance of a pavement in a given climate with a certain level of traffic, and the distress mechanisms that manifest in the pavement with time. The different distress types are discussed in Chapter 14, Section 3. An overview of different pavement types is provided in Figure 11. Pavement Types Surfaced Unsurfaced Flexible Asphalt Seals Semi-rigid / Composite Blocks Rigid Concrete Gravel Need pic Figure 11. Classification of Pavement Types based on Materials In addition to pavement types being differentiated based on the materials in the upper pavement layers, they can also be classified according to their applications and levels of traffic, as summarized in Table 1. Table 1. Classification of Pavements Based on Application and Traffic Facility Traffic Class Loading Freeway Heavy, 30 to 100 MESA Light and heavy vehicles Arterial and Main Road Medium > 3 MESA Light and heavy vehicles Secondary Road Light > 0.3 MESA Low percentage heavies Low Volume Road LVR = 50 to 200 vpd Mainly light vehicles Notes: 1. MESA = million equivalent standard axles (80 kN is the standard in South Africa, even though the maximum axle mass is 90 kN). See Chapter 10, Section 4.1.3. 2. vpd = vehicles per day 3. Traffic Class is also defined in TRH4 according to the upper limit of Equivalent Standard Axles (ES), e.g., ES100 = 30 to 100 million 80 kN axles. Finally, roads and their related pavements can also be classified based upon the importance of their function and the importance of the user trips made on the road. Functional classification is used to differentiate the minimum service levels for each class of road to set intervention levels with related budgetary implications. This functional classification normally entails: Primary Roads provide for high mobility between important cities, countries and transport hubs. Secondary Roads provide secondary mobility links between slightly less important centres or connections to the primary road network. Flexible vs Rigid Flexible pavements typically have asphalt or seal surfacings. They are flexible in that they can bend on the support. Rigid pavements are typically concrete pavements, and the concrete layer acts in a rigid manner in that it does not bend. See Chapter 10 for discussion on many aspects of rigid and flexible pavement design. Section 6: Pavement Types Page 14
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SAPEM Chapter 2 - Sanral

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